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- Front Matter: Volume 9147
- Instrument Programs at Major Observatories
- New Instruments and Upgrades to Existing Instruments
- High Multiplex and Survey Instruments I
- High Multiplex and Survey Instruments II
- High Multiplex and Survey Instruments III
- High Spectral Resolution Instruments I
- High Spectral Resolution Instruments II
- High Spatial Resolution Instruments I
- High Spatial Resolution Instruments II
- Instruments for Extremely Large Telescopes
- Posters Session: Instrument Programs and New Science Instruments and Upgrades
- Poster Session: Survey and High Multiplex Instruments
- Wednesday Plenary Session
- Poster Session: Survey and High Multiplex Instruments
- Poster Session: High Spectral and Spatial Resolution Instruments
- Poster Session: Extremely Large Telescopes and Instruments
Front Matter: Volume 9147
Front Matter: Volume 9147
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This PDF file contains the front matter associated with SPIE Proceedings Volume 9147, including the Title Page, Copyright information, Table of Contents, Invited Panel Discussion, and Conference Committee listing.
Instrument Programs at Major Observatories
Instrumentation at Gemini Observatory
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Gemini South's instrument suite has been completely transformed since our last biennial update. We commissioned
the Gemini Multi-Conjugate Adaptive Optics System (GeMS) and its associated Gemini South Adaptive Optics
Imager (GSAOI) as well as Flamingos-2, our long-slit and multi-object infrared imager and spectrograph, and the
Gemini Planet Imager (GPI). We upgraded the CCDs in GMOS-S, our multi-object optical imager and spectrograph,
with the GMOS-N CCD upgrade scheduled for 2015. Our next instrument, the Gemini High-resolution Optical
SpecTrograph (GHOST) is in its preliminary design stage and we are making plans for the instrument to
follow:Gen4#3.
New developments in instrumentation at the W. M. Keck Observatory
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The W. M. Keck Observatory continues to develop new capabilities in support of our science driven strategic plan which
emphasizes leadership in key areas of observational astronomy. This leadership is a key component of the scientific
productivity of our observing community and depends on our ability to develop new instrumentation, upgrades to
existing instrumentation, and upgrades to supporting infrastructure at the observatory. In this paper we describe the as
measured performance of projects completed in 2014 and the expected performance of projects currently in the
development or construction phases. Projects reaching completion in 2014 include a near-IR tip/tilt sensor for the Keck I
adaptive optics system, a new center launch system for the Keck II laser guide star facility, and NIRES, a near-IR
Echelle spectrograph for the Keck II telescope. Projects in development include a new seeing limited integral field
spectrograph for the visible wavelength range called the Keck Cosmic Web Imager, a deployable tertiary mirror for the
Keck I telescope, upgrades to the spectrograph detector and the imager of the OSIRIS instrument, and an upgrade to the
telescope control systems on both Keck telescopes.
Paranal instrumentation programme
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The development plan for instrumentation at the Paranal Observatory was outlined at SPIE in 2012. Its overall goal
is to keep Paranal at the forefront of ground-based astronomy. In addition to the completion of the current second
generation instruments, the installation of the Adaptive Optics Facility and execution of the Very Large Telescope
Interferometer mid-term implementation plan, it will allow one new instrument, or instrument upgrade, to be
initiated per year. The plan is divided into two phases. Over 2013-2017, instruments are selected and developed with
the criteria of filling the VLT capabilities and maintaining the balance between dedicated and general purpose
facilities. Beyond 2018, the instruments will be deployed in the era of maturity of the European Extremely Large
Telescope (E-ELT). The strategy for the second phase derives from analysis of VLT science in the E-ELT era, to be
fully shaped in the coming five years. The Call for ideas for a new instrument for the New Technology Telescope at
La Silla, fully funded by the community, has just been issued.
An overview and the current status of instrumentation at the Large Binocular Telescope Observatory
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An overview of instrumentation for the Large Binocular Telescope (LBT) is presented. Optical instrumentation
includes the Large Binocular Camera (LBC), a pair of wide-field (24′ × 24′) mosaic CCD imagers at the prime
focus, and the Multi-Object Double Spectrograph (MODS), a pair of dual-beam blue-red optimized long-slit
spectrographs mounted at the left and right direct F/15 Gregorian foci incorporating multiple slit masks for
multi-object spectroscopy over a 6′ field and spectral resolutions of up to 2000. Infrared instrumentation includes
the LBT Near-IR Spectrometer (LUCI), a modular near–infrared (0.9-2.5 μm) imager and spectrograph pair
mounted at the left and right front–bent F/15 Gregorian foci and designed for seeing-limited (FOV: 4′ × 4′)
imaging, long-slit spectroscopy, and multi-object spectroscopy utilizing cooled slit masks and diffraction limited
(FOV: 0'.5 x 0'.5) imaging and long-slit spectroscopy. Strategic instruments under development that can utilize
the full 23 m baseline of the LBT include an interferometric cryogenic beam combiner with near-infrared and
thermal-infrared instruments for Fizeau imaging and nulling interferometry (LBTI) and an optical bench near-
infrared beam combiner utilizing multi-conjugate adaptive optics for high angular resolution and sensitivity
(LINC-NIRVANA). LBTI is currently undergoing commissioning and performing science observations on the
LBT utilizing the installed adaptive secondary mirrors in both single–sided and two–sided beam combination
modes. In addition, a fiber-fed bench spectrograph (PEPSI) capable of ultra high resolution spectroscopy and
spectropolarimetry (R = 40,000-300,000) will be available as a principal investigator instrument. Installation
and testing of the bench spectrograph will begin in July 2014. Over the past four years the LBC pair, LUCI1, and
MODS1 have been commissioned and are now scheduled for routine partner science observations. Both LUCI2
and MODS2 passed their laboratory acceptance milestones in the summer of 2013 and have been installed on
the LBT. LUCI2 is currently being commissioned and the data analysis is well underway. Diffraction–limited
commissioning of its adaptive optics modes will begin in the 2014B semester. MODS2 commissioning began in
May 2014 and will completed in the 2014B semester as well. Binocular testing and commissioning of both the
LUCI and MODS pairs will begin in 2014B with the goal that this capability could be offered sometime in 2015.
The availability of all these instruments mounted simultaneously on the LBT permits unique science, flexible
scheduling, and improved operational support.
SOFIA science instruments: commissioning, upgrades and future opportunities
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The Stratospheric Observatory for Infrared Astronomy (SOFIA) is the world’s largest airborne observatory, featuring a
2.5 meter effective aperture telescope housed in the aft section of a Boeing 747SP aircraft. SOFIA’s current instrument
suite includes: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), a 5-40 μm dual band
imager/grism spectrometer developed at Cornell University; HIPO (High-speed Imaging Photometer for Occultations), a
0.3-1.1μm imager built by Lowell Observatory; GREAT (German Receiver for Astronomy at Terahertz Frequencies), a
multichannel heterodyne spectrometer from 60-240 μm, developed by a consortium led by the Max Planck Institute for
Radio Astronomy; FLITECAM (First Light Infrared Test Experiment CAMera), a 1-5 μm wide-field imager/grism
spectrometer developed at UCLA; FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), a 42-200 μm IFU grating
spectrograph completed by University Stuttgart; and EXES (Echelon-Cross-Echelle Spectrograph), a 5-28 μm highresolution
spectrometer designed at the University of Texas and being completed by UC Davis and NASA Ames
Research Center. HAWC+ (High-resolution Airborne Wideband Camera) is a 50-240 μm imager that was originally
developed at the University of Chicago as a first-generation instrument (HAWC), and is being upgraded at JPL to add
polarimetry and new detectors developed at Goddard Space Flight Center (GSFC). SOFIA will continually update its
instrument suite with new instrumentation, technology demonstration experiments and upgrades to the existing
instrument suite. This paper details the current instrument capabilities and status, as well as the plans for future
instrumentation.
The Daniel K. Inouye Solar Telescope first light instruments and critical science plan
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The Daniel K. Inouye Solar Telescope is a 4-meter-class all-reflecting telescope under construction on Haleakalā
mountain on the island of Maui, Hawai’i. When fully operational in 2019 it will be the world's largest solar telescope
with wavelength coverage of 380 nm to 28 microns and advanced Adaptive Optics enabling the highest spatial resolution
measurements of the solar atmosphere yet achieved. We review the first-generation DKIST instrument designs, select
critical science program topics, and the operations and data handling and processing strategies to accomplish them.
New Instruments and Upgrades to Existing Instruments
Introducing CUBES: the Cassegrain U-band Brazil-ESO spectrograph
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CUBES is a high-efficiency, medium-resolution (R ≃ 20, 000) spectrograph dedicated to the “ground based UV”
(approximately the wavelength range from 300 to 400nm) destined for the Cassegrain focus of one of ESO’s VLT
unit telescopes in 2018/19. The CUBES project is a joint venture between ESO and Instituto de Astronomia,
Geof´ısica e Ciˆencias Atmosf´ericas (IAG) at the Universidade de S˜ao Paulo and the Brazilian Laborat´orio Nacional
de Astrofs´ıca (LNA). CUBES will provide access to a wealth of new and relevant information for stellar as well as
extra-galactic sources. Principle science cases include the study of heavy elements in metal-poor stars, the direct
determination of carbon, nitrogen and oxygen abundances by study of molecular bands in the UV range and the
determination of the Beryllium abundance as well as the study of active galactic nuclei and the inter-galactic
medium. With a streamlined modern instrument design, high efficiency dispersing elements and UV-sensitive
detectors, it will enable a significant gain in sensitivity over existing ground based medium-high resolution
spectrographs enabling vastly increased sample sizes accessible to the astronomical community. We present here
a brief overview of the project, introducing the science cases that drive the design and discussing the design
options and technological challenges.
LRS2: the new facility low resolution integral field spectrograph for the Hobby-Eberly telescope
Show abstract
The second generation Low Resolution Spectrograph (LRS2) is a new facility instrument for the Hobby-Eberly Telescope (HET). Based on the design of the Visible Integral-field Replicable Unit Spectrograph (VIRUS), which is the new flagship instrument for carrying out the HET Dark Energy Experiment (HETDEX), LRS2 provides integral field spectroscopy for a seeing-limited field of 12" x 6". For LRS2, the replicable design of VIRUS has been leveraged to gain broad wavelength coverage from 370 nm to 1.0 μm, spread between two fiber-fed dual- channel spectrographs, each of which can operate as an independent instrument. The blue spectrograph, LRS2-B, covers 370 λ (nm) ≤ 470 and 460 ≤ λ (nm) ≤ 700 at fixed resolving powers of R = λ/δλ ≈ 1900 and 1100, respectively, while the red spectrograph, LRS2-R, covers 650 ≤ λ (nm) ≤ 842 and 818 ≤ λ (nm) ≤ 1050 with both of its channels having R ≈ 1800. In this paper, we present a detailed description of the instrument’s design in which we focus on the departures from the basic VIRUS framework. The primary modifications include the fore-optics that are used to feed the fiber integral field units at unity fill-factor, the cameras’ correcting optics and detectors, and the volume phase holographic grisms. We also present a model of the instrument’s sensitivity and a description of specific science cases that have driven the design of LRS2, including systematically studying the spatially resolved properties of extended Lyα blobs at 2 < z < 3. LRS2 will provide a powerful spectroscopic follow-up platform for large surveys such as HETDEX.
Project status of the Robert Stobie spectrograph near infrared instrument (RSS-NIR) for SALT
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The Robert Stobie Spectrograph Near Infrared Instrument (RSS-NIR), a prime focus facility instrument for the 11-meter
Southern African Large Telescope (SALT), is well into its laboratory integration and testing phase. RSS-NIR will
initially provide imaging and single or multi-object medium resolution spectroscopy in an 8 arcmin field of view at
wavelengths of 0.9 - 1.7 μm. Future modes, including tunable Fabry-Perot spectral imaging and polarimetry, have been
designed in and can be easily added later. RSS-NIR will mate to the existing visible wavelength RSS-VIS via a dichroic
beamsplitter, allowing simultaneous operation of the two instruments in all modes. Multi-object spectroscopy covering a
wavelength range of 0.32 - 1.7 μm on 10-meter class telescopes is a rare capability and once all the existing VIS modes
are incorporated into the NIR, the combined RSS will provide observational modes that are completely unique.
The VIS and NIR instruments share a common telescope focal plane, and slit mask for spectroscopic modes, and
collimator optics that operate at ambient observatory temperature. Beyond the dichroic beamsplitter, RSS-NIR is
enclosed in a pre-dewar box operating at -40 °C, and within that is a cryogenic dewar operating at 120 K housing the
detector and final camera optics and filters. This semi-warm configuration with compartments at multiple operating
temperatures poses a number of design and implementation challenges. In this paper we present overviews of the RSSNIR
instrument design and solutions to design challenges, measured performance of optical components, detector
system optimization results, and an update on the overall project status.
VISIR upgrade overview and status
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We present an overview of the VISIR upgrade project. VISIR is the mid-infrared imager and spectrograph at ESO’s
VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and
ASTRON. The project plan is based on input from the ESO user community with the goal of enhancing the scientific
performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of
instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As AQUARIUS detector
array (Raytheon) which has been carefully characterized in ESO’s IR detector test facility (modified TIMMI 2
instrument). A prism spectroscopic mode will cover the N-band in a single observation. New scientific capabilities for
high resolution and high-contrast imaging will be offered by sub-aperture mask (SAM) and phase-mask coronagraphic
(4QPM/AGPM) modes. In order to make optimal use of favourable atmospheric conditions a water vapour monitor has
been deployed on Paranal, allowing for real-time decisions and the introduction of a user-defined constraint on water
vapour. During the commissioning in 2012 it was found that the on-sky sensitivity of the AQUARIUS detector was
significantly below expectations and that VISIR was not ready to go back to science operations. Extensive testing of the
detector arrays in the laboratory and on-sky enabled us to diagnose the cause for the shortcoming of the detector as
excess low frequency noise (ELFN). It is inherent to the design chosen for this detector and can’t be remedied by
changing the detector set-up. Since this is a form of correlated noise its impact can be limited by modulating the scene
recorded by the detector. We have studied several mitigation options and found that faster chopping using the secondary
mirror (M2) of the VLT offers the most promising way forward. Faster M2 chopping has been tested and is scheduled
for implementation before the end of 2014 after which we plan to re-commission VISIR. In addition an upgrade of the IT
infrastructure related to VISIR is planned in order to support burst-mode operations. The upgraded VISIR will be a
powerful instrument providing close to background limited performance for diffraction-limited observations at an 8-m
telescope. It will offer synergy with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is
available from survey work (e.g. VISTA, WISE). In addition it will bring confirmation of the technical readiness and
scientific value of several aspects of potential mid-IR instrumentation at Extremely Large Telescopes.
The camera of the ASTRI SST-2M prototype for the Cherenkov Telescope Array
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In the context of the Cherenkov Telescope Array observatory project, the ASTRI SST-2M end-to-end prototype
telescope, entirely supported by the Italian National Institute of Astrophysics, is designed to detect cosmic primary
gamma ray energies from few TeV up to hundreds of TeV. The ASTRI SST-2M prototype camera is part of the
challenging synergy of novel optical design, camera sensors, front-end electronics and telescope structure design. The
camera is devoted to imaging and recording the Cherenkov images of air showers induced by primary particles into the
Earth’s atmosphere. In order to match the energy range mentioned above, the camera must be able to trigger events
within a few tens of nanoseconds with high detection efficiency. This is obtained by combining silicon photo-multiplier
sensors and suitable front-end electronics. Due to the characteristic imprint of the Cherenkov image that is a function of
the shower core distance, the signal dynamic range of the pixels and consequently of the front-end electronics must span
three orders of magnitude (1:1000 photo-electrons). These and many other features of the ASTRI SST-2M prototype
camera will be reported in this contribution together with a complete overview of the mechanical and thermodynamic
camera system.
A two-dimensional spectropolarimeter as a first-light instrument for the Daniel K. Inouye Solar Telescope
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The Visible Tunable Filter (VTF) is a narrowband tunable filter system for imaging spectropolarimetry. The instrument
will be one of the first-light instruments of the Daniel K. Inouye Solar Telescope (DKIST) that is currently under construction
on Maui (Hawaii). The DKIST has a clear aperture of 4 meters. The VTF is being developed by the Kiepenheuer
Institut für Sonnenphysik in Freiburg, as a German contribution to the DKIST.
The VTF is designed as a diffraction-limited narrowband tunable instrument for Stokes spectro-polarimetry in the
wavelength range between 520 and 860 nm. The instrument uses large-format Fabry-Perot interferometers (Etalons) as
tunable monochromators with clear apertures of about 240 mm. To minimize the influence of gravity on the interferometer
plates, the Fabry-Perots are placed horizontally. This implies a complex optical design and a three-dimensional support
structure instead of a horizontal optical bench.
The VTF has a field of view of one arc minute squared. With 4096x4096 pixel detectors, one pixel corresponds to an
angle of 0.014” on the sky (10 x 10 km on the Sun). The spectral resolution is 6 pm at a wavelength of 600 nm. One 2Dspectrum
with a polarimetric sensitivity of 5E-3 will be recorded within 13 seconds. The wavelength range of the VTF
includes a number of important spectral lines for the measurement flows and magnetic fields in the atmosphere of the
Sun. The VTF uses three identical large-format detectors, two for the polarimetric measurements, and one for broadband
filtergrams.
The main scientific observables of the VTF are Stokes polarimetric images to retrieve the magnetic field configuration of
the observed area, Doppler images to measure the line-of-sight flow in the solar photosphere, and monochromatic
intensity filtergrams to study higher layers of the solar atmosphere.
Performance of polarization modulation and calibration optics for the Daniel K. Inouye Solar Telescope
Show abstract
The Daniel K. Inouye Solar Telescope (formerly Advanced Technology Solar Telescope) will be the world's largest solar
telescope and polarimeter when completed in 2019. Efficient use of the telescope to address key science priorities calls
for polarization measurements simultaneously over broad wavelength ranges and calibration of the telescope and
polarimeters to high accuracy. Broadband polarization modulation and calibration optics utilizing crystal optics have
been designed for this application. The performance of polarization modulators and calibration retarders is presented
along with a discussion of the unique challenges of this application.
Polarimeters operate over the ranges of 0.38-1.1 microns, 0.5-2.5 microns, and 1.0-5.0 microns. Efficient polarization
modulation over these broad ranges led to modulators utilizing multiple wave plates and that are elliptical, rather than
linear, retarders. Calibration retarders are linear retarders and are constructed from the same sub-component wave plate
pairs as the polarization modulators. Polarization optics must address efficiency over broad wavelength ranges while
meeting beam deflection, transmitted wave front error, and thermal constraints and doing so with designs that, though
large in diameter, can be affordably manufactured.
KIDSpec: an MKID based medium resolution integral field spectrograph
Show abstract
We present a novel concept for a highly sensitive, medium spectral resolution optical through near-IR spectrograph.
KIDSpec, the Kinetic Inductance Detector Spectrograph, uses the intrinsic energy resolving capability of an array of
optical/IR-sensitive MKIDs to distinguish multiple orders from a low line-density (echelle) grating. MKID arrays have a
wide bandpass (0.1-2.5um) and good quantum efficiency, making them strong candidates for replacing CCDs in many
astronomical instruments. By acting as an ‘order resolver’, the MKID array replaces the cross-disperser in an echelle
spectrograph. This greatly simplifies the optical layout of the spectrograph and enables longer slits than are possible with
cross-dispersed instruments. KIDSpec would have similar capabilities to ESO’s X-shooter instrument. It would provide
an R=4000-10,000 spectrum covering the entire optical and near-IR spectral range. In addition to a ‘long-slit’ mode, the
IFU would provide a small (~50 spaxel) field-of-view for spatially resolved sources. In addition, the photon-counting
operation of MKIDs and their photon-energy resolving ability enable a read-noise free spectrum with perfect cosmic ray
removal. The spectral resolution would be sufficient to remove the bright night-sky lines without the additional pixel
noise, making the instrument more sensitive than an equivalent semiconductor-based instrument.
KIDSpec would enhance many existing high-profile science cases, including transient (GRB, SNe, etc.) follow-up,
redshift determination of faint objects and transit spectroscopy of exoplanets. In addition it will enable unique science
cases, such as dynamical mass estimates of the compact objects in ultra-compact binaries.
HIPO in-flight performance improvements
Show abstract
The High-speed Imaging Photometer for Occultations (HIPO) is a special purpose science instrument for SOFIA. HIPO
can be co-mounted with FLITECAM in the so-called FLIPO configuration for stellar occultation or extrasolar planet
transit observations. We gained some flight experience with HIPO and FLITECAM in 2011 as described in a previous
publication (Dunham, et al., Proc SPIE, 8446-42, 2012). Since that time a number of improvements to HIPO have been
made and a deeper understanding of the airborne environment's impact on photometric precision at optical wavelengths
has been obtained. The improvements to HIPO include an improved beamsplitter for the FLIPO configuration, adding
deep depletion CCDs as a detector option, expanding the filter set to include a Sloan Digital Sky Survey filter set as well
as two custom filters for transit work, and an ability to guide the SOFIA telescope using HIPO data being acquired for
science purposes. We now understand that variations in PSF size due to varying static air density has a noticeable
impact on photometric stability while the related effect of Mach number is unimportant. The seriousness of ozone
absorption in the Chappuis band is now understood and an approach to avoid this has been found. Finally we present
demonstration transit data to illustrate our current transit photometry capability.
A near-infrared SETI experiment: instrument overview
Shelley A. Wright,
Dan Werthimer,
Richard R. Treffers,
et al.
Show abstract
We are designing and constructing a new SETI (Search for Extraterrestrial Intelligence) instrument to search for direct
evidence of interstellar communications via pulsed laser signals at near-infrared wavelengths. The new instrument
design builds upon our past optical SETI experiences, and is the first step toward a new, more versatile and sophisticated
generation of very fast optical and near-infrared pulse search devices. We present our instrumental design by giving an
overview of the opto-mechanical design, detector selection and characterization, signal processing, and integration
procedure. This project makes use of near-infrared (950 - 1650 nm) discrete amplification Avalanche Photodiodes
(APD) that have > 1 GHz bandwidths with low noise characteristics and moderate gain (~104). We have investigated the
use of single versus multiple detectors in our instrument (see Maire et al., this conference), and have optimized the
system to have both high sensitivity and low false coincidence rates. Our design is optimized for use behind a 1m
telescope and includes an optical camera for acquisition and guiding. A goal is to make our instrument relatively
economical and easy to duplicate. We describe our observational setup and our initial search strategies for SETI targets,
and for potential interesting compact astrophysical objects.
High Multiplex and Survey Instruments I
Project overview and update on WEAVE: the next generation wide-field spectroscopy facility for the William Herschel Telescope
Show abstract
We present an overview of and status report on the WEAVE next-generation spectroscopy facility for the William
Herschel Telescope (WHT). WEAVE principally targets optical ground-based follow up of upcoming ground-based
(LOFAR) and space-based (Gaia) surveys. WEAVE is a multi-object and multi-IFU facility utilizing a new 2-degree
prime focus field of view at the WHT, with a buffered pick-and-place positioner system hosting 1000 multi-object
(MOS) fibres, 20 integral field units, or a single large IFU for each observation. The fibres are fed to a single
spectrograph, with a pair of 8k(spectral) x 6k (spatial) pixel cameras, located within the WHT GHRIL enclosure on the
telescope Nasmyth platform, supporting observations at R~5000 over the full 370-1000nm wavelength range in a single
exposure, or a high resolution mode with limited coverage in each arm at R~20000. The project is now in the final
design and early procurement phase, with commissioning at the telescope expected in 2017.
4MOST: 4-metre Multi-Object Spectroscopic Telescope
Show abstract
4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory (ESO). Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. 4MOST will in particular provide the spectroscopic complements to the large
area surveys coming from space missions like Gaia, eROSITA, Euclid, and PLATO and from ground-based facilities like VISTA, VST, DES, LSST and SKA. The 4MOST baseline concept features a 2.5 degree diameter field-of-view with ~2400 fibres in the focal surface that are configured by a fibre positioner based on the tilting spine principle. The fibres feed two types of spectrographs; ~1600 fibres go to two spectrographs with resolution R<5000 (λ~390-930 nm) and
~800 fibres to a spectrograph with R>18,000 (λ~392-437 nm and 515-572 nm and 605-675 nm). Both types of spectrographs are fixed-configuration, three-channel spectrographs. 4MOST will have an unique operations concept in which 5 year public surveys from both the consortium and the ESO community will be combined and observed in parallel during each exposure, resulting in more than 25 million spectra of targets spread over a large fraction of the
southern sky. The 4MOST Facility Simulator (4FS) was developed to demonstrate the feasibility of this observing
concept. 4MOST has been accepted for implementation by ESO with operations expected to start by the end of 2020.
This paper provides a top-level overview of the 4MOST facility, while other papers in these proceedings provide more
detailed descriptions of the instrument concept[1], the instrument requirements development[2], the systems engineering implementation[3], the instrument model[4], the fibre positioner concepts[5], the fibre feed[6], and the spectrographs[7].
MOONS: the Multi-Object Optical and Near-infrared Spectrograph for the VLT
M. Cirasuolo,
J. Afonso,
M. Carollo,
et al.
Show abstract
MOONS is a new Multi-Object Optical and Near-infrared Spectrograph selected by ESO as a third generation
instrument for the Very Large Telescope (VLT). The grasp of the large collecting area offered by the VLT (8.2m
diameter), combined with the large multiplex and wavelength coverage (optical to near-IR: 0.8μm - 1.8μm) of MOONS
will provide the European astronomical community with a powerful, unique instrument able to pioneer a wide range of
Galactic, Extragalactic and Cosmological studies and provide crucial follow-up for major facilities such as Gaia,
VISTA, Euclid and LSST. MOONS has the observational power needed to unveil galaxy formation and evolution over
the entire history of the Universe, from stars in our Milky Way, through the redshift desert, and up to the epoch of very
first galaxies and re-ionization of the Universe at redshift z>8-9, just few million years after the Big Bang. On a
timescale of 5 years of observations, MOONS will provide high quality spectra for >3M stars in our Galaxy and the
local group, and for 1-2M galaxies at z>1 (SDSS-like survey), promising to revolutionise our understanding of the
Universe.
The baseline design consists of ~1000 fibers deployable over a field of view of ~500 square arcmin, the largest patrol
field offered by the Nasmyth focus at the VLT. The total wavelength coverage is 0.8μm-1.8μm and two resolution
modes: medium resolution and high resolution. In the medium resolution mode (R~4,000-6,000) the entire wavelength
range 0.8μm-1.8μm is observed simultaneously, while the high resolution mode covers simultaneously three selected
spectral regions: one around the CaII triplet (at R~8,000) to measure radial velocities, and two regions at R~20,000 one
in the J-band and one in the H-band, for detailed measurements of chemical abundances.
MEGARA: a new generation optical spectrograph for GTC
A. Gil de Paz,
J. Gallego,
E. Carrasco,
et al.
Show abstract
MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit (IFU)
and Multi-Object Spectrograph (MOS) designed for the GTC 10.4m telescope in La Palma. MEGARA offers two IFU
fiber bundles, one covering 12.5x11.3 arcsec2 with a spaxel size of 0.62 arcsec (Large Compact Bundle; LCB) and
another one covering 8.5x6.7 arcsec2 with a spaxel size of 0.42 arcsec (Small Compact Bundle; SCB). The MEGARA
MOS mode will allow observing up to 100 objects in a region of 3.5x3.5 arcmin2 around the two IFU bundles.
Both the LCB IFU and MOS capabilities of MEGARA will provide intermediate-to-high spectral resolutions
(RFWHM~6,000, 12,000 and 18,700, respectively for the low-, mid- and high-resolution Volume Phase Holographic
gratings) in the range 3650-9700ÅÅ. These values become RFWHM~7,000, 13,500, and 21,500 when the SCB is used.
A mechanism placed at the pseudo-slit position allows exchanging the three observing modes and also acts as focusing
mechanism. The spectrograph is a collimator-camera system that has a total of 11 VPHs simultaneously available (out of
the 18 VPHs designed and being built) that are placed in the pupil by means of a wheel and an insertion mechanism. The
custom-made cryostat hosts an E2V231-84 4kx4k CCD.
The UCM (Spain) leads the MEGARA Consortium that also includes INAOE (Mexico), IAA-CSIC (Spain), and UPM
(Spain). MEGARA is being developed under a contract between GRANTECAN and UCM. The detailed design,
construction and AIV phases are now funded and the instrument should be delivered to GTC before the end of 2016.
High Multiplex and Survey Instruments II
The WIYN one degree imager 2014: performance of the partially populated focal plane and instrument upgrade path
Show abstract
The One Degree Imager (ODI) was deployed during the summer of 2012 at the WIYN 3.5m telescope, located on Kitt Peak near Tucson, AZ (USA). ODI is an optical imager designed to deliver atmosphere-limited image quality (≤ 0.4” FWHM) over a one degree field of view, and uses Orthogonal Transfer Array (OTA) detectors to also allow for on-chip tip/tilt image motion compensation. At this time, the focal plane is partially populated (”pODI”) with 13 out of 64 OTA detectors, providing a central scientifically usable field of view of about 24′ x 24′; four of the thirteen detectors are installed at outlying positions to probe image quality at all field angles. The image quality has been verified to be indeed better than 0.4′′ FWHM over the full field when atmospheric conditions allow. Based on over one year of operations, we summarize pODIs performance and lessons learned. As pODI has proven the viability of the ODI instrument, the WIYN consortium is engaging in an upgrade project to add 12 more detectors to the focal plane enlarging the scientifically usable field of view to about 40′ x 40′. A design change in the new detectors has successfully addressed a low light level charge transfer inefficiency.
VIRUS: production and deployment of a massively replicated fiber integral field spectrograph for the upgraded Hobby-Eberly
Telescope
Show abstract
The Visible Integral-field Replicable Unit Spectrograph (VIRUS) consists of a baseline build of 150 identical
spectrographs (arrayed as 75 unit pairs) fed by 33,600 fibers, each 1.5 arcsec diameter, at the focus of the upgraded 10
m Hobby-Eberly Telescope (HET). VIRUS has a fixed bandpass of 350-550 nm and resolving power R~700. VIRUS is
the first example of industrial-scale replication applied to optical astronomy and is capable of surveying large areas of
sky, spectrally. The VIRUS concept offers significant savings of engineering effort, cost, and schedule when compared
to traditional instruments.
The main motivator for VIRUS is to map the evolution of dark energy for the Hobby-Eberly Telescope Dark Energy
Experiment (HETDEX), using 0.8M Lyman-α emitting galaxies as tracers. The full VIRUS array is due to be deployed starting at the end of 2014 and will provide a powerful new facility instrument for the HET, well suited to the
survey niche of the telescope, and will open up large area surveys of the emission line universe for the first time.
VIRUS is in full production, and we are about half way through. We review the production design, lessons learned in
reaching volume production, and preparation for deployment of this massive instrument. We also discuss the application
of the replicated spectrograph concept to next generation instrumentation on ELTs.
The construction, alignment, and installation of the VIRUS spectrograph
Show abstract
VIRUS is the massively replicated fiber-fed spectrograph being built for the Hobby-Eberly Telescope to support
HETDEX (the Hobby-Eberly Telescope Dark Energy Experiment). The instrument consists of 156 identical
channels, fed by 34,944 fibers contained in 78 integral field units, deployed in the 22 arcminute field of the
upgraded HET. VIRUS covers 350-550nm at R ≈ 700 and is built to target Lyman α emitters at 1.9 < z < 3.5 to
measure the evolution of dark energy. Here we present the assembly line construction of the VIRUS spectrographs,
including their alignment and plans for characterization. We briefly discuss plans for installation on the telescope.
The spectrographs are being installed on the HET in several stages, and the instrument is due for completion
by the end of 2014.
The Dark Energy Spectroscopic Instrument (DESI)
Show abstract
The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar spectroscopic redshift survey. The DESI instrument consists of a new wide-field (3.2 deg. linear field of view) corrector plus a multi-object spectrometer with up to 5000 robotically positioned optical fibers and will be installed at prime focus on the Mayall 4m telescope at Kitt Peak, Arizona. The fibers feed 10 three-arm spectrographs producing spectra that cover a wavelength range from 360-980 nm and have resolution of 2000-5500 depending on the wavelength. The DESI instrument is designed for a 14,000 sq. deg. multi-year survey of targets that trace the evolution of dark energy out to redshift 3.5 using the redshifts of luminous red galaxies (LRGs), emission line galaxies (ELGs) and quasars. DESI is the successor to the successful Stage-III BOSS spectroscopic redshift survey and complements imaging surveys such as the Stage-III Dark Energy Survey (DES, currently operating) and the Stage-IV Large Synoptic Survey Telescope (LSST, planned start early in the next decade).
Progress with the Prime Focus Spectrograph for the Subaru Telescope: a massively multiplexed optical and near-infrared fiber spectrograph
Show abstract
The Prime Focus Spectrograph (PFS) is an optical/near-infrared multi-fiber spectrograph with 2394 science fibers, which
are distributed in 1.3 degree diameter field of view at Subaru 8.2-meter telescope. The simultaneous wide wavelength
coverage from 0.38 μm to 1.26 μm, with the resolving power of 3000, strengthens its ability to target three main survey
programs: cosmology, Galactic archaeology, and galaxy/AGN evolution. A medium resolution mode with resolving
power of 5000 for 0.71 μm to 0.89 μm also will be available by simply exchanging dispersers. PFS takes the role for the
spectroscopic part of the Subaru Measurement of Images and Redshifts (SuMIRe) project, while Hyper Suprime-Cam
(HSC) works on the imaging part. HSC’s excellent image qualities have proven the high quality of the Wide Field
Corrector (WFC), which PFS shares with HSC. The PFS collaboration has succeeded in the project Preliminary Design
Review and is now in a phase of subsystem Critical Design Reviews and construction.
To transform the telescope plus WFC focal ratio, a 3-mm thick broad-band coated microlens is glued to each fiber tip.
The microlenses are molded glass, providing uniform lens dimensions and a variety of refractive-index selection. After
successful production of mechanical and optical samples, mass production is now complete. Following careful
investigations including Focal Ratio Degradation (FRD) measurements, a higher transmission fiber is selected for the
longest part of cable system, while one with a better FRD performance is selected for the fiber-positioner and fiber-slit
components, given the more frequent fiber movements and tightly curved structure. Each Fiber positioner consists of two
stages of piezo-electric rotary motors. Its engineering model has been produced and tested. After evaluating the statistics
of positioning accuracies, collision avoidance software, and interferences (if any) within/between electronics boards,
mass production will commence. Fiber positioning will be performed iteratively by taking an image of artificially back-illuminated
fibers with the Metrology camera located in the Cassegrain container. The camera is carefully designed so
that fiber position measurements are unaffected by small amounts of high special-frequency inaccuracies in WFC lens
surface shapes.
Target light carried through the fiber system reaches one of four identical fast-Schmidt spectrograph modules, each with
three arms. All optical glass blanks are now being polished. Prototype VPH gratings have been optically tested. CCD
production is complete, with standard fully-depleted CCDs for red arms and more-challenging thinner fully-depleted
CCDs with blue-optimized coating for blue arms. The active damping system against cooler vibration has been proven to
work as predicted, and spectrographs have been designed to avoid small possible residual resonances.
Results of the verification of the NIR MOS EMIR
Show abstract
EMIR is one of the first common user instruments for the GTC, the 10 meter telescope operating at the Roque de los
Muchachos Observatory (La Palma, Canary Islands, Spain). EMIR is being built by a Consortium of Spanish and French
institutes led by the Instituto de Astrofísica de Canarias (IAC). EMIR is primarily designed to be operated as a MOS in
the K band, but offers a wide range of observing modes, including imaging and spectroscopy, both long slit and
multiobject, in the wavelength range 0.9 to 2.5 μm. This contribution reports on the results achieved so far during the
verification phase at the IAC prior to its shipment to the GTC for being commissioned, which is due by mid 2015. After
a long period of design and fabrication, EMIR finally entered into its integration phase by mid 2013. Soon after this, the
verification phase at the IAC was initiated aimed at configuring and tuning the EMIR functions, mostly the instrument
control system, which includes a sophisticated on line data reduction pipeline, and demonstrating the fulfillment of the
top level requirements. We have designed an ambitious verification plan structured along the three kind of detectors at
hand: the MUX and the engineering and scientific grade arrays. The EMIR subsystems are being integrated as they are
needed for the purposes of the verification plan. In the first stage, using the MUX, the full optical system, but with a
single dispersive element out of the three which form the EMIR suite, the two large wheels mounting the filters and the
pseudo-grisms, plus the detector translation unit holding the MUX, were mounted. This stage was mainly devoted to
learn about the capabilities of the instrument, define different settings for its basic operation modes and test the accuracy,
repeatability and reliability of the mechanisms. In the second stage, using the engineering Hawaii2 FPA, the full set of
pseudo-grisms and band filters are mounted, which means that the instrument is fully assembled except for the cold slit
unit, a robotic reconfigurable multislit mask system capable of forming multislit pattern of 55 different slitlets in the
EMIR focal plane. This paper will briefly describe the principal units and features of the EMIR instrument as the main
results of the verification performed so far are discussed. The development and fabrication of EMIR is funded by
GRANTECAN and the Plan Nacional de Astronomía y Astrofísica (National Plan for Astronomy and Astrophysics,
Spain).
DOTIFS: a new multi-IFU optical spectrograph for the 3.6-m Devasthal optical telescope
Show abstract
Devasthal Optical Telescope Integral Field Spectrograph (DOTIFS) is a new multi-object Integral Field Spectrograph
(IFS) being designed and fabricated by the Inter-University Center for Astronomy and Astrophysics (IUCAA), Pune,
India, for the Cassegrain side port of the 3.6m Devasthal Optical Telescope, (DOT) being constructed by the Aryabhatta
Research Institute of Observational Sciences (ARIES), Nainital. It is mainly designed to study the physics and
kinematics of the ionized gas, star formation and H II regions in the nearby galaxies. It is a novel instrument in terms of
multi-IFU, built in deployment system, and high throughput. It consists of one magnifier, 16 integral field units (IFUs),
and 8 spectrographs. Each IFU is comprised of a microlens array and optical fibers and has 7.4” x 8.7” field of view with
144 spaxel elements, each sampling 0.8” hexagonal aperture. The IFUs can be distributed on the telescope side port over
an 8’ diameter focal plane by the deployment system. Optical fibers deliver light from the IFUs to the spectrographs.
Eight identical, all refractive, dedicated spectrographs will produce 2,304 R~1800 spectra over 370-740nm wavelength
range with a single exposure. Volume Phase Holographic gratings are chosen to make smaller optics and get high
throughput. The total throughput of the instrument including the telescope is predicted as 27.5% on average. Observing
techniques, data simulator and reduction software are also under development. Currently, conceptual and baseline design
review has been done. Some of the components have already been procured. The instrument is expected to see its first
light in 2016.
Performance of the K-band multi-object spectrograph (KMOS) on the ESO VLT
Show abstract
KMOS is a multi-object near-infrared integral field spectrograph built by a consortium of UK and German institutes for
the ESO Paranal Observatory. We report on the on-sky performance verification of KMOS measured during three
commissioning runs on the ESO VLT in 2012/13 and some of the early science results.
Demonstration of high-performance cryogenic probe arms for deployable IFUs
Show abstract
We describe the design, development, and laboratory test results of cryogenic probe arms
feeding deployable integral field units (IFUs) for the Mid-resolution InfRAreD Astronomical
Spectrograph (MIRADAS) - a near-infrared multi-object echelle spectrograph for the 10.4-meter
Gran Telescopio Canarias. MIRADAS selects targets using 20 positionable pickoff mirror optics
on cryogenic probe arms, each feeding a 3.7x1.2-arcsec field of view to the spectrograph
integral field units, while maintaining excellent diffraction-limited image quality. The probe arms
are based on a concept developed for the ACES instrument for Gemini and IRMOS for TMT.
We report on the detailed design and opto-mechanical testing of MIRADAS prototype probe
arms, including positioning accuracy, repeatability, and reliability under fully cryogenic
operation, and their performance for MIRADAS. We also discuss potential applications of this
technology to future instruments.
First light results from the Hermes spectrograph at the AAT
Show abstract
The High Efficiency and Resolution Multi Element Spectrograph, HERMES is an facility-class optical spectrograph for
the AAT. It is designed primarily for Galactic Archeology [21], the first major attempt to create a detailed
understanding of galaxy formation and evolution by studying the history of our own galaxy, the Milky Way. The goal of
the GALAH survey is to reconstruct the mass assembly history of the of the Milky Way, through a detailed spatially
tagged abundance study of one million stars. The spectrograph is based at the Anglo Australian Telescope (AAT) and is
fed by the existing 2dF robotic fiber positioning system. The spectrograph uses VPH-gratings to achieve a spectral
resolving power of 28,000 in standard mode and also provides a high-resolution mode ranging between 40,000 to 50,000
using a slit mask. The GALAH survey requires a SNR greater than 100 for a star brightness of V=14. The total spectral
coverage of the four channels is about 100nm between 370 and 1000nm for up to 392 simultaneous targets within the 2
degree field of view. Hermes has been commissioned over 3 runs, during bright time in October, November and
December 2013, in parallel with the beginning of the GALAH Pilot survey starting in November 2013. In this paper we
present the first-light results from the commissioning run and the beginning of the GALAH Survey, including
performance results such as throughput and resolution, as well as instrument reliability. We compare the abundance
calculations from the pilot survey to those in the literature.
High Multiplex and Survey Instruments III
KOSMOS and COSMOS: new facility instruments for the NOAO 4-meter telescopes
Show abstract
We describe the design, construction and measured performance of the Kitt Peak Ohio State Multi-Object Spectrograph
(KOSMOS) for the 4-m Mayall telescope and the Cerro Tololo Ohio State Multi-Object Spectrograph (COSMOS) for
the 4-m Blanco telescope. These nearly identical imaging spectrographs are modified versions of the OSMOS
instrument; they provide a pair of new, high-efficiency instruments to the NOAO user community. KOSMOS and
COSMOS may be used for imaging, long-slit, and multi-slit spectroscopy over a 100 square arcminute field of view with
a pixel scale of 0.29 arcseconds. Each contains two VPH grisms that provide R~2500 with a one arcsecond slit and their
wavelengths of peak diffraction efficiency are approximately 510nm and 750nm. Both may also be used with either a
thin, blue-optimized CCD from e2v or a thick, fully depleted, red-optimized CCD from LBNL. These instruments were
developed in response to the ReSTAR process. KOSMOS was commissioned in 2013B and COSMOS was
commissioned in 2014A.
TAIPAN: optical spectroscopy with StarBugs
Show abstract
TAIPAN is a spectroscopic instrument designed for the UK Schmidt Telescope at the Australian Astronomical Observatory. In addition to undertaking the TAIPAN survey, it will serve as a prototype for the MANIFEST fibre positioner system for the future Giant Magellan Telescope. The design for TAIPAN incorporates up to 300 optical fibres situated within independently-controlled robotic positioners known as Starbugs, allowing precise parallel positioning of every fibre, thus significantly reducing instrument configuration time and increasing observing time. We describe the design of the TAIPAN instrument system, as well as the science that will be accomplished by the TAIPAN survey. We also highlight results from the on-sky tests performed in May 2014 with Starbugs on the UK Schmidt Telescope and briefly introduce the role that Starbugs will play in MANIFEST.
mxSPEC: a massively multiplexed full-disk spectroheliograph for solar physics research
Show abstract
The Massively Multiplexed Spectrograph (mxSPEC) is a new instrument concept that takes advantage of modern high-speed large-format focal plane arrays (FPAs) and high efficiency bandpass isolation filters to multiplex spectra from many slices of the telescope field simultaneously onto the FPAs within a single grating spectrograph. This design greatly reduces the time required to scan a large telescope field, and with current technologies can achieve more than a factor of 50 or more improvement of the system efficiency over a conventional long-slit spectrograph. Furthermore, several spectral lines can be observed at the same time with proper selection of the diffraction grating, further improving the efficiency of this design to more than two orders of magnitude over conventional single-slit, single-wavelength instrument. This paper describes an experimental, proof-of-concept, 40-slit full-disk spectrograph that demonstrates the feasibility of this new instrument concept and its potential for solar physics research including helioseismology, dynamic solar events, and global scale magnetic field observation of the solar disk and the corona. We also present the preliminary design of a 4-line, 55-slit spectroheliograph that can serve as the template for the instruments of the next generation synoptic solar observatory.
BATMAN: a DMD-based multi-object spectrograph on Galileo telescope
Show abstract
Next-generation infrared astronomical instrumentation for ground-based and space telescopes could be based on
MOEMS programmable slit masks for multi-object spectroscopy (MOS). This astronomical technique is used
extensively to investigate the formation and evolution of galaxies.
We are developing a 2048x1080 Digital-Micromirror-Device-based (DMD) MOS instrument to be mounted on the
Galileo telescope and called BATMAN. A two-arm instrument has been designed for providing in parallel imaging and
spectroscopic capabilities. The field of view (FOV) is 6.8 arcmin x 3.6 arcmin with a plate scale of 0.2 arcsec per
micromirror. The wavelength range is in the visible and the spectral resolution is R=560 for 1 arcsec object (typical slit
size). The two arms will have 2k x 4k CCD detectors.
ROBIN, a BATMAN demonstrator, has been designed, realized and integrated. It permits to determine the instrument
integration procedure, including optics and mechanics integration, alignment procedure and optical quality. First images
and spectra have been obtained and measured: typical spot diameters are within 1.5 detector pixels, and spectra generated
by one micro-mirror slits are displayed with this optical quality over the whole visible wavelength range. Observation
strategies are studied and demonstrated for the scientific optimization strategy over the whole FOV.
BATMAN on the sky is of prime importance for characterizing the actual performance of this new family of MOS
instruments, as well as investigating the operational procedures on astronomical objects. This instrument will be placed
on the Telescopio Nazionale Galileo mid-2015.
High Spectral Resolution Instruments I
Infrared Doppler instrument (IRD) for the Subaru telescope to search for Earth-like planets around nearby M-dwarfs
Show abstract
We report the current status of the Infrared Doppler (IRD) instrument for the Subaru telescope, which aims at detecting
Earth-like planets around nearby M darwfs via the radial velocity (RV) measurements. IRD is a fiber-fed, near infrared
spectrometer which enables us to obtain high-resolution spectrum (R~70000) from 0.97 to 1.75 μm. We have been
developing new technologies to achieve 1m/s RV measurement precision, including an original laser frequency comb as
an extremely stable wavelength standard in the near infrared. To achieve ultimate thermal stability, very low thermal
expansion ceramic is used for most of the optical components including the optical bench.
SPIRou: the near-infrared spectropolarimeter/high-precision velocimeter for the Canada-France-Hawaii telescope
Show abstract
SPIRou is a near-IR echelle spectropolarimeter and high-precision velocimeter under construction as a next-
generation instrument for the Canada-France-Hawaii-Telescope. It is designed to cover a very wide simultaneous
near-IR spectral range (0.98-2.35 μm) at a resolving power of 73.5K, providing unpolarized and polarized
spectra of low-mass stars at a radial velocity (RV) precision of 1m/s. The main science goals of SPIRou are
the detection of habitable super-Earths around low-mass stars and the study of stellar magnetism of star at
the early stages of their formation. Following a successful final design review in Spring 2014, SPIRou is now
under construction and is scheduled to see first light in late 2017. We present an overview of key aspects of
SPIRou’s optical and mechanical design.
NRES: the network of robotic Echelle spectrographs
Show abstract
Las Cumbres Observatory Global Network (LCOGT) is building the Network of Robotic Echelle Spectrographs (NRES), which will consist of six identical, optical (390 - 860 nm) high-precision spectrographs, each fiber-fed simultaneously by two 1 meter telescopes and a thorium argon calibration source, one at each of our observatory sites in the Northern and Southern hemispheres. Thus, NRES will be a single, globally-distributed, autonomous observing facility using twelve 1-m telescopes. Simulations suggest we will achieve long-term precision of better than 3 m/s in less than an hour for stars brighter than V = 12. We have been fully funded with an NSF MRI grant, and expect our first spectrograph to be deployed in Spring of 2015, with the full network operation of all 6 units beginning in Spring of 2016. We discuss the NRES design, goals, and robotic operation, as well as the early results from our prototype spectrograph.
High resolution broad-band spectroscopy in the NIR using the Triplespec externally dispersed interferometer at the Hale telescope
Show abstract
High resolution broad-band spectroscopy at near-infrared wavelengths has been performed using externally dis- persed interferometry (EDI) at the Hale telescope at Mt. Palomar. The EDI technique uses a field-widened Michelson interferometer in series with a dispersive spectrograph, and is able to recover a spectrum with a resolution 4 to 10 times higher than the existing grating spectrograph. This method increases the resolution well beyond the classical limits enforced by the slit width and the detector pixel Nyquist limit and, in principle, decreases the effect of pupil variation on the instrument line-shape function. The EDI technique permits arbi- trarily higher resolution measurements using the higher throughput, lower weight, size, and expense of a lower resolution spectrograph. Observations of many stars were performed with the TEDI interferometer mounted within the central hole of the 200 inch primary mirror. Light from the interferometer was then dispersed by the
TripleSpec near-infrared echelle spectrograph. Continuous spectra between 950 and 2450 nm with a resolution
as high as ~27,000 were recovered from data taken with TripleSpec at a native resolution of ∼2,700. Aspects
of data analysis for interferometric spectral reconstruction are described. This technique has applications in im- proving measurements of high-resolution stellar template spectra, critical for precision Doppler velocimetry using conventional spectroscopic methods. A new interferometer to be applied for this purpose at visible wavelengths is under construction.
A design for high-resolution spectroscopy with adaptive optics at the Large Binocular Telescope
Show abstract
The use of spectrographs with telescopes having high order adaptive optics systems offers the possibility of
achieving near diffraction-limited spectral resolving power. The adaptively corrected echelle spectrograph
(ACES) couples the AO-corrected stellar image to the instrument with a near single mode fiber (SMF) for
resolution of R~190,000. The First Light Adaptive Optics system (FLAO) at the Large Binocular Telescope
(LBT) achieves Strehl of >80% in H band, and also delivers useful Strehls in V and R bands. In this paper
we explore the possibility of using ACES with the LBT for simultaneous high resolution, high throughput,
and broad wavelength coverage.
CRIRES+: a cross-dispersed high-resolution infrared spectrograph for the ESO VLT
Show abstract
High-resolution infrared spectroscopy plays an important role in astrophysics from the search for exoplanets to
cosmology. Yet, many existing infrared spectrographs are limited by a rather small simultaneous wavelength coverage.
The AO assisted CRIRES instrument, installed at the ESO VLT on Paranal, is one of the few IR (0.92-5.2 μm) highresolution
spectrographs in operation since 2006. However it has a limitation that hampers its efficient use: the
wavelength range covered in a single exposure is limited to ~15 nanometers. The CRIRES Upgrade project (CRIRES+)
will transform CRIRES into a cross-dispersed spectrograph and will also add new capabilities. By introducing crossdispersion
elements the simultaneously covered wavelength range will be increased by at least a factor of 10 with respect
to the present configuration, while the operational wavelength range will be preserved. For advanced wavelength
calibration, new custom made absorption gas cells and etalons will be added. A spectro-polarimetric unit will allow one
for the first time to record circularly polarized spectra at the highest spectral resolution. This will be all supported by a
new data reduction software which will allow the community to take full advantage of the new capabilities of CRIRES+.
On-sky performance of a high resolution silicon immersion grating spectrometer
Show abstract
High resolution infrared spectroscopy has been a major challenging task to accomplish in astronomy due to the enormous size and cost of IR spectrographs built with traditional gratings. A silicon immersion grating, due to its over three times high dispersion over a traditional reflective grating, offers a compact and low cost design of new generation IR high resolution spectrographs. Here we report the on-sky performance of the first silicon immersion grating spectrometer, called Florida IR Silicon immersion grating spectromeTer (FIRST), commissioned at the 2-meter Automatic Spectroscopic Telescope (AST) of Fairborn Observatory in Arizona in October 2013. The measured spectral resolution is R=50,000 with a 50 mm diameter spectrograph pupil and a blaze angle of 54.7 degree. The 1.4-1.8 m wavelength region (the Red channel) is completely covered in a single exposure with a 2kx2k H2RG IR array while the 0.8-1.35 μm region is nearly completely covered by the cross-dispersed echelle mode (the Blue channel) at R=50,000 in a single exposure. The instrument is operated in a high vacuum (about 1 micro torr) and cryogenic temperatures (the bench at 189K and the detector at 87K) and with a precise temperature control. It is primarily used for high precision Doppler measurements (~3 m/s) of low mass M dwarf stars for the identification and characterization of extrasolar planets. A plan for a high cadence and high precision survey of habitable super-Earths around ~150 nearby M dwarfs and a major upgrade with integral field unit low resolution spectroscopy are also introduced.
A laser frequency comb featuring sub-cm/s precision for routine operation on HARPS
Show abstract
We present a re-engineered version of the laser frequency comb that has proven a few-cm/s calibration repeatability
on the HARPS spectrograph during past campaigns. The new design features even better performance
characteristics. The newly arranged oscillator, filter cavities and fiber injection for spectral broadening allow
robust long term operation, controlled from a remote site. Its automation features enable easy operation for
non-experts. The system is being prepared for installation on the HARPS spectrograph in fall of 2014, and will
subsequently become available to the astronomical community.
Design and early performance of IGRINS (Immersion Grating Infrared Spectrometer)
Show abstract
The Immersion Grating Infrared Spectrometer (IGRINS) is a compact high-resolution near-infrared cross-dispersed
spectrograph whose primary disperser is a silicon immersion grating. IGRINS covers the entire portion of the
wavelength range between 1.45 and 2.45μm that is accessible from the ground and does so in a single exposure with a
resolving power of 40,000. Individual volume phase holographic (VPH) gratings serve as cross-dispersing elements for
separate spectrograph arms covering the H and K bands. On the 2.7m Harlan J. Smith telescope at the McDonald
Observatory, the slit size is 1ʺ x 15ʺ and the plate scale is 0.27ʺ pixel. The spectrograph employs two 2048 x 2048
pixel Teledyne Scientific and Imaging HAWAII-2RG detectors with SIDECAR ASIC cryogenic controllers. The
instrument includes four subsystems; a calibration unit, an input relay optics module, a slit-viewing camera, and nearly
identical H and K spectrograph modules. The use of a silicon immersion grating and a compact white pupil design allows
the spectrograph collimated beam size to be only 25mm, which permits a moderately sized (0.96m x 0.6m x 0.38m)
rectangular cryostat to contain the entire spectrograph. The fabrication and assembly of the optical and mechanical
components were completed in 2013. We describe the major design characteristics of the instrument including the
system requirements and the technical strategy to meet them. We also present early performance test results obtained
from the commissioning runs at the McDonald Observatory.
High resolution near IR spectroscopy with GIANO-TNG
Show abstract
GIANO is the high resolution near IR spectrograph recently commissioned at the 3.58m Telescopio Nazionale Galileo in
La Palma (Spain). GIANO is the first worldwide instrument providing cross-dispersed echelle spectroscopy at a
resolution of 50,000 over the 0.95 – 2.45 micron spectral range in a single exposure. There are outstanding science cases
in the research fields of exo-planets, Galactic stars and stellar populations that could strongly benefit from GIANO
observations down to a magnitude limit comparable to that of 2MASS. The instrument includes a fully cryogenic
spectrograph and an innovative fiber system transmitting out to the K band. It also represents a formidable laboratory to
test performances and prototype solutions for the next generation of high resolution near IR spectrographs at the ELTs.
First results from sky tests at the telescope and science verification occurred between July 2012 and October 2013 will
be presented.
High Spectral Resolution Instruments II
CARMENES instrument overview
Show abstract
This paper gives an overview of the CARMENES instrument and of the survey that will be carried out with it
during the first years of operation. CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths
with Near-infrared and optical Echelle Spectrographs) is a next-generation radial-velocity instrument
under construction for the 3.5m telescope at the Calar Alto Observatory by a consortium of eleven Spanish
and German institutions. The scientific goal of the project is conducting a 600-night exoplanet survey targeting
~ 300 M dwarfs with the completed instrument.
The CARMENES instrument consists of two separate echelle spectrographs covering the wavelength range
from 0.55 to 1.7 μm at a spectral resolution of R = 82,000, fed by fibers from the Cassegrain focus of the telescope.
The spectrographs are housed in vacuum tanks providing the temperature-stabilized environments necessary to
enable a 1 m/s radial velocity precision employing a simultaneous calibration with an emission-line lamp or with
a Fabry-Perot etalon. For mid-M to late-M spectral types, the wavelength range around 1.0 μm (Y band) is the
most important wavelength region for radial velocity work. Therefore, the efficiency of CARMENES has been
optimized in this range.
The CARMENES instrument consists of two spectrographs, one equipped with a 4k x 4k pixel CCD for
the range 0.55 - 1.05 μm, and one with two 2k x 2k pixel HgCdTe detectors for the range from 0.95 - 1.7μm.
Each spectrograph will be coupled to the 3.5m telescope with two optical fibers, one for the target, and one
for calibration light. The front end contains a dichroic beam splitter and an atmospheric dispersion corrector,
to feed the light into the fibers leading to the spectrographs. Guiding is performed with a separate camera;
on-axis as well as off-axis guiding modes are implemented. Fibers with octagonal cross-section are employed to
ensure good stability of the output in the presence of residual guiding errors. The fibers are continually actuated
to reduce modal noise. The spectrographs are mounted on benches inside vacuum tanks located in the coud´e
laboratory of the 3.5m dome. Each vacuum tank is equipped with a temperature stabilization system capable
of keeping the temperature constant to within ±0.01°C over 24 hours. The visible-light spectrograph will be
operated near room temperature, while the near-IR spectrograph will be cooled to ~ 140 K.
The CARMENES instrument passed its final design review in February 2013. The MAIV phase is currently
ongoing. First tests at the telescope are scheduled for early 2015. Completion of the full instrument is planned
for the fall of 2015. At least 600 useable nights have been allocated at the Calar Alto 3.5m Telescope for the
CARMENES survey in the time frame until 2018.
A data base of M stars (dubbed CARMENCITA) has been compiled from which the CARMENES sample can
be selected. CARMENCITA contains information on all relevant properties of the potential targets. Dedicated imaging, photometric, and spectroscopic observations are underway to provide crucial data on these stars that
are not available in the literature.
The Habitable-zone Planet Finder: A status update on the development of a stabilized fiber-fed near-infrared spectrograph for the for the Hobby-Eberly telescope
Show abstract
The Habitable-Zone Planet Finder is a stabilized, fiber-fed, NIR spectrograph being built for the 10m Hobby- Eberly telescope (HET) that will be capable of discovering low mass planets around M dwarfs. The optical design of the HPF is a white pupil spectrograph layout in a vacuum cryostat cooled to 180 K. The spectrograph uses gold-coated mirrors, a mosaic echelle grating, and a single Teledyne Hawaii-2RG (H2RG) NIR detector with a 1.7-micron cutoff covering parts of the information rich z, Y and J NIR bands at a spectral resolution of R∼50,000. The unique design of the HET requires attention to both near and far-field fiber scrambling, which we accomplish with double scramblers and octagonal fibers. In this paper we discuss and summarize the main requirements and challenges of precision RV measurements in the NIR with HPF and how we are overcoming these issues with technology, hardware and algorithm developments to achieve high RV precision and address stellar activity.
ESPRESSO: the radial velocity machine for the VLT
Show abstract
ESPRESSO is the next generation ground based European exoplanets hunter. It will combine the efficiency of modern
echelle spectrograph with extreme radial-velocity and spectroscopic precision. It will be installed at Paranal's VLT in
order to achieve two magnitudes gain with respect to its predecessor HARPS, and the instrumental radial-velocity
precision will be improved to reach 10 cm/s level. We have constituted a Consortium of astronomical research institutes
to fund, design and build ESPRESSO on behalf of and in collaboration with ESO, the European Southern Observatory.
The spectrograph will be installed at the Combined Coudé Laboratory (CCL) of the VLT, it will be linked to the four 8.2
meters Unit Telescopes through four optical "Coudé trains" and will be operated either with a single telescope or with up
to four UTs, enabling an additional 1.5 magnitude gain. Thanks to its characteristics and ability of combining
incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in many fields of astronomy. Our
main scientific objectives are, however, the search and characterization of rocky exoplanets in the habitable zone of
quiet, near-by G to M-dwarfs, and the analysis of the variability of fundamental physical constants. The project is, for
most of its workpackages, in the procurement or development phases, and the CCL infrastructure is presently under
adaptation work. In this paper, we present the scientific objectives, the capabilities of ESPRESSO, the technical solutions
for the system and its subsystems. The project aspects of this facility are also described, from the consortium and
partnership structure to the planning phases and milestones.
PIMMS échelle: the next generation of compact diffraction limited spectrographs for arbitrary input beams
Show abstract
PIMMS échelle is an extension of previous PIMMS (photonic integrated multimode spectrograph) designs, enhanced by using an échelle diffraction grating as the primary dispersing element for increased spectral band- width. The spectrograph operates at visible wavelengths (550 to 780nm), and is capable of capturing ~100 nm of R > 60, 000 (λ/(triangle)λ) spectra in a single exposure. PIMMS échelle uses a photonic lantern to convert an arbitrary (e.g. incoherent) input beam into N diffraction-limited outputs (i.e. N single-mode fibres). This allows a truly diffraction limited spectral resolution, while also decoupling the spectrograph design from the input source.
Here both the photonic lantern and the spectrograph slit are formed using a single length of multi-core fibre. A 1x19 (1 multi-mode fiber to 19 single-mode fibres) photonic lantern is formed by tapering one end of the multi-core fibre, while the other end is used to form a TIGER mode slit (i.e. for a hexagonal grid with sufficient spacing and the correct orientations, the cores of the multi-core fibre can be dispersed such that they do not overlap without additional reformatting). The result is an exceptionally compact, shoebox sized, spectrograph that is constructed primarily from commercial off the shelf components. Here we present a brief overview of the échelle spectrograph design, followed by results from on-sky testing of the breadboard mounted version of the spectrograph at the ‘UK Schmidt Telescope’.
Progress on the Gemini High-Resolution Optical SpecTrograph (GHOST) design
Show abstract
The Gemini High-Resolution Optical SpecTrograph (GHOST) is the newest instrument being developed for the Gemini telescopes, in a collaboration between the Australian Astronomical Observatory (AAO), the NRC - Herzberg in Canada and the Australian National University (ANU). We describe the process of design optimisation that utilizes the unique strengths of the new partner, NRC - Herzberg, the design and need for the slit viewing camera system, and we describe a simplification for the lenslet-based slit reformatting. Finally, we out- line the updated project plan, and describe the unique scientific role this instrument will have in an international context, from exoplanets through to the distant Universe.
High Spatial Resolution Instruments I
The integral field spectrograph for the Gemini planet imager
Show abstract
The Gemini Planet Imager (GPI) is a complex optical system designed to directly detect the self-emission of young
planets within two arcseconds of their host stars. After suppressing the starlight with an advanced AO system and
apodized coronagraph, the dominant residual contamination in the focal plane are speckles from the atmosphere and
optical surfaces. Since speckles are diffractive in nature their positions in the field are strongly wavelength dependent,
while an actual companion planet will remain at fixed separation. By comparing multiple images at different
wavelengths taken simultaneously, we can freeze the speckle pattern and extract the planet light adding an order of
magnitude of contrast. To achieve a bandpass of 20%, sufficient to perform speckle suppression, and to observe the
entire two arcsecond field of view at diffraction limited sampling, we designed and built an integral field spectrograph
with extremely low wavefront error and almost no chromatic aberration. The spectrograph is fully cryogenic and
operates in the wavelength range 1 to 2.4 microns with five selectable filters. A prism is used to produce a spectral
resolution of 45 in the primary detection band and maintain high throughput. Based on the OSIRIS spectrograph at
Keck, we selected to use a lenslet-based spectrograph to achieve an rms wavefront error of approximately 25 nm. Over
36,000 spectra are taken simultaneously and reassembled into image cubes that have roughly 192x192 spatial elements
and contain between 11 and 20 spectral channels. The primary dispersion prism can be replaced with a Wollaston prism
for dual polarization measurements. The spectrograph also has a pupil-viewing mode for alignment and calibration.
The SPHERE IFS at work
Show abstract
SPHERE is an extrasolar planet imager whose goal is to detect giant extrasolar planets in the vicinity of bright stars and
to characterize them through spectroscopic and polarimetric observations. It is a complete system with a core made of an
extreme-Adaptive Optics (AO) turbulence correction, a pupil tracker and NIR and Visible coronagraph devices. At its
back end, a differential dual imaging camera and an integral field spectrograph (IFS) work in the Near Infrared (NIR)
(0.95 ≤λ≤2.32 μm) and a high resolution polarization camera covers the visible (0.6 ≤λ≤0.9 μm). The IFS is a low resolution spectrograph (R~50) operates in the near IR (0.95≤λ≤1.6 μm), an ideal wavelength range for the detection of planetary features, over a field of view of about 1.7 x 1.7 square arcsecs. Form spectra it is possible to reconstruct monochromatic images with high contrast (10-7) and high spatial resolution, well inside the star PSF. In this paper we describe the IFS, its calibration and the results of several performance which IFS underwent. Furthermore, using the IFS characteristics we give a forecast on the planetary detection rate.
The LINC-NIRVANA high resolution imager: challenges from the lab to first light
Show abstract
We present an update on LINC-NIRVANA (LN), an innovative, high-resolution infrared imager for the Large Binocular
Telescope (LBT). LN uses Multi-Conjugate Adaptive Optics (MCAO) for high-sky-coverage diffraction-limited
imagery and interferometric beam combination. The last two years have seen both successes and challenges. On the one
hand, final integration is proceeding well in the lab. We also achieved First Light at the LBT with the Pathfinder
experiment. On the other hand, funding constraints have forced a significant re-planning of the overall instrument
implementation. This paper presents our progress and plans for bringing the instrument online at the telescope.
Operation and performance of the mid-infrared camera, NOMIC, on the Large Binocular Telescope
Show abstract
The mid-infrared (8-13 μm) camera, NOMIC, is a critical component of the Large Binocular Telescope Interferometer
search for exozodiacal light around near-by stars. It is optimized for nulling interferometry but has general capability for
direct imaging, low resolution spectrometry, and Fizeau interferometry. The camera uses a Raytheon 1024x1024 Si:As
IBC Aquarius array with a 30 μm pitch which yields 0.018 arc-second pixels on the sky. This provides spatial resolution
(λ/D) at a 10 μm wavelength of 0.27 arc-seconds for a single 8.4 meter LBT aperture and of 0.10 arcseconds for Fizeau interferometry with the dual apertures. The array is operated with a differential preamplifier and a version of the 16
channel array controller developed at Cornell University for the FORCAST instrument on the Sofia Observatory. With a
2.4 MHz pixel rate the camera can achieve integration times as short as 27 milliseconds full array and 3 milliseconds
partial array. The large range of integration times and two array integration well sizes allow for a wide range of
background flux on the array. We describe the design and operation of the camera and present the performance of this
system in terms of linearity, noise, quantum efficiency, image quality, and photometric sensitivity.
FRIDA, the diffraction limited NIR imager and IFS for the Gran Telescopio Canarias: status report
Show abstract
FRIDA is a diffraction limited imager and integral field spectrometer that is being built for the Gran Telescopio
Canarias. FRIDA has been designed and is being built as a collaborative project between institutions from México, Spain
and the USA. In imaging mode FRIDA will provide scales of 0.010, 0.020 and 0.040 arcsec/pixel and in IFS mode
spectral resolutions R ~ 1000, 4,500 and 30,000. FRIDA is starting systems integration and is scheduled to complete
fully integrated system tests at the laboratory by the end of 2015 and be delivered to GTC shortly after. In this
contribution we present a summary of its design, fabrication, current status and potential scientific applications.
Development and recent results from the Subaru coronagraphic extreme adaptive optics system
Show abstract
The Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument is one of a handful of extreme adaptive
optics systems set to come online in 2014. The extreme adaptive optics correction is realized by a combination of precise
wavefront sensing via a non-modulated pyramid wavefront sensor and a 2000 element deformable mirror. This system
has recently begun on-sky commissioning and was operated in closed loop for several minutes at a time with a loop
speed of 800 Hz, on ~150 modes. Further suppression of quasi-static speckles is possible via a process called "speckle
nulling" which can create a dark hole in a portion of the frame allowing for an enhancement in contrast, and has been
successfully tested on-sky.
In addition to the wavefront correction there are a suite of coronagraphs on board to null out the host star which include
the phase induced amplitude apodization (PIAA), the vector vortex, 8 octant phase mask, 4 quadrant phase mask and
shaped pupil versions which operate in the NIR (y-K bands). The PIAA and vector vortex will allow for high contrast
imaging down to an angular separation of 1 λ/D to be reached; a factor of 3 closer in than other extreme AO systems.
Making use of the left over visible light not used by the wavefront sensor is VAMPIRES and FIRST. These modules are
based on aperture masking interferometry and allow for sub-diffraction limited imaging with moderate contrasts of
~100-1000:1. Both modules have undergone initial testing on-sky and are set to be fully commissioned by the end of
2014.
High contrast polarimetry in the infrared with SPHERE on the VLT
Show abstract
The instrument SPHERE (Spectro-Polarimetric High-contrast Exoplanet REsearch), recently installed on the VLT-UT3,
aims to detected and characterize giant extra-solar planets and the circumstellar environments in the very close vicinity
of bright stars. The extreme brightness contrast and small angular separation between the planets or disks and their parent
stars have so far proven very challenging. SPHERE will meet this challenge by using an extreme AO, stellar
coronagraphs, an infrared dual band and polarimetric imager called IRDIS, an integral field spectrograph, and a visible
polarimetric differential imager called ZIMPOL. Polarimetry allows a separation of the light coming from an unpolarized
source such as a star and the polarized source such as a planet or protoplanetary disks. In this paper we present the
performance of the infrared polarimetric imager based on experimental validations performed within SPHERE before the
preliminary acceptance in Europe. We report on the level of instrumental polarization in the infrared and its calibration
limit. Using differential polarimetry technique, we quantify the level of speckle suppression, and hence improved
sensitivity in the context of imaging extended stellar environments.
High-precision polarimetry at the Mont-Mégantic Observatory with the new polarimeter POMM
Show abstract
A new polarimeter has been built for the “Observatoire du Mont-Mégantic” (POMM) and is now in commissioning
phase. It will allow polarization measurements with a precision of 10-6, an improvement by a factor of 100 over the
previous observatory polarimeter. The characteristics of the instrument that allow this goal are briefly discussed and the
planned science observations are presented. They include exoplanets near their host star (hot Jupiters), transiting
exoplanets, stars with debris disks, young stars with proto-planetary disks, brown dwarfs, massive Wolf-Rayet stars and
comets. The details of the optical and mechanical designs are presented in two other papers.
High-resolution imaging in the visible on large ground-based telescopes
Show abstract
Lucky Imaging combined with a low order adaptive optics system has given the highest resolution images ever taken in
the visible or near infrared of faint astronomical objects. This paper describes a new instrument that has already been
deployed on the WHT 4.2m telescope on La Palma, with particular emphasis on the optical design and the predicted
system performance. A new design of low order wavefront sensor using photon counting CCD detectors and multi-plane
curvature wavefront sensor will allow virtually full sky coverage with faint natural guide stars. With a 2 x 2 array of
1024 x 1024 photon counting EMCCDs, AOLI is the first of the new class of high sensitivity, near diffraction limited
imaging systems giving higher resolution in the visible from the ground than hitherto been possible from space.
High Spatial Resolution Instruments II
ERIS: preliminary design phase overview
Show abstract
The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics near-IR imager and
spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full
use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable
Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for
construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the Max-
Planck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio
Astrofisico di Arcetri and will offer 1 - 5 μm imaging and 1 - 2.5 μm integral field spectroscopic capabilities with a high
Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or
with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly
sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1’
patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace,
with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by
NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP)
coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be
upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector
replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension
of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on
the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet
detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI
upgrade strategy, which is part of the ERIS development plan and the overall project timeline.
High-contrast planet imager for Kyoto 4m segmented telescope
Show abstract
We propose a new high contrast imager for Kyoto 4m segmented telescope called SEICA (Second-generation
Exoplanet Imager with Coronagraphic Adaptive optics), aiming at detection and characterization of selfluminous
gas giants within 10AU around nearby stars. SEICA is aggressively optimized for high performance
at very small inner working angle, 10-6 detection contrast at 0".1 in 1-hour integration. We start the on-sky
commissioning test in 2016 and the science observations in 2017. Since it is the first time to realize the highcontrast
imaging on the segmented telescope, SEICA is an important step toward future high contrast
sciences on Extremely Large Telescopes (ELTs). This paper presents an overall of the SEICA program and
the conceptual design for ultimate performance under given atmospheric conditions.
Construction and status of the CHARIS high contrast imaging spectrograph
Show abstract
Princeton University is building the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS),
an integral field spectrograph (IFS) for the Subaru telescope. CHARIS is funded by the National Astronomical
Observatory of Japan and is designed to take high contrast spectra of brown dwarfs and hot Jovian planets in
the coronagraphic image provided by the Coronagraphic Extreme Adaptive Optics (SCExAO) and the AO188
adaptive optics systems. The project is now in the build and test phase at Princeton University. Once laboratory
testing has been completed CHARIS will be integrated with SCExAO and AO188 in the winter of 2016. CHARIS
has a high-resolution characterization mode in J, H, and K bands. The average spectral resolution in J, H, and
K bands are R82, R68, and R82 respectively, the uniformity of which is a direct result of a new high index
material, L-BBH2. CHARIS also has a second low-resolution imaging mode that spans J,H, and K bands with
an average spectral resolution of R19, a feature unique to this instrument. The field of view in both imaging
modes is 2.07x2.07 arcseconds. SCExAO+CHARIS will detect objects five orders of magnitude dimmer than
their parent star down to an 80 milliarcsecond inner working angle. The primary challenge with exoplanet
imaging is the presence of quasi-static speckles in the coronagraphic image. SCExAO has a wavefront control
system to suppress these speckles and CHARIS will address their impact on spectral crosstalk through hardware
design, which drives its optical and mechanical design. CHARIS constrains crosstalk to be below 1% for an
adjacent source that is a full order of magnitude brighter than the neighboring spectra. Since CHARIS is on the
Nasmyth platform, the optical alignment between the lenslet array and prism is highly stable. This improves the
stability of the spectra and their orientation on the detector and results in greater stability in the wavelength
solution for the data pipeline. This means less uncertainty in the post-processing and less overhead for on-sky
calibration procedures required by the data pipeline. Here we present the science case, design, and construction
status of CHARIS. The design and lessons learned from testing CHARIS highlights the choices that must be
considered to design an IFS for high signal-to-noise spectra in a coronagraphic image. The design considerations
and lessons learned are directly applicable to future exoplanet instrumentation for extremely large telescopes
and space observatories capable of detecting rocky planets in the habitable zone.
Instruments for Extremely Large Telescopes
Status of the instrumentation program for the Giant Magellan Telescope
Show abstract
Instrument development for the 25 m class optical/infrared Giant Magellan Telescope (GMT) is actively underway. Two
instruments have begun their preliminary design phase: an optical (350-1000 nm) high resolution and precision radial
velocity echelle spectrograph (G-CLEF), and a near-IR (YJHK) diffraction-limited imager/integral-field-spectrograph
(GMTIFS). A third instrument will begin its design phase in early 2015: an optical (370-1000 nm) low-to-medium
resolution multi-object spectrograph (GMACS). Two other instrument teams are focusing on prototypes to demonstrate
final feasibility: a near-to-mid-IR (JHKLM) high resolution diffraction-limited echelle (GMTNIRS) spectrograph, and a
facility robotic multi-fiber-feed (MANIFEST). A brief overview of the GMT instrumentation program is presented:
current activities, progress, status, and schedule, as well as a summary of the facility infrastructure needed to support the
instruments.
The E-ELT instrument roadmap: a status report
Show abstract
We present the status of the instrumentation programme for the European Extremely Large Telescope. The
instrumentation planning is governed by the E-ELT Instrument Roadmap, which synthesises the scientific, technical and
managerial influences on the instrument programme into a staged development plan. Preparations for the start of the
design and build phases of the first light instruments and their adaptive optics systems are well underway and are
summarised here. In parallel, the process for development of the next three instruments has begun. Recent work on the
instrument interface to the telescope is described.
An update on the wide field, multi-object, moderate-resolution, spectrograph for the Giant Magellan Telescope
Show abstract
We review a conceptual design for a moderate resolution optical spectrograph for the Giant Magellan Telescope (GMT).
The spectrograph is designed to make use of the large field-of-view of the GMT and be suitable for observations of very
faint objects across a wide range of wavelengths. We also review the status of the instrument and on-going trade studies
designed to update the instrument science objectives and technical requirements.
METIS: the mid-infrared E-ELT imager and spectrograph
Show abstract
METIS will be among the first generation of scientific instruments on the E-ELT. Focusing on highest angular
resolution and high spectral resolution, METIS will provide diffraction limited imaging and coronagraphy from 3-14μm
over an 20x20 field of view, as well as integral field spectroscopy at R ~ 100,000 from 2.9-5.3μm. In addition,
METIS provides medium-resolution (R ~ 5000) long slit spectroscopy, and polarimetric measurements at N band. While
the baseline concept has already been discussed at previous conferences, this paper focuses on the significant
developments over the past two years in several areas: The science case has been updated to account for recent progress
in the main science areas circum-stellar disks and the formation of planets, exoplanet detection and characterization,
Solar system formation, massive stars and clusters, and star formation in external galaxies. We discuss the developments
in the adaptive optics (AO) concept for METIS, the telescope interface, and the instrument modelling. Last but not least
we provide an overview of our technology development programs, which ranges from coronagraphic masks, immersed
gratings, and cryogenic beam chopper to novel approaches to mirror polishing, background calibration and cryo-cooling.
These developments have further enhanced the design and technology readiness of METIS to reliably serve as an early
discovery machine on the E-ELT.
GMTNIRS (Giant Magellan Telescope Near-Infrared Spectrograph): optimizing the design for maximum science productivity and minimum risk
Show abstract
GMTNIRS, the Giant Magellan Telescope near-infrared spectrograph, is a first-generation instrument for the GMT that
will provide detailed spectroscopic information about young stellar objects, exoplanets, and cool and/or obscured stars.
The optical and mechanical design GMTNIRS presented at a conceptual design review in October 2011 covered all
accessible parts of the spectrum from 1.12 to 5.3 microns at R=50,000 (1.12-2.5 microns) and R=100,000 (3-5.3
microns). GMTNIRS uses the GMT adaptive-optics system and has a single 85 milliarcsecond slit. The instrument
includes five separate spectrographs for the different atmospheric windows. By use of dichroics that divide the incident
light between five separate spectrographs, it observes its entire spectral grasp in a single exposure while having only one
cryogenic moving part, a rotating pupil stop.
Large, highly accurate silicon immersion gratings are critical to GMTNIRS, since they both permit a design within the
allowable instrument volume and enable continuous wavelength coverage on existing detectors. We describe the effort
during the preliminary design phase to refine the design of the spectrograph to meet the science goals while minimizing
the cost and risk involved in the grating production. We discuss different design options for the individual spectrographs
at R=50,000, 67,000, 75,000, and 100,000 and their impact on science return.
HIRES: the high resolution spectrograph for the E-ELT
Show abstract
The current instrumentation plan for the E-ELT foresees a High Resolution Spectrograph conventionally indicated as
HIRES. Shaped on the study of extra-solar planet atmospheres, Pop-III stars and fundamental physical constants, HIRES
is intended to embed observing modes at high-resolution (up to R=150000) and large spectral range (from the blue limit to the K band) useful for a large suite of science cases that can exclusively be tackled by the E-ELT. We present in this
paper the solution for HIRES envisaged by the "HIRES initiative", the international collaboration established in 2013 to
pursue a HIRES on E-ELT.
The Infrared Imaging Spectrograph (IRIS) for TMT: instrument overview
Show abstract
We present an overview of the design of IRIS, an infrared (0.84 - 2.4 micron) integral field spectrograph and imaging
camera for the Thirty Meter Telescope (TMT). With extremely low wavefront error (<30 nm) and on-board wavefront
sensors, IRIS will take advantage of the high angular resolution of the narrow field infrared adaptive optics system
(NFIRAOS) to dissect the sky at the diffraction limit of the 30-meter aperture. With a primary spectral resolution of
4000 and spatial sampling starting at 4 milliarcseconds, the instrument will create an unparalleled ability to explore high
redshift galaxies, the Galactic center, star forming regions and virtually any astrophysical object. This paper summarizes
the entire design and basic capabilities. Among the design innovations is the combination of lenslet and slicer integral
field units, new 4Kx4k detectors, extremely precise atmospheric dispersion correction, infrared wavefront sensors, and a
very large vacuum cryogenic system.
HARMONI: the first light integral field spectrograph for the E-ELT
Show abstract
HARMONI is a visible and near-infrared (0.47 to 2.45 μm) integral field spectrometer, providing the E-ELT's core
spectroscopic capability, over a range of resolving powers from R (≡λ/Δλ)~500 to R~20000. The instrument provides simultaneous spectra of ~32000 spaxels at visible and near-IR wavelengths, arranged in a √2:1 aspect ratio contiguous field. HARMONI is conceived as a workhorse instrument, addressing many of the E-ELT’s key science cases, and will
exploit the E-ELT's scientific potential in its early years, starting at first light. HARMONI provides a range of spatial
pixel (spaxel) scales and spectral resolving powers, which permit the user to optimally configure the instrument for a
wide range of science programs; from ultra-sensitive to diffraction limited, spatially resolved, physical (via morphology),
chemical (via abundances and line ratios) and kinematic (via line-of-sight velocities) studies of astrophysical sources.
Recently, the HARMONI design has undergone substantial changes due to significant modifications to the interface with
the telescope and the architecture of the E-ELT Nasmyth platform. We present an overview of the capabilities of
HARMONI, and of its design from a functional and performance viewpoint.
A preliminary design for the GMT-Consortium Large Earth Finder (G-CLEF)
Show abstract
The GMT-Consortium Large Earth Finder (G-CLEF) is an optical-band echelle spectrograph that has been selected as
the first light instrument for the Giant Magellan Telescope (GMT). G-CLEF is a general-purpose, high dispersion
spectrograph that is fiber fed and capable of extremely precise radial velocity measurements. The G-CLEF Concept
Design (CoD) was selected in Spring 2013. Since then, G-CLEF has undergone science requirements and instrument
requirements reviews and will be the subject of a preliminary design review (PDR) in March 2015. Since CoD review
(CoDR), the overall G-CLEF design has evolved significantly as we have optimized the constituent designs of the major
subsystems, i.e. the fiber system, the telescope interface, the calibration system and the spectrograph itself. These
modifications have been made to enhance G-CLEF’s capability to address frontier science problems, as well as to
respond to the evolution of the GMT itself and developments in the technical landscape. G-CLEF has been designed by
applying rigorous systems engineering methodology to flow Level 1 Scientific Objectives to Level 2 Observational
Requirements and thence to Level 3 and Level 4. The rigorous systems approach applied to G-CLEF establishes a well
defined science requirements framework for the engineering design. By adopting this formalism, we may flexibly update
and analyze the capability of G-CLEF to respond to new scientific discoveries as we move toward first light. G-CLEF
will exploit numerous technological advances and features of the GMT itself to deliver an efficient, high performance instrument, e.g. exploiting the adaptive optics secondary system to increase both throughput and radial velocity
measurement precision.
MOSAIC at the E-ELT: A multi-object spectrograph for astrophysics, IGM and cosmology
Show abstract
The Universe is comprised of hundreds of billions of galaxies, each populated by hundreds of billions of stars. Astrophysics aims to understand the complexity of this almost incommensurable number of stars, stellar clusters and galaxies, including their spatial distribution, formation, and current interactions with the interstellar and intergalactic media. A considerable fraction of astrophysical discoveries require large statistical samples, which can only be addressed with multi-object spectrographs (MOS). Here we introduce the MOSAIC study of an optical/near-infrared MOS for the European Extremely Large Telescope (E-ELT), which has capabilities specified by science cases ranging from stellar physics and exoplanet studies to galaxy evolution and cosmology. Recent studies of critical technical issues such as sky-background subtraction and multi-object adaptive optics (MOAO) have demonstrated that such a MOS is feasible with current technology and techniques. In the 2020s the E-ELT will become the world’s largest optical/IR telescope, and we argue that it has to be equipped as soon as possible with a MOS. MOSAIC will provide a vast discovery space, enabled by a multiplex of ∼ 200 and spectral resolving powers of R = 5 000 and 20 000. MOSAIC will also offer the unique capability of 10-to-20 ‘high-definition’ (MOAO) integral-field units, optimised to investigate the physics of the sources of reionisation, providing the most efficient follow-up of observations with the James Webb Space Telescope (JWST). The combination of these modes will enable the study of the mass-assembly history of galaxies over cosmic time, including high-redshift dwarf galaxies and studies of the distribution of the intergalactic medium. It will also provide spectroscopy of resolved stars in external galaxies at unprecedented distances, from the outskirts of the Local Group for main-sequence stars, to a significant volume of the local Universe, including nearby galaxy clusters, for luminous red supergiants.
Conceptual design of the MOBIE imaging spectrograph for TMT
Show abstract
The Multi-Object Broadband Imaging Echellette (MOBIE) is the seeing-limited, visible-wavelength imaging multiobject
spectrograph (MOS) planned for first-light use on the Thirty Meter Telescope (TMT). The MOBIE project to
date has been a collaboration lead by UC Observatories (CA), and including the UH Institute for Astronomy (HI), and
the NAOJ (Tokyo, Japan). The current MOBIE optical design provides two color channels, spanning the 310–550nm
and 550-1000nm passbands, and a combination of reflection gratings, prisms, and mirrors to enable direct imaging and
three spectroscopic modes with resolutions (λ/triangle λ) of roughly 1000, 3000, and 8000 in both color channels, across a field of view that ranges from roughly 8x3 arcmin to 3x3 arcmin, depending on resolution mode. The conceptual design phase for the MOBIE instrument has been underway since 2008 and is expected to end in 2015. We report here on developments since 2010, including assembly of the current project team, instrument and camera optical designs,
instrument control systems, atmospheric dispersion corrector, slit-mask exchange systems, collimator, dichroic and fold
optics, dispersing and cross-dispersing optics, refracting cameras, shutters, filter exchange systems, science detector
systems, and instrument structures.
Astrophotonic micro-spectrographs in the era of ELTs
Show abstract
The next generation of Extremely Large Telescopes (ELT), with diameters up to 39 meters, will start opera- tion in the next decade and promises new challenges in the development of instruments. The growing field of astrophotonics (the use of photonic technologies in astronomy) can partly solve this problem by allowing mass production of fully integrated and robust instruments combining various optical functions, with the potential to reduce the size, complexity and cost of instruments. In this paper, we focus on developments in integrated micro-spectrographs and their potential for ELTs. We take an inventory of the identified technologies currently in development, and compare the performance of the different concepts. We show that in the current context of single-mode instruments, integrated spectrographs making use of, e.g., a photonic lantern can be a solution to reach the desired performance. However, in the longer term, there is a clear need to develop multimode devices to improve overall the throughput and sensitivity, while decreasing the instrument complexity.
Posters Session: Instrument Programs and New Science Instruments and Upgrades
Updated optical design and trade-off study for MOONS, the Multi-Object Optical and Near Infrared spectrometer for the VLT
Show abstract
This paper presents the latest optical design for the MOONS triple-arm spectrographs. MOONS will be a Multi-Object
Optical and Near-infrared Spectrograph and will be installed on one of the European Southern Observatory (ESO) Very
Large Telescopes (VLT). Included in this paper is a trade-off analysis of different types of collimators, cameras,
dichroics and filters.
Optical, mechanical and electronic design and integration of POMM, a polarimeter for the Observatoire du mont Mégantic
Show abstract
A polarimeter, to observe exoplanets in the visible and infrared, was built for the “Observatoire du Mont Mégantic”
(OMM) to replace an existing instrument and reach 10-6 precision, a factor 100 improvement. The optical and
mechanical designs are presented, with techniques used to precisely align the optical components and rotation axes to
achieve the targeted precision. A photo-elastic modulator (PEM) and a lock-in amplifier are used to measure the
polarization. The typical signal is a high DC superimposed to a very faint sinusoidal oscillation. Custom electronics
was developed to measure the AC and DC amplitudes, and characterization results are presented.
Design, motivation, and on-sky tests of an efficient fiber coupling unit for 1-meter class telescopes
Show abstract
We present the science motivation, design, and on-sky test data of a high-throughput fiber coupling unit suitable for automated 1-meter class telescopes. The optical and mechanical design of the fiber coupling is detailed and we describe a flexible controller software designed specifically for this unit. The system performance is characterized with a set of numerical simulations, and we present on-sky results that validate the performance of the controller and the expected throughput of the fiber coupling. This unit was designed specifically for the MINERVA array, a robotic observatory consisting of multiple 0.7 m telescopes linked to a single high-resolution stabilized spectrograph for the purpose of exoplanet discovery using high-cadence radial velocimetry. However, this unit could easily be used for general astronomical purposes requiring fiber coupling or precise guiding.
A polarimetric unit for HARPS-North at the Telescopio Nazionale Galileo: HANPO
Show abstract
Usually observational astronomy is based on direction and intensity of radiation considered as a function of wavelength
and time. Despite the polarisation degree of radiation provides information about asymmetry, anisotropy and magnetic
fields within the radiative source or in the medium along the line of sight, it is commonly ignored. Because of the
importance of high resolution spectropolarimetry to study a large series of phenomena related to the interaction of
radiation with matter, as in stellar atmospheres or more generally stellar envelopes, we designed and built a dual beam
polarimeter for HARPS-N that is in operation at the Telescopio Nazionale Galileo. Since the polarisation degree is
measured from the combination of a series of measurements and accuracy is limited by the instrumental stability, just the
great stability (0.6 m/s) and spectral resolution (R=115000) of the HARPS-N spectrograph should result in an accuracy
in the measurements of Stokes parameters as small as 0.01%. Here we report on the design, realization, assembling,
aligning and testing of the polarimetric unit whose first light is planned in August 2014.
An off-the-shelf guider for the Palomar 200-inch telescope: interfacing amateur astronomy software with professional telescopes for an easy life
Show abstract
We have developed a simple but effective guider for use with the Oxford-SWIFT integral field spectrograph on the Palomar 200-inch telescope. The guider uses mainly off-the-shelf components, including commercial amateur astronomy software to interface with the CCD camera, calculating guiding corrections, and send guide commands to the telescope. The only custom piece of software is an driver to provide an interface between the Palomar telescope control system and the industry standard 'ASCOM' system. Using existing commercial software provided a very cheap guider (<$5000) with minimal (<15 minutes) commissioning time. The final system provides sub-arcsecond guiding, and could easily be adapted to any other professional telescope
Design updates and status of the fourth generation TripleSpec spectrograph
Show abstract
TripleSpec 4 (TS4) is a near-infrared (0.8um to 2.45um) moderate resolution (R ~ 3200) cross-dispersed spectrograph
for the 4m Blanco Telescope that simultaneously measures the Y, J, H and K bands for objects reimaged
within its slit. TS4 is being built by Cornell University and NOAO with scheduled commissioning in 2015.
TS4 is a near replica of the previous TripleSpec designs for Apache Point Observatory's ARC 3.5m, Palomar
5m and Keck 10m telescopes, but includes adjustments and improvements to the slit, fore-optics, coatings and
the detector. We discuss the changes to the TripleSpec design as well as the fabrication status and expected
sensitivity of TS4.
A Fabry-Perot and grism imaging spectrograph LISS (Line Imager and Slit Spectrograph)
Show abstract
LISS (Line Imager and Slit Spectrograph) is an imager and spectrograph equipped with a liquid crystal etalon and a low resolution grism. It is specialized to observe and map the emission and absorption lines of astronomical objects. A fully depleted and back illuminated 2K x 1K Hamamatsu CCD which has high sensitivity at redder wavelengths in optical bands enables this instrument to give a good performance in imaging and spectroscopic observations of emission lines such as [SIII]λλ 906.9/953.2 nm. We successfully carried out commissioning observations at the 1.6-m Pirka telescope of Hokkaido University in September/October 2012 and June/July 2013. In this paper, we describe the design and performance of LISS as well as its early observational results and future prospects.
The mechanical design for the WEAVE prime focus corrector system
Show abstract
WEAVE is the next-generation, wide-field, optical spectroscopy facility for the William Herschel Telescope (WHT) in La Palma, Canary Islands, Spain. The WHT will undergo a significant adaptation to accommodate this facility. A two-
degree Prime Focus Corrector (PFC), that includes an Atmospheric Dispersion Compensator, is being planned and is currently in its final design phase. To compensate for the effects of temperature-induced image degradation, the entire PFC system will be translated along the telescope optical axis. The optical system comprises six lenses, the largest of which will have a diameter of 1.1m. Now that the optical elements are in production, the designs for the lens cells and
the mounting arrangements are being analysed to ensure that the image quality of the complete system is better than 1.0 arcsec (80% encircled energy diameter) over the full field of view. The new PFC system is designed to be routinely
interchanged with the existing top-end ring. This will maximise the versatility of the WHT and allow the two top-end
systems to be interchanged as dictated by the scientific needs of the astronomers that will use WEAVE and other
instruments on the telescope. This manuscript describes the work that has been carried out in developing the designs for
the mechanical subsystems and the plans for mounting the lenses to attain an optical performance that is commensurate with the requirements derived from planning the WEAVE surveys.
Conceptual design of a low resolution spectrograph for the Astronomical Observatory of Córdoba
Show abstract
We present a conceptual design for a low resolution optical spectrograph for the Astronomical Observatory of Cordoba 1.54m telescope. The simple instrument is required to cover a broad wavelength range (4000A<λ <9000A with 3000A simultaneous coverage) at a resolution of R=λ/∆λ ~ 500, allowing its use as a versatile
astronomical spectrograph. In particular, we explore the use of inexpensive commercial off-the-shelf lenses,
gratings, and a CCD system to create a small and simple spectrograph that has reasonable performance. We carefully measure properties of the lenses and demonstrate that they have excellent image quality and high throughput.
The GRAVITY spectrometers: design report of the optomechanics and active cryogenic mechanisms
Show abstract
The work package of the University of Cologne within the GRAVITY consortium included the development and
manufacturing of two spectrometers for the beam combiner instrument. Both spectrometers are optimized for
different tasks. The science spectrometer provides 3 different spectral resolutions. In the highest resolution the
length of the spectral lines is close to the borders of the imaging area of the detector. Also the integration time
of these high resolution images is relative long. Therefor the optical pathes have to be controlled by the feedback
of a faster spectrometer. The fringe tracking spectrometer has only one low resolution to allow much shorter
integration times. This spectrometer provides a feedback for the control loops which stabilize the optical pathes
of the light from the telescope to the instrument. This is a new key feature of the whole GRAVITY instrument.
Based on the optical layout my work was the design of the mechanical structure, mountings, passive and
active adjustment mechanisms. This paper gives a short review about the active mechanisms and the compliant
lens mounts. They are used similarly in both spectrometers. Due to the observation and analysis of near-infrared
light the mechanisms have to run at cryogenic temperatures and in a high vacuum. Except the linear stages, the
motorized mechanisms will get used for several times per observation.
First-generation instrumentation for the Discovery Channel Telescope
Show abstract
The 4.3m Discovery Channel Telescope (DCT) has been conducting part-time science operations since January 2013.
The f/6.1, 0.5° field-of-view at the RC focus is accessible through the Cassegrain instrument cube assembly, which can
support 5 co-mounted instruments with rapid feed selection via deployable fold mirrors. Lowell Observatory has
developed the Large Monolithic Imager (LMI), a 12.3' FOV 6K x 6K single CCD camera with a dual filter wheel, and
installed at the straight-through, field-corrected RC focal station, which has served as the primary early science DCT
instrument. Two low-resolution facility spectrographs are currently under development with first light for each
anticipated by early 2015: the upgraded DeVeny Spectrograph, to be utilized for single object optical spectroscopy, and
the unique Near-Infrared High-Throughput Spectrograph (NIHTS), optimized for single-shot JHK spectroscopy of faint
solar system objects. These spectrographs will be mounted at folded RC ports, and the NIHTS installation will feature
simultaneous optical imaging with LMI through use of a dichroic fold mirror. We report on the design, construction,
commissioning, and progress of these 3 instruments in detail. We also discuss plans for installation of additional facility
instrumentation on the DCT.
POMM: design of rotating mechanism and hexapod structure
Show abstract
The new high precision polarimeter for the “Observatoire du Mont Mégantic” (POMM) is an instrument designed to
observe exoplanets and other targets in the visible and near infrared wavebands. The requirements to achieve these
observation goals are posing unusual challenges to structural and mechanical designers.
In this paper, the detailed design, analysis and laboratory results of the key mechanical structure and sub-systems are
presented.
First, to study extremely low polarization, the birefringence effect due to stresses in the optical elements must be kept to
the lowest possible values. The double-wedge Wollaston custom prism assembly that splits the incoming optical beam is
made of bonded α-BBO to N-BK-7 glass lenses. Because of the large mismatch of coefficients of thermal expansion and
temperatures as low as -40°C that can be encountered at Mont-Mégantic observatory, a finite element analysis (FEA)
model is developed to find the best adhesive system to minimize stresses.
Another critical aspect discussed in details is the implementation of the cascaded rotating elements and the twin rotating
stages. Special attention is given to the drive mechanism and encoding technology. The objective was to reach high
absolute positional accuracy in rotation without any mechanical backlash.
As for many other instruments, mass, size and dimensional stability are important critera for the supporting structure.
For a cantilevered device, such as POMM, a static hexapod is an attractive solution because of the high stiffness to
weight ratio. However, the mechanical analysis revealed that the specific geometry of the dual channel optical layout
also added an off-axis counterbalancing problem. To reach an X-Y displacement error on the detector smaller than 35μm
for 0-45° zenith angle, further structural optimization was done using FEA. An imaging camera was placed at the
detector plane during assembly to measure the actual optical beam shift under varying gravitational loading.
Testing fully depleted CCD
Show abstract
The focal plane of the PAU camera is composed of eighteen 2K x 4K CCDs. These devices, plus four spares, were
provided by the Japanese company Hamamatsu Photonics K.K. with type no. S10892–04(X). These detectors are 200
μm thick fully depleted and back illuminated with an n-type silicon base. They have been built with a specific coating to
be sensitive in the range from 300 to 1,100 nm. Their square pixel size is 15 μm.
The read-out system consists of a Monsoon controller (NOAO) and the panVIEW software package. The deafualt CCD
read-out speed is 133 kpixel/s. This is the value used in the calibration process.
Before installing these devices in the camera focal plane, they were characterized using the facilities of the ICE (CSIC–
IEEC) and IFAE in the UAB Campus in Bellaterra (Barcelona, Catalonia, Spain).
The basic tests performed for all CCDs were to obtain the photon transfer curve (PTC), the charge transfer efficiency
(CTE) using X-rays and the EPER method, linearity, read-out noise, dark current, persistence, cosmetics and quantum
efficiency.
The X-rays images were also used for the analysis of the charge diffusion for different substrate voltages (VSUB).
Regarding the cosmetics, and in addition to white and dark pixels, some patterns were also found. The first one, which
appears in all devices, is the presence of half circles in the external edges. The origin of this pattern can be related to the
assembly process. A second one appears in the dark images, and shows bright arcs connecting corners along the vertical
axis of the CCD. This feature appears in all CCDs exactly in the same position so our guess is that the pattern is due to
electrical fields.
Finally, and just in two devices, there is a spot with wavelength dependence whose origin could be the result of a
defectous coating process.
Readout electronics of physics of accelerating universe camera
Show abstract
The Physics of Accelerating Universe Camera (PAUCam) is a new camera for dark energy studies that will be installed
in the William Herschel telescope. The main characteristic of the camera is the capacity for high precision photometric
redshift measurement. The camera is composed of eighteen Hamamatsu Photonics CCDs providing a wide field of view
covering a diameter of one degree. Unlike the common five optical filters of other similar surveys, PAUCam has forty
optical narrow band filters which will provide higher resolution in photometric redshifts. In this paper a general
description of the electronics of the camera and its status is presented.
Acousto-optical imaging spectropolarimetric devices: new opportunities and developments
Show abstract
We report design and prototype performance of an acousto-optical imaging spectropolarimeter aimed for the 2.5 m telescope at Caucasian Mountain Observatory of Lomonosov Moscow State University. Special geometry of the acousto-optical interaction provides two diffracted beams polarized along the slow and the fast axes of the crystal. The optical system of the spectrometer consisting of plane and elliptical mirrors delivers the images of the object with two orthogonal polarizations to a single CCD matrix, increasing the focal ratio of the telescope.
The near infrared camera for the Subaru Prime Focus Spectrograph
Show abstract
We present the detailed design of the near infrared camera for the SuMIRe (Subaru Measurement of Images and Redshifts) Prime Focus Spectrograph (PFS) being developed for the Subaru Telescope. The PFS spectrograph is designed to collect spectra from 2394 objects simultaneously, covering wavelengths that extend from 380 nm
- 1.26 μm. The spectrograph is comprised of four identical spectrograph modules, with each module collecting roughly 600 spectra from a robotic fiber positioner at the telescope prime focus. Each spectrograph module will have two visible channels covering wavelength ranges 380 nm - 640 nm and 640 nm - 955 nm, and one near infrared (NIR) channel with a wavelength range 955 nm - 1.26 μm. Dispersed light in each channel is imaged by a 300 mm focal length, f/1.07, vacuum Schmidt camera onto a 4k x 4k, 15 µm pixel, detector format. For the NIR channel a HgCdTe substrate-removed Teledyne 1.7 μm cutoff device is used. In the visible channels,
CCDs from Hamamatsu are used. These cameras are large, having a clear aperture of 300 mm at the entrance window, and a mass of ~ 250 kg.
Like the two visible channel cameras, the NIR camera contains just four optical elements: a two-element refractive corrector, a Mangin mirror, and a field flattening lens. This simple design produces very good imaging performance considering the wide field and wavelength range, and it does so in large part due to the use of a Mangin mirror (a lens with a reflecting rear surface) for the Schmidt primary. In the case of the NIR camera, the rear reflecting surface is a dichroic, which reflects in-band wavelengths and transmits wavelengths beyond
1.26 μm. This, combined with a thermal rejection filter coating on the rear surface of the second corrector element, greatly reduces the out-of-band thermal radiation that reaches the detector.
The camera optics and detector are packaged in a cryostat and cooled by two Stirling cycle cryocoolers. The first corrector element serves as the vacuum window, while the second element is thermally isolated and floats cold. An assembly constructed primarily of silicon carbide is used to mount the Mangin mirror, and to support the detector and field flattener. Thermal isolation between the cold optics and warm ambient surroundings is provided by G10 supports, multi-layer insulation, and the vacuum space within the cryostat. In this paper we describe the detailed design of the PFS NIR camera and discuss its predicted optical, thermal, and mechanical performance.
Detector driver systems and photometric estimates for RIMAS
Show abstract
The Rapid infrared IMAger-Spectrometer (RIMAS) is a rapid gamma-ray burst afterglow instrument that will provide photometric and spectroscopic coverage of the Y, J, H, and K bands. RIMAS separates light into two optical arms, YJ and HK, which allows for simultaneous coverage in two photometric bands. RIMAS utilizes two 2048 x 2048 pixel Teledyne HgCdTe (HAWAII-2RG) detectors along with a Spitzer Legacy Indium- Antimonide (InSb) guiding detector in spectroscopic mode to position and keep the source on the slit. We describe the software and hardware development for the detector driver and acquisition systems. The HAWAII- 2RG detectors simultaneously acquire images using Astronomical Research Cameras, Inc. driver, timing, and processing boards with two C++ wrappers running assembly code. The InSb detector clocking and acquisition system runs on a National Instruments cRIO-9074 with a Labview user interface and clocks written in an easily alterable ASCII file. We report the read noise, linearity, and dynamic range of our guide detector. Finally, we present RIMAS’s estimated instrument efficiency in photometric imaging mode (for all three detectors) and expected limiting magnitudes. Our efficiency calculations include atmospheric transmission models, filter models, telescope components, and optics components for each optical arm.
FIFI-LS: the facility far-infrared spectrometer for SOFIA
Show abstract
FIFI-LS is the German far-infrared integral field spectrometer for the SOFIA airborne observatory. The instrument offers
medium resolution spectroscopy (R ~ a few 1000) in the far-infrared with two independent spectrometers covering 50-110
and 100-200 μm. The integral field units of the two spectrometers obtain spectra covering concentric square fields-of-views
sized 3000and 6000, respectively. Both spectrometers can observe simultaneously at any wavelength in their ranges making
efficient mapping of far-infrared lines possible.
FIFI-LS has been commissioned at the airborne observatory SOFIA as a PI instrument in spring 2014. During 2015,
the commissioning as facility instrument will be complete and the SOFIA observatory will take over the operation of
FIFI-LS. The instrument can already be used by the community. Primary science cases are the study of the galactic and
extra-galactic interstellar medium and its processes.
In this presentation, the capabilities of FIFI-LS on the SOFIA telescope will be explained and how they are used by the
offered observing modes. The remaining atmosphere and the warm telescope create a high background situation, which
requires a differential measurement technique. This is achieved by SOFIA’s chopping secondary mirror and nodding the
telescope. Depending on the source size, different observing modes may be used to observe a source. All modes use spatial
and spectral dithering. The resulting data products will be 3D-data cubes.
The observing parameters will be specified using AOTs, like the other SOFIA instruments, and created via the tool
SSPOT which is similar to the Spitzer Space Telescope SPOT tool. The observations will be done in service mode, but
SOFIA invites a few investigators to fly onboard SOFIA during (part of) their observations.
FLITECAM: early commissioning results
Show abstract
We present a status report and early commissioning results for FLITECAM, the 1-5 micron imager and spectrometer for
SOFIA (the Stratospheric Observatory for Infrared Astronomy). In February 2014 we completed six flights with
FLITECAM mounted in the FLIPO configuration, a co-mounting of FLITECAM and HIPO (High-speed Imaging
Photometer for Occultations; PI Edward W. Dunham, Lowell Observatory). During these flights, the FLITECAM modes
from ~1-4 μm were characterized. Since observatory verification flights in 2011, several improvements have been made
to the FLITECAM system, including the elimination of a light leak in the FLITECAM filter wheel enclosure, and
updates to the observing software. We discuss both the improvements to the FLITECAM system and the results from the
commissioning flights, including updated sensitivity measurements. Finally, we discuss the utility of FLITECAM in the
FLIPO configuration for targeting exoplanet transits.
One controlling and driving module based on FPGA in optical fiber positioning device
Show abstract
The previous module on LAMOST (Large Area Multi-Object Fiber Spectroscope Telescope) controls and drives only
one fiber positioning unit, resulting in a low integration. Meanwhile, each unit is driven by two motors respectively
located on the center revolving shaft and the eccentric revolving shaft. In this case, these positioning units require a mass
of power connecting wires that increase flexible connections in excess and decrease the system linearity. To make an
improvement, this paper proposes a new module, which occupies small space in compact structure and is able to drive 37
optical fiber positioning units simultaneously. The module design of the controlling part and the driving part are based
on FPGA with its strong capabilities of parallel processing, large quantities of I/O resources and low power
consumption. With experiments, the new designed module improves the level of system integration, ensures the
reliability and reduces the power consumption, which meets all the requirements as expected.
Weather monitor station and 225 GHz radiometer system installed at Sierra Negra: the Large Millimeter Telescope site
D. Ferrusca,
J. Contreras R.
Show abstract
The Large Millimeter Telescope (LMT) is a 50-m dish antenna designed to observe in the wavelength range of 0.85 to 4
mm at an altitude of 4600 m on the summit of Sierra Negra Puebla, Mexico. The telescope has a new atmospheric
monitoring system that allows technical staff and astronomers to evaluate the conditions at the site and have enough
information to operate the antenna in safe conditions, atmospheric data is also useful to schedule maintenance activities
and conduct scientific observations, opacity data is used to calibrate the astronomical data and evaluate the quality of the
sky at millimeter wavelengths. In this paper we describe the integration of a weather atmospheric monitoring system and
a 225 GHz radiometer to the facilities around the telescope and also describe the hardware integration of these systems
and the software methodology used to save and process the data and then make it available in real time to the
astronomers and outside world through an internet connection. Finally we present a first set of atmospheric
measurements and statistics taken with this new equipment during the wet and dry seasons of 2013/2014.
Near-infrared wavelength calibration of astrophysical spectrographs with the emission spectrum of the CN molecule
Show abstract
Many astrophysical applications require precise wavelength calibration of high resolution spectra. Calibration sources for this purpose at near-infrared wavelengths are sparse. We present an experimental setup for an electrodeless microwave discharge lamp that produces molecular band emission spectra. The discharge is sustained inside a glass cell filled with a combination of different gases producing CN molecules with many spectral lines in the wavelength range between 1 μm and 2.5 μm. We investigate this lamp in terms of its usability for wavelength calibration in high resolution spectroscopy. In this conference contribution, we present the experimental setup and the characterization of the calibration source in terms of line identification, line intensities, and line density. We find approximately 20,000 lines in the spectral region of 1 - 2 μm with relative peak intensities in a range of two orders of magnitude. The results from a first endurance test show that the durability of the spectrum requires careful attention in the course of further development.
The characteristics and development status of the control and housekeeping electronics of FRIDA
Show abstract
FRIDA (inFRared Imager and Dissector for the Adaptive optics system of the Gran Telescopio Canarias) is a diffraction
limited instrument that will offer broad and narrow band imaging and integral field spectroscopy with low, intermediate
and high spectral resolutions in the 0.9 - 2.5 μm wavelength range. FRIDA will be installed at a Nasmyth focus of GTC,
behind the AO system. The characteristics and development status of the Control and Housekeeping Electronics are
described in this contribution.
FRIDA is a collaborative project between the IAC (Spain), UNAM (México), UCM (Spain) and the UF (Florida), lead
by UNAM.
Fibre positioning concept for the WEAVE spectrograph at the WHT
Ian J. Lewis,
Gavin B. Dalton,
Matthew Brock,
et al.
Show abstract
WEAVE is the next-generation wide-field optical spectroscopy facility for the William Herschel Telescope (WHT) in
La Palma, Canary Islands, Spain. It is a multi-object "pick and place" fibre fed spectrograph with more than one
thousand fibres behind a new dedicated 2° prime focus corrector, This is similar in concept to the Australian
Astronomical Observatory's 2dF instrument1 with two observing plates, one of which is observing the sky while other
is being reconfigured by a robotic fibre positioner. It will be capable of acquiring more than 10000 star or galaxy
spectra a night.
The WEAVE positioner concept uses two robots working in tandem in order to reconfigure a fully populated field
within the expected 1 hour dwell-time for the instrument (a good match between the required exposure times and the
limit of validity for a given configuration due to the effects of differential refraction).
Precise angular positioning at 6K: the FIFI-LS grating assembly
Show abstract
The Field Imaging Far Infrared Line Spectrometer (FIFI-LS) obtains spectral data within two wavelength ranges. The observed wavelengths are set by rotating the two diffraction gratings to specific angles. This paper describes on the grating assemblies, designed to rotate and stabilize the gratings. First the assembly itself and its special environment inside FIFI-LS is explained. Then a method is layed out how to monitor the performance of the drive and how to detect upcoming failures before they happen. The last chapter is dedicated to first inflight measurements of the position stability of the grating.
Cryogenic optical systems for the rapid infrared imager/spectrometer (RIMAS)
Show abstract
The Rapid Infrared Imager/Spectrometer (RIMAS) is designed to perform follow-up observations of transient
astronomical sources at near infrared (NIR) wavelengths (0.9 - 2.4 microns). In particular, RIMAS will be used to
perform photometric and spectroscopic observations of gamma-ray burst (GRB) afterglows to compliment the Swift
satellite’s science goals. Upon completion, RIMAS will be installed on Lowell Observatory’s 4.3 meter Discovery
Channel Telescope (DCT) located in Happy Jack, Arizona. The instrument’s optical design includes a collimator lens
assembly, a dichroic to divide the wavelength coverage into two optical arms (0.9 - 1.4 microns and 1.4 - 2.4 microns
respectively), and a camera lens assembly for each optical arm. Because the wavelength coverage extends out to 2.4
microns, all optical elements are cooled to ~70 K. Filters and transmission gratings are located on wheels prior to each
camera allowing the instrument to be quickly configured for photometry or spectroscopy. An athermal optomechanical
design is being implemented to prevent lenses from loosing their room temperature alignment as the system is cooled.
The thermal expansion of materials used in this design have been measured in the lab. Additionally, RIMAS has a guide
camera consisting of four lenses to aid observers in passing light from target sources through spectroscopic slits. Efforts
to align these optics are ongoing.
An update on the development of IO:I: a NIR imager for the Liverpool Telescope
Show abstract
IO:I is a new instrument in development for the Liverpool Telescope, extending current imaging capabilities beyond the optical and into the near infrared. Cost has been minimised by use of a previously decommissioned instrument’s dewar as the base for a prototype, and retrofitting it with a 1.7μm cutoff Hawaii-2RG HgCdTe detector, SIDECAR ASIC controller and JADE2 interface card. Development of this prototype is nearing completion and will be operational mid 2014. In this paper, the mechanical, electronic and cryogenic facets of the dewar retrofitting process will be discussed together with a description of the instrument control system software/hardware setup. Finally, a brief overview of some initial testing undertaken on the engineering grade array will be given, along with future commissioning plans for the instrument.
The precise measurement of the attenuation coefficients of various IR optical materials applicable to immersion grating
Show abstract
Immersion grating is a next-generation diffraction grating which has the immersed the diffraction surface in an optical
material with high refractive index of n > 2, and can provide higher spectral resolution than a classical reflective grating.
Our group is developing various immersion gratings from the near- to mid-infrared region (Ikeda et al.1, 2, 3, 4, Sarugaku et
al.5, and Sukegawa et al.6). The internal attenuation αatt of the candidate materials is especially very important to achieve
the high efficiency immersion gratings used for astronomical applications. Nevertheless, because there are few available
data as αatt < 0.01cm-1 in the infrared region, except for measurements of CVD-ZnSe, CVD-ZnS, and single-crystal Si in
the short near-infrared region reported by Ikeda et al.7, we cannot select suitable materials as an immersion grating in an
aimed wavelength range. Therefore, we measure the attenuation coefficients of CdTe, CdZnTe, Ge, Si, ZnSe, and ZnS
that could be applicable to immersion gratings. We used an originally developed optical unit attached to a commercial
FTIR which covers the wide wavelength range from 1.3μm to 28μm. This measurement system achieves the high
accuracy of (triangle)αatt ~ 0.01cm-1. As a result, high-resistivity single-crystal CdZnTe, single-crystal Ge, single-crystal Si,
CVD-ZnSe, and CVD-ZnS show αatt < 0.01cm-1 at the wavelength range of 5.5 - 19.0μm, 2.0 - 10.5μm, 1.3 - 5.4μm, 1.7 - 13.2μm, and 1.9 - 9.2μm, respectively. This indicates that these materials are good candidates for high efficiency
immersion grating covering those wavelength ranges. We plan to make similar measurement under the cryogenic
condition as T ≤ 10K for the infrared, especially mid-infrared applications.
Mechanical design of mounts for IGRINS focal plane arrays and field flattening lenses
Show abstract
IGRINS, the Immersion GRating INfrared Spectrometer, is a near-infrared wide-band high-resolution spectrograph
jointly developed by the Korea Astronomy and Space Science Institute and the University of Texas at Austin. IGRINS
employs three HAWAII-2RG focal plane array (FPA) detectors. The mechanical mounts for these detectors and for the
final (field-flattening) lens in the optical train serve a critical function in the overall instrument design: Optically, they
permit the only positional compensation in the otherwise “build to print” design. Thermally, they permit setting and
control of the detector operating temperature independently of the cryostat bench. We present the design and fabrication
of the mechanical mount as a single module. The detector mount includes the array housing, housing for the SIDECAR
ASIC, a field flattener lens holder, and a support base. The detector and ASIC housing will be kept at 65 K and the
support base at 130 K. G10 supports thermally isolate the detector and ASIC housing from the support base. The field
flattening lens holder attaches directly to the FPA array housing and holds the lens with a six-point kinematic mount.
Fine adjustment features permit changes in axial position and in yaw and pitch angles. We optimized the structural
stability and thermal characteristics of the mount design using computer-aided 3D modeling and finite element analysis.
Based on the computer simulation, the designed detector mount meets the optical and thermal requirements very well.
ARNICA and LonGSp: the refurbishment of two near infrared instruments
Show abstract
ARNICA and LonGSp are two NICMOS based near infrared instruments developed in the 90's by the Astrophysical Observatory of Arcetri. After more than 10 years from decommissioning we refurbished the two instruments
with a new read-out electronics and control software. We present the performances of the refurbished systems
and compare them with the historic behavior. Both instruments are currently used for testing purposes in the
Lab and at the telescope, we present some example applications.
Revised specifications and current development status of MIMIZUKU: the mid-infrared instrument for the TAO 6.5-m
telescope
Show abstract
The MIMIZUKU is the first-generation mid-infrared instrument for the TAO 6.5-m telescope. It challenges to prove the origin of dust and the formation of planets with its unique capabilities, wide wavelength coverage and precise calibration capability. The wide wavelength coverage (2-38 μm) is achieved by three switchable cameras, NIR, MIR-S, and MIR-L. The specifications of the cameras are revised. A 5μm-cutoff HAWAII-1RG is decided to be installed in the NIR camera. The optical design of the MIR-L camera is modified to avoid detector saturation.
Its final F-number is extended from 5.2 to 10.5. With these modifications, the field of view of the NIR and MIR-L camera becomes 1.2’ × 1.2’ and 31” × 31”, respectively. The sensitivity of each camera is estimated based on the
revised specifications. The precise calibration is achieved by the “Field Stacker” mechanism, which enables the simultaneous observation of the target and the calibration object in different fields. The up-and-down motion
of the cryostat (~ 1 t), critical for the Field Stacker, is confirmed to have enough speed (4 mm/s) and position accuracy (~ 50 μm). A control panel for the Field Stacker is completed, and its controllers are successfully
installed. The current specifications and the development status are reported.
Daytime site characterisation of La Palma, and its relation to night-time conditions
Show abstract
This paper presents preliminary daytime profiles taken using a Wide-Field Shack-Hartmann Sensor at the Swedish
Solar Telescope (SST), La Palma. These are contrasted against Stereo-SCIDAR data from corresponding nights to
assess the validity of the assumptions currently used for simulating the performances of possible Multi-Conjugate
Adaptive Optics (MCAO) systems for future solar telescopes, especially the assumption that the structure of the high
altitude turbulence is mostly similar between the day and the night. We find that for our data both the altitude and the
strength of the turbulence differ between the day and the night, although more data is required to draw any conclusions
about typical behaviour and conditions.
First successful deployment of the ZIMPOL-3 system at the GREGOR telescope
Show abstract
Since several years the Zurich Imaging polarimeter (ZIMPOL) system is successfully used as a high sensitivity
polarimeter. The polarimeter system, which is mainly based on a fast modulator and a special demodulating
camera with a masked CCD, has been continuously improved. The third version of the system (ZIMPOL-3) is
routinely used at IRSOL, Locarno. The fast modulation allows to “freeze” intensity variations due to seeing,
and to achieve a polarimetric sensitivity below 10-5 if the photon statistics is large enough. In October 2013
the ZIMPOL system has been brought and installed for the first time at the GREGOR telescope in Tenerife for
a spectropolarimetric observing campaign. There, the system configuration took advantage from the calibration
unit installed at the primary focus of the GREGOR telescope, while the analyzer was inserted in the optical
path just before the spectrograph slit after several folding mirrors. This setup has been tested successfully by
the authors for the first time in this occasion.
MuSICa image slicer prototype at 1.5-m GREGOR solar telescope
Show abstract
Integral Field Spectroscopy is an innovative technique that is being implemented in the state-of-the-art instruments of the
largest night-time telescopes, however, it is still a novelty for solar instrumentation. A new concept of image slicer,
called MuSICa (Multi-Slit Image slicer based on collimator-Camera), has been designed for the integral field
spectrograph of the 4-m European Solar Telescope. This communication presents an image slicer prototype of MuSICa
for GRIS, the spectrograph of the 1.5-m GREGOR solar telescope located at the Observatory of El Teide. MuSICa at
GRIS reorganizes a 2-D field of view of 24.5 arcsec into a slit of 0.367 arcsec width by 66.76 arcsec length distributed
horizontally. It will operate together with the TIP-II polarimeter to offer high resolution integral field spectropolarimetry.
It will also have a bidimensional field of view scanning system to cover a field of view up to 1 by 1 arcmin.
Gemini Planet Imager observational calibrations I: Overview of the GPI data reduction pipeline
Show abstract
The Gemini Planet Imager (GPI) has as its science instrument an infrared integral field spectrograph/polarimeter (IFS). Integral field spectrographs are scientificially powerful but require sophisticated data reduction systems. For GPI to achieve its scientific goals of exoplanet and disk characterization, IFS data must be reconstructed into high quality astrometrically and photometrically accurate datacubes in both spectral and polarization modes, via flexible software that is usable by the broad Gemini community. The data reduction pipeline developed by the GPI instrument team to meet these needs is now publicly available following GPI’s commissioning.
This paper, the first of a series, provides a broad overview of GPI data reduction, summarizes key steps, and presents the overall software framework and implementation. Subsequent papers describe in more detail the algorithms necessary for calibrating GPI data. The GPI data reduction pipeline is open source, available from planetimager.org, and will continue to be enhanced throughout the life of the instrument. It implements an extensive suite of task primitives that can be assembled into reduction recipes to produce calibrated datasets ready for scientific analysis. Angular, spectral, and polarimetric differential imaging are supported. Graphical tools automate the production and editing of recipes, an integrated calibration database manages reference files, and an interactive data viewer customized for high contrast imaging allows for exploration and manipulation of data.
KOALA, a wide-field 1000 element integral-field unit for the Anglo-Australian Telescope: assembly and commissioning
Show abstract
The KOALA optical fibre feed for the AAOmega spectrograph has been commissioned at the Anglo-Australian
Telescope. The instrument samples the reimaged telescope focal plane at two scales: 1.23 arcsec and 0.70 arcsec per
image slicing hexagonal lenslet over a 49x27 and 28x15 arcsec field of view respectively. The integral field unit consists
of 2D hexagonal and circular lenslet arrays coupling light into 1000 fibres with 100 micron core diameter. The fibre run
is over 35m long connecting the telescope Cassegrain focus with the bench mounted spectrograph room where all fibres
are reformatted into a one-dimensional slit. Design and assembly of the KOALA components, engineering challenges
encountered, and commissioning results are discussed.
Single-lock: a stable Fabry-Perot based wavelength calibrator
Show abstract
Pushing the RV technique to the precision required to detect Earth-like planets around Solar-type stars requires extreme stability in the wavelength calibrator. We are developing a wavelength calibration technique based on a Fabry-Perot interferometer locked to a stabilized laser. This approach offers advantages over other methods: it produces a broadband, emission comb output from 380-790 nm that is difficult to achieve with a laser frequency comb; by injecting into the science fibers before and after observations, weak signals from velocities in the stellar photosphere that would be masked by iodine reference lines can be now be identified; and by locking the laser to an atomic transition, the spectrum will be stabilized to better than 1 part in 10 e-11, corresponding to a wavelength solution that is known to better than 1 cms-1.
225GHz opacity measurements at Summit camp, Greenland, for the GreenLand Telescope (GLT) site testing
Show abstract
We report three winter seasons and two full summer from August 2011 to April 2014 of atmospheric opacity measurements with a 225GHz tipping radiometer at Summit camp in Greenland (Latitude 72°.57 N, Longitude 38°.46 W, Elevation 3250 masl). The summit of the ice cap in Greenland is expected to be the location for the GreenLand Telescope (GLT), a 12 meters aperture millimeter / sub-millimeter telescope with VLBI and single- dish capability. The winter regime (November to April) is of particular interest for sub-millimeter observations since the opacities lower quartile in these months can get as low as 0.042, with occasional opacities as low as 0.025. We then compare Summit zenith opacities to other submillimeter sites.
S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), a new-generation of 3D spectro-imager dedicated to night astronomy
Show abstract
Multichannel Subtractive Double Pass (MSDP) spectrographs have been widely used in solar spectroscopy because of
their ability to provide an excellent compromise between field of view and spatial and spectral resolutions. Compared
with other types of spectrographs, MSDP can deliver simultaneous monochromatic images at higher spatial and spectral
resolutions without any time-scanning requirement (as with Fabry-Perot spectrographs), and with limited loss of flux.
These performances are obtained thanks to a double pass through the dispersive element. Recent advances with VPH
(Volume phase holographic) Grisms as well as with image slicers now make MSDP potentially sensitive to much smaller
fluxes. We present S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), which is a new
concept for extending MSDP to night-time astronomy. It is based on new generation reflecting plane image slicers
working with large apertures specific to night-time telescopes. The resulting design could be potentially very attractive
and innovative for different domains of astronomy, e.g., the simultaneous spatial mapping of accurately flux-calibrated
emission lines between OH sky lines in extragalactic astronomy or the simultaneous imaging of stars, exoplanets and
interstellar medium. We present different possible MSDP/S4EI configurations for these science cases and expected
performances on telescopes such as the VLT.
Development of Nayoro optical camera and spectrograph for 1.6-m Pirka telescope of Hokkaido University
Show abstract
We have developed a visible imager and spectrograph, Nayoro Optical Camera and Spectrograph (NaCS), in- stalled at the f/12 Nasmyth focus of the 1.6-m Pirka telescope of the Hokkaido University in Hokkaido, Japan. The optical and mechanical design is similar to that of WFGS2 of the University of Hawaii 2.2-m telescope (UH88), however the camera is newly designed. The spectral coverage is 380–970 nm, and the field of view is 8.4 × 4.5 arcmin with a pixel scale of 0.247 arcsec pixel-1. The SDSS (g', r', i', z') filters, Johnson (B, V ) filters and a replica grism (R ~300 at 650 nm) are equipped. The slit width can be selected from 2, 3, and 4 arcsec. We selected a 2kx1k fully-depleted back-illuminated Hamamatsu CCD as a detector, because it has a high quantum efficiency (≥ 80 %) over optical wavelength. The Kiso Array Controller (KAC) is used as a CCD controller. The first light observation was done on November 2011. NaCS is used mainly for long-term spectroscopic monitor of active galactic nuclei. It is also used for several astronomical observations such as light-curve measurements of asteroids and search of pre-main-sequence stars and brown dwarfs by slit-less spectroscopy as a major facility instrument of the Pirka telescope. We present the design, construction, integration, and performance of this instrument.
Instrument control software based on LabVIEW for HARPS-N
Show abstract
HARPS-N (High-Accuracy Radial-Velocity planetary Search) is an instrument designed for the measurement of Radial
Velocities (RV) at highest accuracy. It is located in the Northern hemisphere and installed at the TNG on La Palma
Island. It has allowed scientists to confirm and characterize Earth-like mass planets: Kepler-78b. In this paper, we
present the design of Instrument Control Software (ICS) based on LabVIEW, the key features of implementation such as
the XML-RPC, labVIEW Classes and Shared Variables. We also present here the auto-guiding and fibre hole finding
algorithm. Use of XML-RPC in Labview for ICS with COTS hardware has made the development of HARAPS-N ICS
easily in implementing and integrating with other software in a limited construction time scale.
Optomecatronic design and integration of a high resolution equipment Berkut to the 1-meter class telescopes
Show abstract
It is proposed the development and implementation of a High Speed Resolution Camera instrument. The basic principle
of this technique is to take several pictures of short exposure using different filters of an astronomical object of interest .
These images are subsequently processed using specialized software to remove aberrations from atmosphere and from
the instrument itself such as blur and scintillation among others.
In this paper are described electronic and control systems implemented for BERKUT instrument based on FPGA (Field
Programmable Gate Array) generated with VHDL description. An UART communication, using serial protocol, is used
with a friendly User Interface providing an easy way for the astronomer to choose between different lenses and different
filters for capturing the images. All the movements are produced by stepper motors that are driven by a circuit that
powers all the electronics. The camera and the lenses are placed into a linear positioner with the help of a stepper motor
which give us repeatable movements for positioning these optical components.
Besides it is planned to integrate in the same system a pipeline for image data reduction to have one sturdy system that
could fulfill any astronomer needs in the usage of this technique. With this instrument we pretend to confirm the
Hipparcos catalogue of binary stars besides finding exoplanets. This technique requires more simple optical equipment
and it is less sensitive to environmental noise, making it cheaper and provides good quality and great resolution images
for scientific purposes. This equipment will be installed on different 1-m class telescopes in Mexico1 and probably other
countries which makes it a wide application instrument.
VIRUS instrument collimator assembly
Show abstract
The Visual Integral-Field Replicable Unit Spectrograph (VIRUS) instrument is a baseline array 150 identical fiber fed
optical spectrographs designed to support observations for the Hobby-Eberly Telescope Dark Energy Experiment
(HETDEX). The collimator subassemblies of the instrument have been assembled in a production line and are now
complete. Here we review the design choices and assembly practices used to produce a suite of identical low-cost
spectrographs in a timely fashion using primarily unskilled labor.
Reverse and concurrent engineering applied of a high resolution equipment Berkut for 1-meter class telescopes
Show abstract
Several factors make observational astronomy difficult for astronomers; one of them is the atmosphere. The light that a
star emits is refracted when it goes through the earth's atmosphere; the result of this is that the image of a punctual star is
not what the physics would lead us to expect. At the Instituto de Astronomia of the Universidad Nacional Autonoma de
México (IA-UNAM) an instrument has been developed called "Berkut", which uses a high resolution technique to
improve these effects and obtain interesting and valuable scientific studies.
In this paper we present the mechanical reengineering and acceptance test of Berkut. This instrument was design for
taking images of high resolution. Essentially, it is composed by a set basic optics which is aligned and in focus with a 1-
meter class telescope. It has its own electronic components for controlling remotely a filter wheel; that allows the
exchange of the filters according to the requirements of the observer, a couple of objectives mounted in a translation
stage, and a CCD camera for acquiring several images per second that are used in the speckle interferometry technique.
A project like Berkut needs to be multidisciplinary; astronomy, engineering, optics, mechanics, electronics, and image
processing are some of the areas of knowledge used.
Berkut will be used in the telescope of the Observatorio Astronomico Nacional in Tonantzintla, located in the state of
Puebla, Mexico, but it can be used in any telescope 1 meter class. It is pretended to build another Berkuts for being used
simultaneously in different telescopes, so it is important to keep the costs as low as possible. With this instrument we
pretend to confirm the Hipparcos catalogue of binary stars besides finding exoplanets.
Remote and automatic small-scale observatories: experience with an all-sky fireball patrol camera
Show abstract
This paper describes the design of a remote, automatic all-sky camera for capturing bright meteor trails based on a DSLR
camera combined with Liquid Crystal shutter technology for angular velocity measurement. Design, performance and
first results are discussed, as well the up scaling towards a large autonomous network for accurate fireball orbit
determination and meteorite recovery.
Optical integration and verification of LINC-NIRVANA
Show abstract
The LBT (Large Binocular Telescope) located in Mount Graham near Tucson/Arizona at an altitude of about
3200m, is an innovative project being undertaken by institutions from Europe and USA. The structure of the
telescope incorporates two 8.4-meter telescopes on a 14.4 center-to-center common mount. This configuration
provides the equivalent collecting area of a 12m single-dish telescope.
LINC-NIRVANA is an instrument to combine the light from both LBT primary mirrors in an imaging Fizeau
interferometer. Many requirements must be fulfilled in order to get a good interferometric combination of the
beams, being among the most important plane wavefronts, parallel input beams, homotheticity and zero optical path
difference (OPD) required for interferometry. The philosophy is to have an internally aligned instrument first, and
then align the telescope to match the instrument.
The sum of different subsystems leads to a quite ambitious system, which requires a well-defined strategy for
alignment and testing. In this paper I introduce and describe the followed strategy, as well as the different solutions,
procedures and tools used during integration. Results are presented at every step.
The ZIMPOL high contrast imaging polarimeter for SPHERE: system test results
Show abstract
SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a new instrument for the VLT aimed at the direct
detection of exo-planets. It has received its first light in May 2014. ZIMPOL (Zurich Imaging Polarimeter) is the
imaging polarimeter subsystem of the SPHERE instrument. It's capable of both high accuracy and high sensitivity
polarimetry but can also be used as a classical imager. It is located behind an extreme AO system and a stellar
coronagraph. ZIMPOL operates at visible wavelengths (600-900 nm) which is best suited to detect the very faint
reflected and hence polarized visible light from extra solar planets. It has an instantaneous Field of View of 3 x 3 arcsec2
(extendable to 8 arcsec diameter) with an angular resolution of 14 mili-arcsec. We discuss the results that are obtained
from the full SPHERE-ZIMPOL system testing. In particular the optical, polarimetric and high contrast performance.
PANIC in the lab: status before commissioning
Show abstract
PANIC is the new PAnoramic Near-Infrared camera for Calar Alto, a joint project by the MPIA in Heidelberg, Germany,
and the IAA in Granada, Spain. It can be operated at the 2.2m or 3.5m CAHA telescopes to observe a field of view of
30'x30' or 15'x15' respectively, with a sampling of 4096x4096 pixels. It is designed for the spectral bands from Z to K,
and can be equipped with additional narrow-band filters.
The instrument is close to completion and will be delivered to the observatory in Spain in fall 2014. It is currently in the
last stage of assembly, where the optical elements are being aligned, which will be followed by final laboratory tests of
the instrument. This paper contains an update of the recent progress and shows results from the optical alignment and
detector performance tests.
PISCO: the Parallel Imager for Southern Cosmology Observations
Show abstract
We present the design and lab performance of the Parallel Imager for Southern Cosmology Observations (PISCO), a photometer for the 6.5 m diameter Magellan telescopes that produces gl, rl, il, and zl band images simulta- neously within a 9 arcminute field of view. This design provides efficient follow-up observations of faint sources, particularly galaxy clusters and supernovae. Simultaneous imaging speeds the observing cadence by at a factor
of ~ 3 (including optical losses) compared to other photometric imagers. Also, the determination of color (flux
ratio between bands) is relatively immune to time variations in gray opacity due to clouds, so observations can
proceed in less than optimal conditions. First light is expected in September 2014 2014.
SITELLE optical design, assembly, and testing
Show abstract
SITELLE is an imaging FTS that will become a guest instrument at the Canada-France-Hawaii telescope (CFHT) by the
end of 2014. This paper describes the final optical design of SITELLE, shows how the compliance of the sub-optical
components with the design was evaluated, and presents results of the measured optical quality.
Automated alignment and on-sky performance of the Gemini planet imager coronagraph
Show abstract
The Gemini Planet Imager (GPI) is a next-generation, facility instrument currently being commissioned at the Gemini South observatory. GPI combines an extreme adaptive optics system and integral field spectrograph (IFS) with an apodized-pupil Lyot coronagraph (APLC) producing an unprecedented capability for directly imaging and spectroscopically characterizing extrasolar planets. GPI’s operating goal of 10-7 contrast requires very precise alignments between the various elements of the coronagraph (two pupil masks and one focal plane mask) and active control of the beam path throughout the instrument. Here, we describe the techniques used to automatically align GPI and maintain the alignment throughout the course of science observations. We discuss the particular challenges of maintaining precision alignments on a Cassegrain mounted instrument and strategies that we have developed that allow GPI to achieve high contrast even in poor seeing conditions.
Better flat-fielding for ground-based UV spectrographs
Show abstract
A new technological development, the laser driven light source (LDLS), in which a laser excited plasma emits intense
continuum radiation over a wide wavelength range from well below the atmospheric cut-off up to 800 nm, promises to
greatly improve our ability to provide high quality flat-fields for astronomical spectrographs. Its particular strength lies
in the ground-based ultraviolet (UV). We report on tests conducted with a LDLS using FORS2, UVES, X-Shooter and
CRIRES at ESO’s Very Large Telescope (VLT) in August 2013. Comparison with standard calibration sources such as
halogen and deuterium lamps shows that with the LDLS flat-fields with a better balanced dynamic range and excellent
signal to noise ratio can be achieved within short exposure times. This will enable higher quality science at the short
wavelength end of existing spectrographs at the VLT. Furthermore the LDLS provides exceptional stability and long
lifetime as important operational aspects. Optimised UV spectrographs such as the proposed CUBES (wavelength range
300-400 nm) project will be able to take full advantage of this development removing the long-standing limitation of
signal to noise ratios of UV flat-fields.
Developing micro DC-brushless motor driver and position control for fiber positioners
Show abstract
In the large-scale, Dark Energy Spectroscopic Instrument (DESI), thousands of fiber positioners will be used. Those are
robotic positioners, with two axis, and having the size of a pen. They are tightly packed on the focal plane of the
telescope. Dedicated micro-robots have been developed and they use 4mm brushless DC motors. To simplify the
implementation and reduce the space occupancy, each actuator will integrate its own electronic control board. This board
will be used to communicate with the central trajectory generator, manage low level control tasks and motor current
feeding. In this context, we present a solution for a highly compact electronic. This electronic is composed of two layers.
The first is the power stage that can drive simultaneously two brushless motors. The second one consists of a fast
microcontroller and deals with different control tasks: communication, acquisition of the hall sensor signals,
commutation of the motors phases, and performing position and current regulation. A set of diagnostic functions are also
implemented to detect failure in the motors or the sensors, and to sense abnormal load change that may be the result of
two robots colliding.
A miniature cryogenic scanning Fabry-Perot interferometer for mid-IR to submm astronomical observations
Show abstract
We have designed and evaluated a Miniature Cryogenic Scanning Fabry-Perot (MCSF) interferometer which can be
inserted into the optical path of a mid-IR camera to observe fine structure lines in the 25-40 μm wavelength regime. The
MCSF uses free standing metal meshes as its filters and can scan over a length of ~2 mm. The short wavelength range in
which the MCSF will be used requires very tight fabrication tolerances to maintain the parallelism of the meshes to
within 0.15 μm and to obviate the need for dynamic parallelizing adjusters. A monolithic notch flexure design delivers
these properties and minimizes the number of moving parts, maximizing reliability. The scanning mechanism includes a
cryogenic stepper motor that drives a miniature fine-adjustment screw via a worm gear assembly. This allows for a step
resolution of 1 step ~ 14 nm when operating in full step mode. Finite Element Analysis of the MCSF’s monolithic
flexure guided the design and confirmed that the MCSF will remain within required limits over the course of operation.
We developed the MCSF for use in the mid-IR camera FORCAST on the 2.5 meter SOFIA telescope.
The development of ground-based infrared multi-object spectrograph based on the microshutter array
Show abstract
We report on our development of a near-infrared multi-object spectrograph for ground-based applications using the
micro-shutter array, which was originally developed for the Near Infrared Spectrograph of the James Webb Space
Telescope. The micro-shutter array in this case acts as a source selector at a reimaged telescope focal plane. The
developed spectrograph will be implemented either with ground-layer adaptive optics system or multi-conjugate
adaptive optics system on a large telescope. This will enable for the first time fully reconfigurable infrared multi-object
spectroscopy with adaptive optics systems. We envision studying diverse astronomical objects with our spectrograph,
including high-redshift galaxies, galaxy clusters and super star clusters.
Optical design of the SuMIRe/PFS spectrograph
Show abstract
The SuMIRe Prime Focus Spectrograph (PFS), developed for the 8-m class SUBARU telescope, will consist of four
identical spectrographs, each receiving 600 fibers from a 2394 fiber robotic positioner at the telescope prime focus. Each
spectrograph includes three spectral channels to cover the wavelength range [0.38-1.26] um with a resolving power
ranging between 2000 and 4000. A medium resolution mode is also implemented to reach a resolving power of 5000 at
0.8 um.
Each spectrograph is made of 4 optical units: the entrance unit which produces three corrected collimated beams and
three camera units (one per spectral channel: "blue, "red", and “NIR”). The beam is split by using two large dichroics;
and in each arm, the light is dispersed by large VPH gratings (about 280x280mm).
The proposed optical design was optimized to achieve the requested image quality while simplifying the manufacturing
of the whole optical system. The camera design consists in an innovative Schmidt camera observing a large field-of-view
(10 degrees) with a very fast beam (F/1.09). To achieve such a performance, the classical spherical mirror is replaced by
a catadioptric mirror (i.e meniscus lens with a reflective surface on the rear side of the glass, like a Mangin mirror).
This article focuses on the optical architecture of the PFS spectrograph and the perfornance achieved. We will first
described the global optical design of the spectrograph. Then, we will focus on the Mangin-Schmidt camera design. The
analysis of the optical performance and the results obtained are presented in the last section.
Spherical grating spectrometers
Show abstract
We describe designs for spectrometers employing convex dispersers. The Offner spectrometer was the first such
instrument; it has almost exclusively been employed on satellite platforms, and has had little impact on ground-based
instruments.
We have learned how to fabricate curved Volume Phase Holographic (VPH) gratings and, in contrast to the planar gratings
of traditional spectrometers, describe how such devices can be used in optical/infrared spectrometers designed specifically
for curved diffraction gratings. Volume Phase Holographic gratings are highly efficient compared to conventional surface
relief gratings; they have become the disperser of choice in optical / NIR spectrometers.
The advantage of spectrometers with curved VPH dispersers is the very small number of optical elements used (the simplest
comprising a grating and a spherical mirror), as well as illumination of mirrors off axis, resulting in greater efficiency and
reduction in size. We describe a “Half Offner" spectrometer, an even simpler version of the Offner spectrometer. We
present an entirely novel design, the Spherical Transmission Grating Spectrometer (STGS), and discuss exemplary
applications, including a design for a double-beam spectrometer without any requirement for a dichroic.
This paradigm change in spectrometer design offers an alternative to all-refractive astronomical spectrometer designs,
using expensive, fragile lens elements fabricated from CaF2 or even more exotic materials. The unobscured mirror layout
avoids a major drawback of the previous generation of catadioptric spectrometer designs.
We describe laboratory measurements of the efficiency and image quality of a curved VPH grating in a STGS design,
demonstrating, simultaneously, efficiency comparable to planar VPH gratings along with good image quality. The stage
is now set for construction of a prototype instrument with impressive performance.
Inverse analysis method to optimize the optic tolerances of MEGARA: the future IFU and multi-object spectrograph for GTC
Show abstract
Optical tolerances are specified to achieve the desired performance of any optical system. Traditionally the diverse sets of
tolerances of a system are proposed by the designer of each of the subsystems. In this work we propose a method to
corroborate the design tolerances and simultaneously to provide extra data of each parameter to the manufacturer. It
consists of an inverse analysis in which we fix a modified merit function as a constant and evaluate distinct models of
perturbed lenses via Monte Carlo simulations, determining the best possible tolerance for each parameter, and indirectly
providing information of sensitivity of the parameters. The method was used to carry out an extensive tolerance analysis
of MEGARA, a multi-object spectrograph in development for the GTC. The key parameters of the optics are discussed,
the overall performance is tested and diverse recommendations and adjustments to the design tolerances are made towards
fabrication at INAOE and CIO in Mexico.
Status and first results of the Canarias infrared camera experiment (CIRCE) for the Gran Telescopio Canarias
Show abstract
CIRCE is a near-infrared (1-2.5 micron) imager, polarimeter and low-resolution spectrograph intended as a visitor instrument for the Gran Telescopio Canarias 10.-4m telescope. It was built largely by graduate students and postdocs, with help from the UF astronomy engineering group, and is funded by the University of Florida and the U.S. National Science Foundation. CIRCE is intended to help fill the gap in time between GTC first light and the arrival of EMIR, and will also provide the following scientific capabilities to compliment EMIR after its arrival: high- resolution imaging, narrowband imaging, high-time-resolution photometry, imaging- and spectro- polarimetry, low-resolution spectroscopy. In this poster, we review the lab testing results for CIRCE from 2013 and describe the instrument status (currently in shipment to GTC).
LINC-NIRVANA: Diffraction limited optics in cryogenic environment
Show abstract
LINC-NIRVANA is an instrument combining the two 8.4 m telescopes of the Large Binocular Telescope (LBT)
coherently, in order to achieve the optical resolution of the 23 meter baseline. For this interferometric instrument
concept, the common beam combination requires diffraction limited optical performance. The optics, realized as a
Cassegrain telescope design, consists of aluminum mirrors, designed and manufactured to fulfill the challenging
specifications required for interferometric imaging. Due to the science wavelength range from 1 μm to 2.4 μm, covering
the J, H and K band of the atmosphere, the complete beam combiner including the optics is operated in cryogenic
environment at 60 Kelvin. Here, we demonstrate the verification of the optical performance at this temperature for
classical in-coherent and coherent illumination. We outline the test setup and present the achieved results of wavefront
error for the individual beams and fringe contrast for the interferometric point spread function.
This paper continues the already presented integration of the interferometric camera with the focus on the performance
of the cryogenic optics.
A comparison of concepts for a photonic spectrograph
Show abstract
It is possible to significantly improve the performance of astronomical spectroscopy by taking the Point Spread Function from a near diffraction-limited telescope and reformatting it using photonic technologies. This can improve the stability of a conventional instrument or provide an interface to single mode instruments developed for the telecommunications industry. We compare different options for reformatting and interfacing with different types of instruments and examine them using set metrics. We then examine the relative merits for instruments that could be developed for astronomy.
MSE spectrograph optical design: a novel pupil slicing technique
Show abstract
The Maunakea Spectroscopic Explorer shall be mainly devoted to perform deep, wide-field, spectroscopic surveys at
spectral resolutions from ~2000 to ~20000, at visible and near-infrared wavelengths. Simultaneous spectral coverage at
low resolution is required, while at high resolution only selected windows can be covered. Moreover, very high
multiplexing (3200 objects) must be obtained at low resolution. At higher resolutions a decreased number of objects
(~800) can be observed. To meet such high demanding requirements, a fiber-fed multi-object spectrograph concept has
been designed by pupil-slicing the collimated beam, followed by multiple dispersive and camera optics. Different
resolution modes are obtained by introducing anamorphic lenslets in front of the fiber arrays. The spectrograph is able to
switch between three resolution modes (2000, 6500, 20000) by removing the anamorphic lenses and exchanging
gratings. Camera lenses are fixed in place to increase stability. To enhance throughput, VPH first-order gratings has been
preferred over echelle gratings. Moreover, throughput is kept high over all wavelength ranges by splitting light into more
arms by dichroic beamsplitters and optimizing efficiency for each channel by proper selection of glass materials,
coatings, and grating parameters.
New GRISMs for AFOSC based on volume phase holographic gratings in photopolymers
Show abstract
Volume Phase Holographic Gratings (VPHG) can provide an improvement of diffraction efficiency and function- ality in already available astronomical instrumentation. Here, we present the design, manufacturing and testing of two GRISMs mounted on the AFOSC camera (at the 1.8 m Asiago telescope) based on VPHGs. Such diffrac- tion gratings have been written on a new solid and green sensitive photopolymer material produced by Bayer MaterialScience AG that show interesting performances (refractive index modulation, homogeneity, stability). The GRISMs have been designed according to the specific requests of astronomers. One GRISM consists in a very low dispersion VPHG (285 l/mm) that covers the range 500 - 1000 nm and suitable for observations of supernovae. The second one is a 600 l/mm VPHG for the Ha region. Both gratings show peak efficiency close to 90% and same diffraction efficiency is shown by the corresponding GRISMs. This high device’s performances means that the coupling losses are very low, also thanks to the matching of the refractive index between sub- strates and prisms. Some observations have been finally carried out and the gain in terms of efficiency and signal to noise ratio have been calculated in order to compare the photopolymeric VPHGs with the classic GRISMs already mounted and used in the AFOSC spectrometer.
Characterization of the reflectivity of various black materials
Show abstract
We present total and specular reflectance measurements of various materials that are commonly (and uncommonly) used
to provide baffling and/or to minimize the effect of stray light in optical systems. More specifically, we investigate the
advantage of using certain black surfaces and their role in suppressing stray light on detectors in optical systems. We
measure the total reflectance of the samples over a broad wavelength range (250 < λ < 2500 nm) that is of interest to
astronomical instruments in the ultraviolet, visible, and near-infrared regimes. Additionally, we use a helium-neon laser
to measure the specular reflectance of the samples at various angles. Finally, we compare these two measurements and
derive the specular fraction for each sample.
FIFI-LS observation planning and data reduction
Show abstract
We describe observational operations and data reduction for the science instrument FIFI-LS (Field Imaging Far Infrared
Line Spectrometer) onboard SOFIA (Stratospheric Observatory for Infrared Astronomy). First, the observation strategy
is explained, which plans all the various observing modes and parameters based on the targets and the limitations of the
observatory and instrument. Next, the observations must be created in a format readable by instrument control software,
via a system of algorithms. Once the observations have been planned and prepared, they must be scheduled, executed
and analysed, and this process is outlined. The data reduction system which processes the results from these
observations, beginning from retrieving raw data, to obtaining a FITS file data cube readable by analysis programs, is
described in detail.
Tests and procedures for optimizing EMIR cooling system
Show abstract
EMIR is a wide-field camera and a multi-object, intermediate resolution near-infrared spectrograph for the GTC
telescope. EMIR is a cryogenic instrument whose cooling system is based on four two-stage CCCs’ Leybold Coolpower
5/100 whose cooling capacity is 100W@80K, in the 1st stage, and 5W@20K, in the 2nd stage, operated directly by two
compressors in dual mode (two cold heads for each compressor). During the verification phase some phenomena
affecting the cooling system efficiency have been observed. In consequence, the possible influences of the temperature
of the water in the cooling unit the compressor, the compressor input power and the quality of the insulating vacuum in
the instrument have been studied. Contamination in the Closed Helium Cycle is another possible cause that has been
evaluated. The methods used in the tests and the cleaning procedures are described. The results allow us to reach some
conclusions regarding the use and maintenance of this type of cooling systems.
Design, alignment, and deployment of the Hobby Eberly Telescope prime focus instrument package
Show abstract
The Hobby-Eberly Telescope (HET) is undergoing an upgrade to increase the field of view to 22 arc-minutes with the
dark energy survey HETDEX the initial science goal [1]. Here we report on the design, alignment, and deployment of a
suite of instruments located at prime focus of the upgraded HET. This paper reviews the integration of motion control
electronics and software and alignment of those electromechanical systems. Use of laser trackers, alignment telescopes,
and other optical alignment techniques are covered. Deployment onto the upgraded telescope is discussed.
A near-infrared SETI experiment: probability distribution of false coincidences
Show abstract
A Search for Extraterrestrial Life (SETI), based on the possibility of interstellar communication via laser signals, is being designed to extend the search into the near-infrared spectral region (Wright et al, this conference). The dedicated near-infrared (900 to 1700 nm) instrument takes advantage of a new generation of avalanche photodiodes (APD), based on internal discrete amplification. These discrete APD (DAPD) detectors have a high speed response (< 1 GHz) and gain comparable to photomultiplier tubes, while also achieving significantly lower noise than previous APDs. We are investigating the use of DAPD detectors in this new astronomical instrument for a SETI search and transient source observations. We investigated experimentally the advantages of using a multiple detector device operating in parallel to remove spurious signals. We present the detector characterization and performance of the instrument in terms of false positive detection rates both theoretically and empirically through lab measurements. We discuss the required criteria that will be needed for laser light pulse detection in our experiment. These criteria are defined to optimize the trade between high detection efficiency and low false positive coincident signals, which can be produced by detector dark noise, background light, cosmic rays, and astronomical sources. We investigate experimentally how false coincidence rates depend on the number of detectors in parallel, and on the signal pulse height and width. We also look into the corresponding threshold to each of the signals to optimize the sensitivity while also reducing the false coincidence rates. Lastly, we discuss the analytical solution used to predict the probability of laser pulse detection with multiple detectors.
Automatisms in EMIR instrument to improve operation, safety and maintenance
Show abstract
EMIR is the NIR imager and multiobject spectrograph being built as a common user instrument for the 10-m class GTC.
Big cryogenic instruments demand a reliable design and a specific hardware and software to increase its safety and
productivity.
EMIR vacuum, cooling and heating systems are monitored and partially controlled by a Programmable Logic Controller
(PLC) in industrial format with a touch screen. The PLC aids the instrument operator in the maintenance tasks
recovering autonomously vacuum if required or proposing preventive maintenance actions. The PLC and its associated
hardware improve EMIR safety having immediate reactions against eventual failure modes in the instrument or in
external supplies, including hardware failures during the heating procedure or failure in the PLC itself. EMIR PLC
provides detailed information periodically about status and alarms of vacuum and cooling components or external
supplies.
HONIR: an optical and near-infrared simultaneous imager, spectrograph, and polarimeter for the 1.5-m Kanata telescope
Show abstract
We have developed an optical and near-infrared instrument HONIR (Hiroshima Optical and Near-InfraRed
camera) with imaging, spectroscopy, and polarimetry capabilities in two (one optical and one near-infrared)
bands simultaneously. Imaging capability with a field of view of 10 arcmin by 10 arcmin has been available
since 2011, as reported in the previous SPIE conference. In addition, spectroscopic and polarimetric optical
components (grisms, an Wollaston prism, a half-wave plate, and focal masks) were installed in the instrument,
which enabled us to perform spectroscopy and linear polarization measurement by imaging polarimetry and
spectro-polarimetry. Spectral resolution of R = λ/(triangle)λ ~ 440 - 800 is achieved in spectroscopy using a slit
mask with an 1".3 width. In polarimetry, instrumental polarization is less than ~0.05 % with stability of
better than ~0.05 %, which is sufficiently small to achieve an aimed accuracy of polarization measurement
of ~0.1 % at primal observing wavelengths.
PAUCam readout electronics assembly, integration and test (AIT)
Show abstract
The PAUCam is an optical camera with an array of 18 CCDs (Hamamatsu Photonics K.K.) and up to 45 narrow and
broad band filters. The camera will be installed on the William Herschel Telescope (WHT) in the Canary Islands, Spain.
In order to fulfill with the specifications for the camera readout system, it was necessary to test the different readout
electronics subsystems individually before to integrate the final readout work package, which is composed of 4
MONSOON (NOAO) front-ends, 6 fan out boards (MIX), each one driving up to 5 CCDs signals and a pre-amplification
stage (PREAMP) located inside the cryostat. To get the subsystems integration, it was built a small camera prototype
using the same technology as used in the main camera: a carbon fiber cryostat refrigerated by a cryotiger cooling system
but with capacity to allocate just 2 CCDs, which were readout and re-characterized to measure the electronics
performance as conversion factor or gain, readout noise, stability, linearity, etc. while the cross-talk was measured by
using a spot-light.
The aim of this paper is to review the whole process of assembly, integration and test (AIT) of the readout electronics
work package and present the main results to demonstrate the viability of the proposed systems to be use with the
PAUCam camera.
A flux calibration device for the SuperNova Integral Field Spectrograph (SNIFS)
Show abstract
Observational cosmology employing optical surveys often require precise flux calibration. In this context we present SNIFS Calibration Apparatus (SCALA), a flux calibration system developed for the SuperNova Integral Field Spectrograph (SNIFS), operating at the University of Hawaii 2.2 m telescope. SCALA consists of a hexagonal array of 18 small parabolic mirrors distributed over the face of, and feeding parallel light to, the telescope entrance pupil. The mirrors are illuminated by integrating spheres and a wavelength-tunable (from UV to IR) light source, generating light beams with opening angles of 1°. These nearly parallel beams are flat and flux-calibrated at a subpercent level, enabling us to calibrate our “telescope + SNIFS system” at the required precision.
Boresight calibration of FIFI-LS: in theory, in the lab and on sky
Show abstract
The Field-Imaging Far-Infrared Line-Spectrometer (FIFI-LS) entered service on the Stratospheric Observatory for
Infrared Astronomy (SOFIA) on March 2014.
Exact pointing of the instrument is important. The SOFIA telescope provides an absolute pointing stability of 1” rms,
which is sufficient for FIFI-LS. The instrument boresight relative to the telescope reference system is established with
accuracy better than 1”. FIFI-LS has a built-in rotating K-Mirror to derotate the instrument field of view. Perfect
alignment of the optical axis of the K-Mirror and the optical axis of the optical systems in both instrument channels is
practically impossible. The remaining offsets result in a dependence of the instrument boresight on the K-Mirror
position. Therefore a boresight calibration model is established for each channel. With these models the instrument
boresight is calculated and transferred to the telescope control software. Achieving precise calibration of the boresight
has been an ongoing process including the first optical models of the instrument, measurements in different laboratories
and finally measurements during the commissioning flight series. In this paper, the approach used to calibrate FIFI-LS’s
boresight is explained. This includes the model used and an overview of the laboratory, as well as the in-flight
measurements leading to the calibrated boresight model.
SPHERE/IRDIS: final performance assessment of the dual-band imaging and long slit spectroscopy modes
Show abstract
The near-infrared imager and spectrograph IRDIS is one of the three science sub-systems of VLT/SPHERE dedicated to the detection and characterization of giant exoplanets at large orbital radii. It offers a wide
range of observational modes including dual-band imaging (DBI) with very low differential aberrations, and long slit spectroscopy (LSS) coupled with a classical Lyot coronagraph at low (R = ~50) and medium (R = ~330) resolution. Over the course of 2012 and 2013, IRDIS has been extensively tested in laboratory during
the integration and optimization of the SPHERE system. At the beginning of 2014, the instrument has been
shipped to Chile and has been reintegrated at the Paranal observatory. We present here a detailed summary of the performance of the DBI and LSS modes obtained in laboratory. We provide a wide range of results covering different observing conditions and setups for the DBI mode, and we show that the instrument reaches the technical specifications in terms of contrast. We also identify some of the limitations that prevent going down much further in contrast while testing in the laboratory. For the LSS mode, we present results obtained both at low and medium resolution in the main setups that will be offered to future users. We demonstrate that the LSS mode will provide a useful characterization tool for the planets detected in DBI mode. Finally, we present the first results obtained on-sky during the first commissioning run of SPHERE at the VLT.
Characterization of the atmospheric dispersion corrector of the Gemini planet imager
Show abstract
An Atmospheric Dispersion Corrector (ADC) uses a double-prism arrangement to nullify the vertical chromatic
dispersion introduced by the atmosphere at non-zero zenith distances.
The ADC installed in the Gemini Planet Imager (GPI) was first tested in August 2012 while the instrument was
in the laboratory. GPI was installed at the Gemini South telescope in August 2013 and first light occurred later
that year on November 11th.
In this paper, we give an overview of the characterizations and performance of this ADC unit obtained in the
laboratory and on sky, as well as the structure of its control software.
Vibration specifications for VLT instruments
Show abstract
ESO invested enormous effort in developing and commissioning the VLT-Interferometer (VLT-I), a unique facility
providing a spatial resolution equivalent to that of a 200m-telescope. Complementary to the regular VLT operations,
latterly additional 230 nights per year were scheduled to execute scientific observations with large VLT-I baselines. But
to the same degree as the VLT-I performance and stability were improving over the past years, likewise the vibration
sensitivity of the optical system was increasing and stricter requirements on mechanical stability were necessary. As a
consequence ESO started years ago an extensive program to identify and mitigate potential vibration issues. In the scope
of this work, the mechanical vibrations induced by cryo-coolers, widely used in ESO’s VLT instrumentation suite, were
diagnosed as one of the major disturbance sources. In order to be able to better control their impact, the development of a
more significant vibration specification for VLT instruments became essential.
In the course of preparing such a specification, we first followed an experimental approach where we installed a
dedicated dummy instrument equipped with current ESO standard cryo-coolers in different VLT foci configurations and
performed a comprehensive vibration measurement test campaign under real VLT/VLT-I operation conditions. All
obtained vibration measurement data were spectral analyzed with respect to the actual VLT-I optical path length
difference acceptance levels. This campaign gave valuable information about typical cryo-cooler induced vibration levels
and their consequence for VLT-I operations. It also enabled the release if novel conform cryo-cooler instrument design
and operation recommendations.
This paper describes the applied vibration measurement methodology on the basis of examples, the development and
description of the significant VLT instrument vibration specification, and a proposal for a generic verification procedure
for standalone instruments or sub-units prior final acceptance.
ARDOLORES: an Arduino based motors control system for DOLORES
Show abstract
We present ARDOLORES a custom made motor control system for the DOLORES instrument in use at the TNG telescope. ARDOLORES replaced the original PMAC based motor control system at a fraction of the cost. The whole system is composed by one master Arduino ONE with its Ethernet shield, to handle the communications with the external world through an Ethernet socket, and by one Arduino ONE with its custom motor shield for each axis to be controlled. The communication between the master and slaves Arduinos is made possible through the I2C bus. Also a Java web-service has been written to control the motors from an higher level and provides an external API for the scientific GUI. The system has been working since January 2012 handling the DOLORES motors and has demonstrated to be stable, reliable, and with easy maintenance in both the hardware and the software parts.
Design and integration of a mechanism for focusing and alignment of the Echelle spectrograph for the telescope of 2.1 meters of the National Astronomic Observatory
Horacio O. A. Gutiérrez,
Alejandro S. Farah,
Juan M. Echevarria R.,
et al.
Show abstract
This paper is focused on an engineering project applied to astronomy for scientific purposes. The project consisted
elementally on the design, fabrication and characterization of an interface or mechanism to align and focus the lens of the
Echelle spectrograph and its CCD camera. This instrument is part of the 2.1 m telescope of the Observatorio
Astronómico Nacional located at the Sierra de San Pedro Martir, B. C., Mexico (OAN-SPM).
The mechanism described in this article is composed functionally of the next pieces: two half- clamps, three profiles type
"L" (that function as support columns), a fixed plate, a reference sliding plate, and three digital sensors for measuring the
relative position between the camera interface of the spectrograph and the plane of its dewar. The cryostat system has a
lens that must be focused and aligned with the spectrograph. The cryostat and the mechanism have to be attached and it
has to allow rotational movements around the three axes with linear adjustments along them.
Similarly there is a brief description of the adjacent elements to understand the mechanism and functionality design
criteria used in order to ensure the proper functionality of the mechanism that has been tested and integrated in the
telescope. Such results are also described as well as the technical specifications, the manufacturing process and the
manufacturing drawings.
A brief description of the scientific instrument and some finite element simulations are also included in this work.
Finally, some recommendations and future work that may be carried out as a continuous improvement mechanism are
presented.
Gemini planet imager observational calibrations IX: least-squares inversion flux extraction
Show abstract
The Gemini Planet Imager (GPI) is an instrument designed to directly image planets and circumstellar disks
from 0.9 to 2.5 microns (the YJHK infrared bands) using high contrast adaptive optics with a lenslet-based
integral field spectrograph. We develop an extraction algorithm based on a least-squares method to disentangle
the spectra and systematic noise contributions simultaneously. We utilize two approaches to adjust for the effect
of flexure of the GPI optics which move the position of light incident on the detector. The first method is
to iterate the extraction to achieve minimum residual and the second is to cross-correlate the detector image
with a model image in iterative extraction steps to determine an offset. Thus far, this process has made clear
qualitative improvements to the cube extraction by reducing the Moiré pattern. There are also improvements
to the automated routines for finding flexure offsets which are reliable to with ~ 0.5 pixel accuracy compared to
pixel accuracy prior. Further testing and optimization will follow before implementation into the GPI pipeline.
Gemini planet imager one button approach
Show abstract
The Gemini Planet Imager (GPI) is an “extreme” adaptive optics coronagraph system that is now on the
Gemini South telescope in Chile. This instrument is composed of three different systems that historically have
been separate instruments. These systems are the extreme Adaptive Optics system, with deformable mirrors,
including a high-order 64x64 element MEMS system; the Science Instrument, which is a near-infrared
integral field spectrograph; and the Calibration system, a precision IR wavefront sensor that also holds
key coronagraph components. Each system coordinates actions that require precise timing. The
observatory is responsible for starting these actions and has typically done this asynchronously across
independent systems. Despite this complexity we strived to provide an interface that is as close to a onebutton
approach as possible. This paper will describe the sequencing of these systems both internally and
externally through the observatory.
A format standard for efficient interchange of high-contrast direct imaging science products
Show abstract
The present and next few years will see the arrival of several new coronagraphic instruments dedicated to the detection
and characterization of planetary systems. These ground- and space-based instruments (Gemini/GPI, VLT/SPHERE, Subaru/
CHARIS, JWST NIRCam and MIRI coronagraphs among others), will provide a large number of new candidates,
through multiple nearby-star surveys and will complete and extend those acquired with current generation instruments
(Palomar P1640, VLT/NACO, Keck, HST). To optimize the use of the wealth of data, including non-detection results, the
science products of these instruments will require to be shared among the community. In the long term such data exchange
will significantly ease companion confirmations, planet characterization via different type of instruments (integral field
spectrographs, polarimetric imagers, etc.), and Monte-Carlo population studies from detection and non-detection results.
In this context, we initiated a collaborative effort between the teams developing the data reduction pipelines for
SPHERE, GPI, and the JWST coronagraphs, and the ALICE (Archival Legacy Investigations of Circumstellar Environment)
collaboration, which is currently reprocessing all the HST/NICMOS coronagraphic surveys. We are developing a
standard format for the science products generated by high-contrast direct imaging instruments (reduced image, sensitivity
limits, noise image, candidate list, etc.), that is directly usable for astrophysical investigations. In this paper, we present
first results of this work and propose a preliminary format adopted for the science product. We call for discussions in the
high-contrast direct imaging community to develop this effort, reach a consensus and finalize this standard. This action
will be critical to enable data interchange and combination in a consistent way between several instruments and to stiffen
the scientific production in the community.
Environmental control system for Habitable-zone Planet Finder (HPF)
Show abstract
HPF is an ultra-stable, precision radial velocity near infrared spectrograph with a unique environmental
control scheme. The spectrograph will operate at a mid-range temperature of 180K, approximately half
way between room temperature and liquid nitrogen temperature; it will be stable to sub -milli-Kelvin(mK)
levels over a calibration cycle and a few mK over months to years. HPF‟s sensor is a 1.7 micron H2RG
device by Teledyne. The environmental control boundary is a 9 m2 thermal enclosure that completely
surrounds the optical train and produces a near blackbody cavity for all components. A large, pressure -
stabilized liquid nitrogen tank provides the heat sink for the system via thermal straps while a multichannel
resistive heater control system provides the stabilizing heat source. High efficiency multi-layer
insulation blanketing provides the outermost boundary of the thermal enclosure to largely isolate the
environmental system from ambient conditions. The cryostat, a stainless steel shell derived from the
APOGEE design, surrounds the thermal enclosure and provides a stable, high quality vacuum environment.
The full instrument will be housed in a passive „meat -locker‟ enclosure to add a degree of additional
thermal stability and as well as protect the instrument. Effectiveness of this approach is being empirically
demonstrated via long duration scale model testing. The full scale cryostat and environmental control
system are being constructed for a 2016 delivery of the instrument to the Hobby-Eberly Telescope. This
report describes the configuration of the hardware and the scale-model test results as well as projections for
performance of the full system.
Concept study for DREAMS: a Dedicated Robotic EArths-finding single-Mode Spectrograph
Show abstract
The detection of Earth twins with the radial velocity (RV) method requires extreme Doppler precision and long term stability. One of the limiting factors in RV precision is the variation of the instrumental response due primarily to guiding errors, changes in focus or seeing. In order to provide extreme stability, we propose to use single-mode fibers to couple small amateur telescopes to a compact and ultra-stable high-resolution spectrograph. Here, we present a concept study for DREAMS, a Dedicated Robotic EArths-finding single-Mode Spectrograph, which should allow unprecedented RV precision on very bright stars.
Characterizing U-Ne hollow cathode lamps at near-IR wavelengths for the CARMENES survey
Show abstract
Hollow cathode lamps of U and Th are the standard frequency calibrators in astronomical spectrographs. In an effort to
optimize precision radial velocity measurements at near-IR wavelengths for the CARMENES survey, we are
characterizing 12 commercial U-Ne hollow cathode lamps using a high resolution Fourier Transform Spectrograph and
an InGaAs detector to analyze the wavelength range between 950 and 1700 nm. We have recorded spectral atlases of UNe
operated at 8, 10 and 12 mA, which are typical values used at astronomical observatories in order to maximize lamp
lifetimes. In addition to the spectral atlas, we analyze properties like warm-up times, average intensities from lines of
different elements, positions and the width of emission lines, and blends. None of our lamps show strong peculiarities in
the spectra or significant contamination. The identification of the uranium lines is based on the line widths and consistent
with the Redman et al. (2011) catalog. Our line list can add a significant number of lines particularly in the range around
9000 cm-1 (1.1 μm) where the catalog is incomplete because of limited detector sensitivity. We are able to identify the elements emitting additional lines by measuring the line width. The increased number of U lines at wavelengths relevant
to radial velocity surveys can yield a significant improvement in the accuracy of radial velocity measurements.
Gemini planet imager observational calibrations VIII: characterization and role of satellite spots
Show abstract
The Gemini Planet Imager (GPI) combines extreme adaptive optics, an integral field spectrograph, and a high performance coronagraph to directly image extrasolar planets in the near-infrared. Because the coronagraph blocks most of the light from the star, it prevents the properties of the host star from being measured directly. Instead, satellite spots, which are created by diffraction from a square grid in the pupil plane, can be used to locate the star and extract its spectrum. We describe the techniques implemented into the GPI Data Reduction Pipeline to measure the properties of the satellite spots and discuss the precision of the reconstructed astrometry and spectrophotometry of the occulted star. We find the astrometric precision of the satellite spots in an H-band datacube to be 0.05 pixels and is best when individual satellite spots have a signal to noise ratio (SNR) of > 20. In regards to satellite spot spectrophotometry, we find that the total flux from the satellite spots is stable to
~7% and scales linearly with central star brightness and that the shape of the satellite spot spectrum varies on
the 2% level.
MASCARA: opto-mechanical design and integration
Show abstract
MASCARA, the Multi-site All-Sky CAmeRA, consists of several fully-automated stations. Its goal is to find exoplanets transiting the brightest stars, in the mV = 4 to 8 magnitude range. Each station contains five wide- angle cameras monitoring the near-entire sky at each location. The five cameras are located in a temperature- controlled enclosure and look at the sky through five windows. A housing with a moving roof protects MASCARA from the environment. Here, we present the opto-mechanical design of the first MASCARA station.
Study on a multi-delay spectral interferometry for stellar radial velocity measurement
Show abstract
High accuracy radial velocity measurement isn’t only one of the most important methods for detecting earth-like
Exoplanets, but also one of the main developing fields of astronomical observation technologies in future. Externally
dispersed interferometry (EDI) generates a kind of particular interference spectrum through combining a fixed-delay
interferometer with a medium-resolution spectrograph. It effectively enhances radial velocity measuring accuracy by
several times. Another further study on multi-delay interferometry was gradually developed after observation success
with only a fixed-delay, and its relative instrumentation makes more impressive performance in near Infrared band.
Multi-delay is capable of giving wider coverage from low to high frequency in Fourier field so that gives a higher
accuracy in radial velocity measurement. To study on this new technology and verify its feasibility at Guo Shoujing
telescope (LAMOST), an experimental instrumentation with single fixed-delay named MESSI has been built and tested
at our lab. Another experimental study on multi-delay spectral interferometry given here is being done as well. Basically,
this multi-delay experimental system is designed in according to the similar instrument named TEDI at Palomar
observatory and the preliminary test result of MESSI. Due to existence of LAMOST spectrograph at lab, a multi-delay
interferometer design actually dominates our work. It’s generally composed of three parts, respectively science optics,
phase-stabilizing optics and delay-calibrating optics. To switch different fixed delays smoothly during observation, the
delay-calibrating optics is possibly useful to get high repeatability during switching motion through polychromatic
interferometry. Although this metrology is based on white light interferometry in theory, it’s different that integrates all
of interference signals independently obtained by different monochromatic light in order to avoid dispersion error caused
by broad band in big optical path difference (OPD).
Test of multi-object exoplanet search spectral interferometer
Show abstract
Exoplanet detection, a highlight in the current astronomy, will be part of puzzle in astronomical and astrophysical future,
which contains dark energy, dark matter, early universe, black hole, galactic evolution and so on. At present, most of the
detected Exoplanets are confirmed through methods of radial velocity and transit. Guo shoujing Telescope well known
as LAMOST is an advanced multi-object spectral survey telescope equipped with 4000 fibers and 16 low resolution fiber
spectrographs. To explore its potential in different astronomical activities, a new radial velocity method named
Externally Dispersed Interferometry (EDI) is applied to serve Exoplanet detection through combining a fixed-delay
interferometer with the existing spectrograph in medium spectral resolution mode (R=5,000-10,000). This new
technology has an impressive feature to enhance radial velocity measuring accuracy of the existing spectrograph through
installing a fixed-delay interferometer in front of spectrograph. This way produces an interference spectrum with higher
sensitivity to Doppler Effect by interference phase and fixed delay. This relative system named Multi-object Exoplanet
Search Spectral Interferometer (MESSI) is composed of a few parts, including a pair of multi-fiber coupling sockets, a
remote control iodine subsystem, a multi-object fixed delay interferometer and the existing spectrograph. It covers from
500 to 550 nm and simultaneously observes up to 21 stars. Even if it’s an experimental instrument at present, it’s still
well demonstrated in paper that how MESSI does explore an effective way to build its own system under the existing
condition of LAMOST and get its expected performance for multi-object Exoplanet detection, especially instrument
stability and its special data reduction. As a result of test at lab, inside temperature of its instrumental chamber is stable
in a range of ±0.5degree Celsius within 12 hours, and the direct instrumental stability without further observation
correction is equivalent to be ±50m/s every 20mins.
Diffraction-limited lucky imaging with a 12" commercial telescope
Show abstract
Here we demonstrate a novel lucky imaging camera which is designed to produce diffraction-limited imaging using
small telescopes similar to ones used by many academic institutions for outreach and/or student training. We
present a design that uses a Meade 12” SCT paired with an Andor iXon fast readout EMCCD. The PSF of the
telescope is matched to the pixel size of the EMCCD by adding a simple, custom-fabricated, intervening optical
system. We demonstrate performance of the system by observing both astronomical and terrestrial targets. The
astronomical application requires simpler data reconstruction techniques as compared to the terrestrial case. We
compare different lucky imaging registration and reconstruction algorithms for use with this imager for both
astronomical and terrestrial targets. We also demonstrate how this type of instrument would be useful for both
undergraduate and graduate student training. As an instructional aide, the instrument can provide a hands-on
approach for teaching instrument design, standard data reduction techniques, lucky imaging data processing,
and high resolution imaging concepts.
Archon: A modern controller for high performance astronomical CCDs
Show abstract
The rapid evolution of commercial FPGAs and analog ICs has enabled the development of Archon, a new modular high
performance astronomical CCD controller. CCD outputs are digitized by 16-bit 100 MHz ADCs with differential AC-coupled
preamplifiers. The raw data stream from an ADC can be stored in parallel with standard image data into three
onboard 512 MB frame buffers. Pixel values are computed using digital correlated double sampling. At low pixel rates
(< 1 MHz), the dynamic range achievable by averaging hundreds of ADC samples per pixel can exceed 16 bits, so an
option to store 32 bits per pixel is provided. CCD clocks are generated by 14-bit 100 MHz DACs. The scripted timing
core driving the clocks can generate a new target voltage for each clock every 10 ns, and the clock slew rates are
individually programmable. CCD biases are derived from 16-bit DACs, are continuously monitored for voltage and
current, and power up and down in a customizable sequence. Communication between the controller and a host
computer occurs over a gigabit Ethernet interface (fiber or copper). A CCD configuration is specified by a simple text
file. Together, these features simplify the tuning and debugging of scientific CCDs, and enable CCD-limited imaging. I
present details of the controller architecture, examples of CCD tuning, and measured performance data of the controller
alone (dynamic range of 108 dB at 100 kHz and 98 dB at 1 MHz) and in combination with an STA1600LN CCD.
Near field modal noise reduction using annealed optical fiber
Show abstract
Incomplete and unstable mode population has long complicated the application of optical fiber for transferring star and
calibration light to high precision spectrographs. The need for improved precision calibrators in support of radial velocity
planet surveys has led to the introduction of coherent wavelengths sources using single mode fibers that are then coupled
into multi-mode fibers, further exacerbating this problem. We explore mode scrambling in annealed optical fiber with and
without agitation, as compared to that obtained using octagonal fiber and using an integrating sphere. We observe
improved scrambling with annealed fibers compared to conventional and octagonal fibers.
Control and operation of the 1.6 m New Solar Telescope in Big Bear
Show abstract
The 1.6m New Solar Telescope (NST) has developed a modern and comprehensive suite of instruments which allow high resolution observations of the Sun. The current instrument package comprises diffraction limited imaging, spectroscopic and polarimetric instruments covering the wavelength range from 0.4 to 5.0 microns. The instruments include broadband imaging, visible and near-infrared scanning Fabry-Perot interferometers, an imaging spectropolarimeter, a fast visible-light imaging spectrograph, and a unique new scanning cryogenic infrared spectrometer/spectropolarimeter that is nearing completion. Most instruments are operated with a 308 subaperture adaptive optics system, while the thermal-IR spectrometer has a correlation tracker. This paper reports on the current observational programs and operational performance of the telescope and instrumentation. The current control, data processing, and archiving systems are also briefly discussed.
DigiCam: fully digital compact camera for SST-1M telescope
J. A. Aguilar,
W. Bilnik,
L. Bogacz,
et al.
Show abstract
The single mirror Small Size Telescopes (SST-1M), being built by a sub-consortium of Polish and Swiss Institutions of
the CTA Consortium, will be equipped with a fully digital camera with a compact photodetector plane based on silicon
photomultipliers. The internal trigger signal transmission overhead will be kept at low level by introducing a high level
of integration. It will be achieved by massively deploying state-of-the-art multi-gigabit transceivers, beginning from the
ADC flash converters, through the internal data and trigger signals transmission over backplanes and cables, to the
camera’s server 10Gb/s Ethernet links. Such approach will allow fitting the size and weight of the camera exactly to the
SST-1M needs, still retaining the flexibility of a fully digital design. Such solution has low power consumption, high
reliability and long lifetime. The concept of the camera will be described, along with some construction details and
performance results.
Wavelength calibration from 1-5μm for the CRIRES+ high-resolution spectrograph at the VLT
Show abstract
CRIRES at the VLT is one of the few adaptive optics enabled instruments that offer a resolving power of 105 from 1 − 5 μm. An instrument upgrade (CRIRES+) is proposed to implement cross-dispersion capabilities, spectro-polarimetry modes, a new detector mosaic, and a new gas absorption cell. CRIRES+ will boost the simultaneous wavelength coverage of the current instrument (~ γ/70 in a single-order) by a factor of 10 in the cross-dispersed configuration, while still retaining a ~> 10 arcsec slit suitable for long-slit spectroscopy. CRIRES+ dramatically enhances the instrument’s observing efficiency, and opens new scientific opportunities. These include high-precision radial-velocity studies on the 3 m/s level to characterize extra-solar planets and their athmospheres, which demand for specialized, highly accurate wavelength calibration techniques. In this paper, we present a newly developed absorption gas-cell to enable high-precision wavelength calibration for CRIRES+. We also discuss the strategies and developments to cover the full operational spectral range (1 − 5 μµm), employing cathode emission lamps, Fabry-Perot etalons, and absorption gas-cells.
Characterization of new components for a miniaturized heterodyne infrared spectrometer
Show abstract
We report on the development and testing of the building blocks of a possible compact heterodyne setup in the mid-infrared,
which becomes particularly relevant for flight instrumentation. The local oscillator is a Quantum Cascade Laser
(QCL) source at 8.6 μm operable at room temperature. The beam combination of the source signal and the local
oscillator will occur by means of integrated optics for the 10 μm range, which was characterized in the lab. In addition
we investigate the use of superlattice detectors in a heterodyne instrument. This work shows that these different new
components can become valuable tools for a compact heterodyne setup.
MUSE from Europe to the Chilean Sky
Show abstract
MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument, built for ESO (European Southern
Observatory) and dedicated to the VLT (Very Large Telescope). This instrument is an innovative integral field
spectrograph (1x1 arcmin2 Field of View), operating in the visible wavelength range, from 465 nm to 930 nm. The
MUSE project is supported by a European consortium of 7 institutes.
After the finalisation of its integration and test in Europe validated by its Preliminary Acceptance in Europe, the MUSE
instrument has been partially dismounted and shipped to the VLT (Very Large Telescope) in Chile. From October 2013
till February 2014, it has then been reassembled, tested and finally installed on the telescope its final home. From there
it will collect its first photons coming from the outer limit of the visible universe.
To come to this achievement, many tasks had to be completed and challenges overcome. These last steps in the project
life have certainly been ones of the most critical. Critical in terms of risk, of working conditions, of operational
constrains, of schedule and finally critical in terms of outcome: The first light and the final performances of the
instrument on the sky.
Spectrophotometric calibration of the Swope and duPont telescopes for the Carnegie supernova project 2
Show abstract
We present results from the spectrophotometric calibration of the new E2V CCD camera on the Swope telescope and of
RetroCam on the DuPont Telescope. We measured the relative sensitivity of each pixel vs wavelength over the whole
wavelength sensitivity range of each camera, for all the filters that will be used during the 5 years of the CSP2 survey. We
used a tunable light source and fiber delivery system conceived and built in our lab to achieve +/-1% precision calibration
from 300nm to 1100nm and +/-3% from 1100nm to 1800nm. Achieving this relatively high precision at low light levels
was made possible by using Si, Ge and InGaAs photodiodes coupled to custom high gain amplifiers. Comparison of these
results to results obtained 3 years before, allowed us to confirm that the intrinsic transmission bandpass of the filters has
not changed over time but that the mirror reflectivity and the introduction of a new CCD camera drastically changed the
total telescope sensitivity. The analysis of the spatial response of the new E2V CCD vs wavelength also shows a slight
gradient in the color response of the CCD both in the UV and Infrared.
Poster Session: Survey and High Multiplex Instruments
Fibre system of DESI
Show abstract
We describe the fiber system of the Dark Energy Spectroscopic Instrument (DESI). Its primary science goal is to provide
a survey of 14,000 square degrees of the extragalactic sky using the Mayall 4m telescope in five years. The fibre system
will provide a multiplex gain of 5000 so that more than 20 million galaxies can surveyed. Applying a number of tests to
the survey dataset should allow the evolution of the equation of state of the universe to be determined to greater accuracy
than before. The fibre system will provide a multiplex gain of 5000 with very high levels of performance.
MEGARA fiber bundles
Show abstract
MEGARA (Multi Espectrógrafo en GTC de Alta Resolución para Astronomía) is the future optical Integral-Field Unit
(IFU) and Multi-Object Spectrograph (MOS) for the 10.4-m Gran Telescopio CANARIAS (GTC). MEGARA has three
different fiber bundles, the Large Central Bundle covering 12.5 arcsec x 11.3 arcsec on sky, the Small Compact Bundle,
of 8.5 arcsec x 6.7 arcsec, and a Fiber MOS positioner system that is able to place up to 100 mini-bundles with 7 fibers
each in MOS configuration within a 3.5 arcmin x 3.5 arcmin FOV. The MEGARA focal plane subsystems are located at
one of the GTC Folded Cassegrain focal stations. A field lens provides a telecentric focal plane, where the fibers are
located. Micro-lenses arrays couple the telescope beam to the collimator focal ratio at the entrance of the fibers. Finally,
the fibers, organized in bundles conducted the light from the focal plane to the pseudo-slit plates at the entrance of the
MEGARA spectrograph, which shall be located at one of the Nasmyth platforms. This article also summarizes the
prototypes already done and describes the set-up that shall be used to integrate fibers and micro-lens and characterize the
fiber bundles.
Wednesday Plenary Session
Highlights from the Multi Unit Spectroscopic Explorer (MUSE): a 2nd generation VLT instrument for the VLT (Presentation Video)
Show abstract
The Multi Unit Spectroscopic Explorer (MUSE) is a second-generation VLT panoramic integral-field spectrograph. The instrument has been designed to take advantage of the VLT ground layer adaptive optics ESO facility using four laser guide stars. MUSE couples the discovery potential of a large imaging device to the measuring capabilities of a high-quality spectrograph, while taking advantage of the increased spatial resolution provided by adaptive optics. The MUSE hardware is composed of 24 identical modules, each one consisting of an advanced slicer, a spectrograph and a (4k)² detector. A series of fore-optics and splitting and relay optics is in charge of derotating and partitioning the square field of view into 24 sub-fields. With its almost 7 tons of opto-mechanics, MUSE is one of the biggest integral field unit ever built. After a successful preliminary acceptance in Europe in fall 2013, MUSE has been dismounted, shipped to Chile and re-integrated in the Paranal new integration hall and finally installed on the Nasmyth platform of UT4 late January this year. During the 2 commissioning runs, hundreds of millions of spectra have been obtained in order to validate the instrument and measured its achieved performance. To demonstrate its power, a number of show-case and spectacular observations have also been obtained. Preliminary results demonstrate that MUSE is likely to become a new reference in the field of integral field spectroscopy thanks to its large field of view, very high throughput, excellent image quality, good spectral resolution, wide simultaneous spectral range and state-of-the art control and data reduction software. I will review this success story, from the call of idea to the deployment on the VLT, including the latest performances and showcase observations.
Poster Session: Survey and High Multiplex Instruments
Prime focus instrument of prime focus spectrograph for Subaru telescope
Show abstract
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph design for the prime focus
of the 8.2m Subaru telescope. PFS will cover 1.3 degree diameter field with 2394 fibers to complement the imaging
capability of Hyper SuprimeCam (HSC). The prime focus unit of PFS called Prime Focus Instrument (PFI) provides the
interface with the top structure of Subaru telescope and also accommodates the optical bench in which Cobra fiber
positioners are located. In addition, the acquisition and guiding (AG) cameras, the optical fiber positioner system, the
cable wrapper, the fiducial fibers, illuminator, and viewer, the field element, and the telemetry system are located inside
the PFI. The mechanical structure of the PFI was designed with special care such that its deflections sufficiently match
those of the HSC’s Wide Field Corrector (WFC) so the fibers will stay on targets over the course of the observations
within the required accuracy.
MEGARA main optics opto-mechanics
Show abstract
MEGARA is the future integral-field and multi-object spectrograph for the GTC 10.4m telescope located in the
Observatorio del Roque de los Muchachos in La Palma. INAOE is a member of the MEGARA Consortium and it is
in charge of the Optics Manufacturing work package. In addition to the manufacturing of 73 elements, the work
package includes the opto-mechanics i.e. the opto-mechanical design, manufacture, tests and integration of the
complete assembly of the main optics composed by the collimator and camera subsystems. MEGARA passed the
Optics Detailed Design Review in May 2013 and will have the Detailed Design Review of the complete instrument
early 2014. Here we describe the detailed design of the collimator and camera barrels. We also present the finite
elements models developed to simulate the behavior of the barrel, sub-cells and other mechanical elements. These
models verify that the expected stress fields and the gravitational displacements on the lenses are compatible with
the optical quality tolerances. The design is finished and ready for fabrication.
Metrology camera system of prime focus spectrograph for Subaru telescope
Show abstract
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber spectrograph designed for the prime
focus of the 8.2m Subaru telescope. The metrology camera system of PFS serves as the optical encoder of the COBRA
fiber motors for the configuring of fibers. The 380mm diameter aperture metrology camera will locate at the Cassegrain
focus of Subaru telescope to cover the whole focal plane with one 50M pixel Canon CMOS sensor. The metrology
camera is designed to provide the fiber position information within 5μm error over the 45cm focal plane. The positions
of all fibers can be obtained within 1s after the exposure is finished. This enables the overall fiber configuration to be
less than 2 minutes.
Multiplexed astronomical images: advantages, method, and prototype instrument
Sagi Ben-Ami,
Barak Zackay,
Adam Rubin,
et al.
Show abstract
In some optical systems in which a large field of view (and hence a large detector) is required, it is the detector which drives the total system cost. We propose a concept, and demonstrate an optical system, for an astronomical multiplexer. The instrument projects different portions of the telescope focal plane into a single (possibly) small detector without changing the original plate scale of the image. The resulting image is a superposition of the different portions of the field of view. Since in most cases astronomical images are sparse, photometric measurements can be done directly on the combined images for most objects in the field. We discuss an outline of the concept of multiplexing, in terms of its signal-to-noise properties, and multiplexed image reconstruction algorithm. Furthermore, we present an optical design for an astronomical multiplexer we recently constructed along with some first light images.
BOMBOLO: A 3-arms optical imager for SOAR Observatory
Show abstract
BOMBOLO is a new multi-passband visitor instrument for the SOAR observatory. It is a three-arm imager covering the
near-UV and optical wavelengths. The three arms work simultaneously and independently, providing synchronized
imaging capability for rapid astronomical events. BOMBOLO leading science cases are: 1) Simultaneous Multiband
Flickering Studies of Accretion Phenomena; 2) Near UV/Optical Diagnostics of Stellar Evolutionary Phases; 3)
Exoplanetary Transits; 4) Microlensing Follow-Up and 5) Solar Systems Studies. The instrument is at the Conceptual
Design stage, having been approved by the SOAR Board of Directors as a visitor instrument in 2012 and having been
granted full funding from CONICYT, the Chilean State Agency of Research, in 2013. The Design Phase has begun and
will be completed in late 2014, followed by a construction phase in 2015 and 2016A, with expected Commissioning in
2016B and 2017A.
MMP: multi mini prism device for ESPRESSO APSU, prototyping, and integration
Show abstract
The multiprism device is a crucial component of the Espresso Anamorphic pupil Slicer (APSU). At the end of the slicer,
is necessary to differently fold each field to correctly illuminate the echelle. The solution is made by gluing cylindrical
prisms with proper bending low angle onto a support double plate silica window. We present here the integrated robotic
system conceived to reach the required tolerances in term of alignment and Integration. It consist in a tip tilt stage to
select the folding angle, coupled to an x-y stage to position the elements and a z axis to perform the gluing.
Keywords: Extra-solar Planet Atmospheres, High Resolution Spectroscopy, Espresso, front End
Volume phase holographic gratings for the Subaru Prime Focus Spectrograph: performance measurements of the prototype grating set
Show abstract
The Prime Focus Spectrograph (PFS) is a major instrument under development for the 8.2 m Subaru telescope on Mauna Kea. Four identical, fixed spectrograph modules are located in a room above one Nasmyth focus. A 55 m fiber optic cable feeds light into the spectrographs from a robotic fiber positioner mounted at the telescope prime focus, behind the wide field corrector developed for Hyper Suprime-Cam. The positioner contains 2400 fibers and covers a 1.3 degree hexagonal field of view. Each spectrograph module will be capable of simultaneously acquiring 600 spectra.
The spectrograph optical design consists of a Schmidt collimator, two dichroic beamsplitters to separate the light into three channels, and for each channel a volume phase holographic (VPH) grating and a dual- corrector, modified Schmidt reimaging camera. This design provides a 275 mm collimated beam diameter, wide simultaneous wavelength coverage from 380 nm to 1.26 µm, and good imaging performance at the fast f/1.1 focal ratio required from the cameras to avoid oversampling the fibers. The three channels are designated as the blue, red, and near-infrared (NIR), and cover the bandpasses 380–650 nm (blue), 630–970 nm (red), and 0.94–1.26 µm
(NIR). A mosaic of two Hamamatsu 2k×4k, 15 µm pixel CCDs records the spectra in the blue and red channels, while the NIR channel employs a 4k×4k, substrate-removed HAWAII-4RG array from Teledyne, with 15 µm pixels and a 1.7 µm wavelength cutoff.
VPH gratings have become the dispersing element of choice for moderate-resolution astronomical spectro- graphs due their potential for very high diffraction efficiency, low scattered light, and the more compact instru- ment designs offered by transmissive dispersers. High quality VPH gratings are now routinely being produced in the sizes required for instruments on large telescopes. These factors made VPH gratings an obvious choice for PFS. In order to reduce risk to the project, as well as fully exploit the performance potential of this technology, a set of three prototype VPH gratings (one each of the blue, red, and NIR designs) was ordered and has been recently delivered. The goal for these prototype units, but not a requirement, was to meet the specifications for the final gratings in order to serve as spares and also as early demonstration and integration articles. In this paper we present the design and specifications for the PFS gratings, the plan and setups used for testing both the prototype and final gratings, and results from recent optical testing of the prototype grating set.
Integration and test activities for the SUMIRE prime focus spectrograph at LAM
Show abstract
The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project for Subaru
telescope consists in four identical spectrographs feed by 600 fibers each. Each spectrograph is composed by an optical
entrance unit that creates a collimated beam and distributes the light to three channels, two visible and one near infrared.
We present here the integration process of the first spectrograph channel.
The verification requirements, the specific integration requirements and the product tree are the main drivers from the
top plan for the Assembly Integration and Test (AIT) development process. We then present the AIT flow-down, the
details for the AIT processes as well as opto-mechanical alignment procedures and tests setup.
In parallel, we are developing and validating dedicated tools to secure and facilitate the AIT activities, as we have to
assemble eight visible cameras, integrate and align four fiber slits, integrate and align the components of four
spectrographs.
Efficient and affordable catadioptric spectrograph designs for 4MOST and Hector
Show abstract
Spectrograph costs have become the limiting factor in multiplexed fiber-based spectroscopic instruments, because tens of
millions of resolution elements (spectral x spatial) are now required. Catadioptric (Schmidt-like) designs allow faster
cameras and hence reduced detector costs, and recent advances in aspheric lens production make the overall optics costs
competitive with transmissive designs. Classic Schmidt designs suffer from obstruction losses caused by the detector
being within the beam. A new catadioptric design puts the detector close to the spectrograph pupil, and hence largely in
the shadow of the telescope top-end obstruction. The throughput is competitive with the best transmissive designs, and
much better in the Blue, where it is usually most valuable. The design also has milder aspheres and is more compact than
classic Schmidts, and avoids most of their operational difficulties.
The fast cameras mean that with 15micron pixels, the PSF sampling is close to the Nyquist limit; this minimises the
effects of read-noise, which for sky-limited observations, far outweighs any difference in throughput. It does introduce
pixellation penalties; these are investigated and found to be modest.
For 4MOST, low and high resolution designs are presented, with 300mm beams, 3 arms with f/1.3 cameras, and standard
61mm x 61mm detectors. Coverage is 380-930nm at R=5000-7000, or R~20000 in three smaller ranges. A switchable
design is also presented. For Hector, a design is presented with 2 arms, 380-930nm coverage, and R=3000-4500; a 4-
armed design with smaller beam-size and detectors is also presented. The designs are costed, and appear to represent
excellent value.
Current status of the spectrograph system for the SuMIRe/PFS
Show abstract
The Prime Focus Spectrograph (PFS) is a new facility instrument for Subaru Telescope which will be installed in around
2017. It is a multi-object spectrograph fed by about 2400 fibers placed at the prime focus covering a hexagonal field-ofview
with 1.35 deg diagonals and capable of simultaneously obtaining data of spectra with wavelengths ranging from
0.38 um to 1.26 um.
The spectrograph system is composed of four identical modules each receiving the light from 600 fibers. Each module
incorporates three channels covering the wavelength ranges 0.38–0.65 mu (“Blue”), 0.63–0.97 mu (“Red”), and 0.94–
1.26 mu (“NIR”) respectively; with resolving power which progresses fairly smoothly from about 2000 in the blue to
about 4000 in the infrared. An additional spectral mode allows reaching a spectral resolution of 5000 at 0.8mu (red). The
proposed optical design is based on a Schmidt collimator facing three Schmidt cameras (one per spectral channel). This
architecture is very robust, well known and documented. It allows for high image quality with only few simple elements
(high throughput) at the expense of the central obscuration, which leads to larger optics.
Each module has to be modular in its design to allow for integration and tests and for its safe transport up to the
telescope: this is the main driver for the mechanical design. In particular, each module will be firstly fully integrated and
validated at LAM (France) before it is shipped to Hawaii. All sub-assemblies will be indexed on the bench to allow for
their accurate repositioning.
This paper will give an overview of the spectrograph system which has successfully passed the Critical Design Review
(CDR) in 2014 March and which is now in the construction phase.
Focal ratio degradation performance of fiber positioning technology used in the Dark Energy Spectroscopic Instrument (DESI)
Show abstract
The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment and will be used to conduct a five year survey covering 14,000 deg2 to z=3.5. This survey is accomplished using five thousand robotically positioned optical fibers that can be quickly reconfigured with a 5 μm positioning accuracy. The fiber performance in the near and far field of two types of robotic positioners are currently being investigated: tilting spine mechanical simulators and eccentric axis (or θ-φ) positioners. The far field performance of the fiber is important since the instrument efficiency is adversely affected if light from the fibers enters the spectrograph at a faster focal ratio than the spectrograph can accept (f/3.57 in the DESI design). This degradation of the focal ratio of light is caused by light entering the fiber off axis (tiliting positioner) or bending, twisting, and stress of the fiber (eccentric axis) positioner. The stability of the near field intensity distribution of the fiber is important since this determines the spectrograph point spread function (PSF). If the PSF changes from the calibration to the science exposures, this will result in an extraction bias. For DESI, a particular concern is the distortions in the PSF due to movement of the fibers during
re-pointing.
Virtual MOONS: a focal plane simulator for the MOONS thousand-fiber NIR spectrograph
Show abstract
MOONS will be the next near infrared fiber fed multi-object spectrograph for the Very Large Telescope, that will offer a
one thousand multiplexing capability and a simultaneous coverage of the wavelength range from 0.8 to 1.8 μm.
With the aim of quantitatively i) assessing the instrument performances with respect to sensitivity and OH subtraction, ii)
blind-testing the 1D spectra extraction and calibration, provided by the data reduction pipeline, and iii) testing the
technical solutions adopted for reaching the outstanding instrument requirements, we have developed “Virtual
MOONS”, an end-to-end software simulator, which quantitatively computes high fidelity focal plane raw images,
emulating the output of the detector electronics.
Starting from an ideal photon image derived from the geometrical optics propagation and Point Spread Function (PSF)
variations computed by the ZEMAX optical design, the end-to-end optical budget is introduced along with the stray light
contributions, resulting in the expected photon counts impinging the detector pixels. Then the photon image plus photon
noise is converted to digital counts by means of a detailed detector simulation, including pixel-to-pixel response
variation, dark, bias, read-out noise, cosmetics, charge diffusion, flatness and read-out schemes. Critical points like fiber
differential response, PSF haloes and sky emission variations have been also taken into account.
The current status of this work is presented with an example simulated image and numerical results.
Design and performance of a F/#-conversion microlens for prime focus spectrograph at Subaru Telescope
Show abstract
The PFS is a multi-object spectrograph fed by 2394 fibers at the prime focus of Subaru telescope. Since the F/# at the prime focus is too fast for the spectrograph, we designed a small concave-plano negative lens to be attached to the tip of each fiber that converts the telescope beam (F/2.2) to F/2.8. We optimized the lens to maximize the number of rays that can be confined inside F/2.8 while maintaining a 1.28 magnification. The microlenses are manufactured by glass molding, and an ultra-broadband AR coating (<1.5% for λ = 0.38 - 1.26μm) will be applied to the front surface.
Preliminary results on the characterization and performances of ZBLAN fiber for infrared spectrographs
Show abstract
Present telescopes and future extremely large telescopes make use of fiber-fed spectrographs to observe at optical and
infrared wavelengths. The use of fibers largely simplifies the interfacing of the spectrograph to the telescope. At a high
spectral resolution (R>50,000) the fibers can be used to achieve very high spectral accuracy.
GIANO is an infrared (0.95-2.5μm) high resolution (R=50,000) spectrometer[1] [2] [3] that was recently commissioned
at the TNG telescope (La Palma). This instrument was designed and built for direct feeding from the telescope [4].
However, due to constraints imposed on the telescope interfacing during the pre-commissioning phase, it had to be
positioned on the rotating building, far from the telescope focus. Therefore, a new interface to the telescope, based on
IR-transmitting ZBLAN fibers with 85μm core, was developed.
In this article we report the first, preliminary results of the effects of these fibers on the quality of the recorded spectra
with GIANO and with a similar spectrograph that we set-up in the laboratory. The effects can be primarily associated to
modal-noise (MN) that, in GIANO, is much more evident than in optical spectrometers, because of the much longer
wavelengths.
The hardware control system for WEAVE at the William Herschel telescope
Show abstract
This work describes the hardware control system of the Prime Focus Corrector (PFC) and the Spectrograph, two of the
main parts of WEAVE, a multi-object fiber spectrograph for the WHT Telescope. The PFC and Spectrograph control
system hardware is based on the Allen Bradley’s Programmable Automation Controller and its modules. Mechanisms,
sensors and actuators of both systems are summarized and their functionality described, showing how they meet the
instrument requirements.
4MOST fiber feed concept design
Show abstract
4MOST, the 4m Multi-Object Spectroscopic Telescope, features a 2.5 degree diameter field-of-view with ~2400 fibers in
the focal plane that are configured by a fiber positioner based on the tilting spine principle (Echidna/FMOS) arranged in
a hexagonal pattern. The fibers feed two types of spectrographs; ~1600 fibers go to two spectrographs with resolution
R>5000 and ~800 fibers to a spectrograph with R>18,000. Part of the ongoing optimization of the fiber feed subsystem
design includes early prototyping and testing of key components such as fiber connectors and fiber cable management.
Performance data from this testing will be used in the 4MOST instrument simulator (TOAD) and 4MOST system design
optimization. In this paper we give an overview of the current fiber feed subsystem design, simulations and prototyping
plans.
Scrambling and modal noise mitigation in the Habitable Zone Planet Finder fiber feed
Show abstract
We present the baseline fiber feed design for the Habitable-zone Planet Finder (HPF), a precision radial velocity (RV) spectrograph designed to detect Earth analogs around M-dwarfs. HPF is a stabilized, fiber-fed, R∼50,000
spectrograph operating in the near-infrared (NIR) from 0.82 to 1.3 µm, and will be deployed on the Hobby- Eberly Telescope (HET) in Texas. While the essential function of the optical fibers is to deliver high throughput, this mode of light transport also provides the opportunity to introduce radial and azimuthal scrambling, which boosts instrument stability and thereby RV precision. Based on the unique requirements of HPF on the HET, we present initial tests showing very high scrambling gains via a compact scrambler in conjunction with octagonal fibers. Conversely, the propagation of light through the fibers injects modal noise, which can limit achievable RV precision. Laboratory tests of a custom-built mechanical agitator show significant gains over a static fiber feed. Overall, the fiber feed is designed to provide high relative throughput, excellent scrambling, and reliable modal noise suppression. We will also attempt to minimize focal ratio degradation (FRD) to the extent possible with the chosen configuration. HPF inculcates several other new technologies developed by the Penn State Optical-Infrared instrumentation group, including a rigorous calibration system, which are discussed separately in these proceedings.
Development of a new readout system for the near-infrared detector of HONIR
Show abstract
We developed a new readout system for the near-infrared detector VIRGO-2K (2kx2k HgCdTe array) installed in the optical-infrared simultaneous camera, HONIR, for the 1.5 m Kanata telescope at Higashi-Hiroshima observatory. The main goal of this development is to read out one frame within ~ 1 second through 16 output readout mode of the detector, in order to reduce the overhead time per exposure. The system is based on a CCD controller, Kiso Array Controller (KAC). We redesigned the analog part of KAC to fit VIRGO-2K. We employed a fully differential input circuit and a third order Bessel low-pass filter for noise reduction and a constant current system to improve the linearity of the detector. We set the cutoff frequency of the Bessel low-pass filter at the readout clock rate (120 kHz). We also set the constant current at 200 μA according to the data sheet of VIRGO-2K. We tested the new readout system at room temperature and confirmed that the low-pass filter works well as designed. The fluctuation of the current level of the constant current system is less than 2% for the typical output voltage range of VIRGO-2K (3.2-4.4 V). We measured the readout noise caused by the new readout system (connected to cooled multiplexer) and found that it is 30-40 μV rms, being comparable to or slightly higher than the typical readout noise of VIRGO-2K, ∼ 37 μV rms.
Okayama astrophysical observatory wide field camera
Show abstract
Okayama Astrophysical Observatory Wide Field Camera: OAOWFC is a near-infrared (0.9-2.5 μm) survey telescope, whose aperture is 0.91m. It works at Y, J, H, and Ks bands. The optics are consisted of forward Cassegrain and quasi Schmidt which yield the image circle of Φ 52 mm or Φ 1.3 deg at the focal plane. The overall F-ratio is F/2.51 which is one of the fastest among near infrared imagers in the world. A HAWAII-1 detector array placed at the focal plane cuts the central 0.48 deg. x 0.48 deg. with a pixel scale of 1.67 arcsec/pix. It will be used to survey the Galactic plane for variability and search for transients such as Gamma-ray burst afterglows optical counterpart of gravitational wave sources.
Polarization properties of a birefringent fiber optic image slicer for diffraction-limited dual-beam spectropolarimetry
Show abstract
The birefringent fiber optic image slicer design, or BiFOIS, adapts integral field spectroscopy methods to the special needs of high-sensitivity, spatially-resolved spectropolarimetry. In solar astronomy these methods are of particular importance, as dynamic magnetism lies at the heart of various multi-scaled phenomena in the solar atmosphere. While integral field units (IFU) based on fiber optics have been in continual development for some time, standard stock multimode fibers do not typically preserve polarization. The importance of a birefringent fiber optic IFU design stems from the need for dual-beam spatio-temporal polarimetric modulation to correct for spurious polarization signals induced either by platform jitter or atmospheric seeing. Here we characterize the polarization response of a second generation BiFOIS IFU designed for solar spectropolarimetry. The unit provides 60 × 64 spatial imaging pixels in a densely-packed, high filling factor configuration. Particular attention is placed on the spatial uniformity of the IFU polarization response. Calibrated first-light solar observations are also presented to demonstrate the performance of the device in a real application.
The S4I prototype, a beam-slicer dedicated to the new generation Multichannel Subtractive Double Pass for EST imaging
spectropolarimetry
Frédéric Sayède,
Pierre Mein,
Jean-Marie Malherbe,
et al.
Show abstract
For the future European Solar Telescope (EST) the Observatoire de Paris proposes a new generation of MSDP, an
imaging spectro-polarimetry instrument. To validate this new generation, we develop a plane micro-mirrors beam slicer
prototype that is tested and validated on an optical bench and on existing telescopes.
The prototype called S4I (Spectral Sampling with Slicer for Solar Instrumentation) is built and tested at the Observatoire
de Paris. It validates the opto-mechanical feasibility of the new beam slicer. After a complete description of the system,
we present the first images. We evaluate the performances of the prototype and compare them to the requirements for the
beam-slicer dedicated to the future EST.
The design of the WEAVE spectrograph
Show abstract
WEAVE is the next-generation optical spectroscopy facility for the William Herschel Telescope and aims at
spectroscopic follow-up of ground-based (LOFAR) and space-based (Gaia) surveys. WEAVE places in the re-fitted
prime focus either 1000 fibres, 20 fibre-coupled mini-IFUs or a single large 600 fibre IFU. A spectrograph on the
Nasmyth platform analyses the light and supports, in a single exposure, either R~5,000 observations over the full 366-
975 nm wavelength range or simultaneous R~20,000 observations over two out of three pre-specified bands within this
wavelength range. This paper describes the requirements, optical design and mechanical design of the WEAVE
spectrograph.
The 4MOST instrument concept overview
Show abstract
The 4MOST[1] instrument is a concept for a wide-field, fibre-fed high multiplex spectroscopic instrument facility on the
ESO VISTA telescope designed to perform a massive (initially >25x106 spectra in 5 years) combined all-sky public
survey. The main science drivers are: Gaia follow up of chemo-dynamical structure of the Milky Way, stellar radial
velocities, parameters and abundances, chemical tagging; eROSITA follow up of cosmology with x-ray clusters of
galaxies, X-ray AGN/galaxy evolution to z~5, Galactic X-ray sources and resolving the Galactic edge;
Euclid/LSST/SKA and other survey follow up of Dark Energy, Galaxy evolution and transients. The surveys will be
undertaken simultaneously requiring: highly advanced targeting and scheduling software, also comprehensive data
reduction and analysis tools to produce high-level data products. The instrument will allow simultaneous observations of
~1600 targets at R~5,000 from 390-900nm and ~800 targets at R<18,000 in three channels between ~395-675nm
(channel bandwidth: 45nm blue, 57nm green and 69nm red) over a hexagonal field of view of ~ 4.1 degrees. The initial
5-year 4MOST survey is currently expect to start in 2020. We provide and overview of the 4MOST systems: optomechanical,
control, data management and operations concepts; and initial performance estimates.
Development of a simultaneous two-color near-infrared multi-object spectrograph SWIMS for the TAO 6.5-m telescope
Show abstract
Simultaneous Color Wide-field Infrared Multi-object Spectrograph, SWIMS, is one of the first generation in- struments for the University of Tokyo Atacama Observatory (TAO) 6.5m Telescope now under construction. A dichroic mirror being inserted in the collimated beam, it is capable of two-color simultaneous imaging with FoV
of 9:16φ or R ∼ 1000 multi-object spectroscopy at 0.9–2.5μm wavelength range in one shot, and enables us to
carry out efficient NIR imaging/spectroscopic survey of objects such as distant galaxies and young stellar objects.
All the major components have been fabricated and we will start integration and laboratory cool-down test in the summer of 2014. After the engineering and initial science observations at the Subaru telescope, SWIMS will be transported to TAO telescope and see the first light in 2018.
Sky background subtraction with fiber-fed spectrographs
Show abstract
Fiber-fed spectrographs can now have throughputs equivalent to slit spectrographs. However, the sky
subtraction accuracy that can be reached on such instruments has often been pinpointed as one of their major
issues, in relation to difficulties in scattered light and flat-field corrections or throughput losses associated
with fibers. Using technical time observations with FLAMES-GIRAFFE, two observing techniques, namely
dual staring and cross beam switching modes, were tested and the resulting sky subtraction accuracy reached
in both cases was quantified. Results indicate that an accuracy of 0.6% on the sky subtraction can be reached,
provided that the cross beam switching mode is used. This is very encouraging regarding the detection of very
faint sources with future fiber-fed spectrographs such as VLT/MOONS or E-ELT/MOSAIC.
Accuracy research for survey telescope fiber position measurement
Show abstract
Multi-objects survey system because of its high efficiency have been planned to build in many telescope such as
Mayall 4m telescope and have been working well on LAMOST. The telescope could control massively robotic fiber-positioners
carried with fibers on the top, received thousand galaxies and quasi-stellar objects at one time observation.
How to measure every fiber's position accurately is the key techniques for the telescope to improve its performance.
There is a good way to measure the fiber’s position by photogrammetry with no touches measurement. The camera
could capture the position of backside illuminated fibers. In this paper we described the trial measurement for multi
positioners system in different measuring parameters, and compared these conditions which influenced the measuring
accuracy. Finally the test results were presented the baseline parameters for the measurement system to provide a site
measurement option for the positioner location.
Development of multi-object spectroscopy unit for simultaneous-color wide-field infrared multi-object spectrograph
Show abstract
SWIMS (Simultaneous-color Wide-field Infrared Multi-object Spectrograph) has a multi-object spectroscopic function including IFU in addition to the imaging capability. The mechanism in order to achieve this function is Multi-Object Spectroscopy Unit. This is the function that can derive spectra of simultaneous 20–30 objects over range from 0.9 to 2.5μmm. To set or exchange a slit mask on telescope focal plane, MOSU consists of the slit-mask dewar (carrousel), focal plane dewar, and robotic arm called mask catcher. There are many structural and mechanical features in MOSU to achieve its performance in cooling system, positional repeatability of slit mask and so on. We present here its unique components and its specifications and performance.
Achieving decameter velocity precision with a multi-object spectrograph
Show abstract
Fiber-fed multi-object spectrographs have proven to be powerful tools in astronomy, capable of developing large
kinematic samples in a fraction of the time required by single-object spectroscopy. The recently commissioned Michigan
Magellan Fiber System (M2FS) is a multi-mode, multi-object, fiber-fed optical spectrograph capable of observing up to
256 targets with its 1.2" fibers. By using M2FS’s adjustable slit mechanism with telluric lines as a wavelength reference
we have developed an instrument capable of measuring absolute velocities to 25 m/s for up to 256 objects
simultaneously. We briefly describe M2FS’s baseline capabilities and then discuss the fiber slit mechanism we created
for M2FS. Finally we review our analysis methods, highlighting both the additional calibration opportunities presented
by multi-object observations and the effects of atmospheric models on our achieved precision.
Wide FastCam: a wide field imaging camera for the TCS
Show abstract
The FastCam instrument, jointly developed by the IAC and the UPCT, allows, in real-time, acquisition, selection and
storage of images with a resolution that reaches the diffraction limit of medium-sized telescopes. FastCam incorporates a
specially designed software package to analyze series of tens of thousands of images in parallel with the data acquisition
at the telescope.
This instrument, well tested and used, has lead to another instrument with slightly different characteristics: Wide
FastCam. Although it uses the same software for data acquisition, this time the objective does not look for lucky imaging
but fast observations (some frames per second) in a much larger field of view. Wide FastCam consists of a 1k x 1k
EMCCD detector and different optics offering a ~8 arcmin FOV.
IDOM collaborated with IAC in the design of a high stability optical bench for the implementation of FastCam at the
Telescopio Carlos Sánchez (TCS) and is currently collaborating in the implementation of Wide FastCam at the same
telescope.
The DESI wide field corrector optics
Show abstract
The Dark Energy Spectroscopic instrument (DESI) is a 5000 fiber multi-object spectrometer system under development
for installation on the National Optical Astronomy Observatory (NOAO) Kitt Peak 4m telescope (the Mayall telescope).
DESI is designed to perform a 14,000° (square) galaxy and Quasi-Stellar Object (QSO) redshift survey to improve
estimates of the dark energy equation of state. The survey design imposes numerous constraints on a prime focus
corrector design, including field of view, geometrical blur, stability, fiber injection efficiency, zenith angle, mass and
cost. The DESI baseline wide-field optical design described herein provides a 3.2° diameter field of view with six 0.8-
1.14m diameter lenses and an integral atmospheric dispersion compensator.
MEGARA cryostat advanced design
Show abstract
MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is an optical Integral-Field Unit and
Multi-Object Spectrograph designed for the GTC (Gran Telescopio de Canarias) 10.4m telescope in La Palma.
MEGARA project has already passed preliminary design review and the optics critical design review, first-light it is
expected to take place at the end of 2016. MEGARA is a development under a GRANTECAN contract.
In this paper we summarize the current status of the LN2 open-cycle cryostat which has been designed by the
“Astronomical Instrumentation Lab for Millimeter Wavelengths” at the Instituto Nacional de Astrofísica, Óptica y
Electrónica (INAOE) and emphasize the key parts of the system that have updated since the Preliminary Design, the
main activities related to acceptance, integration, fabrication and maintenance plans which fit into the overall structure of
the management plan of MEGARA are also described. The cryogenic work package of MEGARA has completed all the
design stages and is ready for its Critical Design Review and then proceed to fabrication.
Performance of the Southern African Large Telescope (SALT) High Resolution Spectrograph (HRS)
Show abstract
The Southern African Large Telescope (SALT) High Resolution Spectrograph (HRS) is a fibre-fed R4 échelle
spectrograph employing a white pupil design with red and blue channels for wavelength coverage from 370–890nm.
The instrument has four modes, each with object and sky fibres: Low (R~15000), Medium (R~40000) and High
Resolution (R~65000), as well as a High Stability mode for enhanced radial velocity precision at R~65000. The High
Stability mode contains a fibre double-scrambler and offers optional simultaneous Th-Ar arc injection, or the inclusion
of an iodine cell in the beam. The LR mode has unsliced 500μm fibres and makes provision for nod-and-shuffle for
improved background subtraction. The MR mode also uses 500μm fibres, while the HR and HS fibres are 350μm. The
latter three modes employ modified Bowen-Walraven image-slicers to subdivide each fibre into three slices. All but the
High Stability bench is sealed within a vacuum tank, which itself is enclosed in an interlocking Styrostone enclosure, to
insulate the spectrograph against temperature and atmospheric pressure variations. The Fibre Instrument Feed (FIF)
couples the four pairs of fibres to the telescope focal plane and allows the selection of the appropriate fibre pair for a
given mode, and adjustment of the fibre separation to optimally position the sky fibre. The HRS employs a
photomultiplier tube for an exposure meter and has a dedicated auto-guider attached to the FIF. We report here on the
commissioning results and overall instrument performance since achieving first light on 28 September 2013.
VIRUS instrument enclosures
Show abstract
The Visible Integral-Field Replicable Unit Spectrograph (VIRUS) instrument will be installed at the Hobby-Eberly
Telescope† in the near future. The instrument will be housed in two enclosures that are mounted adjacent to the
telescope, via the VIRUS Support Structure (VSS). We have designed the enclosures to support and protect the
instrument, to enable servicing of the instrument, and to cool the instrument appropriately while not adversely affecting
the dome environment. The system uses simple HVAC air handling techniques in conjunction with thermoelectric and
standard glycol heat exchangers to provide efficient heat removal. The enclosures also provide power and data transfer
to and from each VIRUS unit, liquid nitrogen cooling to the detectors, and environmental monitoring of the instrument
and dome environments. In this paper, we describe the design and fabrication of the VIRUS enclosures and their subsystems.
Presenting a high accuracy Theta-Phi-style fiber-positioner prototype with a 15-mm pitch
Show abstract
We present a Θ - Φ-style fiber-positioner prototype, which will be controlled via the EMI-robust CAN-Bus. Our positioner points without iterations or a metrology system. Due to the overlapping patrol disc of 17.3 mm diameter, we reach a filling factor of 100 %. The positioners diameter is 14.6 mm, containing the control electronics on a contemporary PCB of 13.5 mm width. While moving, the power consumption does not lead to a significant rise in temperature. Given a mechanical reference point measured by stall detection, the absolute accuracy is 27 μm (1σ = 14 µm) and pointings are repeatable with 7 μm (1σ = 4 μm). Better positioning may be reachable with upcoming calibration.
ROS2: a multichannel vision for the robotic REM telescope
Show abstract
During 2013, a new visible camera has been finally installed and tested at the 60cm, robotic REM
telescope in the la Silla Observatory. REM is an Italian, fast-reacting telescope initially designed and built for the
immediate response to GRB automatic alerts, but since the first light in 2003 its usage has been covering a wider
range of astronomical interests. While the IR camera REMIR was reaching the expected limiting magnitudes, the
original ROSS visible camera suffered, since the beginning, of a rather poor performance. We set therefore to
implement a newer optical camera, leading to the design, tests and integration of ROS2, a dichroic-based four
channels imaging camera. The four Sloan-like pass bands are imaged, at the same time, in four quadrants of the
CCD, an Andor multilevel Peltier detector. The tests during the science commissioning show an impressive
improvement in the limiting magnitudes, reaching two magnitudes fainter than ROSS. Here we show the concept,
the tests and the user level product we are now offering at REM.
Towards a spectroscopic survey of one hundred thousand spatially resolved galaxies with Hector
Show abstract
Hector is an instrument concept for a multi integral-field-unit spectrograph aimed at obtaining a tenfold increase in
capability over the current generation of such instruments. The key science questions for this instrument include how do
galaxies get their gas, how is star formation and nuclear activity affected by environment, what is the role of feedback,
and what processes can be linked to galaxy groups and clusters. The baseline design for Hector incorporates multiple
hexabundle fibre integral-field-units that are each positioned using Starbug robots across a three-degree field at the
Anglo-Australian Telescope. The Hector fibres feed dedicated fixed-format spectrographs, for which the parameter space
is currently being explored.
Monitoring the atmospheric throughput at Cerro Tololo Inter-American Observatory with aTmCam
Show abstract
We have built an Atmospheric Transmission Monitoring Camera (aTmCam), which consists of four telescopes and
detectors each with a narrow-band filter that monitors the brightness of suitable standard stars. Each narrowband filter is
selected to monitor a different wavelength region of the atmospheric transmission, including regions dominated by the
precipitable water vapor and aerosol optical depth. The colors of the stars are measured by this multi narrow-band
imager system simultaneously. The measured colors, a model of the observed star, and the measured throughput of the
system can be used to derive the atmospheric transmission of a site on sub-minute time scales. We deployed such a
system to the Cerro Tololo Inter-American Observatory (CTIO) and executed two one-month-long observing campaigns
in Oct-Nov 2012 and Sept-Oct 2013. We have determined the time and angular scales of variations in the atmospheric
transmission above CTIO during these observing runs. We also compared our results with those from a GPS Water
Vapor Monitoring System and find general agreement. The information for the atmospheric transmission can be used to
improve photometric precision of large imaging surveys such as the Dark Energy Survey and the Large Synoptic Survey
Telescope.
Methods for the detection and the characterization of low mass companions using the IFS of SPHERE
Show abstract
SPHERE is an instrument aimed to the search for low mass companions around young stars in the solar neighborhood. To achieve this goal light from the host star (and in particular the speckle pattern due to the telescope aberrations) should be strongly attenuated while avoiding to cancel out the light from the faint companion. Different techniques can be used to fulfill this aim exploiting the multi-wavelength datacube produced by the Integral Field Spectrograph that is one of the scientific modules that composes SPHERE. In particular we have tested the application of the Spectral Deconvolution and of the Principal Components Analysis techniques. Both of them allow us to obtained a contrast better than 10−5 with respect to the central star at separations of the order of 0.4 arcsec. A further improvement of one order of magnitude can be obtained by combining one of these techniques to the Angular Differential Imaging. To investigate the expected performance of IFS in characterizing detected objects we injected in laboratory data synthetics planets with different intrinsic fluxes and projected separations from the host star. We performed a complete astrometric and photometric analysis of these images to evaluate the expected errors on these measurements, the spectral fidelity and the differences between the reduction methods. The main issue is to avoid the strong self-cancellation that is inherent to all the reduction methods. We have in particular tested two possible solutions: the use of a mask during the reduction on the positions of the companions or, alternatively, using a KLIP procedure for the IFS. This latter seems to give better results in respect o the classical PCA, allowing us to obtain a good spectral reconstruction for simulated objects down to a contrast of ~10-5.
MEGARA optical manufacturing process
Show abstract
MEGARA is the future visible integral-field and multi-object spectrograph for the GTC 10.4-m telescope
located in La Palma. INAOE is a member of the MEGARA Consortium and it is in charge of the Optics
Manufacturing work package. MEGARA passed the Optics Detailed Design Review in May 2013, and the
blanks of the main optics have been already ordered and their manufacturing is in progress. Except for
the optical fibers and microlenses, the complete MEGARA optical system will be manufactured in
Mexico, shared between the workshops of INAOE and CIO. This includes a field lens, a 5-lenses collimator, a
7-lenses camera and a complete set of volume phase holographic gratings with 36 flat windows and 24 prisms,
being all these elements very large and complex. Additionally, the optical tests and the complete assembly of
the camera and collimator subsystems will be carried out in Mexico. Here we describe the current status of the
optics manufacturing process.
High speed wide field CMOS camera for Transneptunian Automatic Occultation Survey
Show abstract
The Transneptunian Automated Occultation Survey (TAOS II) is a three robotic telescope project to detect the stellar
occultation events generated by Trans Neptunian Objects (TNOs). TAOS II project aims to monitor about 10000 stars
simultaneously at 20Hz to enable statistically significant event rate. The TAOS II camera is designed to cover the 1.7
degree diameter field of view (FoV) of the 1.3m telescope with 10 mosaic 4.5kx2k CMOS sensors. The new CMOS
sensor has a back illumination thinned structure and high sensitivity to provide similar performance to that of the backillumination thinned CCDs. The sensor provides two parallel and eight serial decoders so the region of interests can be
addressed and read out separately through different output channels efficiently. The pixel scale is about 0.6"/pix with the
16μm pixels. The sensors, mounted on a single Invar plate, are cooled to the operation temperature of about 200K by a
cryogenic cooler. The Invar plate is connected to the dewar body through a supporting ring with three G10 bipods. The
deformation of the cold plate is less than 10μm to ensure the sensor surface is always within ±40μm of focus range. The
control electronics consists of analog part and a Xilinx FPGA based digital circuit. For each field star, 8×8 pixels box
will be readout. The pixel rate for each channel is about 1Mpix/s and the total pixel rate for each camera is about
80Mpix/s. The FPGA module will calculate the total flux and also the centroid coordinates for every field star in each
exposure.
Final optical design for the WEAVE two-degree prime focus corrector
Show abstract
WEAVE is the next-generation wide-field optical spectroscopy facility for the William Herschel Telescope (WHT) in La
Palma, Canary Islands, Spain. We present the final optical design for the two-degree Prime Focus Corrector (PFC) for
the WHT optimised for WEAVE. The nominal optical design provides a polychromatic PSF that does not exceed 0.6
arcsec (80% encircled energy diameter) over a wavelength range from 370 to 1000 nm covering a two-degree field-of-view
(FOV) for zenith angles up to 65 degrees. We describe the optical issues that had to be addressed prior to the Final
Design Review (FDR) and present the trade-offs that were necessary between manufacturability and performance. We
detail the results of an in-depth Monte Carlo simulation that contains all the manufacturing, alignment and stability
issues that affect the PSF error budget of the Prime Focus Corrector. As a result of multiple iterations regarding the
different tolerances of the system, the polychromatic PSF (80% encircled energy diameter) including all errors stays
below the required 1 arcsec.
The guider and wavefront curvature sensor subsystem for the Large Synoptic Survey Telescope
Show abstract
The Large Synoptic Survey Telescope instrument include four guiding and wavefront sensing subsystems called corner
raft subsystems, in addition to the main science array of 189 4K x 4K CCDs. These four subsystems are placed at the
four corners of the instrumented field of view. Each wavefront/guiding subsystem comprises a pair of 4K x 4K guide
sensors, capable of producing 9 frames/second, and a pair of offset 2K x 4K wavefront curvature sensors from which the
images are read out at the cadence of the main camera system, providing 15 sec integrations. These four
guider/wavefront corner rafts are mechanically and electrically isolated from the science sensor rafts and can be installed
or removed independently from any other focal plane subsystem. We present the implementation of this LSST
subsystem detailing both hardware and software development and status.
VIRUS: assembly, testing and performance of 33,000 fibres for HETDEX
Show abstract
VIRUS is the visible, integral-field replicable unit spectrograph for the Hobby-Eberly-Telescope (HET) consisting of 75
integral-field-units that feed 150 spectrographs. The full VIRUS instrument features over 33,000 fibres, each projecting
to 1.5 arcseconds diameter on sky, deployed at the prime focus of the upgraded 10m HET. The assembly and acceptance
testing for all IFUs includes microscopic surface quality inspections, astrometry of fibre positions, relative throughput
measurements, focal-ratio-degradation evaluation, and system acceptance using a VIRUS reference spectrograph to
verify the image quality, spectral transmission, stability, or to detect any stray light issues.
A multi-pixel room-temperature local oscillator subsystem for array receivers at 1.9 THz
Show abstract
We report on the first room-temperature modular multi-pixel Schottky diode-based, tunable, frequency-multiplied local
oscillator sub-system at 1.9 THz. This source has been developed to enable efficient high-resolution mapping of the C+
line using suborbital platforms such as the SOFIA aircraft and balloons, as well as space instruments. This compact LO
source features four multipliers (X3X2X3X3) to up-convert Ka-band power to 1.9 THz. Preliminary results at 300 K
demonstrate more than 5 μW per pixel at 1.9 THz. The source is designed to provide a large output power dynamic
range and can be expanded to larger array receivers.
Multi-object fibre spectroscopy at the WHT: performance enhancements of AF2+WYFFOS
Show abstract
AF2+WYFFOS is the multi-object one degree field-of-view fibre-fed spectrograph at the prime focus of the 4.2 m
William Herschel Telescope (WHT) at the Observatorio del Roque de Los Muchachos (ORM). Demand for this has been
decreasing over the years due to its low overall throughput. Given the strategic importance of multi-fibre spectroscopy
for the WHT’s future, with the coming of WEAVE (the powerful next-generation multi-object spectrograph for the
WHT to be commissioned in 2017), during 2013 and 2014 ING staff carried out an end-to-end analysis of the reasons for
low throughput. The investigations addressed target-acquisition/positioning/guiding, focal-plane geometry, optical
transmission and overall system throughput measurements.
AF2+WYFFOS performance has improved significantly as a result of these enhancements, and it is ready now to
perform as a useful precursor and science test-bed for surveys with WEAVE, the new wide-field multi-object
spectroscopy facility at the WHT.
The Zwicky transient facility observing system
Show abstract
The Zwicky Transient Facility (ZTF) is a synoptic optical survey for high-cadence time-domain astronomy. Building
upon the experience and infrastructure of the highly successful Palomar Transient Factory (PTF) team, ZTF will survey
more than an order of magnitude faster than PTF in sky area and volume in order to identify rare, rapidly varying optical
sources. These sources will include a trove of supernovae, exotic explosive transients, unusual stellar variables,
compact binaries, active galactic nuclei, and asteroids. The single-visit depth of 20.4 mag is well matched to
spectroscopic follow-up observations, while the co-added images will provide wide sky coverage 1.5 – 2 mag deeper
than SDSS. The ZTF survey will cover the entire Northern Sky and revisit fields on timescales of a few hours, providing
hundreds of visits per field each year, an unprecedented cadence, as required to detect fast transients and
variability. This high-cadence survey is enabled by an observing system based on a new camera having 47 deg2 field of
view – a factor of 6.5 greater than the existing PTF camera - equipped with fast readout electronics, a large, fast
exposure shutter, faster telescope and dome drives, and various measures to optimize delivered image quality. Our
project has already received an initial procurement of e2v wafer-scale CCDs and we are currently fabricating the camera
cryostat. International partners and the NSF committed funds in June 2014 so construction can proceed as planned to
commence engineering commissioning in 2016 and begin operations in 2017. Public release will allow broad utilization
of these data by the US astronomical community. ZTF will also promote the development of transient and variable
science methods in preparation for the seminal first light of LSST.
Poster Session: High Spectral and Spatial Resolution Instruments
Gemini planet imager observational calibrations X: non-redundant masking on GPI
Show abstract
The Gemini Planet Imager (GPI) Extreme Adaptive Optics Coronograph contains an interferometric mode: a 10-hole non-redundant mask (NRM) in its pupil wheel. GPI operates at Y, J, H, and K bands, using an integral field unit spectrograph (IFS) to obtain spectral data at every image pixel. NRM on GPI is capable of imaging with a half resolution element inner working angle at moderate contrast, probing the region behind the coronagraphic spot. The fine features of the NRM PSF can provide a reliable check on the plate scale, while also acting as an attenuator for spectral standard calibrators that would otherwise saturate the full pupil. NRM commissioning data provides details about wavefront error in the optics as well as operations of adaptive optics control without pointing control from the calibration system. We compare lab and on-sky results to evaluate systematic instrument properties and examine the stability data in consecutive exposures. We discuss early on-sky performance, comparing images from integration and tests with the first on-sky images, and demonstrate resolving a known binary. We discuss the status of NRM and implications for future science with this mode.
InnoPOL: an EMCCD imaging polarimeter and 85-element curvature AO system on the 3.6-m AEOS telescope for cost effective polarimetric speckle suppression
Show abstract
The Hokupa’a-85 curvature adaptive optics system components have been adapted to create a new AO-corrected
coud´e instrument at the 3.67m Advanced Electro-Optical System (AEOS) telescope. This new AO-corrected
optical path is designed to deliver an f/40 diffraction-limited focus at wavelengths longer than 800nm. A new
EMCCD-based dual-beam imaging polarimeter called InnoPOL has been designed and is presently being installed
behind this corrected f/40 beam. The InnoPOL system is a flexible platform for optimizing polarimetric
performance using commercial solutions and for testing modulation strategies. The system is designed as a
technology test and demonstration platform as the coud´e path is built using off-the-shelf components wherever
possible. Models of the polarimetric performance after AO correction show that polarization modulation at rates
as slow as 200Hz can cause speckle correlations in brightness and focal plane location sufficient enough to change
the speckle suppression behavior of the modulators. These models are also verified by initial EMCCD scoring
camera data at AEOS. Substantial instrument trades and development efforts are explored between instrument
performance parameters and various polarimetric noise sources.
APSU @ ESPRESSO: final design towards the integration
Show abstract
This paper presents the Espresso Anamorphic pupil Slicer (APSU) implementation. For ESPRESSO that will be installed
on ESO’s Very Large Telescope (VLT). In this work we will present the design and trade off for the pupil slicing system
introduced in order to increase the resolving power, effectively decreasing slit width. It’s based onto simplified optical
component that introduce large anamorphism while keeping low aberrations by means of cylindrical optics. We describe
here the trade off between slicing through two adjacent squared doublets and two achromatic prisms. Preliminary
integration and procurement is also discussed here.
Design of a radial velocity spectrograph for the Moletai Astronomical Observatory
Show abstract
The Yale Exoplanet Laboratory is under contract to design, build, and deliver a high-resolution (R = 60,000) echelle
spectrograph for the Moletai Astronomical Observatory 1.65-meter telescope at the Vilnius University. We present a
fiber-fed, white-pupil architecture that will operate from 400 to 880nm. The optomechanical design implements a
modular approach for stability and ease of alignment that can be reproduced for other telescopes. It will utilize highperformance
off-the-shelf optical components with a custom designed refractive camera for high throughput and good
image quality.
ESPRESSO front end: modular opto-mechanical integration for astronomical instrumentation
Show abstract
The opto-mechanical conceptual design for the Front-End unit and the calibration unit of the ESPRESSO Spectrograph is
described in this paper. The front end system exploits a modular concept. Each FEU receive the beam directly from the
relative Telescope Coudé Train and the calibration light from the calibration unit. On the other side the FEU feeds the
fibers that carry the light to the spectrograph, corresponding in number and size to the scientific observing modes
conceived for Espresso. The selection is made through a Toggling Unit. Purpose of the Front/End is to provide the
needed connection between the input signal, i.e. Object light, Sky light, Calibration light, and the given output fiber in
any of the foreseen observing modes.
Gemini planet imager observational calibrations IV: wavelength calibration and flexure correction for the integral field spectograph
Show abstract
We present the wavelength calibration for the lenslet-based Integral Field Spectrograph (IFS) that serves as the science instrument for the Gemini Planet Imager (GPI). The GPI IFS features a 2.7" x 2.7" field of view and a 190 x 190 lenslet array (14.3 mas/lenslet) operating in Y, J, H, and K bands with spectral resolving power ranging
from R ~ 35 to 78. Due to variations across the field of view, a unique wavelength solution is determined for each
lenslet characterized by a two-dimensional position, the spectral dispersion, and the rotation of the spectrum
with respect to the detector axes. The four free parameters are fit using a constrained Levenberg-Marquardt least-squares minimization algorithm, which compares an individual lenslet’s arc lamp spectrum to a simulated arc lamp spectrum. This method enables measurement of spectral positions to better than 1/10th of a pixel on the GPI IFS detector using Gemini’s facility calibration lamp unit GCAL, improving spectral extraction accuracy compared to earlier approaches. Using such wavelength calibrations we have measured how internal flexure of the spectrograph with changing zenith angle shifts spectra on the detector. We describe the methods used to compensate for these shifts when assembling datacubes from on-sky observations using GPI.
RHEA: the ultra-compact replicable high-resolution exoplanet and Asteroseismology spectrograph
Show abstract
We present the opto-mechanical design and the characterization of the Replicable High-resolution Exoplanet and Asteroseismology (RHEA) spectrograph. RHEA is an ultra-compact fiber-fed echelle spectrograph designed to be used at 0.2-0.4 m class robotic telescopes where long term dedicated projects are possible. The instrument will be primarily used for radial velocity (RV) studies of low to intermediate-mass giant stars for the purpose of searching for hot Jupiters and using asteroseismology to simultaneously measure the host star parameters and de-correlate stellar pulsations. The optical design comprises a double-pass (i.e. near Littrow) configuration with
prism cross-disperser and single-mode fiber (SMF) input. The spectrograph has a resolving power of R>70,000 and operates at 430–670 nm with minimum order separation of ~180 μm. This separation allows a 1x6 photonic
lantern integration at a later stage which is currently under development. The current design is built with the aim of creating an inexpensive and replicable unit. The spectrograph is optimised for long-baseline RV observations through careful temperature stabilisation and simultaneous wavelength calibration. As a further improvement the echelle grating is housed in a vacuum chamber to maintain pressure stability. The performance of the current prototype is currently being tested on a 0.4 m telescope at the Macquarie University Observatory.
SHARK (System for coronagraphy with High order Adaptive optics from R to K band): a proposal for the LBT 2nd generation instrumentation
Show abstract
This article presents a proposal aimed at investigating the technical feasibility and the scientific capabilities of high
contrast cameras to be implemented at LBT. Such an instrument will fully exploit the unique LBT capabilities in
Adaptive Optics (AO) as demonstrated by the First Light Adaptive Optics (FLAO) system, which is obtaining excellent
results in terms of performance and reliability. The aim of this proposal is to show the scientific interest of such a
project, together with a conceptual opto-mechanical study which shows its technical feasibility, taking advantage of the
already existing AO systems, which are delivering the highest Strehl experienced in nowadays existing telescopes.
Two channels are foreseen for SHARK, a near infrared channel (2.5-0.9 um) and a visible one (0.9 – 0.6 um), both
providing imaging and coronagraphic modes. The visible channel is equipped with a very fast and low noise detector
running at 1.0 kfps and an IFU spectroscopic port to provide low and medium resolution spectra of 1.5 x 1.5 arcsec
fields.
The search of extra solar giant planets is the main science case and the driver for the technical choices of SHARK, but
leaving room for several other interesting scientific topics, which will be briefly depicted here.
Gemini planet imager observational calibrations III: empirical measurement methods and applications of high-resolution microlens PSFs
Show abstract
The newly commissioned Gemini Planet Imager (GPI) combines extreme adaptive optics, an advanced coronagraph, precision wavefront control and a lenslet-based integral field spectrograph (IFS) to measure the spectra of young extrasolar giant planets between 0.9-2.5 μm. Each GPI detector image, when in spectral model, consists
of ~37,000 microspectra which are under or critically sampled in the spatial direction. This paper demonstrates
how to obtain high-resolution microlens PSFs and discusses their use in enhancing the wavelength calibration,
flexure compensation and spectral extraction. This method is generally applicable to any lenslet-based integral field spectrograph including proposed future instrument concepts for space missions.
A laser locked Fabry-Perot etalon with 3 cm/s stability for spectrograph calibration
Show abstract
Accurate wavelength calibration is crucial for attaining superior Doppler precision with high resolution spectrographs. Upcoming facilities aim for 10 cm/s or better radial velocity precision to access the discovery space for Earth-like exoplanets. To achieve such precision over timescales of years, currently used wavelength cal- ibrators such as thorium-argon lamps and iodine cells will need to be replaced by more precise and stable sources. The ideal wavelength calibrator would produce an array of lines that are uniformly spaced, narrower than the spectrograph resolution, of equal brightness, cover the entire wavelength range of the spectrograph, and whose frequencies do not change with time. Laser frequency combs are an extremely accurate and stable, albeit technically challenging and costly, option that has received much attention recently. We present an alter- native method that uses a Fabry-Perot (FP) etalon illuminated by a white light source to produce a comb-like spectrum over a wide wavelength range. Previous work focused on the development of passively stabilized FP etalons for wavelength calibration. We improve on this method by locking the etalon to an atomic transition,
the frequency of which is known to < 2 x 10-11.7 We use a diode laser to observe both the rubidium (Rb) D2 transition at 780 nm and the etalon transmission spectrum. Saturated absorption spectroscopy is used to resolve the Rb hyperfine lines and precisely determine their locations. Since the etalon spectrum is probed with the same laser, the etalon can be locked by ensuring that one of its transmission peaks coincides with a particular Rb hyperfine peak (via either temperature tuning or a piezoelectric transducer incorporated into the etalon). By measuring the frequency of one etalon peak directly via comparison with the Rb, we remove any drifts or aging effects of the etalon that could cause problems for passively stabilized etalon references. We demonstrate a locking precision that is equivalent to a Doppler precision of 3 cm/s RMS.
Our setup is simple and robust, can be used with various etalons, and works in the infrared as well as the visible part of the spectrum. The combination of low cost, ease of use, and high precision make this calibration system an attractive option for new spectrographs and as a retrofit for existing facilities.
Gemini planet imager observational calibrations II: detector performance and calibration
Show abstract
The Gemini Planet Imager is a newly commissioned facility instrument designed to measure the near-infrared spectra of young extrasolar planets in the solar neighborhood and obtain imaging polarimetry of circumstellar disks. GPI’s science instrument is an integral field spectrograph that utilizes a HAWAII-2RG detector with a SIDECAR ASIC readout system. This paper describes the detector characterization and calibrations performed by the GPI Data Reduction Pipeline to compensate for effects including bad/hot/cold pixels, persistence, non- linearity, vibration induced microphonics and correlated read noise.
How to inject light efficiently into single-mode fibers
Show abstract
A key avenue to improving the precision of radial velocity measurements is by using photonic devices to collect the
light from the focal plane and delivering the beams to the slit of spectrograph via a single-mode fiber. Single-mode
fibers have the favorable property that they allow light to propagate in a single energy distribution characterized by a
Gaussian shape with a flat wavefront which is temporarily stable and independent of changes to the injection. These
properties mean that the point spread function delivered to the input slit of a spectrograph is highly stable with time
and independent of changes to the injection which is currently a key limitation to precision radial velocity
measurements and known as "Modal Noise". Further light delivery via single-mode fibers is the key requirement to
realize long baseline interferometers such as the Optical Hawaiian Array for Nanoradian Astronomy.
Injecting into single-mode fibers efficiently is inherently difficult because it requires closely matching the intensity
and wavefront of the focused beam to that supported by the fiber. The atmosphere is currently the key roadblock to
efficient injection. However, extreme adaptive optics systems such as Subaru Coronagraphic Extreme Adaptive
Optics (SCExAO) system currently being commissioned will enable high order wavefront correction and make
efficient coupling into single-mode fibers possible. In addition, pupil apodization optics used for coronagraphy,
known as phase induced amplitude apodization lenses also present in the SCExAO instrument, allow for close
matching of the intensity distributions.
We report on the progress and lessons learnt on developing an efficient single-mode injection unit within the
SCExAO instrument. As part of the PANDORA project we aim to use this injection and combine it with several
other photonic technologies to enable high precision radial velocity measurements in new and innovative ways.
Manufacturing, integration, and test results of the MATISSE cold optics bench
Show abstract
MATISSE is the second-generation mid-infrared interferometric spectrograph and imager for ESO’s Very Large
Telescope Interferometer (VLTI). NOVA-ASTRON is responsible for the Cold Optics Bench (COB), representing the
last part of the optics train where the four beams are re-arranged, spectrally dispersed and combined.
The COB consist of two sister units, one for the LM-band, one for the N-band, which were successively completed at
NOVA-ASTRON in autumn 2013 and spring 2014. The LM-band COB is under cryogenic test in its cryostat at
MPIA/Heidelberg; the N-band COB finished cryogenic tests and has been installed at OCA/Nice for integration together
with the Warm Optics. This paper focuses on the manufacturing, integration and test results of the COBs, and gives an overview of the current status.
Concept and optical design of the cross-disperser module for CRIRES+
Show abstract
CRIRES, the ESO high resolution infrared spectrometer, is a unique instrument which allows astronomers to access a
parameter space which up to now was largely uncharted. In its current setup, it consists of a single-order spectrograph
providing long-slit, single-order spectroscopy with resolving power up to R=100,000 over a quite narrow spectral range.
This has resulted in sub-optimal efficiency and use of telescope time for all the scientific programs requiring broad
spectral coverage of compact objects (e.g. chemical abundances of stars and intergalactic medium, search and
characterization of extra-solar planets). To overcome these limitations, a consortium was set-up for upgrading CRIRES
to a cross-dispersed spectrometer, called CRIRES+. This paper presents the updated optical design of the cross-dispersion
module for CRIRES+. This new module can be mounted in place of the current pre-disperser unit. The new
system yields a factor of >10 increase in simultaneous spectral coverage and maintains a quite long slit (10”), ideal for
observations of extended sources and for precise sky-background subtraction.
Opto-mechanical design of a new cross dispersion unit for the CRIRES+ high resolution spectrograph for the VLT
Show abstract
CRIRES is one of the few IR (0.92-5.2 μm) high-resolution spectrographs in operation at the VLT since 2006. Despite
good performance it suffers a limitation that significantly hampers its ability: a small spectral coverage per exposure. The
CRIRES upgrade (CRIRES+) proposes to transform CRIRES into a cross-dispersed spectrograph while maintaining the
high resolution (100000) and increasing the wavelength coverage by a factor 10 compared to the current capabilities. A
major part of the upgrade is the exchange of the actual cryogenic pre-disperser module by a new cross disperser unit. In
addition to a completely new optical design, a number of important changes are required on key components and
functions like the slit unit and detectors units. We will outline the design of these new units fitting inside a predefined
and restricted space. The mechanical design of the new functions including a description and analysis will be presented.
Finally we will present the strategy for the implementation of the changes.
HiJaK: the high-resolution J, H and K spectrometer
Show abstract
We present the science drivers, design requirements and a preliminary design for a high-resolution, broad- bandwidth, slit-fed cross-dispersed near-infrared spectrometer for 5-meter-class telescopes. Our concept, called the High-Resolution J, H and K Spectrometer, or HiJaK, utilizes an R6 echelle in a white-pupil design to achieve high resolution in a compact configuration with a 2048 x 2048 pixel infrared detector. We present a preliminary ray-traced optical design matched to the new 4.3-meter Discovery Channel Telescope in Happy Jack, Arizona. We also discuss mechanical and cryogenic options to house our optical design.
Combining vector-phase coronagraphy with dual-beam polarimetry
Show abstract
Utilizing the so-called vector phase of polarized light, both focal-plane coronagraphs (e.g. the Vector Vortex Coronagraph) and pupil-plane coronagraphs (e.g. the vector Apodizing Phase Plate) are powerful components for high-contrast imaging. These coronagraphs can be built and optimized with polarization techniques and liquid crystal technology, that enable patterning at the micron level and furnish broad-band performance. The contrast between the residual starlight and the (polarized) reflected light off exoplanets can be further bridged by incorporating sensitive, dual-beam imaging polarimetry. As vector-phase coronagraphs use polarizers to enhance their performance, we introduce optimally integrated solutions that combine advanced coronagraphy and polarimetry. For both the VVC and the vAPP we present polarization beam-splitting concepts, with polarization analyzers either behind or in front of the coronagraphic optics. We discuss design solutions for the implementation of polarization optics, and set the stage for a trade-off between the improvement of coronagraphic and polarimetric performance and the ensuing degradation on the high-contrast imaging performance due to wavefront errors.
An atmospheric turbulence and telescope simulator for the development of AOLI
Show abstract
AOLI, Adaptive Optics Lucky Imager, is the next generation of extremely high resolution instruments in the optical
range, combining the two more promising techniques: Adaptive optics and lucky imaging. The possibility of reaching
fainter objects at maximum resolution implies a better use of weak energy on each lucky image. AOLI aims to achieve
this by using an adaptive optics system to reduce the dispersion that seeing causes on the spot and therefore increasing
the number of optimal images to accumulate, maximizing the efficiency of the lucky imaging technique.
The complexity of developments in hardware, control and software for in-site telescope tests claim for a system to
simulate the telescope performance. This paper outlines the requirements and a concept/preliminary design for the
William Herschel Telescope (WHT) and atmospheric turbulence simulator. The design consists of pupil resemble, a
variable intensity point source, phase plates and a focal plane mask to assist in the alignment, diagnostics and calibration
of AOLI wavefront sensor, AO loop and science detectors, as well as enabling stand-alone test operation of AOLI.
Stable Imaging for Astronomy (SIA)
Show abstract
One of the most challenging fields of astronomical instrumentation is probably high-contrast imaging since it ultimately
combines ultra-high sensitivity at low flux and the ability to cope with photon flux contrasts of several hundreds of
millions or even more. These two aspects implicitly require that high-contrast instruments should be highly stable in the
sense of the reproducibility of their measurements at different times, but also, continuously stable over time. In most
high contrast instruments or experiments, their sensitivity is broken after at most tens of minutes of operation due to
uncontrolled and unknown behaviour of the whole experiment regarding the environmental conditions. In this paper, we
introduce a general approach of an exhaustive stability study for high-contrast imaging that has been initiated at
Lagrange Laboratory, Observatoire de la Côte d'Azur (OCA). On a practical ground, one of the fundamental issues of
this study is the metrology, which is the basis of all reproducible measurements. We describe a small experiment
designed to understand the behaviour of one of our ultra-precise metrology tools (a commercial sub-nanometric 3-way
interferometer) and derive the conditions under which its operation delivers reliable results. The approach will apply to
the high-contrast imaging test-bench SPEED, under development at OCA.
Adapting a very high resolution echelle spectrograph to an 8 meter class telescope
Show abstract
The Adaptively Corrected Echelle Spectrograph (ACES) high resolution echelle spectrograph was
originally developed at Steward Observatory to couple adaptively-corrected stellar images to the instrument
using a near single mode optical fiber to give R~190,000 at V band. We explore here the feasibility of
using the spectrograph with the 2x8.4m Large Binocular Telescope (LBT), preserving the fiber coupling
for instrument isolation and illumination stability, but employing either a narrow slit or image slicer to
offset the smaller component size and thereby preserve high resolution. Such a combination could offer
simultaneously higher resolution with greater wavelength coverage per exposure than the configuration of
alternate instruments.
Development of compact and ultra-high-resolution spectrograph with multi-GHz optical frequency comb
Show abstract
In recent years, a calibration method for an astronomical spectrograph using an optical frequency comb (OFC) with a
repetition rate of more than ten GHz has been developed successfully [1-5]. But controlling filtering cavities that are
used for thinning out longitudinal modes precludes long term stability. The super-mode noise coming from the
fundamental repetition rate is an additional problem. We developed a laser-diode pumped Yb:Y2O3 ceramic oscillator,
which enabled the generation of 4-GHz (maximum repetition rate of 6.7 GHz) pulse trains directly with a spectrum
width of 7 nm (full-width half-maximum, FWHM), and controlled its optical frequency within a MHz level of accuracy
using a beat note between the 4-GHz laser and a 246-MHz Yb-fiber OFC. The optical frequency of the Yb-fiber OFC
was phase locked to a Rb clock frequency standard. Furthermore we also built a table-top multi-pass spectrograph with a
maximum frequency resolution of 600 MHz and a bandwidth of 1 nm using a large-size high-efficiency transmission
grating. The resolution could be changed by selecting the number of passes through the grating. This spectrograph could
resolve each longitudinal mode of our 4-GHz OFC clearly, and more than 10% throughput was obtained when the
resolution was set to 600 MHz. We believe that small and middle scale astronomical observatories could easily
implement such an OFC-calibrated spectrograph.
The habitable-zone planet finder calibration system
Show abstract
We present the design concept of the wavelength calibration system for the Habitable-zone Planet Finder instrument (HPF), a precision radial velocity (RV) spectrograph designed to detect terrestrial-mass planets around M-dwarfs. HPF is a stabilized, fiber-fed, R~50,000 spectrograph operating in the near-infrared (NIR) z/Y/J bands from 0.84 to 1.3 microns. For HPF to achieve 1 m s-1 or better measurement precision, a unique calibration system, stable to several times better precision, will be needed to accurately remove instrumental effects at an unprecedented level in the NIR. The primary wavelength calibration source is a laser frequency comb (LFC), currently in development at NIST Boulder, discussed separately in these proceedings. The LFC will be supplemented by a stabilized single-mode fiber Fabry-Perot interferometer reference source and Uranium-Neon lamp. The HPF calibration system will combine several other new technologies developed by the Penn State Optical-Infrared instrumentation group to improve RV measurement precision including a dynamic optical coupling system that significantly reduces modal noise effects. Each component has been thoroughly tested in the laboratory and has demonstrated significant performance gains over previous NIR calibration systems.
A stable and inexpensive wavelength reference for precise wavelength calibration of radial velocity spectrographs
Show abstract
We present a stable, inexpensive wavelength reference, based on a white-light interferometer for the use on current and future (arrays of) diffraction-limited radial velocity (RV) spectrographs. The primary aim of using an interferometer is to obtain a dense sinusoidal wavelength reference with spectral coverage between 450-650 nm. Its basic setup consists of an unbalanced fiber Mach-Zehnder interferometer (FMZI) that creates an interference pattern in the spectral domain due to superposition of phase delayed light, set by a fixed optical path-length difference (OPD). To achieve long-term stability, the interferometer is actively locked to a stable atomic line. The system operates in closed-loop using a thermo-optic modulator as the phase feedback component. We conducted stability measurements by superimposing the wavelength reference with thorium-argon (ThAr) emission lines
and found the differential RMS shift to be ~5 m s-1 within 30 minute bins in an experiment lasting 5 hours.
Performance modeling of an upgraded NIRSPEC on Keck
Show abstract
NIRSPEC is a high-resolution near-infrared (1-5 micron) echelle spectrometer in use on the Keck II telescope. We are
designing an upgrade to the spectrometer, and here we present modeling for the expected performance of the upgraded
system. The planned upgrade will (1) replace the Aladdin III science detector with a Teledyne H2RG, (2) update the slitviewing
camera (SCAM) detector to an H1RG and replace the optics, and (3) upgrade the instrument control
electronics. The new spectrometer detector has smaller pixels but a larger format, and its improved noise characteristics
will provide a dramatic increase in sensitivity, especially between OH lines in H-band and shorter wavelengths. Optical
modeling shows that the upgraded system is expected to achieve higher spectral resolution and a larger spectral grasp.
Also, preliminary modeling of the SCAM optical design aims to permit operation from 1-5 μm, overcoming a limitation
with the existing system.
Optical cavity characterization of the Tor Vergata Fabry-Pérot interferometer
Show abstract
We report the first optical and control performances of the Tor Vergata Fabry-P´erot interferometer prototype designed and realized in the framework of the ADvanced Astronomy for HELIophysics (ADAHELI) solar mission project. The characterization of the the coated surfaces of the two plates defining the optical cavity has been carried out with a Zygo interferometer able to measure the microroughness and global curvature of the cavity. The peak-to-valley errors are compliant with the manufacturer specifications and correspond to λ/70 and λ/80
@632.8 nm respectively. In addition, we present a first estimate of the interferometer spectral stability in stable open-air condition. A spectral uncertainty equal to 0.95 pm is found as the typical RMS over one hour of the passband central wavelength position.
Gemini planet imager observational calibrations VII: on-sky polarimetric performance of the Gemini planet imager
Show abstract
We present on-sky polarimetric observations with the Gemini Planet Imager (GPI) obtained at straight Cassegrain focus on the Gemini South 8-m telescope. Observations of polarimetric calibrator stars, ranging from nearly un- polarized to strongly polarized, enable determination of the combined telescope and instrumental polarization. We find the conversion of Stokes I to linear and circular instrumental polarization in the instrument frame to
be I → (QIP, UIP, PIP, VIP) = (-0.037 ± 0.010%, +0.4338 ± 0.0075%, 0.4354 ± 0.0075%, -6.64 ± 0.56%). Such
precise measurement of instrumental polarization enables ~0.1% absolute accuracy in measurements of linear
polarization, which together with GPI’s high contrast will allow GPI to explore scattered light from circumstellar
disk in unprecedented detail, conduct observations of a range of other astronomical bodies, and potentially even study polarized thermal emission from young exoplanets. Observations of unpolarized standard stars also let us quantify how well GPI's differential polarimetry mode can suppress the stellar PSF halo. We show that GPI polarimetry achieves cancellation of unpolarized starlight by factors of 100-200, reaching the photon noise limit for sensitivity to circumstellar scattered light for all but the smallest separations at which the calibration for instrumental polarization currently sets the limit.
Gemini planet imager observational calibrations V: astrometry and distortion
Show abstract
We present the results of both laboratory and on sky astrometric characterization of the Gemini Planet Imager (GPI). This characterization includes measurement of the pixel scale* of the integral field spectrograph (IFS), the position of the
detector with respect to north, and optical distortion. Two of these three quantities (pixel scale and distortion) were
measured in the laboratory using two transparent grids of spots, one with a square pattern and the other with a random pattern. The pixel scale in the laboratory was also estimate using small movements of the artificial star unit (ASU) in the
GPI adaptive optics system. On sky, the pixel scale and the north angle are determined using a number of known binary or multiple systems and Solar System objects, a subsample of which had concurrent measurements at Keck Observatory. Our current estimate of the GPI pixel scale is 14.14 ± 0.01 millarcseconds/pixel, and the north angle is -1.00 ± 0.03°. Distortion is shown to be small, with an average positional residual of 0.26 pixels over the field of view, and is corrected using a 5th order polynomial. We also present results from Monte Carlo simulations of the GPI Exoplanet Survey (GPIES) assuming GPI achieves ~1 milliarcsecond relative astrometric precision. We find that with this precision, we
will be able to constrain the eccentricities of all detected planets, and possibly determine the underlying eccentricity
distribution of widely separated Jovians.
Gemini planet imager observational calibrations VI: photometric and spectroscopic calibration for the integral field spectrograph
Show abstract
The Gemini Planet Imager (GPI) is a new facility instrument for the Gemini Observatory designed to provide direct detection and characterization of planets and debris disks around stars in the solar neighborhood. In addition to its extreme adaptive optics and coronagraphic systems which give access to high angular resolution and high-contrast imaging capabilities, GPI contains an integral field spectrograph providing low resolution spectroscopy across five bands between 0.95 and 2.5 μm. This paper describes the sequence of processing steps required for the spectro-photometric calibration of GPI science data, and the necessary calibration files. Based on calibration observations of the white dwarf HD 8049 B we estimate that the systematic error in spectra extracted from GPI observations is less than 5%. The flux ratio of the occulted star and fiducial satellite spots within coronagraphic GPI observations, required to estimate the magnitude difference between a target and any resolved companions, was measured in the H-band to be ∆m = 9.23 ± 0.06 in laboratory measurements and
∆m = 9.39 ± 0.11 using on-sky observations. Laboratory measurements for the Y, J , K1 and K2 filters are also presented. The total throughput of GPI, Gemini South and the atmosphere of the Earth was also measured in each photometric passband, with a typical throughput in H-band of 18% in the non-coronagraphic mode, with some variation observed over the six-month period for which observations were available. We also report ongoing development and improvement of the data cube extraction algorithm.
A robotic, compact, and extremely high resolution optical spectrograph for a close-in super-Earth survey
Show abstract
One of the most astonishing results from the HARPS and Kepler planet surveys is the recent
discovery of close-in super-Earths orbiting more than half of FGKM dwarfs. This new
population of exoplanets represents the most dominant class of planetary systems known to date,
is totally unpredicted by the classical core-accretion disk planet formation model. High cadence
and high precision Doppler spectroscopy is the key to characterize properties of this new
population and constrain planet formation models.
A new robotic, compact high resolution optical spectrograph, called TOU (formerly called
EXPERT-III), was commissioned at the Automatic Spectroscopic Telescope (AST) at Fairborn
Observatory in Arizona in July 2013 and has produced a spectral resolution of about 100,000 and
simultaneous wavelength coverage of 0.38-0.9 μm with a 4kx4k back-illuminated Fairchild CCD
detector. The instrument holds a very high vacuum of 1 micro torr and about 2 mK temperature
stability over a month. The early on-sky RV measurements show that this instrument is
approaching a Doppler precision of 1 m/s (rms) for bright reference stars (such as Tau Ceti) with
5 min exposures and better than 3 m/s (P-V, RMS~1 m/s) daily RV stability before calibration
exposures are applied. A pilot survey of 20 V<9 FGK dwarfs, including known super-Earth
systems and known RV stable stars, is being launched and every star will be observed ~100
times over ~300 days time window between this summer and next spring, following up with a
full survey of ~150 V< 10 FGKM dwarfs in 2015-2017.
Characterizing instrumental effects on polarization at a Nasmyth focus using NaCo
Show abstract
We propose a new calibration scheme to determine the instrumental polarization (IP) and crosstalk induced
by either the telescope or an instrument at Nasmyth focus. We measure the polarized blue sky at zenith with
VLT/UT4/NaCo for different NaCo derotator and telescope azimuth angles. Taking multiple measurements
after rotating both the instrument and the telescope with angles of 90° allows use to determine the IP and most
crosstalk components separately for the telescope and the instrument. This separation of the Mueller matrices
of UT4 and the NaCo is especially important for measurements taken in the conventional polarimetric mode
(field stabilized), because the rotation of the instrument with respect to M3 causes a variation in the IP and
crosstalk throughout the measurement. The technique allows us to determine the IP with an accuracy of 0.4%,
and constrain or determine lower or upper limits for most crosstalk components. Most notably, the UT4 U → V
crosstalk is substantially larger than theory predicts. An angular offset in NaCo's half wave plate orientation is
a possible source of systematic errors. We measure this offset to be 1.8° ± 0.5°.
The upgrade of a high dispersion spectro-polarimeter, VESPolA: new circular polarimetry mode and extremely high resolution mode
Show abstract
VESPolA is a high dispersion spectro-polarimeter, mounted on the 1.3m Araki telescope at Koyama Astronomical
Observatory of Kyoto Sangyo University. It employs an echelle type spectrograph and a non-ripple super-achromatic
half wave plate, resulting in the highly polarimetric accuracy of δP < 0.1% with the spectral resolution of R = 8,000 and
a wide wavelength coverage of δλ = 150nm - 300nm in a single exposure. It is specialized for the 1-2 m class small
telescope with Cassegrain focus. Because VESPolA can observed a dozen of polarization line profiles in the targets
simultaneously, we can obtain complementary information on both the geometry and the velocity fields of the
circumstellar envelope of variable stars, such as WR stars, Be stars, Herbig Ae/Be stars, T Tau stars, and so on.
VESPolA has achieved the high accuracy of δP ~ {(0.05)2 + (0.09)2P2}1/2% with spectral resolution of R ~ 8,000 for liner polarization. Recently, a new scientific program, search for magnetic pole-shift of stars (Nakamichi et al. 20129), was accepted at the Koyama Astronomical Observatory. Therefore, we plan to add a new modes, a high resolution mode (R = 20,000) and a circular polarimetry mode for this study, to VESPolA. We employ an alumina (Al2O3) slit as the new slit for the high resolution mode to minimize the instrumental polarization generated at the edge of the slit. However, because the slit width should be very narrow (= 35μm), it is technically difficult to realize the smooth slit without burr or
chipping. We are trying the various processing methods, machining, etching, laser cutting, and so on. The circular
polarimetry mode can be realized with a new non-ripple super-achromatic quarter wave plate and the high precision
rotary unit, which is located just below the existing the half wave plate unit. We will finish the update within 2015 and
start the science observations.
FIDEOS: a high resolution echelle spectrograph for the ESO 1m telescope at La Silla
Show abstract
FIDEOS (FIbre Dual Echelle Optical Spectrograph) is a fibre-fed bench-mounted high-resolution echelle spec- trograph for the 1-m telescope at ESO in La Silla, Chile. It is based on a 44.41 lines/mm 70° blaze angle
echelle grating in quasi-Littrow mode, providing spectral resolution of R ~ 42 000, covering the spectral range from 400 nm to 680 nm. The detector is a 2k×2k CCD with 15 μm pixels. The spectrograph will be fed by two 50
µm core diameter fibres for the astronomical object and the simultaneous calibration lamp, respectively. Alter- natively, an iodine cell will be mounted on the telescope-spectrograph interface, providing a secondary spectral calibration source. In addition, the instrument will be mounted on a fixed optical-bench without movable parts rather than the CCD shutter and its enclosure will be thermally controlled to ensure opto-mechanical stability. Since the FIDEOS will deliver high resolution and spectral stability, it will be optimized for precision radial velocities.
HARPS-N @ TNG, two year harvesting data: performances and results
Show abstract
The planet hunter HARPS-N[1], in operation at the Telescopio Nazionale Galileo (TNG)[13] from April 2012 is a highresolution
spectrograph designed to achieve a very high radial velocity precision measurement thanks to an ultra stable
environment and in a temperature-controlled vacuum. The main part of the observing time was devoted to Kepler field and
achieved a very important result with the discovery of a terrestrial exoplanet. After two year of operation, we are able to
show the performances and the results of the instrument.
Development of infrared Echelle spectrograph and mid-infrared heterodyne spectrometer on a small telescope at Haleakala, Hawaii for planetary observation
Show abstract
We report the development of infrared Echelle spectrograph covering 1 - 4 micron and mid-infrared heterodyne
spectrometer around 10 micron installed on the 60-cm telescope at the summit of Haleakala, Hawaii (alt.=3000m). It is
essential to carry out continuous measurement of planetary atmosphere, such as the Jovian infrared aurora and the
volcanoes on Jovian satellite Io, to understand its time and spatial variations. A compact and easy-to-use high resolution
infrared spectrometer provide the good opportunity to investigate these objects continuously. We are developing an
Echelle spectrograph called ESPRIT: Echelle Spectrograph for Planetary Research In Tohoku university. The main
target of ESPRIT is to measure the Jovian H3+ fundamental line at 3.9 micron, and H2 nu=1 at 2.1 micron. The 256x256
pixel CRC463 InSb array is used. An appropriate Echelle grating is selected to optimize at 3.9 micron and 2.1 micron for
the Jovian infrared auroral observations. The pixel scale corresponds to the atmospheric seeing (0.3 arcsec/pixel). This
spectrograph is characterized by a long slit field-of-view of ~ 50 arcsec with a spectral resolution is over 20,000. In
addition, we recently developed a heterodyne spectrometer called MILAHI on the 60 cm telescope. MILAHI is
characterized by super high-resolving power (more than 1,500,000) covering from 7 - 13 microns. Its sensitivity is 2400
K at 9.6 micron with a MCT photo diode detector of which bandwidth of 3000 MHz. ESPRIT and MILAHI is planned to
be installed on 60 cm telescope is planned in 2014.
ERIS: the exoplanet high-resolution image simulator for CHARIS
Show abstract
ERIS is an image simulator for CHARIS, the high-contrast exoplanet integral field spectrograph (IFS) being built at Princeton University for the Subaru telescope. We present here the software design and implementation of the ERIS code. ERIS simulates CHARIS FITS images and data cubes that are used for developing the data reduction pipeline and verifying the expected CHARIS performance. Components of the software include detailed models of the light source (such as a star or exoplanet), atmosphere, telescope, adaptive optics systems (AO188 and SCExAO), CHARIS IFS and the Hawaii2-RG infrared detector. Code includes novel details such as the phase errors at the lenslet array, optical wavefront error maps and pinholes for reducing crosstalk, just to list a few. The details of the code as well as several simulated images are presented in this paper. This IFS simulator is critical for the CHARIS data analysis pipeline development, minimizing troubleshooting in the lab and on-sky and the characterization of crosstalk.
The solar system at 10 parsec: exploiting the ExAO of LBT in the visual wavelengths
Show abstract
By exploiting the high strehl ratio PSF (point spread function) provided by the large binocular telescope (LBT), a high
contrast visual camera working in the range 650-700 nm can deliver impressive results with the help of a simple
coronagraph. In the framework of a feasibility study of such instrument, numerical simulations have been conducted to
assess its performances in terms of contrast enhancement in real seeing conditions. Both simulated and recorded time
series of adaptive optics residual aberrations are in fact used to estimate the contrast enhancement achieved with this
imager in different seeing conditions and with different occulting masks. The results obtained are extremely promising
and provide useful information for the detection of reflected light of Jupiter-like planets orbiting nearby stars in the range
of 5÷10 pc.
SPRAT: Spectrograph for the Rapid Acquisition of Transients
Show abstract
We describe the development of a low cost, low resolution (R ~ 350), high throughput, long slit spectrograph covering visible (4000-8000) wavelengths. The spectrograph has been developed for fully robotic operation with
the Liverpool Telescope (La Palma). The primary aim is to provide rapid spectral classification of faint (V ∼ 20)
transient objects detected by projects such as Gaia, iPTF (intermediate Palomar Transient Factory), LOFAR,
and a variety of high energy satellites. The design employs a volume phase holographic (VPH) transmission grating as the dispersive element combined with a prism pair (grism) in a linear optical path. One of two peak spectral sensitivities are selectable by rotating the grism. The VPH and prism combination and entrance slit are deployable, and when removed from the beam allow the collimator/camera pair to re-image the target field onto the detector. This mode of operation provides automatic acquisition of the target onto the slit prior to spectrographic observation through World Coordinate System fitting. The selection and characterisation of optical components to maximise photon throughput is described together with performance predictions.
DIPOL-2: a double image high precision polarimeter
Show abstract
We have built a new broad-band polarimeter (DIPOL-2), capable of measuring polarization with the precision at the 10-5
level. Two dichroic beam-splitters are used to split light into three passbands (BVR), simultaneously recorded with three
CCDs. A rotatable superachromatic λ/2 (or λ/4) plate is used as the polarization modulator and a plane parallel calcite
plate as the polarization analyzer. Simple yet effective design with small number of optical elements and moving
mechanical parts makes DIPOL-2 a highly versatile and reliable instrument with negligible instrumental polarization,
very well suitable for observations with remotely controlled telescopes. Current and planned observing programs are
briefly described.
H.O.R.S. a new visiting instrument for G.T.C. based on the Utrecht Echelle Spectrograph
Show abstract
The High Optical Resolution Spectrograph (HORS) is a proposed high-resolution spectrograph for the
10-m Gran Telescopio Canarias (GTC) based on components from UES, a spectrograph which was in
use at the 4.2-m William Herschel Telescope (WHT) between 1992 and 2001.
HORS is designed as a cross-dispersed echelle spectrograph to observe in the range 380-800 nm with
a FWHM resolving power of about 50,000. HORS would operate on the GTC as a general-purpose
high-resolution spectrograph, and it would serve as a test-bed for some of the technologies proposed
for ESPRESSO – an ultra-high stability spectrograph planned for the Very Large Telescope (VLT) of
the European Southern Observatory.
The HORS spectrograph will be placed in the Coudé room, where it can enjoy excellent thermal and
mechanical stability, fiber fed from the Nasmyth focus, which is shared with OSIRIS. Inside the
spectrograph, incoming light will hit a small folder mirror before reaching the collimator. After a
second folder, the light will go through a set of three prisms and an Echelle grating before entering the
spectrograph camera and, finally, reaching the detector.
This manuscript contains a summary of the whole process that has transformed UES into HORS, with
all the mechanical and optical modifications that have been introduced to reach the final layout.
ESPRESSO front end exposure meter: a chromatic approach to radial velocity correction
Show abstract
This paper presents the Espresso Exposure Meter (EM) implementation. ESPRESSO, the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, will be installed on ESOs Very Large Telescope (VLT). The light coming from the Telescope through a Coude Focus of all the Four Telescope Units (UTs) will be collected by the Front End Unit that provides Field and Pupil stabilisation and injects the beams into the Spectrograph fibers. An advanced Exposure Meter system will be used to correct Radial Velocity (RV) obtained from the scientific spectrum for the Earth relative motion. In this work we will present the performance of an innovative concept for the Exposure Meter system based on a Charge Coupled Device (CCD) with a chromatic approach for the calculation of the Mean Time of Exposure (MTE). The MTE is a fundamental quantity used for the correction of RV for the Earth relative motion during exposure. In particular, splitting the light in different chromatic channels on the CCD, we will probe for potential chromatic effects on the calculation of the MTE in each channel and how they could be used in order to perform the correction of RV. The paper is accompanied by a fully described numerical analysis that keeps into view a key performance evaluation for different stellar spectral types (B to M spectral main sequence classes).
First calibration and visible wavelength observations of Khayyam, a tunable spatial heterodyne spectroscopy (SHS)
Show abstract
We describe results from a new instrument-telescope configuration that combines all of the capabilities necessary to obtain high resolving power visible band spectra of diffuse targets from small aperture on-axis telescopes where significant observing time can be obtained. This instrument, Khayyam, is a tunable all-reflective spatial heterodyne spectrometer (TSHS) that is mounted to a fixed focal plane shared by the 0.6m Coude auxiliary telescope on Mt. Hamilton, CA. Khayyam has up to 55 arcsec input field of view, resolving power up to 176000, and a tunable bandpass covering (triangle)λB < 100nm. Khayyam is being field tested to study spatially extended astronomical targets where high resolving power is necessary to separate multimodal signals, crowded molecular bands, and to sample low (<10 km/s) velocities at rapid temporal cadence. Here we will discuss the design considerations going into this new system, its installation, testing of the interferometer-telescope combination, the first science target observations and future plans.
The metrology system for the multi-object optical and near-infrared spectrograph MOONS
Show abstract
The Multi-Object Optical and Near-infrared Spectrograph (MOONS) is a new fiber-fed spectrograph for the VLT. MOONS will exploit the full 500 square arcmin field of view offered by the Nasmyth focus of VLT and will be equipped with two dual-arm spectrographs covering the wavelength range 0.8 µm-1.8 μm, with a possible extension down to 0.5 μm. Each double-arm spectrograph will produce spectra for 250 targets simultaneously, each with its own dedicated sky fiber for optimal sky subtraction. The system will have both a medium resolution (R 3000 - 5000) mode and a high resolution (R 20000) mode to allow detailed dynamical and chemical studies. To ensure the accurate positioning of the 500 fiber pairs over the focal plane that has 880 mm in diameter, a metrology system has been designed to provide position measurements within 7.5 μm considering that the final positioning accuracy of each fiber with respect to the target object must be less than 15 μm. The metrology system is composed by a circular array of 12 cameras located at VLT’s de-rotator ring around the Nasmyth focus. The paper presents the design of the metrology system and discusses the proposed methodology to align multiple the views of the focal plane array.
Green astro-comb for HARPS-N
Show abstract
We report the design, installation and testing of a broadband green astro-comb on the HARPS-N spectrograph at the
TNG telescope. The astro-comb consists of over 7000 narrow lines (<10-6 nm width) spaced by 16 GHz (0.02 nm at 550
nm) with wavelengths stabilized to the Global Positioning System (GPS) and with flat power from 500 to 620 nm. The
narrow lines are used to calibrate the spectrograph and measure its line profile. The short term sensitivity of HARPS-N
is measured to be less than 2 cm/s and the long-term drift of the spectrograph is approximately 10 cm/s/day. The astrocomb
has been partially automated with future work planned to turn the astro-comb into a fully automated, push button
instrument.
A coronagraph based on two spatial light modulators for active amplitude apodizing and phase corrections
Show abstract
Almost all high-contrast imaging coronagraphs proposed until now are based on passive coronagraph optical
components. Recently, Ren and Zhu proposed for the first time a coronagraph that integrates a liquid crystal array (LCA)
for the active pupil apodizing and a deformable mirror (DM) for the phase corrections. Here, for demonstration purpose,
we present the initial test result of a coronagraphic system that is based on two liquid crystal spatial light modulators
(SLM). In the system, one SLM is served as active pupil apodizing and amplitude correction to suppress the diffraction
light; another SLM is used to correct the speckle noise that is caused by the wave-front distortions. In this way, both
amplitude and phase error can be actively and efficiently compensated. In the test, we use the stochastic parallel gradient
descent (SPGD) algorithm to control two SLMs, which is based on the point spread function (PSF) sensing and
evaluation and optimized for a maximum contrast in the discovery area. Finally, it has demonstrated a contrast of 10-6 at an inner working angular distance of ~6.2 λ/D, which is a promising technique to be used for the direct imaging of young exoplanets on ground-based telescopes.
Novel infrared polarimeter for the ESO CRIRES+ instrument
Show abstract
The CRIRES infrared spectrograph at the European Southern Observatory (ESO) Very Large Telescope (VLT)
facility will soon receive an upgrade. This upgrade will include the addition of a module for performing highresolution
spectropolarimetry. The polarimetry module will incorporate a novel infrared beamsplitter based on
polarization gratings (PGs). The beamsplitter produces a pair of infrared output beams, with opposite circular
polarizations, which are then fed into the spectrograph. Visible light passes through the module virtually
unaltered and is then available for use by the CRIRES adaptive optics system. We present the design of the
polarimetry module and measurements of PG behavior in the 1 to 2.7 μm wavelength range.
ESPRESSO Coudé-Train: complexities of a simultaneous optical feeding from the four VLT unit telescopes
Show abstract
ESPRESSO is a fibre-fed, cross-dispersed, high-resolution, echelle spectrograph. Being the first purpose of ESPRESSO
to develop a competitive and innovative high-resolution spectrograph to fully exploit the VLT (Very Large Telescope),
and allow new science, it is important to develop the VLT array concept bearing in mind the need to obtain the highest
stability, while preserving its best efficiency. This high-resolution ultra-stable spectrograph will be installed in the VLT
at the Combined Coudé Laboratory (CCL), fed by four Coudé Trains, which brings the light from the Nasmyth platforms
of the four VLT Unit Telescopes to the CCL. ESPRESSO will combine the efficiency of modern echelle spectrograph
with extreme radial-velocity precision. It will achieve a gain of two magnitudes with respect to its predecessor HARPS,
and the instrumental radial-velocity precision will be improved to reach cm/s level. Thanks to its ability of combining
incoherently the light of the 4 UTs, ESPRESSO will offer new possibilities in various fields of astronomy. The Coudé
Train is composed of a set of prisms, mirrors and lenses to deliver a pupil and an image in the CCL, including an
Atmospheric Dispersion Compensator. The use of mainly refractive optics, and Total Internal Reflection, has the
advantage of the inherent higher throughput, especially in the blue region of the spectrum.
In this paper, we present the design of the Coudé Train, the evolution of the concept towards the manufacturing phase, its
main characteristics and performances, and detail its subsystems: optical, mechanical and control electronics and
software.
Fast multichannel astronomical photometer based on silicon photo multipliers mounted at the Telescopio Nazionale Galileo
Show abstract
The realization of low-cost instruments with high technical performance is a goal that deserves efforts in an epoch of fast
technological developments. Such instruments can be easily reproduced and therefore allow new research programs to be
opened in several observatories. We realized a fast optical photometer based on the SiPM (Silicon Photo Multiplier)
technology, using commercially available modules. Using low-cost components, we developed a custom electronic chain
to extract the signal produced by a commercial MPPC (Multi Pixel Photon Counter) module produced by Hamamatsu
Photonics to obtain sub-millisecond sampling of the light curve of astronomical sources (typically pulsars). We built a
compact mechanical interface to mount the MPPC at the focal plane of the TNG (Telescopio Nazionale Galileo), using
the space available for the slits of the LRS (Low Resolution Spectrograph). On February 2014 we observed the Crab
pulsar with the TNG with our prototype photometer, deriving its period and the shape of its light curve, in very good
agreement with the results obtained in the past with other much more expensive instruments. After the successful run at
the telescope we describe here the lessons learned and the ideas that burst to optimize this instrument and make it more
versatile.
Photometric study of the Paranal observatory using MASS database
Show abstract
The atmospheric extinction is an important parameter for an astronomical site. The extinction directly affects
the observations reducing the available radiation, but the most relevant effect on the quality of the astronomical
data is the variation of the extinction across the sky and in the course of the observation at night. The aim is
to trace the atmospheric transparency at any astronomical site using MASS data.
The main goal of the present work is estimating the atmospheric extinction coefficient (mag/airmass) from
MASS database. Multi Aperture Scintillation Sensor called MASS is an instrument to measure the vertical
distribution of turbulence in terrestrial atmosphere by analyzing the scintillation of bright stars. Here we are
briefly reminding you of the principles of a MASS instrument and presenting also the detailed description of the
output data. In order to gain better understanding of the atmospheric photometry, we compute the atmospheric
extinction coefficient, its rms, and the associated information from MASS database using the evolution of flux
values of a star measured at ground level versus air mass which accounts for the flux loss. The technique used is
based on the Bouguer low. To treat the statistics data correctly and compute the correct extinction, one has
to know the filter. Correct value of the extinction is critical at most. For this reason, the atmospheric extinction
must be extracted only by good measurements. We then used the quality control of MASS data.
Also, in the current paper, we focus on the evaluation of nocturnal atmospheric extinction coefficient
(mag/airmass) and others statistics (time of acquisition, accumulation time, air mass, and HR number is used as
a star name only for information . . .) at Paranal observatory (70°24’05” W, 24°37’24” S, altitude 2635 m a.s.l,
in Chile.). In addition, the rms error of the coefficient has been calculated. It is absolutely needed to evaluate
the accuracy of each extinction measurement. For the first time, they were obtained from MASS database photo metric processing during 885 nights in the years 2004, 2005, 2006 and 2007. These results will almost lead to
complete its characterization. The project is implemented in the frame of the European Southern Observatory
contract No. PO 014190/HNEU.
First performance of the GeMS+GMOS system
Show abstract
During the 2012 commissioning of the Gemini MCAO System (GeMS) in Gemini South Observatory, we briefly explored the performance improvement brought by pairing GeMS with the Gemini Multi-Object Spectrograph (GMOS), compared to GMOS in natural seeing mode. GMOS is an instrument sensitive in the visible band with imaging and spectroscopic capabilities, hence pushing MCAO toward the visible, a mode for which it was not specifically designed.
We report in this paper the first results obtained with the GeMS +GMOS pair. Several globular clusters were observed in imaging mode only. We have derived performance in term of FWHM and determined the improvement against natural seeing. We also obtain photometric, relative and absolute astrometric precision for the AO enhanced images. We also studied the influence of the NGS constellation on the photometric performance.
Finally, we also looked at the expected performance of the GeMS+GMOS system once the CCD upgrade, scheduled during 2014, will occur.
Poster Session: Extremely Large Telescopes and Instruments
Design and analysis of a large-diameter precision optical mount for NFIRAOS
Show abstract
This study describes the design evolution, finite element analysis (FEA) and experimental testing completed to develop
the large optical mounts for the Near-Field IR Adaptive Optics System (NFIRAOS), the facility Adaptive Optics system
for the Thirty Meter Telescope (TMT). The mount design incorporates a unique combination of bonded flexure-based
linear actuators and a roller-chain radial support. Extensive FEA was completed to refine the design to ensure the final
mount design will meet the required operational performance. Experimental work was conducted to ensure that the
suitability of the bonded interface between the optic and the flexures and to verify that the high bond stiffness did not
cause fracture of the glass during thermal cycling.
HARMONI instrument control electronics
Show abstract
HARMONI is an integral field spectrograph working at visible and near-infrared wavelengths over a
range of spatial scales from ground layer corrected to fully diffraction-limited. The instrument has been
chosen to be part of the first-light complement at the European Extremely Large Telescope (E-ELT). This
paper describes the instrument control electronics to be developed at IAC. The large size of the
HARMONI instrument, its cryogenic operation, and the fact that it must operate with enhanced reliability
is a challenge from the point of view of the control electronics design. The present paper describes a
design proposal based on the current instrument requirements and intended to be fully compliant with the
ESO E-ELT standards, as well as with the European EMC and safety standards. The modularity of the
design and the use of COTS standard hardware will benefit the project in several aspects, as reduced
costs, shorter schedule by the use of commercially available components, and improved quality by the use
of well proven solutions.
A novel systems engineering approach to the design of a precision radial velocity spectrograph: the GMT-Consortium Large Earth
Finder (G-CLEF)
Show abstract
One of the first light instruments for the Giant Magellan Telescope (GMT) will be the GMT-Consortium Large Earth
Finder (G-CLEF). It is an optical band echelle spectrograph that is fiber fed to enable high stability. One of the key
capabilities of G-CLEF will be its extremely precise radial velocity (PRV) measurement capability. The RV precision
goal is 10 cm/sec, which is expected to be achieved with advanced calibration methods and the use of the GMT adaptive
optics system. G-CLEF, as part of the GMT suite of instruments, is being designed within GMT's automated
requirements management system. This includes requirements flow down, traceability, error budgeting, and systems
compliance. Error budgeting is being employed extensively to help manage G-CLEF technical requirements and ensure
that the top level requirements are met efficiently. In this paper we discuss the G-CLEF error budgeting process,
concentrating on the PRV precision and instrument throughput budgets. The PRV error budgeting process is covered in
detail, as we are taking a detailed systems error budgeting approach to the PRV requirement. This has proven
particularly challenging, as the precise measurement of radial velocity is a complex process, with error sources that are
difficult to model and a complex calibration process that is integral to the RV measurement. The PRV budget combines
traditional modeling and analysis techniques, where applicable, with semi-empirical techniques, as necessary.
Extrapolation from existing PRV instruments is also used in the budgeting process.
The infrared imaging spectrograph (IRIS) for TMT: volume phase holographic grating performance testing and discussion
Show abstract
Maximizing the grating efficiency is a key goal for the first light instrument IRIS (Infrared Imaging Spectrograph)
currently being designed to sample the diffraction limit of the TMT (Thirty Meter Telescope). Volume Phase
Holographic (VPH) gratings have been shown to offer extremely high efficiencies that approach 100% for high line
frequencies (i.e., 600 to 6000l/mm), which has been applicable for astronomical optical spectrographs. However, VPH
gratings have been less exploited in the near-infrared, particularly for gratings that have lower line frequencies. Given
their potential to offer high throughputs and low scattered light, VPH gratings are being explored for IRIS as a potential
dispersing element in the spectrograph. Our team has procured near-infrared gratings from two separate vendors. We
have two gratings with the specifications needed for IRIS current design: 1.51-1.82μm (H-band) to produce a spectral
resolution of 4000 and 1.19-1.37μm (J-band) to produce a spectral resolution of 8000. The center wavelengths for each
grating are 1.629μm and 1.27μm, and the groove densities are 177l/mm and 440l/mm for H-band R=4000 and J-band
R=8000, respectively. We directly measure the efficiencies in the lab and find that the peak efficiencies of these two
types of gratings are quite good with a peak efficiency of ~88% at the Bragg angle in both TM and TE modes at H-band,
and 90.23% in TM mode, 79.91% in TE mode at J-band for the best vendor. We determine the drop in efficiency off the
Bragg angle, with a 20-23% decrease in efficiency at H-band when 2.5° deviation from the Bragg angle, and 25%-28%
decrease at J-band when 5° deviation from the Bragg angle.
Development of a subwavelength grating vortex coronagraph of topological charge 4 (SGVC4)
Show abstract
One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector
vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal plane of the telescope with a
phase singularity in its center. Such an optical vortex is characterized by its topological charge, i.e., the number of times
the phase accumulates 2π radians along a closed path surrounding the singularity. Over the past few years, we have been
developing a charge-2 VVC induced by rotationally symmetric subwavelength gratings (SGVC2), also known as the
Annular Groove Phase Mask (AGPM). Since 2013, several SGVC2s (or AGPMs) were manufactured using synthetic
diamond substrate, then validated on dedicated optical benches, and installed on 10-m class telescopes. Increasing the
topological charge seems however mandatory for cancelling the light of bright stars which will be partially resolved by
future Extremely Large Telescopes in the near-infrared. In this paper, we first detail our motivations for developing an
SGVC4 (charge 4) dedicated to the near-infrared domain. The challenge lies in the design of the pattern which is
unrealistic in the theoretically perfect case, due to state-of-the-art manufacturing limitations. Hence, we propose a new
realistic design of SGVC4 with minimized discontinuities and optimized phase ramp, showing conclusive improvements
over previous works in this field. A preliminary validation of our concept is given based on RCWA simulations, while
full 3D finite-difference time-domain simulations (and eventually laboratory tests) will be required for a final validation.
Integral field spectroscopy of high redshift galaxies with the HARMONI spectrograph on the European Extremely Large Telescope
Show abstract
We present here results of simulated integral field spectroscopic observations with the HARMONI instrument for the 39-m European Extremely Large Telescope. HARMONI (PI: N. Thatte) will provide adaptive optics- assisted 3D spectroscopy at a range of spatial scales and spectral resolutions. The instrument will for the first time allow the spectroscopic study of z = 2 - 5 galaxies at the scales of individual star-forming complexes
(∼100 pc). Using a sophisticated instrument simulator we show here innovative simulated observations of a
star-forming galaxy at z = 3, based on output from cosmological simulations using the RAMSES code. Our simulator includes realistic adaptive optics point spread functions, atmospheric and instrumental noise models
and observational parameters. Using these simulations, we can test analysis methods for the study of the galaxy’s dynamics and kinematics and compare these against predictions from galaxy evolution models. We thus demonstrate a methodology for predicting future observables from cosmological simulations.
Trade-off study for high resolution spectroscopy in the near infrared with ELT telescopes: seeing-limited vs. diffraction limited instruments
Show abstract
HIRES, a high resolution spectrometer, is one of the first five instruments foreseen in the ESO roadmap for the E-ELT. This spectrograph should ideally provide full spectral coverage from the UV limit to 2.5 microns, with
a resolving power from R∼10,000 to R∼100,000. At visual/blue wavelengths, where the adaptive optics (AO)
cannot provide an efficient light-concentration, HIRES will necessarily be a bulky, seeing-limited instrument.
The fundamental question, which we address in this paper, is whether the same approach should be adopted in the near-infrared range, or HIRES should only be equipped with compact infrared module(s) with a much smaller aperture, taking advantage of an AO-correction. The main drawbacks of a seeing-limited instrument at all wavelengths are: i) Lower sensitivities at wavelengths dominated by thermal background (red part of the K-band). ii) Much higher volumes and costs for the IR spectrograph module(s). The main drawbacks of using smaller, AO-fed IR module(s) are: i) Performances rapidly degrading towards shorter wavelengths (especially J e Y bands). ii) Different spatial sampling of extended objects (the optical module see a much larger area on the sky). In this paper we perform a trade-off analysis and quantify the various effects that contribute to improve or deteriorate the signal to noise ratio. In particular, we evaluate the position of the cross-over wavelength at which AO-fed instruments starts to outperform seeing-limited instruments. This parameter is of paramount importance for the design of the part of HIRES covering the K-band.
Simulations of high-z galaxy observations with an ELT-MOS
Show abstract
We present simulated observations of one of the major science cases for the 39m E-ELT, namely the detection of very high-z galaxies. We simulated the detection of UV interstellar lines at z = 7 and the detection of the Lyman alpha line and the Lyman break at z = 9, both with MOAO-assisted IFUs and GLAO-fed fibers. These simulations are performed with the scientific simulator we developped in the frame of the E-ELT phase A studies. First, we give a functional description of this simulator, which is coupled to a public web interface WEBSIM, and we then give an example of its practical use to constrain the high level specifications of MOSAIC, a new multi-object spectrograph concept for the E-ELT. Our simulations show that the most constraining case is the detection of UV interstellar lines. The optimal pixel size is found to be ~80 mas, which allows detecting
UV lines up to JAB ~27 in 40 hours of integration time. Lyman Alpha Emitters and Lyman Break Galaxies are detected respectively up to JAB ~30 and JAB ~28 with a 80 mas/pixel IFU and within only 10 hours of integration time. Detection limits are typically ~0.5-1 mag fainter using MOAO-fed IFUs than using GLAO-fed fibers, but the multiplex is one magnitude larger in the mode using GLAO-fed fibers. We explore the optimal observational strategy for each observing mode considering these observing limits as well as the expected target densities.
All-sky homogeneity of precipitable water vapour over Paranal
Show abstract
A Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics
GmbH (RPG), is used to monitor sky conditions over ESO’s Paranal observatory in support of VLT science operations.
The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the
low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.4 mm). The instrument consists
of a humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared camera (~10 μm) for cloud
detection. We present, for the first time, a statistical analysis of the homogeneity of all-sky PWV using 21 months of
periodic (every 6 hours) all-sky scans from the radiometer. These data provide unique insight into the spatial and
temporal variation of atmospheric conditions relevant for astronomical observations, particularly in the infrared. We find
the PWV over Paranal to be remarkably homogeneous across the sky down to 27.5° elevation with a median variation of
0.32 mm (peak to valley) or 0.07 mm (rms). The homogeneity is a function of the absolute PWV but the relative
variation is fairly constant at 10-15% (peak to valley) and 3% (rms). Such variations will not be a significant issue for
analysis of astronomical data. Users at ESO can specify PWV – measured at zenith – as an ambient constraint in service
mode to enable, for instance, very demanding observations in the infrared that can only be conducted during periods of
very good atmospheric transmission and hence low PWV. We conclude that in general it will not be necessary to add
another observing constraint for PWV homogeneity to ensure integrity of observations. For demanding observations
requiring very low PWV, where the relative variation is higher, the optimum support could be provided by observing
with the LHATPRO in the same line-of-sight simultaneously. Such a mode of operations has already been tested but will
have to be justified in terms of scientific gain before implementation can be considered. This will be explored further in
the future.
Simulating observations with HARMONI: the integral field spectrograph for the European Extremely Large Telescope
Show abstract
With the next generation of extremely large telescopes commencing construction, there is an urgent need for detailed quantitative predictions of the scientific observations that these new telescopes will enable. Most of these new telescopes will have adaptive optics fully integrated with the telescope itself, allowing unprecedented spatial resolution combined with enormous sensitivity. However, the adaptive optics point spread function will be strongly wavelength dependent, requiring detailed simulations that accurately model these variations. We have developed a simulation pipeline for the HARMONI integral field spectrograph, a first light instrument for the European Extremely Large Telescope. The simulator takes high-resolution input data-cubes of astrophysical objects and processes them with accurate atmospheric, telescope and instrumental effects, to produce mock observed cubes for chosen observing parameters. The output cubes represent the result of a perfect data reduc- tion process, enabling a detailed analysis and comparison between input and output, showcasing HARMONI’s capabilities. The simulations utilise a detailed knowledge of the telescope’s wavelength dependent adaptive op- tics point spread function. We discuss the simulation pipeline and present an early example of the pipeline functionality for simulating observations of high redshift galaxies.
The MANIFEST fibre positioning system for the Giant Magellan Telescope
Show abstract
MANIFEST is a fibre feed system for the Giant Magellan Telescope that, coupled to the seeing-limited instruments
GMACS and G-CLEF, offers qualitative and quantitative gains over each instrument’s native capabilities in terms of
multiplex, field of view, and resolution. The MANIFEST instrument concept is based on a system of semi-autonomous
probes called “Starbugs” that hold and position hundreds of optical fibre IFUs under a glass field plate placed at the
GMT Cassegrain focal plane. The Starbug probes feature co-axial piezoceramic tubes that, via the application of
appropriate AC waveforms, contract or bend, providing a discrete stepping motion. Simultaneous positioning of all
Starbugs is achieved via a closed-loop metrology system.
A mechanical design concept for EAGLE on the revised E-ELT
Show abstract
ESO have recently revisited the design of the E-ELT with a view to reducing cost, leading to de-scopes which include a
smaller primary aperture and removal of the Gravity Invariant Focal Station (GIFS). In its original concept, the EAGLE
instrument was designed to be located at the GIFS and consequently a major mechanical re-design was required to enable
the instrument to be placed on its side in a conventional straight-through Nasmyth configuration. In this paper, a conceptual
design for a new instrument structure is presented. A preliminary finite element analysis was carried out to assess the
structure’s behaviour under operating loading conditions (e.g. gravity loads). The results of this analysis demonstrate that
the proposed design is viable, without any significant degradation in performance compared to the original GIFS design.
Science case and requirements for the MOSAIC concept for a multi-object spectrograph for the European Extremely Large Telescope
Show abstract
Over the past 18 months we have revisited the science requirements for a multi-object spectrograph (MOS) for the
European Extremely Large Telescope (E-ELT). These efforts span the full range of E-ELT science and include input
from a broad cross-section of astronomers across the ESO partner countries. In this contribution we summarise the key
cases relating to studies of high-redshift galaxies, galaxy evolution, and stellar populations, with a more expansive
presentation of a new case relating to detection of exoplanets in stellar clusters. A general requirement is the need for
two observational modes to best exploit the large (≥40 arcmin2) patrol field of the E-ELT. The first mode (‘high
multiplex’) requires integrated-light (or coarsely resolved) optical/near-IR spectroscopy of >100 objects simultaneously.
The second (‘high definition’), enabled by wide-field adaptive optics, requires spatially-resolved, near-IR of >10
objects/sub-fields. Within the context of the conceptual study for an ELT-MOS called MOSAIC, we summarise the toplevel
requirements from each case and introduce the next steps in the design process.
The spectrograph units for the HARMONI integral field spectrograph
Show abstract
The spectrograph sub-system is responsible for dispersing the light from the slicer with the required spectral resolving
power and imaging the spectra on to a detector. Each image slicer creates a single exit slit feeding a single spectrograph
unit containing visible (VIS) and infrared (IR) cameras. The four HARMONI slicers in total create four exit slits, feeding
four spectrograph units comprising of collimators, dispersers, and cameras. The focal plane of each camera contains a
mosaic of two 4Kx4K detectors, leading to 8K pixels along the length of the slit. The HARMONI wavelength range
(0.43 μm to 2.45 μm) splits into a visible and a near-infrared wavelength range with a transition wavelength at 0.8 μm. The optical design of HARMONI up to the dispersers is fully reflective and therefore the pre-optics and IFU subsystems,
as well the spectrograph collimator, can be used for both the visible and near-infrared wavelength range. Only
the dispersers and the spectrograph cameras are different for the visible and near infrared spectral ranges. To not
duplicate sub-systems unnecessarily the wavelength split in the spectrograph is realised by inserting a dichroic in the
collimated beam before the disperser to either direct the light towards the visible disperser and camera, or let it pass
toward the near-infrared disperser and camera. In contrast to the Phase A study all of HARMONI spectrograph unit will
have both visible and near infrared disperser and cameras.
Mid-IR AGPMs for ELT applications
Show abstract
The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet
and its host star with respect to the visible and near-infrared wavelength regimes. This contrast may be further
improved with Vector Vortex Coronagraphs (VVCs), which allow us to cancel the starlight. One flavour of
the VVC is the AGPM (Annular Groove Phase Mask), which adds the interesting properties of subwavelength
gratings (achromaticity, robustness) to the already known properties of the VVC. In this paper, we present
the optimized designs, as well as the expected performances of mid-IR AGPMs etched onto synthetic diamond
substrates, which are considered for the E-ELT/METIS instrument.
The opto-mechanical design of the GMT-consortium large earth finder (G-CLEF)
Show abstract
The GMT-Consortium Large Earth Finder (G-CLEF) is a fiber fed, optical echelle spectrograph that has been selected as
a first light instrument for the Giant Magellan Telescope (GMT) currently under construction at the Las Campanas
Observatory in Chile’s Atacama desert region. We designed G-CLEF as a general-purpose echelle spectrograph with
precision radial velocity (PRV) capability used for exoplanet detection. The radial velocity (RV) precision goal of GCLEF
is 10 cm/sec, necessary for detection of Earth-sized planets orbiting stars like our Sun in the habitable zone. This
goal imposes challenging stability requirements on the optical mounts and the overall spectrograph support structures.
Stability in instruments of this type is typically affected by changes in temperature, orientation, and air pressure as well
as vibrations caused by telescope tracking. For these reasons, we have chosen to enclose G-CLEF’s spectrograph in a
thermally insulated, vibration isolated vacuum chamber and place it at a gravity invariant location on GMT’s azimuth
platform. Additional design constraints posed by the GMT telescope include: a limited space envelope, a thermal
emission ceiling, and a maximum weight allowance. Other factors, such as manufacturability, serviceability, available
technology and budget are also significant design drivers. All of the previously listed considerations must be managed
while ensuring that performance requirements are achieved.
In this paper, we discuss the design of G-CLEF’s optical mounts and support structures including technical choices made
to minimize the system’s sensitivity to thermal gradients. A more general treatment of the properties of G-CLEF can be
found elsewhere in these proceedings1. We discuss the design of the vacuum chamber which houses the irregularly
shaped optical bench and optics while conforming to a challenging space envelope on GMT’s azimuth platform. We also
discuss the design of G-CLEF’s insulated enclosure and thermal control systems which maintain the spectrograph at
milli-Kelvin level stability while simultaneously limiting the maximum thermal emission into the telescope dome
environment. Finally, we discuss G-CLEF’s front-end assembly and fiber-feed system as well as other interface
challenges presented by the telescope, enclosure and neighboring instrumentation.
SKA pulsar search: technological challenges and best algorithms development
Show abstract
One of the key scientific projects of the SKA radio telescope is a large survey for pulsars both in isolated and
binary systems. The data rate of the pulsar search engine is expected to reach 0.6TeraSamples/sec. For the
purposes of extracting hidden pulses from these streams, we need a complex search strategy which allows us
to explore a three dimensional parameter space and it requires approximately 10PetaFlops. This problem is
well suited for a parallel computing engine, but the dimensions of SKA bring this problem to a new level of
complexity. An up-to-date study shows that this operation would require more than 2000 GPUs. In this report
we will present possible mitigation strategies.
The infrared imaging spectrograph (IRIS) for TMT: reflective ruled diffraction grating performance testing and discussion
Show abstract
We present the efficiency of near-infrared reflective ruled diffraction gratings designed for the InfraRed Imaging
Spectrograph (IRIS). IRIS is a first light, integral field spectrograph and imager for the Thirty Meter Telescope
(TMT) and narrow field infrared adaptive optics system (NFIRAOS). IRIS will operate across the near-infrared
encompassing the ZYJHK bands (~0.84 - 2.4μm) with multiple spectral resolutions. We present our experimental
setup and analysis of the efficiency of selected reflective diffraction gratings. These measurements are used as a
comparison sample against selected candidate Volume Phase Holographic (VPH) gratings (see Chen et al., this
conference). We investigate the efficiencies of five ruled gratings designed for IRIS from two separate vendors.
Three of the gratings accept a bandpass of 1.19-1.37μm (J band) with ideal spectral resolutions of R=4000 and
R=8000, groove densities of 249 and 516 lines/mm, and blaze angles of 9.86° and 20.54° respectively. The other
two gratings accept a bandpass of 1.51-1.82μm (H Band) with an ideal spectral resolution of R=4000, groove
density of 141 lines/mm, and blaze angle of 9.86°. The fraction of flux in each diffraction mode was compared to
both a pure reflection mirror as well as the sum of the flux measured in all observable modes. We measure the
efficiencies off blaze angle for all gratings and the efficiencies between the polarization transverse magnetic (TM)
and transverse electric (TE) states. The peak reflective efficiencies are 98.90 ± 3.36% (TM) and 84.99 ± 2.74%
(TM) for the H-band R=4000 and J-band R=4000 respectively. The peak reflective efficiency for the J-band R=8000
grating is 78.78 ± 2.54% (TE). We find that these ruled gratings do not exhibit a wide dependency on incident angle
within ±3°. Our best-manufactured gratings were found to exhibit a dependency on the polarization state of the
incident beam with a ~10-20% deviation, consistent with the theoretical efficiency predictions. This work will
significantly contribute to the selection of the final grating type and vendor for the IRIS optical system, and are also
pertinent to current and future near-infrared astronomical spectrographs.
Three possible types of coronagraphs for the E-ELT PCS instrument
Show abstract
The spectral characterization in the near infrared of Neptune-like planets and super-Earths is one of the main science objectives of the E-ELT. The planetary camera and spectrograph (PCS) will be in charge of making it possible. We have designed three different instruments: pure apodizers, apodized Lyot coronagraphs, and apodized vortex coronagraphs. In each cases the central obscuration and the secondary supports are taken into account in the design of the apodizer. We present a trade study of the imaging performance of these coronagraphs, and we describe how sensitive these coronagraphs are to various aberrations. This is used to assess the potential complementarity between these three types of instruments. Finally, we also consider the feasibility of an active control of aperture discontinuities and/or a phase induced amplitude apodization using the two deformable mirrors of an extreme adaptive optics system associated with the coronagraphs.
The high contrast imaging modes of MICADO
Show abstract
We present in this paper an overview of the high contrast imaging modes of the wide-field imager MICADO. MICADO is a near-IR camera for the European Extremely Large Telescope (E-ELT), featuring a wide field (75”), spectroscopic and coronagraphic capabilities. It has been chosen by ESO as one of the two first-light instruments. MICADO will be optimized for the multi-conjugate adaptive optics module MAORY and will also work in SCAO mode. This SCAO mode will provide MICADO with a high-level, on-axis correction, making use of the M4 adaptive mirror in the telescope.
After presenting the scientific interest for high contrast imaging modes in MICADO, we describe the technical choices we are studying. We present the hypotheses chosen for our simulation tools and contrast as well as planet detection performance derived from this tool.
An aperture masking mode for the MICADO instrument
Show abstract
MICADO is a near-IR camera for the European ELT, featuring an extended field (75” diameter) for imaging, and also spectrographic and high contrast imaging capabilities. It has been chosen by ESO as one of the two first-light instruments. Although it is ultimately aimed at being fed by the MCAO module called MAORY, MICADO will come with an internal SCAO system that will be complementary to it and will deliver a high performance on axis correction, suitable for coronagraphic and pupil masking applications. The basis of the pupil masking approach is to ensure the stability of the optical transfer function, even in the case of residual errors after AO correction (due to non common path errors and quasi-static aberrations). Preliminary designs of pupil masks are presented. Trade-offs and technical choices, especially regarding redundancy and pupil tracking, are explained.
The G-CLEF spectrograph optical design
Show abstract
The GMT-Consortium Large Earth Finder (G-CLEF) is a fiber fed, optical echelle spectrograph, which has been selected
as a first light instrument for the Giant Magellan Telescope (GMT) currently under construction at the Las Campanas
Observatory. We designed G-CLEF as a general-purpose echelle spectrograph with a precision radial velocity (PRV)
capability goal of 0.1 m/s, which will enable it to detect/measure the mass of an Earth-sized planet orbiting a Solar-type
star in its habitable zone. This goal imposes challenging requirements on all aspects of the instrument and some of those
are best incorporated directly into the optical design process. In this paper we describe the preliminary optical design of
the G-CLEF instrument and briefly describe some novel solutions we have introduced into the asymmetric white pupil
echelle configuration.
On-instrument wavefront sensor design for the TMT infrared imaging spectrograph (IRIS) update
Show abstract
The first light instrument on the Thirty Meter Telescope (TMT) project will be the InfraRed Imaging Spectrograph
(IRIS). IRIS will be mounted on a bottom port of the facility AO instrument NFIRAOS. IRIS will report guiding
information to the NFIRAOS through the On-Instrument Wavefront Sensor (OIWFS) that is part of IRIS. This will be in
a self-contained compartment of IRIS and will provide three deployable wavefront sensor probe arms. This entire unit
will be rotated to provide field de-rotation. Currently in our preliminary design stage our efforts have included:
prototyping of the probe arm to determine the accuracy of this critical component, handling cart design and reviewing
different types of glass for the atmospheric dispersion.
DKIST visible broadband imager interference filters
Show abstract
The Visible Broadband Imager (VBI) is one of several first-light instruments of the Daniel K. Inouye Solar Telescope (DKIST, formerly known as the Advanced Technology Solar Telescope (ATST)). Operating at discrete wavelengths within a range of 390-860 nm, the VBI will be capable of sampling the solar atmosphere in several layers at the diffraction limit of DKIST’s 4 meter aperture. The layers are selected by the peak wavelength and bandpass width of its interference filters that have to be manufactured to very tight specifications. We present the results of testing performed at the National Solar Observatory’s Dunn Solar Telescope (DST) to confirm that the requirements were met by the vendor.
Optical and mechanical design of the fore-optics of HARMONI
Show abstract
HARMONI is a visible and near-infrared (0.47μm to 2.5μm) integral field spectrometer providing the E-ELT's core
spectroscopic capability. It will provide ~32000 simultaneous spectra of a rectangular field of view at four foreseen
different spatial sample (spaxel) scales. The HARMONI fore-optics re-formats the native telescope plate scale to suitable
values for the downstream instrument optics. This telecentric adaptation includes anamorphic magnification of the plate
scale to optimize the performance of the IFU, which contains the image slicer, and their four spectrographs. In addition,
it provides an image of the telescope pupil to assemble a cold stop shared among all the scales allowing efficient
suppression of the thermal background. A pupil imaging unit also re-images the pupil cold stop onto the image slicer to
check the relative alignment between the E-ELT and HARMONI pupils. The scale changer will also host the filter wheel
with the long-pass filters to select the wavelength range. The main reasoning specifying the importance of the
HARMONI fore-optics and its current optical and mechanical design is described in this contribution.
Beating the heat! automated characterization of piezoelectric tubes for Starbugs
Show abstract
The Australian Astronomical Observatory has extensively prototyped a new robotic positioner to allow simultaneous
positioning of optical fibers at the focal plane called ‘Starbugs’. The Starbug devices each consist of two concentric
piezoelectric tubes that ‘walk’ the optical fiber over the focal plane to accuracy of several microns. Ongoing research has
led to the development of several Starbug prototypes, but lack of performance data has hampered further progress in the
design of the Starbug positioners and the support equipment required to power and control them. Furthermore, Starbugs
have been selected for the TAIPAN instrument, a prototype for MANIFEST on the GMT. A need now arises to measure
and characterize 100’s of piezoelectric tubes before full scale production of Starbugs for TAIPAN. The manual
measurements of these piezoelectric tubes are a time consuming process taking several hours. Therefore, a versatile
automated system is needed to measure and characterize these tubes in the laboratory before production of Starbugs. We
have solved this problem with the design of an automated LabVIEW application that significantly reduces test times to
several minutes. We present the various design aspects of the automation system and provide analyses of example
piezoelectric tubes for Starbugs.
Wireless software update system based on Zigbee for LAMOST
Show abstract
Large Sky Area Multi-object Fiber Spectroscopic Telescope - LAMOST, has a 1.75m-diameter focal plane on which 4000
optical fibers are arranged in order to obtain the spectrums of astrometric objects. Each optical fiber is installed on a
mechanical unit which is driven by a cell controller. The mechanical units are installed on the focal plane one by one
closely with high density, and the focal plane is above-ground, so the cell controllers are very inconvenient to remove and
install. Each time when we maintain or upgrade the motor drive system of LAMOST, we need to download new program to
the cell controllers. But it always takes a lot of time to take out the cell controllers from the focal plane.
So we propose a wireless program-updated technology based on Zigbee which can download the program to the cell
controllers without removing and installing. In order to realize the goal, we need to update the FLASH of target controllers
without hardware connection. So we transmit the program through Zigbee wireless network which has been used in
LAMOST already. After we use the wireless update system based on Zigbee, it is much easier and convenient for us to
maintain or upgrade the motor drive system of LAMOST. In this paper we illustrate how to realize the wireless update
system from hardware and software.
Cryogenic testing of components for the HARMONI spectrograph
Show abstract
HARMONI is an integral field spectrograph working in the visible and near-infrared (0.47 to 2.45 μm) and will provide
the E-ELT’s core spectroscopic capability, starting at first light. To minimise the thermal background it will be a
cryogenic instrument with the optomechanics inside the cryostat having an operating temperature of 130K. We have
designed three different thermally compensating lens mounts and have started analysing their performance by measuring
the position of a glass blank relative to the mount to look for any displacement and tilt as it cooled down to operating
temperature. The suitability of a commercial iris shutter for use in HARMONI is also assessed and found to work down
to 120K, though further work is needed to prove it is reliable enough to be included in HARMONI, including an
accelerated lifetime test.
The fiber-fed preslit of GIANO at T.N.G.
Show abstract
Giano is a Cryogenic Spectrograph located in T.N.G. (Spain) and commissioned in 2013. It works in the range 950-2500
nm with a resolving power of 50000.
This instrument was designed and built for direct feeding from the telescope [2]. However, due to constraints imposed on
the telescope interfacing during the pre-commissioning phase, it had to be positioned on the rotating building, far from
the telescope focus. Therefore, a new interface to the telescope, based on IR-transmitting ZBLAN fibers with 85μm core,
was developed. Originally designed to work directly at the f/11 nasmyth focus of the telescope, in 2011 it has decided to
use a fiber to feed it.
The beam from the telescope is focused on a double fiber boundle by a Preslit Optical Bench attached to the Nasmith A
interface of the telescope. This Optical Bench contains the fiber feeding system and other important features as a guiding
system, a fiber viewer, a fiber feed calibration lamp and a nodding facility between the two fibers. The use of two fibers
allow us to have in the echellogram two spectrograms side by side in the same acquisition: one of the star and the other
of the sky or simultaneously to have the star and a calibration lamp. Before entering the cryostat the light from the fiber
is collected by a second Preslit Optical Bench attached directly to the Giano cryostat: on this bench the correct f-number
to illuminate the cold stop is generated and on the same bench is placed an image slicer to increase the efficiency of the
system.
Simultaneous phase and amplitude retrieval with COFFEE: from theory to laboratory results
Show abstract
The final performance of current and future instruments dedicated to exoplanet detection and characterization (such as
SPHERE on the VLT, GPI on Gemini North or future instruments on the ELTs) is limited by intensity residuals in the
scientific image plane, which originate in uncorrected optical aberrations. After correction of the atmospheric turbulence,
the main contribution to these residuals comes from the quasi-static aberrations introduced upstream of the coronagraph
which create long-lived speckles in the detector plane that can easily be mistaken for a planet. In order to reach very high
contrast such as the ones required to image earth-like planets, these aberrations needs to be compensated for. We have
recently proposed a dedicated focal-plane wave-font sensor called COFFEE (for COronagraphic Focal-plane wave-Front
Estimation for Exoplanet detection), which consists in an extension of conventional phase diversity to a coronagraphic
system: aberrations both upstream and downstream of the coronagraph are estimated using two coronagraphic focal-plane
images, recorded from the scientific camera itself, without any differential aberration. Such a system has been successfully
validated on the SPHERE instrument, where COFFEEs estimation has been used to compensate for the phase aberration
upstream of the coronagraph, leading to a contrast optimization in the whole focal plane area controlled by the AO loop.
If compensating for phase aberrations only was acceptable to reach levels of contrast of 106, it will no longer be the case
for instruments that aim at imaging earth-like planets. Such targets, which would be the ones of a planet-finder instrument
integrated on an ELT, require a level of contrast better than 109. To reach this level, neglecting amplitude aberrations
(inhomogeneous intensity in the pupil, Fresnel propagation effect) is no longer possible. In this communication, we
present an extension of COFFEE able to perform a simultaneous estimation of both phase and amplitude aberration from
three focal plane images. After a theoretical presentation, we present a study of its performances. Notably, we analyze
the contrast that can be achieved in a compensation process when this estimation method is combined with our non-linear
dark hole method, demonstrating that the nanometric precision estimation that can be achieved with COFFEE allow one
to reach very high contrast levels. It is worth mentioning that both estimation (COFFEE) and compensation (the nonlinear
dark hole) methods are model based, and thus easily adaptable to a broad class of coronagraphic device. Lastly, we
validate our complex field estimator on the LAM (Laboratoire dAstrophysique de Marseille) XAO test bench, described
in this communication. We introduce calibrated phase and amplitude aberration in the entrance pupil plane. Then, we
demonstrate the ability of our extended version of COFFEE to estimate both phase and amplitude aberration from three
coronagraphic focal plane images that differs from a known aberration.
Infrared differential imager and spectrograph for SPHERE: performance assessment for on-sky operation
Show abstract
SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research) is a second-generation instrument for the VLT,
optimized for very high-contrast imaging around bright stars. Its primary goal is the detection and characterization of
new giant planets around nearby stars, together with the observation of early planetary systems and disks. The Infrared
Dual Imager and Spectrograph (IRDIS), one of the three SPHERE subsystems, will provide dual-band imaging in the
near-infrared, among with other observing modes such as long slit spectroscopy, classical imaging and infrared
polarimetry. IRDIS is able to achieve very high contrast with the help of extreme-AO turbulence compensation,
coronography, exceptional image quality, very accurate calibration strategies and advanced data processing. IRDIS
underwent extensively laboratory testing during the integration and optimization of SPHERE at IPAG and it is now
integrated to the VLT/ESO. We will present the results of performances and operations validations performed with
SPHERE. In particular we present the achievable level of contrast and compare it with on-sky results obtained at the
VLT/ESO.
Fully cryogenic phased array prototype camera for the Arecibo radio telescope
Show abstract
We have developed a fully cryogenically cooled, 19-element phased array feed (PAF), prototype camera for the
Arecibo Radio Telescope. The 19 PAF elements are dual polarized dipoles over a ground plane, and they sit
behind a 70 cm diameter vacuum window transparent to RF.
LOTUCE2: a dome-seeing instrument for the E-ELT
Show abstract
Free-atmosphere, and surface-layer optical-turbulence have been extensively monitored over the years. The
optical-turbulence inside a telescope enclosure en the other hand has yet to be as fully characterized. For this
latest purpose, an experimental concept, LOTUCE (LOcal TUrbulenCe Experiment) has been developed in
order to measure and characterise the so-called dome-seeing. LOTUCE2 is an upgraded prototype whose main
aim is to measure optical turbulence characteristics more precisely by minimising cross-contamination of signals.
This characterisation is both quantitative (optical turbulence strength) and qualitative (assessing the optical
turbulence statistical model). We present the new opto-mechanical design, with the theoretical capabilities and
limitations to the actual models.
The infrared imaging spectrograph (IRIS) for TMT: overview of innovative science programs
Show abstract
IRIS (InfraRed Imaging Spectrograph) is a first light near-infrared diffraction limited imager and integral field
spectrograph being designed for the future Thirty Meter Telescope (TMT). IRIS is optimized to perform astronomical
studies across a significant fraction of cosmic time, from our Solar System to distant newly formed galaxies (Barton et
al. [1]). We present a selection of the innovative science cases that are unique to IRIS in the era of upcoming space and
ground-based telescopes. We focus on integral field spectroscopy of directly imaged exoplanet atmospheres, probing
fundamental physics in the Galactic Center, measuring 104 to 1010 M supermassive black hole masses, resolved
spectroscopy of young star-forming galaxies (1 < z < 5) and first light galaxies (6 < z < 12), and resolved spectroscopy
of strong gravitational lensed sources to measure dark matter substructure. For each of these science cases we use the
IRIS simulator (Wright et al. [2], Do et al. [3]) to explore IRIS capabilities. To highlight the unique IRIS capabilities, we
also update the point and resolved source sensitivities for the integral field spectrograph (IFS) in all five broadband
filters (Z, Y, J, H, K) for the finest spatial scale of 0.004" per spaxel. We briefly discuss future development plans for the
data reduction pipeline and quicklook software for the IRIS instrument suite.
Drift scanning technique for mid-infrared background subtraction
Show abstract
Accurate calibration of ground-based, mid-infrared observations is challenging due to the strong and rapidly varying thermal background emission. The classical solution is the chopping/nodding technique where the secondary mirror and the telescope are being moved by several tens of arcseconds on the sky. However, chopping is generally inefficient and limited in accuracy and frequency by the mass and size of the secondary mirror. A more elegant solution is a drift scan where the telescope slowly drifts across or around the region of interest; the source moves on the detector by at least one FWHM of the PSF within the time over which the detector performance and the background emission can be considered stable. The final image of a drift scan is mathematically reconstructed from a series of adjacent short exposures. The drift scan approach has recently received a lot of interest, mainly for two reasons: first, some of the new, large-format mid-IR Si:As detectors (AQUARIUS) suffer from excess low frequency noise (ELFN). To reach the nominal performance limit of the detectors, chopping would have to be performed at a high frequency, faster than what most telescopes can handle; second, the next generation of extremely large telescopes will not offer chopping/nodding, and alternative methods need to be developed and tested. In this paper we present the results from simulated drift scan data. We use drift scanning to simultaneously obtain an accurate detector flat field and the sky background. The results are relevant for the future operation and calibration of VISIR at the VLT as well as for METIS, the thermal infrared instrument for the E-ELT.