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- Front Matter: Volume 8446
- Instrumentation at Major Observatories
- New Instruments
- Multi-Object Instruments I
- Multi-Object Instruments II
- Imaging Surveyors I
- Imaging Surveyors II
- Airborne Instruments
- Solar Instruments
- ELT Instruments I
- ELT Instruments II
- ELT Instruments III
- Planet Finders I
- Planet Finders II
- High Resolution and AO Instruments
- Posters: New Instruments and Upgrades/Reports on Existing Instruments
- Posters: Multi-Object Instruments
- Posters: Imaging Surveyors/Solar Instrumentation/Airborne Instrumentation
- Posters: ELT Instruments
- Posters: Planet Finders/High Resolution AO Instruments
Front Matter: Volume 8446
Front Matter: Volume 8446
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This PDF file contains the front matter associated with SPIE Proceedings Volume 8446, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.
Instrumentation at Major Observatories
Advances in instrumentation at the W. M. Keck Observatory
Show abstract
In this paper we describe both recently completed instrumentation projects and our current development efforts in terms
of their role in the strategic plan, the key science areas they address, and their performance as measured or predicted.
Projects reaching completion in 2012 include MOSFIRE, a near IR multi-object spectrograph, a laser guide star adaptive
optics facility on the Keck I telescope, and an upgrade to the guide camera for the HIRES instrument on Keck I. Projects
in development include a new seeing limited integral field spectrograph for the visible wavelength range called the Keck
Cosmic Web Imager (KCWI), an upgrade to the telescope control systems on both Keck telescopes, a near-IR tip/tilt
sensor for the Keck I adaptive optics system, and a new grating for the OSIRIS integral field spectrograph.
Overview of the ESO instrumentation programme
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The ESO instrumentation programme now encompasses both an on-going programme for La-Silla Paranal observatory
and a new programme for construction of the instruments for the E-ELT. The scale and ambition of the combined
programme will present a future challenge for the European instrument-building community and for ESO as managing
organisation. The current status and plans are summarised.
Instrumentation at the Subaru Telescope
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In these two years, FMOS was fully commissioned and the laser guide star mode of AO188 became available for
open use. The telescope was recovered from coolant leak accident and the two damaged instruments, Suprime-Cam and FOCAS, will both be back in operation in 2012. All the components of the Hyper Suprime-Cam (HSC)
were transported to the telescope site and on-sky engineering will start in the summer 2012. As a future facility
instrument, Prime-Focus Spectrograph (PFS), an optical to near-IR multi-object spectrograph with 2400 fibers,
was endorsed by Japanese community and the project is in PDR phase. Upgrading MOIRCS, IRCS and HDS
are on going. Several visiting instruments are also planed. The feasibility of a ground-layer AO with a wide-field
NIR instrument is beeing investigated for a possible next facility instrument after PFS.
Gemini's instrumentation program: latest results and long-range plan
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The Gemini Observatory is going through an extraordinary time with astronomical instrumentation. New powerful
capabilities are delivered and are soon entering scientific operations. In parallel, new instruments are being planned and
designed to align the strategy with community needs and enhance the competitiveness of the Observatory for the next
decade. We will give a broad overview of the instrumentation program, focusing on achievements, challenges and
strategies within a scientific, technical and management perspective. In particular we will discuss the following
instruments and projects (some will have dedicated detailed papers in this conference): GMOS-CCD refurbishment,
FLAMINGOS-2, GeMS (MCAO system and imager GSAOI), GPI, new generation of A&G, GRACES (fiber feed to
CFHT ESPaDOnS) and GHOS (Gemini High-resolution Optical Spectrograph), and provide some updates about
detector controllers, mid-IR instruments, Altair, GNIRS, GLAO and future workhorse instruments.
An overview of instrumentation for the Large Binocular Telescope
Show abstract
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 (27′ x 27′) 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 Spectroscopic Utility with Camera and Integral Field Unit for Extragalactic Research (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 multiobject
spectroscopy utilizing cooled slit masks and diffraction limited (FOV: 0′.5 × 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 on the LBT and 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. Over the past four years the LBC pair, LUCI1, and MODS1 have been commissioned
and are now scheduled for routine partner science observations. The delivery of both LUCI2 and MODS2 is
anticipated before the end of 2012. The availability of all these instruments mounted simultaneously on the LBT
permits unique science, flexible scheduling, and improved operational support.
The La Silla-Paranal (LSP) instrumentation program
Show abstract
Beyond 2020 La Silla - Paranal Observatory (LSP) will still play, together with ALMA and the E-ELT, a crucial role in
European ground based astronomy. ESO has created a dedicated LSP Instrumentation program, with the aim of keeping
its instrumentation at the forefront beyond year 2020, in the ELT era. The LSP instrumentation program is fully
dedicated to this task, and foresees, in addition to the completion of running projects (IInd generation VLT/I instruments,
Adaptive Secondary for the VLT) to start one new project every year in the 2014 - 2020 period. A roadmap for the
development of the instrumentation plan is also being developed.
New Instruments
The SALT HRS spectrograph: instrument integration and laboratory test results
Show abstract
SALT HRS is a fibre-fed, high dispersion échelle spectrograph currently being constructed for the Southern African
Large Telescope (SALT). In this paper we highlight the performance of key optical components, describe the integration
tasks that have taken place and present some first light results from the laboratory. The instrument construction is well
advanced and we report on the attainment of the required mechanical and thermal stability and provide a measurement of
the input optics performance (including the fibre feed). The initial optical alignment of both the fibre input optics,
including image slicers, and the spectrograph optics has taken place and is described.
Performance of the CHIRON high-resolution Echelle spectrograph
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CHIRON is a fiber-fed Echelle spectrograph with observing modes for resolutions from 28,000 to 120,000, built
primarily for measuring precise radial velocities (RVs). We present the instrument performance as determined during
integration and commissioning. We discuss the PSF, the effect of glass inhomogeneity on the cross-dispersion prism,
temperature stabilization, stability of the spectrum on the CCD, and detector characteristics. The RV precision is
characterized, with an iodine cell or a ThAr lamp as the wavelength reference. Including all losses from the sky to the
detector, the overall efficiency is about 6%; the dominant limitation is coupling losses into the fiber due to poor guiding.
VISIR upgrade overview and status
Show abstract
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 demonstrated very good performance (sensitivity, stability) in the laboratory 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 userdefined
constraint on water vapour. Improved pipelines based on the ESO Reflex concept will provide better support to
astronomers. The upgraded VISIR will be a powerful instrument providing 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 intervention on VISIR and installation of hardware has been completed in July and
commissioning will take place during July and August. VISIR is scheduled to be available to the users starting Oct 2012.
ARCONS: a 1024 pixel superconducting integral field spectrograph
Show abstract
ARCONS, the Array Camera for Optical to Near-infrared Spectrophotometry, was recently commissioned at the
Coude focus of the 200-inch Hale Telescope at the Palomar Observatory. At the heart of this unique instrument
is a 1024-pixel Microwave Kinetic Inductance Detector (MKID), exploiting the Kinetic Inductance effect to
measure the energy of the incoming photon to better than several percent. The ground-breaking instrument is
lens coupled with a pixel scale of 0.23"/pixel, with each pixel recording the arrival time (< 2 _μsec) and energy of
a photon (~10%) in the optical to near-IR (0.4-1.1 microns) range. The scientific objectives of the instrument
include the rapid follow-up and classi_cation of the transient phenomena
On-sky performance of the Multi-Object Double Spectrograph for the Large Binocular Telescope
Show abstract
The Multi-Object Double Spectrographs (MODS) are two identical high-throughput optical dichroic-split double-beam
low- to medium-dispersion CCD spectrometers being deployed at the Large Binocular Telescope (LBT). They operate in
the 3200-10500Å range at a nominal resolution of λ/δλ≈2000. MODS1 saw first-light at the LBT in September 2010,
finished primary commissioning in May 2011, and began regular partner science operations in September 2011. MODS2
is being readied for delivery and installation at the end of 2012. This paper describes the on-sky performance of MODS1
and presents highlights from the first year of science operations.
Performance of the Apache Point Observatory Galactic Evolution Experiment (APOGEE) high-resolution near-infrared multi-object fiber spectrograph
Show abstract
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) uses a dedicated 300-fiber, narrow-band
near-infrared (1.51-1.7 μm), high resolution (R~22,500) spectrograph to survey approximately 100,000 giant stars across
the Milky Way. This three-year survey, in operation since late-summer 2011 as part of the Sloan Digital Sky Survey III
(SDSS III), will revolutionize our understanding of the kinematical and chemical enrichment histories of all Galactic
stellar populations. We present the performance of the instrument from its first year in operation. The instrument is
housed in a separate building adjacent to the 2.5-m SDSS telescope and fed light via approximately 45-meter fiber runs
from the telescope. The instrument design includes numerous innovations including a gang connector that allows
simultaneous connection of all fibers with a single plug to a telescope cartridge that positions the fibers on the sky,
numerous places in the fiber train in which focal ratio degradation had to be minimized, a large mosaic-VPH (290 mm x
475 mm elliptically-shaped recorded area), an f/1.4 six-element refractive camera featuring silicon and fused silica
elements with diameters as large as 393 mm, three near-infrared detectors mounted in a 1 x 3 mosaic with sub-pixel
translation capability, and all of these components housed within a custom, LN2-cooled, stainless steel vacuum cryostat
with dimensions 1.4-m x 2.3-m x 1.3-m.
FLAMINGOS-2: the facility near-infrared wide-field imager and multi-object spectrograph for Gemini
Show abstract
We report on the design, on-sky performance, and status of the FLAMINGOS-2 instrument – the fully-cryogenic facility
near-infrared imager and multi-object spectrograph for the Gemini 8-meter telescopes. FLAMINGOS-2 has a refractive
all-spherical optical system providing 0.18-arcsecond pixels and a 6.2-arcminute circular field-of-view on a 2048x2048-
pixel HAWAII-2 0.9-2.4 μm detector array. A slit/decker wheel mechanism allows the selection of up to 9 multi-object
laser-machined plates or 3 long slits for spectroscopy over a 6x2-arcminute field of view, and selectable grisms provide
resolutions from ~1300 to ~3000 over the entire spectrograph bandpass. FLAMINGOS-2 is also compatible with the
Gemini Multi-Conjugate Adaptive Optics system, providing multi-object spectroscopic capabilities over a 3x1-arcminute
field with high spatial resolution (0.09-arcsec/pixel). We review the designs of optical, mechanical, electronics,
software, and On-Instrument WaveFront Sensor subsystems. We also present the on-sky performance measured during
acceptance testing in 2009, as well as current status of the project and future plans.
MOSFIRE, the multi-object spectrometer for infra-red exploration at the Keck Observatory
Show abstract
This paper describes the as-built performance of MOSFIRE, the multi-object spectrometer and imager for the Cassegrain
focus of the 10-m Keck 1 telescope. MOSFIRE provides near-infrared (0.97 to 2.41 μm) multi-object spectroscopy over
a 6.1' x 6.1' field of view with a resolving power of R~3,500 for a 0.7" (0.508 mm) slit (2.9 pixels in the dispersion
direction), or imaging over a field of view of ~6.9' diameter with ~0.18" per pixel sampling. A single diffraction grating
can be set at two fixed angles, and order-sorting filters provide spectra that cover the K, H, J or Y bands by selecting 3rd,
4th, 5th or 6th order respectively. A folding flat following the field lens is equipped with piezo transducers to provide
tip/tilt control for flexure compensation at the <0.1 pixel level. Instead of fabricated focal plane masks requiring frequent
cryo-cycling of the instrument, MOSFIRE is equipped with a cryogenic Configurable Slit Unit (CSU) developed in
collaboration with the Swiss Center for Electronics and Microtechnology (CSEM). Under remote control the CSU can
form masks containing up to 46 slits with ~0.007-0.014" precision. Reconfiguration time is < 6 minutes. Slits are formed
by moving opposable bars from both sides of the focal plane. An individual slit has a length of 7.0" but bar positions can
be aligned to make longer slits in increments of 7.5". When masking bars are retracted from the field of view and the
grating is changed to a mirror, MOSFIRE becomes a wide-field imager. The detector is a 2K x 2K H2-RG HgCdTe
array from Teledyne Imaging Sensors with low dark current and low noise. Results from integration and commissioning
are presented.
Multi-Object Instruments I
Status of the KMOS multi-object near-infrared integral field spectrograph
Show abstract
KMOS is a multi-object near-infrared integral field spectrograph being built by a consortium of UK and German
institutes. We report on the final integration and test phases of KMOS, and its performance verification, prior to
commissioning on the ESO VLT later this year.
Subaru FMOS now and future
Show abstract
Fiber Multi Object Spectrograph “FMOS” on Subaru Telescope is capable of configuring 400 fibers on the 30-
arcmin diameter field of view at the prime focus for near-infrared (0.9–1.8 μm) spectroscopy, and this instrument
has been open as a common-use instrument since May 2010. In this article, an overview of the instrument is
given first, and then the typical operational sequence in science observation and a few notable features of the
instrument are explained. In (see manuscript) 5, the instrument performance in terms of fiber positioning, auto guiding, and
sensitivity to emission lines are highlighted. Recently (since March 2012) a Subaru Strategic Program (SSP)
has started with FMOS to conduct a wide-field galaxy survey for a cosmological experiment. Upgrading fiber
configuration by using a “metrology camera” has also been under discussion, which will enable to measure the
positions of the 400 fibers quickly and shorten the fiber configuration time significantly. We will also report the
status of these recent activities.
VIRUS: production of a massively replicated 33k 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 units, each with a pair of spectrographs) fed by 33,600 fibers, each 1.5 arcsec diameter,
deployed over the 22 arcminute field of the upgraded 10 m Hobby-Eberly Telescope (HET). The goal is to deploy 82
units. 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 spectral surveys of large areas of sky. This
approach, in which a relatively simple, inexpensive, unit spectrograph is copied in large numbers, 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
by early 2014 and will provide a powerful new facility instrument for the HET, well suited to the survey niche of the
telescope. VIRUS and HET will open up wide-field surveys of the emission-line universe for the first time. We present
the production design and current status of VIRUS.
SuperMOS: a new class of low resolution multiobject spectrographs
Show abstract
Microwave Kinetic Inductance Detector (MKID) arrays, recently demonstrated at the Palomar 200 inch telescope, are a new superconducting detector technology that has great potential for astrophysics. We propose a new type of instrument, a Superconducting Multi-Object Spectrograph (SuperMOS), that uses MKIDs in conjunction with a focal plane mask. We present the design and science goals of a SuperMOS designed for LSST follow-up named Giga-z. Housing a 100,000 pixel MKID array with energy resolution R=50{100 and a 0.35-1.35 μm bandwidth, it will be capable of measuring 2 billion spectra and determining redshifts over 20,000 square degrees in 3 years down to mi ≈ 24.5 on a dedicated 4-meter telescope. Compared to LSST alone, Giga-z should improve the redshift precision by a factor of three with a much lower catastrophic failure rate.
Multi-Object Instruments II
WEAVE: the next generation wide-field spectroscopy facility for the William Herschel Telescope
Show abstract
We present the preliminary design of the WEAVE next generation spectroscopy facility for the William Herschel
Telescope (WHT), principally targeting optical ground-based follow up of upcoming ground-based (LOFAR) and spacebased
(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 or up to 30
integral field units 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.
Mapping the universe with BigBOSS
Show abstract
[The BigBOSS experiment is a redshift survey designed to map the large scale structure of the universe and probe the nature of dark energy. Using massively-multiplexed _ber spectroscopy over 14,000 deg2 of sky, the survey will deliver more than 20 million galaxy and quasar redshifts. The resulting three dimensional sky map will contain signatures from primordial baryon acoustic oscillations (BAO) that set a "standard ruler" distance scale. Using the BAO signature, BigBOSS will measure the cosmological distance scale to < 1% accuracy from 0.5<z<3.0, shedding new light on the expansion history and growth of large scale structure in the Universe at a time when dark energy began to dominate. In this work, we give an overview of the BigBOSS survey goals and methodology, focusing on measuring the [O II] λ3727 emission line doublet from star-forming galaxies. We detail a new spectral simulation tool used in generating BigBOSS observations for emission-line galaxy targets. We perform a trade study of the detected galaxy redshift distribution under two observational cases relative to the baseline survey and discuss the impact on the BigBOSS science goal.
CARMENES. I: instrument and survey overview
Show abstract
CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a next-generation instrument for the 3.5m telescope at the Calar Alto Observatory, built by a consortium of eleven Spanish and German institutions. The CARMENES instrument consists of two separate échelle spectrographs covering the wavelength range from 0.55 μm to 1.7 μm at a spectral resolution of R = 82, 000, fed by fibers from the Cassegrain focus of the telescope. Both spectrographs are housed in temperature-stabilized vacuum tanks, to enable a long-term 1 m/s radial velocity precision employing a simultaneous calibration with Th-Ne and U-Ne emission line lamps. CARMENES has been optimized for a search for terrestrial planets in the habitable zones (HZs) of low-mass stars, which may well provide our first chance to study environments capable of supporting the development of life outside the Solar System. With its unique combination of optical and near-infrared ´echelle spectrographs, CARMENES will provide better sensitivity for the detection of low-mass planets than any comparable instrument, and a powerful tool for discriminating between genuine planet detections and false positives caused by stellar activity. The CARMENES survey will target 300 M dwarfs in the 2014 to 2018 time frame.
MOONS: a multi-object optical and near-infrared spectrograph
for the VLT
M. Cirasuolo,
J. Afonso,
R. Bender,
et al.
Show abstract
MOONS is a new conceptual design for a Multi-Object Optical and Near-infrared Spectrograph for the Very Large
Telescope (VLT), selected by ESO for a Phase A study. 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.
The grasp of the 8.2m Very Large Telescope (VLT) combined with the large multiplex and wavelength coverage of
MOONS – extending into the near-IR – will provide the observational power necessary to study galaxy formation and
evolution over the entire history of the Universe, from our Milky Way, through the redshift desert and up to the epoch
of re-ionization at z<8-9. At the same time, the high spectral resolution mode will allow astronomers to study chemical
abundances of stars in our Galaxy, in particular in the highly obscured regions of the Bulge, and provide the necessary
follow-up of the Gaia mission. Such characteristics and versatility make MOONS the long-awaited workhorse near-IR
MOS for the VLT, which will perfectly complement optical spectroscopy performed by FLAMES and VIMOS.
4MOST: 4-metre multi-object spectroscopic telescope
Roelof S. de Jong,
Olga Bellido-Tirado,
Cristina Chiappini,
et al.
Show abstract
The 4MOST consortium is currently halfway through a Conceptual Design study for ESO with the aim to develop a wide-field ( < 3 square degree, goal < 5 square degree), high-multiplex ( < 1500 fibres, goal 3000 fibres) spectroscopic survey facility for an ESO 4m-class telescope (VISTA). 4MOST will run permanently on the telescope to perform a 5 year public survey yielding more than 20 million spectra at resolution R∼5000 (λ=390–1000 nm) and more than 2 million spectra at R~20,000 (395–456.5 nm and 587–673 nm). The 4MOST design is especially intended to complement three key all-sky, space-based observatories of prime European interest: Gaia, eROSITA and Euclid. Initial design and performance estimates for the wide-field corrector concepts are presented. Two fibre positioner concepts are being considered for 4MOST. The first one is a Phi-Theta system similar to ones used on existing and planned facilities. The second one is a new R-Theta concept with large patrol area. Both positioner concepts effectively address the issues of fibre focus and pupil pointing. The 4MOST spectrographs are fixed configuration two-arm spectrographs, with dedicated spectrographs for the high- and low-resolution fibres. A full facility simulator is being developed to guide trade-off decisions regarding the optimal field-of-view, number of fibres needed, and the relative fraction of high-to-low resolution fibres. The simulator takes mock catalogues with template spectra from Design Reference Surveys as starting point, calculates the output spectra based on a throughput simulator, assigns targets to fibres based on the capabilities of the fibre positioner designs, and calculates the required survey time by tiling the fields on the sky. The 4MOST consortium aims to deliver the full 4MOST facility by the end of 2018 and start delivering high-level data products for both consortium and ESO community targets a year later with yearly increments.
Final design of SITELLE: a wide-field imaging Fourier transform spectrometer for the Canada-France-Hawaii Telescope
Show abstract
We report here on the current status of SITELLE, an imaging Fourier transform spectrometer to be installed on the
Canada-France Hawaii Telescope in 2013. SITELLE is an Integral Field Unit (IFU) spectrograph capable of obtaining
the visible (350 nm – 900 nm) spectrum of every pixel of a 2k x 2k CCD imaging a field of view of 11 x 11 arcminutes,
with 100% spatial coverage and a spectral resolution ranging from R = 1 (deep panchromatic image) to R < 104 (for gas
dynamics). SITELLE will cover a field of view 100 to 1000 times larger than traditional IFUs, such as GMOS-IFU on
Gemini or the upcoming MUSE on the VLT. SITELLE follows on the legacy of BEAR, an imaging conversion of the
CFHT FTS and the direct successor of SpIOMM, a similar instrument attached to the 1.6-m telescope of the
Observatoire du Mont-Mégantic in Québec. SITELLE will be used to study the structure and kinematics of HII regions
and ejecta around evolved stars in the Milky Way, emission-line stars in clusters, abundances in nearby gas-rich
galaxies, and the star formation rate in distant galaxies.
KOALA: a wide-field 1000 element integral-field unit for the Anglo-Australian Telescope
Show abstract
KOALA, the Kilofibre Optimised Astronomical Lenslet Array, is a wide-field, high efficiency integral field unit
being designed for use with the bench mounted AAOmega spectrograph on the AAT. KOALA will have 1000
fibres in a rectangular array with a selectable field of view of either 1390 or 430 sq. arcseconds with a spatial
sampling of 1.25" or 0.7" respectively. To achieve this KOALA will use a telecentric double lenslet array with
interchangeable fore-optics. The IFU will feed AAOmega via a 31m fibre run. The efficiency of KOALA is
expected to be ≈ 52% at 3700A and ≈ 66% at 6563°Å with a throughput of > 52% over the entire wavelength
range.
Integrating the HERMES spectrograph for the AAT
Show abstract
The High Efficiency and Resolution Multi Element Spectrograph, HERMES is an optical spectrograph designed
primarily for the GALAH, Galactic Archeology Survey, the first major attempt to create a detailed understanding of
galaxy formation and evolution by studying the history of our own galaxy, the Milky Way1. 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 in the Milky Way. The spectrograph will be based at the Anglo Australian
Telescope (AAT) and be fed with the existing 2dF robotic fibre 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 aiming 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.
Current efforts are focused on manufacturing and integration. The delivery date of spectrograph at the telescope is
scheduled for 2013. A performance prediction is presented and a complete overview of the status of the HERMES
spectrograph is given. This paper details the following specific topics:
The approach to AIT, the manufacturing and integration of the large mechanical frame, the opto-mechanical slit
assembly, collimator optics and cameras, VPH gratings, cryostats, fibre cable assembly, instrument control hardware and
software, data reduction.
SAMI: a new multi-object IFS for the Anglo-Australian Telescope
Show abstract
SAMI (Sydney-AAO Multi-object Integral field spectrograph) has the potential to revolutionise our understanding
of galaxies, with spatially-resolved spectroscopy of large numbers of targets. It is the first on-sky application of
innovative photonic imaging bundles called hexabundles, which will remove the aperture effects that have biased
previous single-fibre multi-object astronomical surveys. The hexabundles have lightly-fused circular multi-mode
cores with a covering fraction of 73%. The thirteen hexabundles in SAMI, each have 61 fibre cores, and feed
into the AAOmega spectrograph at the Anglo-Australian Telescope (AAT). SAMI was installed at the AAT in
July 2011 and the first commissioning results prove the effectiveness of hexabundles on sky. A galaxy survey of
several thousand galaxies to z 0.1 will begin with SAMI in mid-2012.
Prime focus spectrograph: Subaru's future
Show abstract
The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project has been
endorsed by Japanese community as one of the main future instruments of the Subaru 8.2-meter telescope at Mauna Kea,
Hawaii. This optical/near-infrared multi-fiber spectrograph targets cosmology with galaxy surveys, Galactic archaeology,
and studies of galaxy/AGN evolution.
Taking advantage of Subaru’s wide field of view, which is further extended with the recently completed Wide Field
Corrector, PFS will enable us to carry out multi-fiber spectroscopy of 2400 targets within 1.3 degree diameter. A
microlens is attached at each fiber entrance for F-ratio transformation into a larger one so that difficulties of spectrograph design are eased. Fibers are accurately placed onto target positions by positioners, each of which consists of two stages
of piezo-electric rotary motors, through iterations by using back-illuminated fiber position measurements with a widefield
metrology camera. Fibers then carry light to a set of four identical fast-Schmidt spectrographs with three color arms
each: the wavelength ranges from 0.38 μm to 1.3 μm will be simultaneously observed with an average resolving power
of 3000.
Before and during the era of extremely large telescopes, PFS will provide the unique capability of obtaining spectra of
2400 cosmological/astrophysical targets simultaneously with an 8-10 meter class telescope. The PFS collaboration, led
by IPMU, consists of USP/LNA in Brazil, Caltech/JPL, Princeton, and JHU in USA, LAM in France, ASIAA in Taiwan,
and NAOJ/Subaru.
Imaging Surveyors I
Hyper Suprime-Cam
Show abstract
Hyper Suprime-Cam (HSC) is an 870 Mega pixel prime focus camera for the 8.2 m Subaru telescope. The wide field corrector delivers sharp image of 0.25 arc-sec FWHM in r-band over the entire 1.5 degree (in diameter) field of view. The collimation of the camera with respect to the optical axis of the primary mirror is realized by hexapod actuators whose mechanical accuracy is few microns. As a result, we expect to have seeing limited image most of the time. Expected median seeing is 0.67 arc-sec FWHM in i-band. The sensor is a p-ch fully depleted CCD of 200 micron thickness (2048 x 4096 15 μm square pixel) and we employ 116 of them to pave the 50 cm focal plane. Minimum interval between exposures is roughly 30 seconds including reading out arrays, transferring data to the control computer and saving them to the hard drive. HSC uniquely features the combination of large primary mirror, wide field of view, sharp image and high sensitivity especially in red. This enables accurate shape measurement of faint galaxies which is critical for planned weak lensing survey to probe the nature of dark energy. The system is being assembled now and will see the first light in August 2012.
First light with RATIR: an automated 6-band optical/NIR imaging camera
Show abstract
The Reionization and Transients InfraRed camera (RATIR) is a simultaneous optical/NIR multi-band imaging
camera which is 100% time-dedicated to the followup of Gamma-ray Bursts. The camera is mounted on the
1.5-meter Johnson telescope of the Mexican Observatorio Astronomico Nacional on Sierra San Pedro Martir in
Baja California. With rapid slew capability and autonomous interrupt capabilities, the system will image GRBs
in 6 bands (i, r, Z, Y, J, and H) within minutes of receiving a satellite position, detecting optically faint afterglows
in the NIR and quickly alerting the community to potential GRBs at high redshift (z>6-10). We report here
on this Spring's first light observing campaign with RATIR. We summarize the instrumental characteristics,
capabilities, and observing modes.
Status of the Dark Energy Survey Camera (DECam) project
Show abstract
The Dark Energy Survey Collaboration has completed construction of the Dark Energy Camera (DECam), a 3 square
degree, 570 Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be
used to perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the
remainder of the time, and after the survey, DECam will be available as a community instrument. All components of
DECam have been shipped to Chile and post-shipping checkout finished in Jan. 2012. Installation is in progress. A
summary of lessons learned and an update of the performance of DECam and the status of the DECam installation and
commissioning will be presented.
The Keck Cosmic Web Imager: a capable new integral field spectrograph for the W. M. Keck Observatory
Show abstract
The Keck Cosmic Web Imager (KCWI) is a new facility instrument being developed for the W. M. Keck Observatory
and funded for construction by the Telescope System Instrumentation Program (TSIP) of the National Science
Foundation (NSF). KCWI is a bench-mounted spectrograph for the Keck II right Nasmyth focal station, providing
integral field spectroscopy over a seeing-limited field up to 20"x33" in extent. Selectable Volume Phase Holographic
(VPH) gratings provide high efficiency and spectral resolution in the range of 1000 to 20000. The dual-beam design of
KCWI passed a Preliminary Design Review in summer 2011. The detailed design of the KCWI blue channel (350 to
700 nm) is now nearly complete, with the red channel (530 to 1050 nm) planned for a phased implementation contingent
upon additional funding. KCWI builds on the experience of the Caltech team in implementing the Cosmic Web Imager
(CWI), in operation since 2009 at Palomar Observatory. KCWI adds considerable flexibility to the CWI design, and will
take full advantage of the excellent seeing and dark sky above Mauna Kea with a selectable nod-and-shuffle observing
mode. In this paper, models of the expected KCWI sensitivity and background subtraction capability are presented,
along with a detailed description of the instrument design. The KCWI team is lead by Caltech (project management,
design and implementation) in partnership with the University of California at Santa Cruz (camera optical and
mechanical design) and the W. M. Keck Observatory (program oversight and observatory interfaces).
Imaging Surveyors II
Design of FOSC for 360-cm Devasthal Optical Telescope
A. Omar,
R. K. S. Yadav,
V. Shukla,
et al.
Show abstract
A Faint Object Spectrograph and Camera (FOSC) is designed for the upcoming 360-cm optical telescope at
Devasthal. The design is based on other available similar instruments, having a collimator and camera unit. The
instrument converts F/9 beam from the telescope to a nearly F/4.3 beam. The collimator and camera optics
have 7 and 5 elements respectively with one aspheric component. The low dispersion glasses such as CaF2 and
PBM/PBL/FSL are used in order to minimize the chromatic aberrations. These glasses also have very good
transmission near blue wavelengths. The imaging is possible both in narrow and broad band filters up to the
field of view of ~ 14' x 14' or 19' along the diagonal. The spectroscopy can be performed in the wavelength
range 350 - 900 nm with several choices of grisms and slits with resolution in the range of 250 - 2000. The
theoretical spot sizes in the imaging mode are expected in the range 0:04" - 0:11". The overall transmission of
the camera and collimator optics is expected as ~ 75% at 350 nm and > 95% at wavelengths above 400 nm.
The total weight of the instrument as designed is around 350 kg. The instrument is currently planned to be
assembled in the Institute laboratory and to be commissioned on the 360-cm telescope in October 2013. The
design methodology, techniques, and expected performance of the optics are presented here.
Airborne Instruments
The FORCAST mid-infrared facility instrument and in-flight performance on SOFIA
Show abstract
FORCAST has completed 16 engineering and science flights as the “First Light” U. S. science instrument aboard SOFIA
and will be commissioned as a SOFIA facility instrument in 2013. FORCAST offers dual channel imaging (diffractionlimited
at wavelengths < 15 microns) using a 256 x 256 pixel Si:As blocked impurity band (BIB) detector at 5 - 28
microns and a 256 x 256 pixel Si:Sb BIB detector at 28 - 40 microns. FORCAST images a 3.4 arcmin × 3.2 arcmin fieldof-
view on SOFIA with a rectified plate scale of 0.768 arcsec/pixel. In addition to imaging capability, FORCAST offers
a facility mode for grism spectroscopy that will commence during SOFIA Cycle 1. The grism suite enables spectroscopy
over nearly the entire FORCAST wavelength range at low resolution (~140 - 300). Optional cross-dispersers boost the
spectroscopic resolution to ~1200 at 5 - 8 microns and ~800 at 9.8 – 13.7 microns. Here we describe the FORCAST
instrument including observing modes for SOFIA Cycle 1. We also summarize in-flight results, including detector and
optical performance, sensitivity performance, and calibration.
The SOFIA far-infrared spectrometer FIFI-LS: spearheading a post Herschel era
Sebastian Colditz,
Fabio Fumi,
Norbert Geis,
et al.
Show abstract
FIFI-LS (Field-Imaging Far-Infrared Line Spectrometer) is an imaging spectrograph for SOFIA comprised of two
medium resolution (R~2200) grating spectrometers feeding two 16x25 pixel detector arrays, which enable simultaneous
line observations across two wavelength ranges (42-110 μm and 110-210μm) each across a field of view of 5x5 pixel.
FIFI-LS will be the extragalactic spectroscopic workhorse for SOFIA. FIFI-LS has enough sensitivity to observe a
substantial sample of nearby galaxies. It also has the right combination of wavelength range and spatial resolution to
carry out unique new observations beyond those possible with Herschel, Spitzer, ISO and IRAS. As the effective
sensitivity of FIFI-LS is only about a factor of 3-5 lower than the PACS spectrometer onboard Herschel, mainly due to
an enhanced multiplexing advantage, FIFI-LS will build upon recent exciting scientific results and spearhead the post-
Herschel far-infrared era.
FIFI-LS is scheduled for commissioning onboard SOFIA in early 2014. An account on the instrument and its current
stratus will be presented.
HIPO in-flight performance aboard SOFIA
Show abstract
HIPO is a special purpose science instrument for SOFIA that was also designed to be used for Observatory test work. It
was used in a series of flights from June to December 2011 as part of the SOFIA Characterization and Integration
(SCAI) flight test program. Partial commissioning of HIPO and the co-mounted HIPO-FLITECAM (FLIPO)
configuration were included within the scope of the SCAI work. The commissioning measurements included such
things as optical throughput, image size and shape as a function of wavelength and exposure time, image motion
assessment over a wide frequency range, scintillation noise, photometric stability assessment, twilight sky brightness,
cosmic ray rate as a function of altitude, telescope pointing control, secondary mirror control, and GPS time and position
performance. As part of this work we successfully observed a stellar occultation by Pluto, our first SOFIA science data.
We report here on the observed in-flight performance of HIPO both when mounted alone and when used in the FLIPO
configuration.
FLITECAM: current status and results from observatory verification flights
Show abstract
This paper describes the current status of FLITECAM, the near-infrared (1 - 5 μm) camera and spectrometer for
NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA). Due to a change in schedule FLITECAM’s
delivery was advanced, allowing it to be co-mounted with the HIPO instrument and used on four flights in October 2011
for observatory verification. Although not part of FLITECAM’s commissioning time, some preliminary performance
characteristics were determined. Image size as a function of wavelength was measured prior to the installation of active
mass dampers on the telescope. Preliminary grism spectroscopy was also obtained. In addition, FLITECAM was used to
measure the emissivity of the telescope and warm optics in the co-mounted configuration. New narrow band filters were
added to the instrument, including a Paschen alpha filter for line emission. Results are illustrated.
Preflight performance of the Echelon-Cross-Echelle spectrograph for SOFIA
Show abstract
The Echelon-Cross-Echelle Spectrograph (EXES) is one of the first generation instruments for the Stratospheric Observatory for Infrared Astronomy (SOFIA). The primary goal of EXES is to provide high-resolution, cross-dispersed spectroscopy, with resolutions of 50,000-100,000 and wavelength coverage of 0.5-1.5% between 4.5 μm and 28.3 μm. EXES will also have medium (R=5000-25000) and low (R=1500-4000) modes available, as well as a target acquisition imaging mode and a pupil-imaging mode for alignment testing. EXES is scheduled for commissioning flights in February 2014. It will be available to the public for shared-risk observations in SOFIA’s Cycle 2. Here we give an overview of the design and capabilities of EXES as well as its laboratory performance to date.
Solar Instruments
ATST visible broadband imager
Show abstract
The Advanced Technology Solar Telescope (ATST) is a 4 meter class telescope for observation of the solar atmosphere
currently in the construction phase. The Visible Broadband Imager (VBI) is a diffraction limited imaging instrument
planned to be the first-light instrument in the ATST instrumentation suite. The VBI is composed of two branches, the
"VBI blue" and the "VBI red", and uses state-of-the-art narrow bandwidth interference filters and two custom designed
high speed filter wheels to take bursts of images that will be re-constructed using a Graphics Processing Unit (GPU)
optimized near-real-time speckle image reconstruction engine. At first light, the VBI instrument will produce
diffraction-limited movies of solar activity at eight discrete wavelengths with a field of view of 2 arc minutes square. In
this contribution, the VBI design team will discuss the capabilities of the VBI and describe the design of the instrument,
highlighting the unique challenges faced in the development of this unique instrument.
Developments of the wideband spectropolarimeter of the Domeless Solar Telescope at Hida Observatory
Show abstract
We developed a new universal spectropolarimeter on the Domeless Solar Telescope at Hida Observatory to realize
precise spectropolarimetric observations in a wide range of wavelength in visible and near infrared. The
system aims to open a new window of plasma diagnostics by using Zeeman effect, Hanle effect, Stark effect, and
impact polarization to measure the external magnetic field, electric field, and anisotropies in atomic excitation
in solar atmosphere. The polarimeter consists of a 60 cm aperture vacuum telescope, a high dispersion vacuum
spectrograph, polarization modulator and analyser composed of a continuously rotating waveplate whose
retardation is constant in 400 - 1100 nm and Wallaston prisms located closely behind the focus of the telescope,
and a fast and high sensitive CCD camera or a infrared camera. The duration for this polarimeter's achieving
photometric accuracy of 10-3 is 30 - 60 s. Instrumental polarization of the telescope is calibrated by using a
remotely controllable turret accommodating linear polarizer attached at the entrance window of the telescope to
induce well known polarized light into the telescope. Thus a Mueller matrix model of the telescope is established
to compensate the instrumental polarization included in observed data within the required accuracy.
SPIES: the spectropolarimetric imager for the energetic sun
Show abstract
The SpectroPolarimetric Imager for the Energetic Sun (SPIES) is a project to develop a new class of spectropolarimetric
instrument for the study of highly dynamic solar phenomena. Understanding the physics of dynamic
solar phenomena requires detailed information about the magnetic, thermal, and dynamic properties of the solar
atmosphere at every stage of their evolution. Although these properties can be obtained with existing highperformance
spectropolarimeters such as the SpectroPolarimeter onboard the Hinode space solar observatory or
the Facility IR Spectropolarimeter of the Dunn Solar Telescope, these instruments cannot observe the required
field of view with temporal resolution that can resolve the dynamic timescale of these energetic events. SPIES-2K
is an experimental true-imaging spectropolarimeter developed under this program to address this deficiency in
our observing capability. It is based on a fiber-optic integral field unit containing 2,048 standard multimode
fused silica fibers, and is capable of observing a 64 x 32 pixels field simultaneously with high spatial and spectral
resolution. Moreover, it can obtain the full Stokes spectra of the field with a maximum temporal resolution
of a few seconds. This paper presents the design and characteristics of the instrument, as well as preliminary
results obtained at Fe I 1565 nm wavelength. Additionally, this paper also reports on recent studies of the
polarization maintenance optical fiber ribbon constructed from rectangular element fibers for the Birefringence
Fiber-Optic Image Slicer, and discusses its application to future generation of SPIES and other astronomical
spectropolarimetry projects.
ELT Instruments I
A roadmap for the E-ELT instrument suite
Show abstract
We present plans for instrumentation on the European Extremely Large Telescope. ESO is working with its community
of astronomers and instrument builders to develop the E-ELT Instrumentation Roadmap. The roadmap is a timeline of
the steps towards the full instrument programme, from specification of the scientific requirements, via a technology
development phase, to selection of the instrument concepts. Key goals are to be flexibile to new ideas and to ensure the
timely, on-budget delivery of instruments that meet the community's scientific needs. The result is an exciting
programme of seven instruments planned over the first decade of the telescope construction phase.
The instrumentation program for the Thirty Meter Telescope
Show abstract
An overview of the current status of the Thirty Meter Telescope (TMT) instrumentation program is presented. Science cases and operational concepts as well as their links to the instruments are continually revisited and updated through a series of workshops and conferences. Work on the three first-light instruments (WFOS IRIS, and IRMS) has made significant progress, and many groups in TMT partner communities are developing future instrument concepts. Other instrument-related subsystems are also receiving considerable attention given their importance to the scientific end-to-end performance of the Observatory. As an example, we describe aspects of the facility instrument cooling system that are crucially important to successful diffraction-limited observations on an extremely large telescope.
The instrument development and selection process for the Giant Magellan Telescope
Show abstract
The Giant Magellan Telescope (GMT) is a 25.4-m optical/infrared telescope constructed from seven 8.4-m primary
mirror segments. The collecting area is equivalent to a 21.6-m filled aperture. The instrument development program was
formalized about two years ago with the initiation of 14-month conceptual design studies for six candidate instruments.
These studies were completed at the end of 2011 with a design review for each. In addition, a feasibility study was
performed for a fiber-feed facility that will direct the light from targets distributed across GMT's full 20 arcmin field of
view simultaneously to three spectrographs. We briefly describe the features and science goals for these instruments, and
the process used to select those instruments that will be funded for fabrication first. Detailed reports for most of these
instruments are presented separately at this meeting.
ELT Instruments II
The GMT-CfA, Carnegie, Catolica, Chicago Large Earth Finder (G-CLEF): a general purpose optical echelle spectrograph for the GMT with precision radial velocity capability
Show abstract
The GMT-CfA, Carnegie, Catolica, Chicago Large Earth Finder (G-CLEF) is a fiber fed, optical echelle spectrograph
that has undergone conceptual design for consideration as a first light instrument at the Giant Magellan Telescope. GCLEF
has been designed to be a general-purpose echelle spectrograph with precision radial velocity (PRV) capability.
We have defined the performance envelope of G-CLEF to address several of the highest science priorities in the Decadal
Survey1. The spectrograph optical design is an asymmetric, two-arm, white pupil design. The asymmetric white pupil
design is adopted to minimize the size of the refractive camera lenses. The spectrograph beam is nominally 300 mm,
reduced to 200 mm after dispersion by the R4 echelle grating. The peak efficiency of the spectrograph is >35% and the
passband is 3500-9500Å. The spectrograph is primarily fed with three sets of fibers to enable three observing modes:
High-Throughput, Precision-Abundance and PRV. The respective resolving powers of these modes are R~ 25,000,
40,000 and 120,000. We also anticipate having an R~40,000 Multi-object Spectroscopy mode with a multiplex of ~40
fibers. In PRV mode, each of the seven 8.4m GMT primary mirror sub-apertures feeds an individual fiber, which is
scrambled after pupil-slicing. The goal radial velocity precision of G-CLEF is ∂V <10 cm/sec radial. In this paper, we
provide a flowdown from fiducial science programs to design parameters. We discuss the optomechanical, electrical,
structural and thermal design and present a roadmap to first light at the GMT.
GMT integral-field spectrograph (GMTIFS) conceptual design
Show abstract
The Giant Magellan Telescope (GMT) Integral-Field Spectrograph (GMTIFS)c is one of six potential first-light
instruments for the 25m-diameter Giant Magellan Telescope. The Australian National University has completed a
Conceptual Design Study for GMTIFS. The science cases for GMTIFS are summarized, and the instrument capabilities
and design challenges are described. GMTIFS will be the work-horse adaptive-optics instrument for GMT. It contains an
integral-field spectrograph (IFS) and Imager accessing the science field, and an On-Instrument Wave-Front Sensor
(OIWFS) that patrols the 90 arcsec radius guide field. GMTIFS will address a wide range of science from epoch of
reionization studies to forming galaxies at high redshifts and star and planet formation in our Galaxy. It will fully exploit
the Laser Tomography Adaptive Optics (LTAO) system on the telescope. The tight image quality and positioning
stability requirements that this imposes drive the design complexity. Some cryogenic mechanisms in the IFS must set to
~ 1 μm precision. The Beam-Steering mechanism in the OIWFS must set to milli-arcsecond precision over the guide
field, corresponding to ~ 1 μm precision in the f/8 focal plane. Differential atmospheric dispersion must also be corrected
to milli-arcsecond precision. Conceptual design solutions addressing these and other issues are presented and discussed.
The EAGLE instrument for the E-ELT: developments since delivery of Phase A
Show abstract
The EAGLE instrument is a Multi-Object Adaptive Optics (MOAO) fed, multiple Integral Field Spectrograph (IFS),
working in the Near Infra-Red (NIR), on the European Extremely Large Telescope (E-ELT). A Phase A design study
was delivered to the European Southern Observatory (ESO) leading to a successful review in October 2009. Since that
time there have been a number of developments, which we summarize here. Some of these developments are also
described in more detail in other submissions at this meeting.
The science case for the instrument, while broad, highlighted in particular: understanding the stellar populations of
galaxies in the nearby universe, the observation of the evolution of galaxies during the period of rapid stellar build-up
between redshifts of 2-5, and the search for 'first light' in the universe at redshifts beyond 7. In the last 2 years substantial
progress has been made in these areas, and we have updated our science case to show that EAGLE is still an essential
facility for the E-ELT. This in turn allowed us to revisit the science requirements for the instrument, confirming most of
the original decisions, but with one modification.
The original location considered for the instrument (a gravity invariant focal station) is no longer in the E-ELT
Construction Proposal, and so we have performed some preliminary analyses to show that the instrument can be simply
adapted to work at the E-ELT Nasmyth platform.
Since the delivery of the Phase A documentation, MOAO has been demonstrated on-sky by the CANARY experiment at
the William Herschel Telescope.
Second-Earth imager for TMT (SEIT): concept and its numerical simulation
Show abstract
Thirty Meter Telescope (TMT) will see the first light in 2019. We propose Second-Earth Imager for TMT (SEIT) as a
future instrument of TMT. The central science case of SEIT is direct imaging and characterization of habitable planets
around nearby late-type stars. Focusing on simultaneous spectroscopy of the central star and the planet, SEIT allows us
to remove an impact from the telluric absorption and then reveal the presence of oxygen molecules on the Earth-like
planets.
In order to achieve such a science goal, an extreme AO, a coronagraph, and a post-process technique for achieving high
contrast at the small inner working angle are key components. The combination of a shearing nulling interferometer and
a pupil remapping interferometer is applied to the first SEIT concept. The shearing nulling interferometer suppresses the
diffracted starlight after the extreme AO wavefront correction, and then the pupil remapping interferometer tackles the
speckle noise from starlight. Focusing on a fact that the pupil remapping interferometer has difficulty reconstructing the
wavefront from only the speckle noise, we found an unbalnced nulling technique enhances the performance of the pupil
remapping interferometer. We performed a numerical simulation to validate this concept and found this concept achieves
the 5-sigma detection contrast down to 8x10-8 at 10 mas for 5 hours. Thus, the SEIT concept detects habitable planets
with a radius two times that of the Earth around ten nearby M stars.
The opto-mechanical design of HARMONI: a first light integral field spectrograph for the E-ELT
Show abstract
HARMONI is a visible and near-IR integral field spectrograph, providing the E-ELT's spectroscopic capability at first
light. It obtains simultaneous spectra of 32000 spaxels, at a range of resolving powers from R~4000 to R~20000,
covering the wavelength range from 0.47 to 2.45 μm. The 256 × 128 spaxel field of view has four different plate scales,
with the coarsest scale (40 mas) providing a 5″ × 10″ FoV, while the finest scale is a factor of 10 finer (4mas).
We describe the opto-mechanical design of HARMONI, prior to the start of preliminary design, including the main subsystems
- namely the image de-rotator, the scale-changing optics, the splitting and slicing optics, and the spectrographs.
We also present the secondary guiding system, the pupil imaging optics, the field and pupil stops, the natural guide star
wavefront sensor, and the calibration unit.
ELT Instruments III
METIS: the thermal infrared instrument for the E-ELT
Show abstract
The ‘Mid-infrared ELT Imager and Spectrograph’ (METIS) will be the third instrument on the European Extremely
Large Telescope (E-ELT). METIS will provide diffraction limited imaging in the atmospheric L/M and N-band from 3
to 14 μm over an 18˝×18˝ field of view, as well as high contrast coronagraphy, medium-resolution (R ≤ 5000) long slit
spectroscopy, and polarimetry. In addition, an integral field spectrograph will provide a spectral resolution of R ~
100,000 at L/M band. Focusing on highest angular resolution and high spectral resolution, METIS will deliver unique
science, in particular in the areas of exo-planets, proto-planetary-disks and high-redshift galaxies, which are illustrated in
this paper. The reduction of the E-ELT aperture size had little impact on the METIS science case. With the recent
positive developments in the area of detectors, the METIS instrument concept has reached a high level of technology
readiness. For some key components (cryogenic chopping mirror, immersed grating, sorption cooler and cryogenic
derotator) a development and test program has been launched successfully.
GMACS: a wide field, multi-object, moderate-resolution, optical spectrograph for the Giant Magellan Telescope
Show abstract
We present 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 optical wavelengths. We show some details of the optical and mechanical design of
the instrument.
NIRMOS: a wide-field near-infrared spectrograph for the Giant Magellan Telescope
Show abstract
NIRMOS (Near-Infrared Multiple Object Spectrograph) is a 0.9 to 2.5 μm imager/spectrograph concept proposed for the
Giant Magellan Telescope1 (GMT). Near-infrared observations will play a central role in the ELT era, allowing us to
trace the birth and evolution of galaxies through the era of peak star formation. NIRMOS' large field of view, 6.5′ by
6.5′, will be unique among imaging spectrographs developed for ELTs. NIRMOS will operate in Las Campanas' superb
natural seeing and is also designed to take advantage of GMT's ground-layer adaptive optics system. We describe
NIRMOS' high-performance optical and mechanical design.
TIGER: a high contrast infrared imager for the Giant Magellan Telescope
Show abstract
The Thermal Infrared imager for the GMT which provides Extreme contrast and Resolution (TIGER) is intended as a
small-scale, targeted instrument capable of detecting and characterizing exoplanets and circumstellar disks, around both
young systems in formation, and more mature systems in the solar neighborhood. TIGER can also provide general
purpose infrared imaging at wavelengths from 1.5-14 μm. The instrument will utilize the facility adaptive optics (AO)
system. With its operation at NIR to MIR wavelengths (where good image quality is easier to achieve), and much of the
high-impact science using modestly bright guide stars, the instrument can be used early in the operation of the GMT.
The TIGER concept is a dual channel imager and low resolution spectrometer, with high contrast modes of observations
to fulfill the above science goals. A long wavelength channel (LWC) will cover 7-14 μm wavelength, while a short
wavelength channel (SWC) will cover the 1.5-5 μm wavelength region. Both channels will have a 30° FOV. In addition
to imaging, low-resolution spectroscopy (R=300) is possible with TIGER for both the SWC and LWC, using insertable
grisms.
Planet Finders I
ESPRESSO: the ultimate rocky exoplanets hunter for the VLT
Show abstract
ESPRESSO, the VLT rocky exoplanets hunter, will combine the efficiency of modern echelle spectrograph with extreme
radial-velocity precision. It will be installed at Paranal on ESO's VLT in order to achieve a gain of two magnitudes 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 project has passed the preliminary design
review in November 2011. The spectrograph will be installed at the so-called "Combined Coudé Laboratory" of the
VLT, it will be linked to the four 8.2 meters Unit Telescopes (UT) through four optical "Coudé trains" and will be
operated either with a single telescope or with up to four UTs. In exchange of the major financial and human effort the
building Consortium will be awarded with guaranteed observing time (GTO), which will be invested in a common
scientific program. Thanks to its characteristics and the 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. In this paper, we present the ambitious scientific objectives, the
capabilities of ESPRESSO, the technical solutions for the system and its subsystems, enlightening the main differences
between ESPRESSO and its predecessors. The project aspects of this facility are also described, from the consortium and
partnership structure to the planning phases and milestones.
The Habitable-zone Planet Finder: a stabilized fiber-fed NIR spectrograph for the Hobby-Eberly Telescope
Show abstract
We present the scientific motivation and conceptual design for the recently funded Habitable-zone Planet Finder (HPF), a stabilized fiber-fed near-infrared (NIR) spectrograph for the 10 meter class Hobby-Eberly Telescope (HET) that will be capable of discovering low mass planets around M dwarfs. The HPF will cover the NIR Y and J bands to enable precise radial velocities to be obtained on mid M dwarfs, and enable the detection of low mass planets around these stars. The conceptual design is comprised of a cryostat cooled to 200K, a dual fiber-feed with a science and calibration fiber, a gold coated mosaic echelle grating, and a Teledyne Hawaii-2RG (H2RG) *NIR detector with a 1.7μm cutoff. A uranium-neon hollow-cathode lamp is the baseline wavelength calibration source, and we are actively testing laser frequency combs to enable even higher radial velocity precision. We will present the overall instrument system design and integration with the HET, and discuss major system challenges, key choices, and ongoing research and development projects to mitigate risk. We also discuss the ongoing process of target selection for the HPF survey.
Infrared Doppler instrument for the Subaru Telescope (IRD)
Show abstract
IRD is the near-infrared high-precision radial velocity instrument for the Subaru 8.2-m telescope. It is a relatively compact (~1m size) spectrometer with a new echelle-grating and Volume-Phase Holographic gratings covering 1-2 micron wavelengths combined with an original frequency comb using optical pulse synthesizer. The spectrometer will employ a 4096x4096-pixel HgCdTe array under testing at IfA, University of Hawaii. Both the telescope/Adaptive Optics and comb beams are fed to the spectrometer via optical fibers, while the instrument is placed at the Nasmyth platform of the Subaru telescope. Expected accuracy of the Doppler-shifted velocity measurements is about 1 m s-1. Helped with the large collecting area and high image quality of the Subaru telescope, IRD can conduct systematic radial velocity surveys of nearby middle-to-late M stars aiming for down to one Earth-mass planet. Systematic observational and theoretical studies of M stars and their planets for the IRD science are also ongoing. We will report the design and preliminary development progresses of the whole and each component of IRD.
The Gemini Planet Imager: integration and status
Show abstract
The Gemini Planet Imager is a next-generation instrument for the direct detection and characterization of young warm exoplanets, designed to be an order of magnitude more sensitive than existing facilities. It combines a 1700-actuator adaptive optics system, an apodized-pupil Lyot coronagraph, a precision interferometric infrared wavefront sensor, and a integral field spectrograph. All hardware and software subsystems are now complete and undergoing integration and test at UC Santa Cruz. We will present test results on each subsystem and the results of end-to-end testing. In laboratory testing, GPI has achieved a raw contrast (without post-processing) of 10-6 5σ at 0.4”, and with multiwavelength speckle suppression, 2x10-7 at the same separation.
Planet Finders II
Harps-N: the new planet hunter at TNG
Show abstract
The Telescopio Nazionale Galileo (TNG)[9] hosts, starting in April 2012, the visible spectrograph HARPS-N. It is based
on the design of its predecessor working at ESO's 3.6m telescope, achieving unprecedented results on radial velocity
measurements of extrasolar planetary systems. The spectrograph's ultra-stable environment, in a temperature-controlled
vacuum chamber, will allow measurements under 1 m/s which will enable the characterization of rocky, Earth-like
planets. Enhancements from the original HARPS include better scrambling using octagonal section fibers with a shorter
length, as well as a native tip-tilt system to increase image sharpness, and an integrated pipeline providing a complete set
of parameters.
Observations in the Kepler field will be the main goal of HARPS-N, and a substantial fraction of TNG observing time
will be devoted to this follow-up. The operation process of the observatory has been updated, from scheduling
constraints to telescope control system. Here we describe the entire instrument, along with the results from the first
technical commissioning.
Achieving a few cm/sec calibration repeatability for high resolution spectrographs: the laser frequency comb on HARPS
Show abstract
The laser frequency comb, with its extreme precision, opens a new window for high precision spectroscopy for current
facilities, as well as for the ELT's. We report on the latest performance of the laser frequency comb obtained in combination
with the HARPS spectrograph, which allowed calibration with cm/sec repeatability. The laser frequency comb system
developed is described. Details of its laboratory set-up, characterization and integration with HARPS are shown. The results
of the recent test campaigns are presented, showing excellent performance in terms of repeatability as well as wavelength
coverage. Preliminary on sky data and next activities to integrate such a system in HARPS are presented.
A demonstration test of the dual-beam polarimetry differential imaging system for the high-contrast observation
Show abstract
We propose a dual-beam polarimetry differential imaging test system that can be used for the direct imaging of the
exoplanets. The system is composed of a liquid crystal variable retarder (LCVR) in the pupil to switch between two
orthogonal polarized states, and a Wollaston prism (WP) that will be inserted before the final focal focus of the system to
create two polarized images for the differential subtraction. Such a system can work separately or be integrated in the
coronagraph system to enhance the high-contrast imaging. To demonstrate the feasibility of the proposed system, here
we show the initial test result both with and without integrating our developed coronagraph. A unique feature for this
system is that each channel can subtract with itself by using the retarder to rotate the planet's polarization orientation,
which has the best performance according to our lab test results. Finally, it is shown that the polarimetry differential
imaging system is a promising technique and can be used for the direct imaging observation of reflected lights from the
exoplanets.
High Resolution and AO Instruments
FIRST - a fibered aperture masking instrument: on-sky results
Show abstract
We present on-sky results obtained with the visible light prototype of the Fibered Imager foR Single Telescope
(FIRST) mounted on the 3-m Shane Telescope at Lick Observatory and using its Adaptive Optics system. This
instrument is dedicated to high angular resolution and high dynamic range imaging. Its principle combines both
techniques of single-mode fiber interferometry and pupil remapping. Simulations predict a dynamic range up
to 106 at /D, or at a few tens of milliarcseconds at 630nm using an 8-m telescope. Laboratory experiments
based on a 9-fiber prototype working in the 600nm–900nm spectral band successfully demonstrated the power
of the concept. The same prototype has been set-up on the 3-m Shane telescope in July 2010. In this paper, we
present the on-sky results obtained in October 2011 with an improved version of the instrument using 18 fibers.
They clearly show the detection of the binary star Capella at the diffraction limit of the telescope.λ
The design of ERIS for the VLT
Show abstract
The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation instrument planned for the Very Large
Telescope (VLT) and the Adaptive Optics Facility (AOF)1. It is an AO assisted instrument that will make use of the
Deformable Secondary Mirror and the new Laser Guide Star Facility (4LGSF), and it is designed for the Cassegrain
focus of the telescope UT4. The project just concluded its conceptual design phase and is awaiting formal approval to
continue to the next phase. ERIS will offer 1-5 μm imaging and 1-2.5 μm integral field spectroscopic capabilities with
high Strehl performance. As such it will replace, with much improved single conjugated AO correction, the most
scientifically important and popular observing capabilities currently offered by NACO2 (diffraction limited imaging in JM
band, Sparse Aperture Masking and APP coronagraphy) and by SINFONI3, whose instrumental module, SPIFFI, will
be re-used in ERIS. The Cassegrain location and the performance requirements impose challenging demands on the
project, from opto-mechanical design to cryogenics to the operational concept. In this paper we describe the baseline
design proposed for ERIS and discuss these technical challenges, with particular emphasis on the trade-offs and the
novel solutions proposed for building ERIS.
AOLI: Adaptive Optics Lucky Imager: diffraction limited imaging in the visible on large ground-based telescopes
Show abstract
The highest resolution images ever taken in the visible were obtained by combining Lucky Imaging and low order
adaptive optics. This paper describes a new instrument to be deployed on the WHT 4.2m and GTC 10.4 m telescopes on
La Palma, with particular emphasis on the optical design and the expected system performance. A new design of low
order wavefront sensor using photon counting CCD detectors and multi-plane curvature wavefront sensor will allow
dramatically fainter reference stars to be used, allowing virtually full sky coverage with a natural guide star. This paper
also describes a significant improvements in the efficiency of Lucky Imaging, important advances in wavefront
reconstruction with curvature sensors and the results of simulations and sensitivity limits. With a 2 x 2 array of 1024 x
1024 photon counting EMCCDs, AOLI is likely to be 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.
15x optical zoom and extreme optical image stabilisation: diffraction limited integral field spectroscopy with the SWIFT spectrograph
Show abstract
When commissioned in November 2008 at the Palomar 200 inch Hale Telescope, the Oxford SWIFT I and z band integral field spectrograph, fed by the adaptive optics system PALAO, provided a wide (3×) range of spatial resolutions: three plate scales of 235 mas, 160 mas, and 80 mas per spaxel over a contiguous field-of-view of 89×44 pixels. Depending on observing conditions and guide star brightness we can choose a seeing limited scale of 235 mas per spaxel, or 160 mas and 80 mas per spaxel for very bright guide star AO with substantial increase of enclosed energy.
Over the last two years PALAO was upgraded to PALM-3000: an extreme, high-order adaptive optics system with two deformable mirrors with more than 3000 actuators, promising diffraction limited performance in SWIFT's wavelength range. In order to take advantage of this increased spatial resolution we upgraded SWIFT with new pre-optics allowing us to spatially Nyquist sample the diffraction limited PALM-3000 point spread function with 16 mas resolution, reducing the spaxel scale by another factor of 5×. We designed, manufactured, integrated and tested the new pre-optics in the first half of 2011 and commissioned it in December 2011. Here we present the opto-mechanical design and assembly of the new scale changing optics, as well as laboratory and on-sky commissioning results. In optimal observing conditions we achieve substantial Strehl ratios, delivering the near diffraction limited spatial resolution in the I and z bands.
Compact high-resolution spectrographs for large and extremely large telescopes: using the diffraction limit
Show abstract
As telescopes get larger, the size of a seeing-limited spectrograph for a given resolving power becomes larger also, and for ELTs the size will be so great that high resolution instruments of simple design will be infeasible. Solutions include adaptive optics (but not providing full correction for short wavelengths) or image slicers (which give feasible but still large instruments). Here we develop the solution proposed by Bland-Hawthorn and Horton: the use of diffraction-limited spectrographs which are compact even for high resolving power. Their use is made possible by the photonic lantern, which splits a multi-mode optical fiber into a number of single-mode fibers. We describe preliminary designs for such spectrographs, at a resolving power of R ~ 50,000. While they are small and use relatively simple optics, the challenges are to accommodate the longest possible fiber slit (hence maximum number of single-mode fibers in one spectrograph) and to accept the beam from each fiber at a focal ratio considerably faster than for most spectrograph collimators, while maintaining diffraction-limited imaging quality. It is possible to obtain excellent performance despite these challenges. We also briefly consider the number of such spectrographs required, which can be reduced by full or partial adaptive optics correction, and/or moving towards longer wavelengths.
Current status of FRIDA: diffraction limited NIR instrument for the GTC
Show abstract
FRIDA (inFRared Imager and Dissector for the Adaptive optics system of the Gran Telescopio Canarias) is designed as
a diffraction limited instrument that will offer broad and narrow band imaging and integral field spectroscopy capabilities
with low (R ~ 1,500), intermediate (R ~ 4,500) and high (R ~ 30,000) spectral resolutions to operate in the wavelength
range 0.9 - 2.5 μm. The integral field unit is based on a monolithic image slicer. The imaging and IFS observing modes
will use the same Teledyne 2K x 2K detector. FRIDA will be based at the Nasmyth B platform of GTC, behind the AO
system. The key scientific objectives of the instrument include studies of solar system bodies, low mass objects,
circumstellar outflow phenomena in advanced stages of stellar evolution, active galactic nuclei, high redshift galaxies,
resolved stellar populations, semi-detached binary systems, young stellar objects and star forming environments. FRIDA
is a collaborative project between the main GTC partners, namely, Spain, México and Florida. In this paper, we present
the status of the instrument design as it is currently being prepared for its manufacture, after an intensive prototypes'
phase and design optimization. The CDR was held in September 2011.
Posters: New Instruments and Upgrades/Reports on Existing Instruments
Design of a full-Stokes polarimeter for VLT/X-shooter
Show abstract
X-shooter is one of the most popular instruments at the VLT, offering instantaneous spectroscopy from 300 to 2500 nm. We present the design of a single polarimetric unit at the polarization-free Cassegrain focus that serves all three spectrograph arms of X-shooter. It consists of a calcite Savart plate as a polarizing beam-splitter and a rotatable crystal retarder stack as a "polychromatic modulator". Since even “superachromatic" wave plates have a wavelength range that is too limited for X-shooter, this novel modulator is designed to offer close-to-optimal polarimetric efficiencies for all Stokes parameters at all wavelengths. We analyze the modulator design in terms of its polarimetric performance, its temperature sensitivity, and its polarized fringes. Furthermore, we present the optical design of the polarimetric unit. The X-shooter polarimeter will furnish a myriad of science cases: from measuring stellar magnetic fields (e.g., Ap stars, white dwarfs, massive stars) to determining asymmetric structures around young stars and in supernova explosions.
Concept of SPARC4: a simultaneous polarimeter and rapid camera in 4 bands
Show abstract
We present a summary of the concept design report of a new astronomical instrument: SPARC4, Simultaneous
Polarimeter and Rapid Camera in 4 bands. SPARC4 will provide photometry and polarimetry in four optical
broad bands (griz SDSS) simultaneously. This is achieved by the use of dichroic beam splitters. The square eld
of view is around 5.6 arcmin on a side. SPARC4 time resolution is sub-second for photometry and somewhat
longer for polarimetry. This is provided by the use of fast EMCCDs. The main motivation for building SPARC4
is to explore astrophysical objects which exhibit fast temporal variability in
ux and polarization. The instrument
will be installed at the 1.6-m telescope of the Observatorio do Pico dos Dias (Brazil).
The F/5 instrumentation suite for the Clay Telescope
Show abstract
The f/5 instrumentation suite for the Clay telescope was developed to provide the Magellan Consortium observer community with wide field optical imaging and multislit NIR spectroscopy capability. The instrument suite consists of several major subsystems including two focal plane instruments. These instruments are Megacam and MMIRS. Megacam is a panoramic, square format CCD mosaic imager, 0.4° on a side. It is instrumented with a full set of Sloan filters. MMIRS is a multislit NIR spectrograph that operates in Y through K band and has long slit and imaging capability as well. These two instruments can operate both at Magellan and the MMT. Megacam requires a wide field refractive corrector and a Topbox to support shutter and filter selection functions, as well as to perform wavefront sensing for primary mirror figure correction. Both the corrector and Topbox designs were modeled on previous designs for MMT, however features of the Magellan telescope required considerable revision of these designs. In this paper we discuss the optomechanical, electrical, software and structural design of these subsystems, as well as operational considerations that attended delivery of the instrument suite to first light.
The AAO's Gemini High-Resolution Optical SpecTrograph (GHOST) concept
Show abstract
The Gemini High-Resolution Optical SpecTrograph (GHOST) will fill an important gap in the current suite of Gemini
instruments. We will describe the Australian Astronomical Observatory (AAO)-led concept for GHOST, which consists
of a multi-object, compact, high-efficiency, fixed-format, fiber-fed design. The spectrograph itself is a four-arm variant
of the asymmetric white-pupil echelle Kiwispec spectrograph, Kiwisped, produced by Industrial Research Ltd. This
spectrograph has an R4 grating and a 100mm pupil, and separate cross-disperser and camera optics for each of the four
arms, carefully optimized for their respective wavelength ranges. We feed this spectrograph with a miniature lensletbased
IFU that sub-samples the seeing disk of a single object into 7 hexagonal sub-images, reformatting this into a slit
with a second set of double microlenses at the spectrograph entrance with relatively little loss due to focal-ratio
degradation. This reformatting enables high spectral resolution from a compact design that fits well within the relatively
tight GHOST budget. We will describe our baseline 2-object R~50,000 design with full wavelength coverage from the
ultraviolet to the silicon cutoff, as well as the high-resolution single-object R~75,000 mode.
GRACES, the Gemini remote access CFHT ESPaDOnS spectrograph: initial design and testing
Show abstract
The Gemini Remote Access CFHT ESPaDOnS Spectrograph (GRACES) is an innovative instrumentation experiment
that will demonstrate if ESPaDOnS, a bench-mounted high-resolution optical spectrograph at CFHT, can be fed by a
270-m long fiber from the Gemini-North telescope with low enough losses to remain competitive with conventional
spectrographs on other 8 to 10-m telescopes. Detailed simulations have shown that GRACES should be more sensitive
than the HIRES spectrograph at Keck Observatory at wavelengths longer than about 600-700 nm. This result is possible
by using FPB-type of optical fibers made by Polymicro Technologies and by keeping the critical focal ratio degradation
(FRD) losses to less than 10%. Laboratory tests on these FPB optical fibers are underway and show that for 36-m lengths
that the FRD losses are as low as 0.8% with a repeatability of 1%. Tests are currently underway on 280-m lengths.
BASIS: Bayfordbury single-object integral field spectrograph
Show abstract
We present an inexpensive (<US$500) and easily replicable integral field unit for use on small aperture telescopes.
Based on a commercial small spectrograph (SBIG Self-Guiding Spectrograph) and a 37 optical fibre bundle integral field
unit with each fibre having 50μm cores and a pitch of 125μm. It has an overall field-of-view of 40 arc seconds
(2.6arcsec/core), a resolution of 9Å from 3995Å to 7170Å and an average system efficiency of 9%, yielding a signal-tonoise
ratio of 10 for a 20min exposure of a 13mag/arcsec2 source. Still in commissioning, we present first light
observations of Vega and M57.
iSHELL: a 1-5 micron cross-dispersed R=70,000 immersion grating spectrograph for IRTF
Show abstract
iSHELL is 1.15-5.4 μm high spectral resolution spectrograph being built for the NASA Infrared Telescope Facility on
Mauna Kea, Hawaii. Dispersion is accomplished with silicon immersion gratings in order to keep the instrument small
enough to be mounted at the Cassegrain focus of the telescope. The white pupil spectrograph is designed to produce
resolving powers of up to R=70,000. Cross-dispersing gratings mounted in a tilt-able mechanism at the second pupil
allow observers to select different wavelength ranges and, in combination with a slit wheel and dekker mechanism, slit
lengths ranging from 5″ to 25″. One Teledyne 2048x2048 Hawaii 2RG array is used in the spectrograph, and one
Raytheon 512x512 Aladdin 2 array is used in a slit viewer for object acquisition, guiding, and imaging. About $4 million
in funding has been provided by NSF, NASA and the University of Hawaii. First light is expected in about 2015. In this
paper we discuss the science drivers, instrument design and expected performance.
The AAO fiber instrument data simulator
Michael Goodwin,
Tony Farrell,
Scott Smedley,
et al.
Show abstract
The fiber instrument data simulator is an in-house software tool that simulates detector images of fiber-fed spectrographs
developed by the Australian Astronomical Observatory (AAO). In addition to helping validate the instrument designs,
the resulting simulated images are used to develop the required data reduction software. Example applications that have
benefited from the tool usage are the HERMES and SAMI instrumental projects for the Anglo-Australian Telescope
(AAT). Given the sophistication of these projects an end-to-end data simulator that accurately models the predicted
detector images is required. The data simulator encompasses all aspects of the transmission and optical aberrations of the
light path: from the science object, through the atmosphere, telescope, fibers, spectrograph and finally the camera
detectors. The simulator runs under a Linux environment that uses pre-calculated information derived from ZEMAX
models and processed data from MATLAB. In this paper, we discuss the aspects of the model, software, example
simulations and verification.
Front end of the SPIRou spectropolarimeter for Canada-France Hawaii Telescope
Show abstract
SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a nextgeneration
instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of
detecting Earth-like planets around low-mass stars and magnetic fields of forming stars. The unique scientific and
technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the Front End of the
instrument is presented. Positioned at the Cassegrain Focal plane of the telescope, the front end is constituted of an
atmospheric dispersion corrector, a field viewer with an image stabilization unit (0.03 arc seconds RMS stabilization
goal), a calibration wheel and an achromatic polarimeter unit based on Fresnel Rhombs. The polarimeter permits the
circular and linear polarization analysis. The retardance of the Fresnel rhombs is nominal to better than 0.5% in the
whole spectral domain. The evaluation and the reduction of the thermal background of the Front end is a challenging part
of the instrument.
Pressure and temperature stabilization of an existing Echelle spectrograph III
Show abstract
The Echelle spectrograph FOCES1 is currently located at the laboratories of Munich University Observatories
under pressure and temperature stabilized conditions. It is being used as a test bed for a number of different
stability issues related to high precision radial velocity spectroscopy.
We utilize FOCES to study spectrograph stability, illumination stability and fiber transport stability. With
this work we continue the series of papers that present our efforts to obtain temperature and pressure stabilization
in the spectrograph environment. In particular we present first optical measurement results and compare them
to simulations previously published. We show the movement of the image on the CCD with changes of pressure
and temperature and the stability of the spot positions in the stabilized system using measurements done by a
ThAr gas discharge source.
Gemini high-resolution optical spectrograph conceptual optical design
Show abstract
The instrument group of the Herzberg Institute of Astrophysics has been commissioned by the Gemini Observatory as one of the three competing organizations to conduct a conceptual design study for a new Gemini High-Resolution Optical Spectrograph (GHOS). This paper outlines the main features of the optical design, including the Cassegrain-mounted science input unit, the bench-mounted spectrograph and the fibre relay system. The predicted imaging performance and efficiency are presented with the design trade offs explored in the study.
A single-shot optical linear polarimeter for asteroid studies
Show abstract
Polarimetric studies of minor Solar System bodies are useful to access physical parameters, such as albedo and
diameter, which are both important and difficult to derive by other techniques. Current activities in this field are limited
since most instruments adopted in recent observing campaigns involve photomultipliers detectors. These sensors are
suitable for observations of objects with fast polarization variations, but usually suffer from low quantum efficiency.
This severely limits the number of accessible targets. For asteroids, the polarization evolves slowly enough to allow
more sensitive albeit slower detectors (CCD-based polarimeters). However, polarimetric measurement accuracy may be
hampered with usual "sequential" polarimeters. Indeed, retarder plate swapping time, readout and exposure time add up.
Consequently, the time laps between complementary polarization measurements (some minutes) may be non-negligible
in some cases, compared to the evolution time of the polarization parameters. Moreover, polarimetric accuracy may also
be limited by airmass variations between complementary exposures.
We are developing a new "single-shot" CCD polarimeter based on a "double-Wollaston" configuration already
described in literature [9][10]. This allows simultaneous acquisition of the three Stokes parameters I, Q, U without any
moving parts. So, the linear polarization degree can be measured accurately, even for targets with fast polarization
and/or airmass variations. Presently, the polarization analyzer is in calibration phase, and will be installed soon at the
F/12.5 Cassegrain focus of the West telescope at the "Centre Pédagogique Planète et Univers" facility (C2PU,
Observatoire de la Côte d'Azur, Plateau de Calern, France).
Gemini high-resolution optical spectrograph conceptual mechanical design
Show abstract
The Herzberg Institute of Astrophysics was recently selected by the Gemini Observatory as one of the three competing
organizations to conduct a conceptual design study for a new Gemini High-Resolution Optical Spectrograph (GHOS).
This paper outlines the main features of the mechanical design, including the Cassegrain-mounted science input unit, the
bench-mounted spectrograph and the fiber relay system. Topics include the design challenges associated with multiobject
fiber relays in the science unit, environmental stability of the spectrograph bench and routing and handling of
fibers in the Gemini dome environment.
RINGO3: a multi-colour fast response polarimeter
Show abstract
GRB jets contain rapidly moving electrons which will spiral around magnetic field lines. This causes them to
emit polarized synchrotron emission. We have built a series of polarimeters (RINGO and RINGO2) to investigate
this by measuring the polarization of optical light from GRBs at a certain single wavelength. The instruments
are mounted on the Liverpool Telescope, which is a fully robotic (i.e. unmanned) telescope on La Palma which
reacts to triggers from satellites such as the NASA SWIFT mission. This has had great success, with the first
ever detections of early time optical polarization being made. In addition, the first measurements of the change
in optical polarization from a GRB as the jet expands have recently been obtained.
In this paper we describe the design and construction of RINGO3. This will be a multi-colour instrument
that can observe simultaneously at three wavelengths. By doing so we will be able to unambiguously identify
where in the burst the polarized emission is coming from. This will allow us to distinguish between three
possibilities: (1) Magnetic instabilities generated in the shock front, (2) Line of sight effects and (3) Large-scale
magnetic fields present throughout the relativistic outflow. The instrument design combines a rapidly rotating
polaroid, specially designed polarization insensitive dichroic mirrors and three electron multiplying CCD cameras
to provide simultaneous wavelength coverage with a time resolution of 1 second.
ECHARPE mechanical design
Show abstract
ECHARPE spectrograph - Espectrógrafo ECHelle de Alta Resolução para o telescópio Perkin-Elmer - is being
designed at LNA - Laboratório Nacional de Astrofísica, Brazil - to be mounted on 1.60 meter telescope at Pico dos
Dias Observatory, Brazil. It will offer a spectral resolution of R ~ 50000, in the interval 390-900 nm and in a single
exposition. It will be a fiber fed, bench spectrograph with two channels: blue and red, fed by two optical fibers (object,
sky or calibration) with aperture of 1.5 or 2.0 arcseconds. This paper reports on technical characteristics of the
spectrograph mechanical design and presents a new developed mounting system for echelle grating and collimator and
relay mirrors, which allows linear and rotational adjustments in all degrees of freedom without using springs.
aTmcam: a simple atmospheric transmission monitoring camera for sub 1% photometric precision
Show abstract
Traditional color and airmass corrections can typically achieve ~0.02 mag precision in photometric observing conditions.
A major limiting factor is the variability in atmospheric throughput, which changes on timescales of less than a night.
We present preliminary results for a system to monitor the throughput of the atmosphere, which should enable
photometric precision when coupled to more traditional techniques of less than 1% in photometric conditions. The
system, aTmCam, consists of a set of imagers 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, aerosol optical depth, etc. We have built a
prototype system to test the notion that an atmospheric model derived from a few color indices measurements can be an
accurate representation of the true atmospheric transmission. We have measured the atmospheric transmission with both
narrowband photometric measurements and spectroscopic measurements; we show that the narrowband imaging
approach can predict the changes in the throughput of the atmosphere to better than ~10% across a broad wavelength
range, so as to achieve photometric precision less than 0.01 mag.
Image quality tests on the Canarias InfraRed Camera Experiment (CIRCE)
Show abstract
In this paper we present the results of image quality tests performed on the optical system of the Canarias InfraRed Camera Experiment (CIRCE), a visitor-class near-IR imager, spectrograph, and polarimeter for the 10.4 meter Gran Telescopio Canarias (GTC). The CIRCE optical system is comprised of eight gold-coated aluminum alloy 6061 mirrors. We present surface roughness analysis of each individual component as well as optical quality of the whole system. We found all individual mirror surface roughness are within specifications except Fold mirrors 1 and 2. We plan to have these components re-cut and re-coated. We used a flat 0.2-arcseconds pinhole mask placed in the focal plane of the telescope to perform the optical quality tests of the system. The pinhole mask covers the entire field of view of the instrument. The resulting image quality allows seeing-limited performance down to seeing of 0.3 arcseconds FWHM. We also observed that our optical system produces a negative field curvature, which compensates the field curvature of the Ritchey-Chretien GTC design once the instrument is on the telescope.
Upgrading CRIRES-VLT to cross-dispersed mode
Show abstract
The cryogenic high resolution IR echelle spectrograph CRIRES is the ESO infrared (0.95−5.4 μm) high
resolution spectrograph operating at the Nasmyth A focus of VLT-UT1. The instrument provides long-slit
(31") spectroscopy with resolving power up to R=100,000 over a quite narrow wavelengths range, about 1/70 of
the central wavelength. Observations of compact objects (e.g. stellar photospheres) could be made much more
efficient by implementing a cross-dispersed mode, which increases the simultaneous spectral coverage by an order
of magnitude or more.
This paper presents the design of a relatively simple system to add cross-dispersed modes to CRIRES with a
minimum impact on the instrument optics and mechanics.
MSI: a visible multi-spectral imager for 1.6-m telescope of Hokkaido University
Show abstract
We have built a visible multi-spectral imager (MSI) for the 1.6-m Pirka telescope of the Hokkaido University
in Hokkaido, Japan. The instrument is equipped with two liquid crystal tunable filters and a 512 × 512 pixel
EMCCD camera. One of the major purposes of this instrument is to obtain multi-spectral images (series of
narrow-band images at many different wavelengths) of the solar planets rapidly. These tunable filters are a
Lyot filter with liquid crystal variable retarders and thus can tune the transmitting wavelength rapidly without
moving parts. Their spectral ranges are 400–720 nm and 650–1100 nm and the bandwidth is typically 10 nm on
both filters. The EMCCD camera can obtain images at a frame rate of about 32 Hz, which also enables us to
improve the spatial resolution with the shift-and-add or the Lucky imaging techniques. The field of view is 3.3
× 3.3 arcmin with a pixel scale of 0.39 arcsec pixel−1. The instrument also has UBV RI-band broad-band filters
and several narrow-band filters. MSI is mounted at the f/12 Cassegrain focus of the telescope. It had the first
light on February 2011, and then have been used for several astronomical and planetary science programs as a
major facility instrument at this telescope. We describe the design, construction, integration, and performance
of this multi-spectral imager.
The MUSE instrument detector system
Show abstract
The MUSE (Multi Unit Spectroscopic Explorer) instrument (see Bacon et al., this conference) for ESO's Very Large
Telescope VLT employs 24 integral field units (spectrographs). Each of these is equipped with its own cryogenically
cooled CCD head. The heads are individually cooled by continuous flow cryostats. The detectors used are deep depletion
e2v CCD231-84 with 4096x4112 active 15 μm pixels. The MUSE Instrument Detector System is now in the final
integration and test phase on the instrument.
This paper gives an overview of the architecture and performance of the complex detector system including ESO's New
General detector Controllers (NGC) for the 24 science detectors, the detector head electronics and the data acquisition
system with Linux Local Control Units. NGC is sub-divided into 4 Detector Front End units each operating 6 CCDs. All
CCDs are simultaneously read out through 4 ports to achieve short readout times at low noise levels.
All science grade CCDs were thoroughly characterized on ESO's optical detectors testbench facility and the test results
processed and documented in a semi-automated, reproducible way. We present the test methodology and the results that
fully confirm the feasibility of these detectors for their use in this challenging instrument.
Laboratory performance tests of PANIC, the panoramic NIR imager for Calar Alto
Josef W. Fried,
Armin Huber,
Clemens Storz,
et al.
Show abstract
PANIC is developed at MPIA, Heidelberg, Germany and IAA, Granada, Spain. This instrument will cover a field of
view of 0.5x0.5 degrees at the 2.2m telescope in the spectral bands Z to K. All hardware has been manufactured, the
instrument is currently assembled and tested. In this contribution we describe results of some tests.
SPIRou @ CFHT: fiber links and pupil slicer
Show abstract
SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a next-generation instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of
detecting Earth-like planets around low mass stars and magnetic fields of forming stars. The unique scientific and
technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the fiber links which
connects the polarimeter unit to the cryogenic spectrograph unit (35 meter apart) are described. The pupil slicer which
forms a slit compatible with the spectrograph entrance specifications is also discussed in this paper.
Some challenging aspects are presented. In particular this paper will focus on the manufacturing of 35 meter fibers with a
very low loss attenuation (< 13dB/km) in the non-usual fiber spectral domain from 0.98 μm to 2.35 μm. Other aspects as
the scrambling performance of the fiber links to reach high accuracy radial velocity measurements (1m/s) and the design
of the pupil slicer exposed at a cryogenic and vacuum environment will be discussed.
Control and protection of outdoor embedded camera for astronomy
F. Rigaud,
I. Jegouzo,
J. Gaudemard,
et al.
Show abstract
The purpose of CABERNET- Podet-Met (CAmera BEtter Resolution NETwork, Pole sur la Dynamique de
l'Environnement Terrestre - Meteor) project is the automated observation, by triangulation with three cameras, of
meteor showers to perform a calculation of meteoroids trajectory and velocity. The scientific goal is to search the parent
body, comet or asteroid, for each observed meteor.
To install outdoor cameras in order to perform astronomy measurements for several years with high reliability requires a
very specific design for the box. For these cameras, this contribution shows how we fulfilled the various functions of
their boxes, such as cooling of the CCD, heating to melt snow and ice, the protecting against moisture, lightning and
Solar light. We present the principal and secondary functions, the product breakdown structure, the technical solutions
evaluation grid of criteria, the adopted technology products and their implementation in multifunction subsets for
miniaturization purpose. To manage this project, we aim to get the lowest manpower and development time for every
part. In appendix, we present the measurements the image quality evolution during the CCD cooling, and some pictures
of the prototype.
Design and construction progress of LRS2-B: a new low resolution integral-field spectrograph for the Hobby-Eberly Telescope
Show abstract
The upcoming Wide-Field Upgrade (WFU) has ushered in a new era of instrumentation for the Hobby-Eberly Telescope (HET). Here, we present the design, construction progress, and lab tests completed to date of the blue-optimized second generation Low Resolution Spectrograph (LRS2-B). LRS2-B is a dual-channel, fiber fed instrument that is 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-B utilizes a microlens-coupled integral field unit (IFU) that covers a 7”x12” area on the sky having unity fill-factor with ~300 spatial elements that subsample the median HET image quality. The fiber feed assembly includes an optimized dichroic beam splitter that allows LRS2-B to simultaneously observe 370 <λ(nm) < 470 and 460 < λ(nm) < 700 at fixed resolving powers of R ≈ λ/Δλ ≈ 1900 and 1200, respectively. We discuss the departures from the nominal VIRUS design, which includes the IFU, fiber feed, camera correcting optics, and volume phase holographic grisms. Additionally, the motivation for the selection of the wavelength coverage and spectral resolution of the two channels is briefly discussed. One such motivation is the follow-up study of spectrally and (or) spatially resolved Lyα emission from z ≈ 2.5 star-forming galaxies in the HETDEX survey. LRS2-B is planned to be a commissioning instrument for the HET WFU and should be on-sky during quarter 4 of 2013. Finally, we mention the current state of LRS2-R, the red optimized sister instrument of LRS2-B.
Optical design of a red-sensitive spectrograph
Show abstract
We present a preliminary design for a red-sensitive spectrograph. The spectrograph is optimized to operate over the 600-
1000 nm spectral range at a resolution of R = λ/▵λ ~2000 and is designed specifically for the 2.7-m Harlan J. Smith
Telescope at McDonald Observatory. The design is compact and cost effective and should have very high throughput.
The principles of the design can be extended to other purposes, such as a unit spectrograph for the DESpec project or
other projects that require good performance in the red. In this paper, we will discuss the selection of components as well
as the choice of optical layouts and the theoretical throughput of the instrument.
Optimal resolutions for optical and NIR spectroscopy
Show abstract
We study the effects of atmospheric emission lines in the night sky on spectroscopic measurements in the 0.4-2.4 μm
range at resolutions 100≤R≤50000 to determine an optimal observing resolution. We build a model of the background
sky spectrum at various moon phases and calculate the fraction of pixels free of emission lines in 7 different band passes
while varying the resolution. We then discuss the effect of the background emission on the signal-to-noise of constant
flux targets to determine an optimal resolution at which to observe. Preliminary results show that the emission lines have
little to no effect on the selection of resolution in the optical, but that in the wavelengths ranging from 1.0-2.4 μm the
effects of atmospheric emission line suggests observing at a resolution of R>2000 is recommended.
HexPak and GradPak: variable-pitch dual-head IFUs for the WIYN 3.5m Telescope Bench Spectrograph
Show abstract
We describe the design, construction, and expected performance of two new fiber integral field units (IFUs) -
HexPak and GradPak - for the WIYN 3.5m Telescope Nasmyth focus and Bench Spectrograph. These are the
first IFUs to provide formatted fiber integral field spectroscopy with simultaneous sampling of varying angular
scales. HexPak and GradPak are in a single cable with a dual-head design, permitting easy switching between
the two different IFU heads on the telescope without changing the spectrograph feed: the two heads feed a
variable-width double-slit. Each IFU head is comprised of a fixed arrangement of fibers with a range of fiber
diameters. The layout and diameters of the fibers within each array are scientifically-driven for observations
of galaxies: HexPak is designed to observe face-on spiral or spheroidal galaxies while GradPak is optimized
for edge-on studies of galaxy disks. HexPak is a hexagonal array of 2.9 arcsec fibers subtending a 40.9 arcsec
diameter, with a high-resolution circular core of 0.94 arcsec fibers subtending 6 arcsec diameter. GradPak is a
39 by 55 arcsec rectangular array with rows of fibers of increasing diameter from angular scales of 1.9 arcsec to
5.6 arcsec across the array. The variable pitch of these IFU heads allows for adequate sampling of light profile
gradients while maintaining the photon limit at different scales.
A new deep-depletion CCD for the red channel of the Palomar Double Spectrograph
Show abstract
The red channel of the Palomar Double Spectrograph (DBSP) on the 200-inch Hale Telescope has been upgraded with a
new deep-depletion CCD from LBNL. Its redder response produced a significant increase of the throughput above
550 nm, and its longer dimension more than doubled the spectral coverage. A special Dewar was designed to
accommodate a detector mount which includes features to minimize CCD motion due to thermal cycling, in spite of the
very simple "picture frame" packaging of the CCD. The new Dewar also includes some novel features to improve the
liquid nitrogen hold time while staying within the size envelope allowed in the Cassegrain cage. We describe these
changes along with the detector characterization.
SPIRou @ CFHT: spectrograph optical design
Show abstract
SPIRou is a near-infrared, echelle spectropolarimeter/velocimeter under design for the 3.6m Canada-France-Hawaii
Telescope (CFHT) on Mauna Kea, Hawaii. The unique scientific capabilities and technical design features are described
in the accompanying (eight) papers at this conference. In this paper we focus on the lens design of the optical
spectrograph. The SPIROU spectrograph is a near infrared fiber fed double pass cross dispersed spectrograph. The
cryogenic spectrograph is connected with the Cassegrain unit by the two science fibers. It is also fed by the fiber coming
from the calibration box and RV reference module of the instrument. It includes 2 off-axis parabolas (1 in double pass),
an echelle grating, a train of cross disperser prisms (in double pass), a flat folding mirror, a refractive camera and a
detector. This paper describes the optical design of the spectrograph unit and estimates the performances. In particular,
the echelle grating options are discussed as the goal grating is not available from the market.
STELES mechanical design
Show abstract
The SOAR Telescope Echelle Spectrograph - STELES - is part of the Brazilian participation on the 4.1m SOAR
telescope second-generation instrumentation. In view of SOAR´s high image quality and moderately large collecting
area and the near UV capability, it will be able to yield high quality spectroscopic data for a large variety of objects of
astrophysical interests. The spectrograph is a R4 cross-dispersed echelle fed by the SOAR Nasmyth focus, operating in a
quasi-Littrow white pupil configuration, and a resolving power of R ≈ 50,000, covering the 300-900nm spectral range in
one shot.
STELES is a bench spectrograph which will be mounted vertically on one side of the SOAR Telescope fork. The ninetydegree
inversion of the mechanical components, due to the vertical position of the instrument, plus the close proximity of
most components, due to the spectrograph compactness, were requirements carefully observed during the mechanical
design process. This paper describes the mechanical characteristics of the individual assemblies that make up the
STELES mechanical design. The STELES instrument can be separated into two sections, the fore optics, and the
spectrograph. The fore optics has the mechanisms from the SOAR telescope down to the STELES bench spectrograph,
and the bench spectrograph has the mechanisms for the spectrograph covering the red and blue spectrum.
CARMENES. II: optical and opto-mechanical design
Show abstract
CARMENES is a fiber-fed high-resolution échelle spectrograph for the Calar Alto 3.5m telescope. The instrument is
built by a German-Spanish consortium under the lead of the Landessternwarte Heidelberg. The search for planets around
M dwarfs with a radial velocity accuracy of 1 m/s is the main focus of the planned science. Two channels, one for the
visible, another for the near-infrared, will allow observations in the complete wavelength range from 550 to 1700 nm. To
ensure the stability, the instrument is working in vacuum in a thermally controlled environment. The optical design of
both channels of the instrument and the front-end, as well as the opto-mechanical design, are described.
Perfomance verification of the ground-based mid-infrared camera MAX38 on the MiniTAO Telescope
Show abstract
We have evaluated on-sky performances of a mid-infrared camera MAX38 (Mid-infrared Astronomical eXploerer)
on the miniTAO 1-meter telescope. A Strehl ratio at the N-band is estimated to be 0.7-0.8, and it reaches to 0.9
at the 37.7 micron, indicating that diffraction limited angular resolution is almost achieved at the wavelength
range from 8 to 38 micron. System efficiencies at the N and the Q-band are estimated with photometry of
standard stars. The sensitivity at the 30 micron cannot be exactly estimated because there are no standard stars
bright enough. We use the sky brightness instead. The estimated efficiencies at the 8.9, 18.7, and 31.7 micron
are 4%, 3%, 15% , respectively. One-sigma sensitivity in 1 sec integration of each filter is also evaluated. These
give good agreements with the designed values. Preliminary scientific results are briefly reported.
Gemini high-resolution optical spectrograph conceptual design
Show abstract
A multiplexed moderate resolution (R = 34,000) and a single object high resolution (R = 90,000) spectroscopic facility
for the entire 340 - 950nm wavelength region has been designed for Gemini. The result is a high throughput, versatile
instrument that will enable precision spectroscopy for decades to come. The extended wavelength coverage for these
relatively high spectral resolutions is achieved by use of an Echelle grating with VPH cross-dispersers and for the R =
90,000 mode utilization of an image slicer. The design incorporates a fast, efficient, reliable system for acquiring targets
over the7 arcmin field of Gemini. This paper outlines the science case development and requirements flow-down process
that leads to the configuration of the HIA instrument and describes the overall GHOS conceptual design. In addition, this
paper discusses design trades examined during the conceptual design study instrument group of the Herzberg Institute of
Astrophysics has been commissioned by the Gemini Observatory as one of the three competing organizations to conduct
a conceptual design study for a new Gemini High-Resolution Optical Spectrograph (GHOS). This paper outlines the
science case development and requirements flow-down process that leads to the configuration of the HIA instrument and
describes the overall GHOS conceptual design. In addition, this paper discusses design trades examined during the
conceptual design study.
ECHARPE: a fiber-fed echelle spectrograph for the Pico dos Dias Observatory
Show abstract
At least during the last ten years, the Brazilian astronomical community has been asking for an echelle spectrograph for
the 1.6 m telescope installed at Pico dos Dias Observatory (Brazópolis, MG, Brazil, OPD/MCTI/LNA). Among the
scientific cases are topics related to the chemical evolution of the Galaxy, asteroseismology, chemical composition and
chromospheric activities of solar type stars and the relations between solar analogues and terrestrial planets. During 2009
the project finally got started. The called ECHARPE spectrograph (Espectrógrafo ECHelle de Alta Resolução para o
telescópio Perkin-Elmer) is being projected to offer a spectral resolution of R ~ 50000, in the range 390-900 nm and with
a single exposition. It will be a bench spectrograph with two channels: blue and red, fed by two optical fibers (object, sky
or calibration) with aperture of 1.5 or 2.0 arcseconds. The instrument will be placed in one of the telescope pillar
ramification, in the originals installations of a Coudé spectrograph and in a specially created environment controlled
room. In this work we will present the scientific motivations, the conceptual optical design, the expected performance of
the spectrograph, and the status of its development. ECHARPE is expected to be delivered to the astronomical
community in 2014, fully prepared and optimized for remote operations.
An experimental VLT cryo-cooler instrumentation vibration analysis
Show abstract
Cryo-coolers are widely used to provide the required temperature levels of ESO’s VLT instrumentation suite, mainly for infrared instruments and their detectors. Nevertheless, mechanical vibrations induced by these refrigerator systems became a serious issue over the last years. Especially for the extremely sensitive VLT-Interferometer even micro vibration levels can be critical. As a consequence ESO started some time ago a comprehensive vibration reduction program. Major tasks involved are the quantification of typical cryo-cooler instrument vibration levels and their impact on the VLT / VLT-I optical stability. This paper describes the design, construction and calibration of a dedicated VLT dummy instrument comprising six powerful state-of-the-art 2-stage cold heads and the subsequent comprehensive vibration measurement test campaign. As a result trendsetting cryo-cooler instrument design and operation recommendations are presented.
A simple, high efficiency, high resolution spectropolarimeter
Show abstract
A simple concept is described that uses volume phase holographic gratings as polarizing dispersers for a high efficiency, high resolution spectropolarimeter. Although the idea has previously been mentioned in the literature as possible, such a concept has not been explored in detail. Performance analysis is presented for a VPHG spectropolarimeter concept that could be utilized for both solar and night-time astronomy. Instrumental peak efficiency can approach 100% with spectral dispersions permitting R~200,000 spectral resolution with diffraction limited telescopes. The instrument has 3-channels: two dispersed image planes with orthogonal polarization and an undispersed image plane. The concept has a range of versatility where it could be configured (with appropriate half-wave plates) for slit-fed spectroscopy or without slits for snapshot/hyperspectral/tomographic spectroscopic imaging. Multiplex gratings could also be used for the
simultaneous recording of two separate spectral bands or multiple instruments could be daisy chained with beam splitters
for further spectral coverage.
CYCLOPS2: the fibre image slicer upgrade for the UCLES high resolution spectrograph
Show abstract
CYCLOPS2 is an upgrade for the UCLES high resolution spectrograph on the Anglo-Australian Telescope, scheduled for commissioning in semester 2012A. By replacing the 5 mirror Coud´e train with a Cassegrain mounted fibre-based image slicer CYCLOPS2 simultaneously provides improved throughput, reduced aperture losses and increased spectral resolution. Sixteen optical fibres collect light from a 5.0 arcsecond2 area of sky and reformat it into the equivalent of a 0.6 arcsecond wide slit, delivering a spectral resolution of R= 70000 and up to twice as much flux as the standard 1 arcsecond slit of the Coud´e train. CYCLOPS2 also adds support for simultaneous ThAr wavelength calibration via a dedicated fibre. CYCLOPS2 consists of three main components, the fore-optics unit, fibre bundle and slit unit. The fore optics unit incorporates magnification optics and a lenslet array and is designed to mount to the CURE Cassegrain instrument interface, which provides acquisition, guiding and calibration facilities. The fibre bundle transports the light from the Cassegrain focus to the UCLES spectrograph at Coud´e and also includes a fibre mode scrambler. The slit unit consists of the fibre slit and relay optics to project an image of the slit onto the entrance aperture of the UCLES spectrograph. CYCLOPS2 builds on experience with the first generation CYCLOPS fibre system, which we also describe in this paper. We present the science case for an image slicing fibre feed for echelle spectroscopy and describe the design of CYCLOPS and CYCLOPS2.
Echelle gratings for the near-infrared
Show abstract
We report on echelle gratings produced by diamond turning with groove spacings coarser than 20 lines per mm. Increasing the groove spacing of an echelle reduces the free spectral range allowing infrared orders to be matched to the detector size. Reflection echelle gratings designed for the near-infrared have potential wide application in both ambient temperature as well as cryogenic astronomical spectrographs. Diamond turned reflection echelle gratings are currently employed in space-based high-resolution spectrographs for 2 – 4 μm planetary spectroscopy. Using a sample diamond turned grating we investigate the suitability of a 15 line/mm R3 echelle for use in ground-based 1 – 5 μm spectroscopy. We find this grating suitable for 3 – 5 μm high signal-to-noise, high-resolution applications. Controlling wavefront errors by an additional factor of two would permit use at high-resolution in the 1.5 – 2.5 μm region.
Fully optimized shaped pupils: preparation for a test at the Subaru Telescope
Show abstract
The SCExAO instrument at the Subaru telescope, mainly based on a PIAA coronagraph can benefit from the addition of a robust and simple shaped pupil coronagraph. New shaped pupils, fully optimized in 2 dimensions, make it possible to design optimal apodizers for arbitrarily complex apertures, for instance on-axis telescopes such as the Subaru telescope. We have designed several masks with inner working angles as small as 2.5 λ / D, and for high-contrast regions with different shapes. Using Princeton University nanofabrication facilities, we have manufactured two masks by photolithography. These masks have been tested in the laboratory, both in Princeton and in the facilities of the National Astronomical Observatory of Japan (NAOJ) in Hilo. The goal of this work is to prepare tests on the sky of a shaped pupil coronagraph in 2012.
From the most plain coronagraph to the most populated spectrograph: a suite of some new instruments for LBT
Show abstract
The Large Binocular Telescope is one of the most unusual 8 m class telescope and surely it has been inspirational to a number of novel concepts and innovations. We present here a couple of recently traced opto-mechanical designs to fit some niches in the parameters space of astrophysical usage. A coronagraph, as simple as possible, to take advantage of the LBT XAO ability dedicated to the ExoPlanets detection and a multiple very wide field spectrograph in which a large number of tiny cameras is foreseen, all with equal optical elements but for the pupil aberration corrector.
Optical bi-stable shutter development/improvement
Show abstract
Two of the VLT instruments (Giraffe and VIMOS) are using the large magnetic E/150 from Prontor (with an aperture
diameter of 150 mm). As we were facing an unacceptable number of failures with this component some improvement
plan was discussed already in 2004. The final decision for starting this program was conditioned by the decision from the
constructor to stop the production.
The opportunity was taken to improve the design building a fully bi-stable mechanism in order to reduce the thermal
dissipation.
The project was developed in collaboration between the two main ESO sites doing the best use of the manpower and of
the technical capability available at the two centers. The project took advantage of the laser Mask Manufacturing Unit
and the invar sheets used to prepare the VIMOS MOS mask to fabricate the shutter petals.
Our paper describes the development including the intensive and long optimization period. To conclude this optimization
we proceed with a long life test on two units. These units have demonstrate a very high level of reliability (up to 100 000
cycles without failure which can be estimated to an equivalent 6 years of operation of the instrument)
A new bi-stable shutter driver and controller have also been developed. Some of the highlights of this unit are the fully
configurable coil driving parameters, usage of braking strategy to dump mechanical vibration and reduce mechanical
wearing, configurable usage of OPEN and CLOSE sensors, non volatile storage of parameters, user friendly front panel
interface.
An integrated 1-5 micron test bench for the characterization of cryogenic optical elements
Show abstract
We report on the final design and current status of a 1-5 micron infrared test bench at the ETH Zurich Institute for
Astronomy. This facility will enable us to characterize infrared optics, both reflective and transmissive, at cryogenic
operating temperatures for both ground- and space-based applications. A focus of our lab is to facilitate the detection and characterization of extra-solar planets. The test bench is designed to characterize a range of spectrally dispersive and diffraction suppression optics such as filters, grisms, gratings, as well as both focal and pupil plane coronagraphs. The test bench is built around a 2048x2048 HAWAII-2RG detector from Teledyne Imaging Systems. The optical bench is envisioned to operate down to 30 K. “First light” is expected in the second half of 2012. We outline the status of the project, and describe the capabilities of the test bench in detail in order to alert potential collaborators to this new capability.
Demonstration and design of a compact diffraction limited spectrograph
Show abstract
PIMMS IR is a prototype high resolution diraction limited spectrograph operating in the near infrared. Its
current conguration has a bandwidth of 8nm centred on 1550nm with a resolving power, λ/Δλ, of 31000 with the option to increase this to ~60000 using a dual grating system. Remarkably, this is 85% of the theoretical
limit for Gaussian illumination of a diraction grating. It is based upon the PIMMS#0 (photonic integrated
multi-mode micro-spectrograph), a design that utilises the multi-mode to single-mode conversion of the photonic
lantern. By feeding the spectrograph with the single-mode bres we are able to design and build a spectrograph
whose performance is diraction limited and independent of the input source (i.e. a telescope) it is attached to.
The spectrograph has with a throughput of ~70% (that is the light from the single-mode entrance slit that lands
on the detector). The spectrograph is also extremely compact with a footprint of just 450mm x 190mm. Here
we present the design of PIMMS IR and its performance characteristics determined from ray tracing, physical
optics simulations and experimental measurements.Δ
Redesign of the integrated photonic spectrograph for improved astronomical performance
Show abstract
The Integrated Photonic Spectrograph (IPS) is a complete spectrograph within a single silica photonic chip, that has no
moving parts, is highly resistant to stress and temperature induced flexure and is far smaller than existing bulk-optic
spectrographs. There has been considerable development in this all-photonic approach, culminating in a recent successful
on-telescope test, which saw the world's first astronomical spectra taken using a photonic spectrograph. However, the
device's performance (in terms of resolving power and wavelength coverage) was limited by the predominantly
telecommunications-grade design parameters used in chip manufacturing, and at this stage warrants a substantial
redesign of the arrayed waveguide grating structure inside the IPS chips, to optimize it for astronomy. In this body of
work we present a comprehensive redesign of arrayed waveguide grating chips to improve specific performance
parameters of interest to astronomy. These include the free-spectral range, resolving power and the operational
wavelength for the devices, with an analysis of the limitations and benefits of the redesigns for typical astronomical
goals. We propose how the redesigns, along with other advancements in astrophotonics, can be used in conjunction with
adaptive-optics systems to make a prototype instrument with competitive throughput and resolving power.
GNOSIS: a novel near-infrared OH suppression unit at the AAT
Show abstract
GNOSIS has provided the first on-telescope demonstration of a concept to utilize complex aperioidc fiber Bragg
gratings to suppress the 103 brightest atmospheric hydroxyl emission doublets between 1.47-1.7 μm. The unit is
designed to be used at the 3.9-meter Anglo-Australian Telescope (AAT) feeding the IRIS2 spectrograph. Unlike
previous atmospheric suppression techniques GNOSIS suppresses the lines before dispersion. We present the
results of laboratory and on-sky tests from instrument commissioning. These tests reveal excellent suppression
performance by the gratings and high inter-notch throughput, which combine to produce high fidelity OH-free
spectra.
A water vapour monitor at Paranal Observatory
Show abstract
We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO’s
Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by
Radiometer Physics GmbH (RPG), has been selected. 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 ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5 – 9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer’s ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.
High resolution Florida IR silicon immersion grating spectrometer and an M dwarf planet survey
Show abstract
We report the system design and predicted performance of the Florida IR Silicon immersion grating
spectromeTer (FIRST). This new generation cryogenic IR spectrograph offers broad-band high resolution
IR spectroscopy with R=72,000 at 1.4-1.8 μm and R=60,000 at 0.8-1.35 μm in a single exposure with a
2kx2k H2RG IR array. It is enabled by a compact design using an extremely high dispersion silicon
immersion grating (SIG) and an R4 echelle with a 50 mm diameter pupil in combination with an Image
Slicer. This instrument is operated in vacuum with temperature precisely controlled to reach long term
stability for high precision radial velocity (RV) measurements of nearby stars, especially M dwarfs and
young stars. The primary technical goal is to reach better than 4 m/s long term RV precision with J<9 M
dwarfs within 30 min exposures. This instrument is scheduled to be commissioned at the Tennessee State
University (TSU) 2-m Automatic Spectroscopic Telescope (AST) at Fairborn Observatory in spring 2013.
FIRST can also be used for observing transiting planets, young stellar objects (YSOs), magnetic fields,
binaries, brown dwarfs (BDs), ISM and stars.
We plan to launch the FIRST NIR M dwarf planet survey in 2014 after FIRST is commissioned at the
AST. This NIR M dwarf survey is the first large-scale NIR high precision Doppler survey dedicated to
detecting and characterizing planets around 215 nearby M dwarfs with J< 10. Our primary science goal is
to look for habitable Super-Earths around the late M dwarfs and also to identify transiting systems for
follow-up observations with JWST to measure the planetary atmospheric compositions and study their
habitability. Our secondary science goal is to detect and characterize a large number of planets around M
dwarfs to understand the statistics of planet populations around these low mass stars and constrain planet
formation and evolution models. Our survey baseline is expected to detect ~30 exoplanets, including 10
Super Earths, within 100 day periods. About half of the Super-Earths are in their habitable zones and one
of them may be a transiting planet. The AST, with its robotic control and ease of switching between
instruments (in seconds), enables great flexibility and efficiency, and enables an optimal strategy, in terms
of schedule and cadence, for this NIR M dwarf planet survey.
Commissioning of the WWFI for the Wendelstein Fraunhofer Telescope
Show abstract
Ludwig-Maximilians-Universitat Munchen operates an astrophysical observatory on the summit of Mt. Wendelstein 1 which has been equipped with a modern 2m-class telescope.2-4 The new Fraunhofer telescope is designed to sustain the excellent (< 0:8" median) seeing of the site [1, Fig. 1] over a FoV of 0:2 deg2 utilizing a camera built around a customized 64 MPixel Mosaic (Spectral Instruments, 4 × (4k)2 15μm e2v CCDs). The Wendelstein Wide Field Imager5 had its commissioning in the lab in the course of the last few months and now waits to see first light on sky in the near future, i.e. when telescope commissioning allows to test science instruments.
Testing of the "Tor Vergata" Fabry-Pérot interferometer prototype
Show abstract
In this contribution we present preliminary mechanical and optical tests of the Fabry-P´erot interferometer pro-
totype developed at the "Tor Vergata" University Solar Physics Laboratory. Fabry-P´erot narrow filters are of
great interest for the study of extended astronomical sources, such as the solar photosphere and chromosphere.
The high transparency of the instrument allows for the necessary high time-resolution for fast dynamic processes
observations. A dedicated software has been developed to control both coarse and fine piezo-actuated move-
ments, allowing for fast (1ms) tuning capabilities. General mechanical behaviour has been tested for use at the
focal plane of ground based telescopes and in the perspective of a new space-qualified prototype.
Commissioning results of MMT-POL: the 1-5um imaging polarimeter leveraged from the AO secondary of the 6.5m MMT
Show abstract
MMT-POL is an adaptive optics optimized imaging polarimeter designed for use at the 6.5m MMT. By taking full
advantage of the adaptive optics secondary mirror of the MMT, this polarimeter offers diffraction-limited polarimetry with very low instrumental polarization and minimal thermal background. MMT-POL permits observations as diverse as protoplanetary discs, comets, red giant winds, (super)novae and ejecta, galaxies, and AGN. We report on the initial on-sky commissioning results of the instrument including a description of the instrument.
New scientific results with SpIOMM: a testbed for CFHT's imaging
Fourier transform spectrometer SITELLE
Show abstract
We present new data obtained with SpIOMM, the imaging Fourier transform spectrometer attached to the 1.6-m
telescope of the Observatoire du Mont-Megantic in Québec. Recent technical and data reduction improvements have
significantly increased SpIOMM's capabilities to observe fainter objects or weaker nebular lines, as well as continuum
sources and absorption lines, and to increase its modulation efficiency in the near ultraviolet. To illustrate these
improvements, we present data on the supernova remnant Cas A, planetary nebulae M27 and M97, the Wolf-Rayet ring
nebula M1-67, spiral galaxies M63 and NGC 3344, as well as the interacting pair of galaxies Arp 84.
The GIANO spectrometer: towards its first light at the TNG
E. Oliva,
L. Origlia,
R. Maiolino,
et al.
Show abstract
GIANO is a high resolution (R50,000) IR spectrograph which provides a quasi-complete coverage of the 0.95-
2.5μm wavelengths range in a single exposure. The instrument was integrated and tested in Arcetri-INAF
(Florence, Italy) and will be commisioned at the 3.58m TNG Italian telescope in La Palma. The major scientific goals include the search for rocky planets with habitable conditions around low-mass stars, quantitative spectroscopy of brown dwarfs, accurate chemical abundances of high metallicity stars and stellar clusters. This presentation describes the status of the instrument and presents the first results obtained in laboratory during the acceptance tests.
Testing Giano spectral stability
Show abstract
Giano is a high resolution (R'50,000) infrared spectrograph with a near-complete coverage of the 0.95-2.5 microns
wavelengths range. It was assembled in Arcetri-INAF (Florence) and is beeing shipped to the its final destination
at the TNG telescope (La Palma)
We present our measurements of internal wavelength stability of Giano spectra. We are using a new approach
which gives both the wavelength and field tilts. We also show the comparison with the usual mono-dimensional
approach.
Improved red sensitivity deep depletion e2v devices for the Gemini North GMOS instrument
Show abstract
The GMOS-N instrument was upgraded with new CCDs in October 2011, improving the instrument sensitivity at both red and blue wavelengths. The deep depletion devices are manufactured by e2v (42-90 with multi-layer 3 coating) and extend the useful wavelength range of GMOS-N to 0.98 microns (compared to 0.94 microns previously). These detectors also exhibit much lower fringing than the original EEV detectors that had been in use since GMOS-N was commissioned in 2002. All other characteristics of the new detectors (readout speed, pixel size and format, detector controller, noise, gain) are similar to the original CCDs. Operating the new detectors in all amps mode (2 per CCD) has effectively improved the readout speed by a factor of 2. The new devices were selected to provide a quick and relatively simply upgrade route while technical issues with the Hamamatsu devices, originally planned for the upgrade, were investigated and resolved. We discuss the rationale for this interim upgrade, the upgrade process and attending issues. The new detectors have been used for science since November 2011. We present commissioning results illustrating the resulting gain in sensitivity over the original detector package. Gemini is still committed to installing Hamamatsu devices, which will further extend the useful wavelength range of GMOS to 1.03 microns, in both North and South GMOS instruments. We discuss the status of the Hamamatsu project and the current planned schedule for these future upgrades.
DeSSpOt: an instrument for stellar spin orientation determination
Show abstract
We designed and constructed a special instrument to enable the determination of the stellar's spin orientation. The
Differential image rotator for Stellar Spin Orientation, DeSSpOt, allows the simultaneous observations of two anti-parallel
orientations of the star on the spectrum. On a high resolution ´echelle spectrum, the stellar rotation causes a slight line tilt
visible in the spatial direction which is comparable to a rotation curve. We developed a new method, which exploits the
variations in these tilts, to estimate the absolute position angle of the rotation axis. The line tilt is retrieved by a spectroastrometric
extraction of the spectrum.
In order to validate the method, we observed spectroscopic binaries with known orbital parameters. The determination of
the orbital position angle is equivalent to the determination of the stellar position angle, but is easier to to detect.
DeSSpOt was successfully implemented on the high resolution Coud´e spectrograph of the Th¨uringer Landessternwarte
Tautenburg. The observations of Capella led to the determination of the orbital position angle. Our value of 37.2° is in
agreement with the values previously found in the literature. As such we verified that both method and instrument are valid.
An alignment strategy for the optics of LINC-NIRVANA
Show abstract
LINC-NIRVANA is an instrument to combine the light from both LBT primary mirrors in an imaging Fizeau interferometer. The goals in terms of resolution and field of view are quite ambitious, which leads to a complex instrument consisting of a bunch of subsystems. The layer oriented MCAO system alone is already quite complicated and to get everything working together properly is not a small challenge. As we are reaching the completion of LINC-NIRVANA's subsystems, it becomes more and more important to define a strategy to align all these various subsystems. The specific layout of LINC-NIRVANA imposes some restrictions and difficulties on the sequence and the method of this alignment. The main problem for example is that we have to get two perfectly symmetrical focal planes to be able to properly combine them interferometrically. This is the major step on which all further alignment is based on, since all the subsystems (collimator and camera optics, wavefront sensors, cold IR optics, etc.) rely on these focal planes as a reference. I will give a small introduction on the optics of the instrument and line out the resulting difficulties as well as the strategy that we want to apply in order to overcome these.
First light observation of GIGMICS (germanium immersion grating mid-infrared cryogenic spectrograph) by Kanata 1.5-m Telescope at Higashi-Hiroshima Observatory
Yasuhiro Hirahara,
Keishin Aoki,
Kanako Ohta,
et al.
Show abstract
We have developed a germanium immersion grating mid-infrared cryogenic spectrograph (GIGMICS) designed for the Nasmyth focus stage of NAOJ Subaru 8.2-m telescope, which operates at N-band (8-13 μm) in wavelength (λ) with maximum resolving power R（≡λ/Δλ） ~ 50,000. A single crystal germanium echelle immersion grating (30 × 30 × 72 mm) for collimated beam size of 28 mmφ was fabricated by utilizing ultra precision micro-grinding method coupled with the ELID (ELectrolytic In-process Dressing) technique (Ohmori, H. 1992, Ebizuka et al. 2003, Tokoro et al. 2003). After the critical test for the application to the laboratory gas-phase IR high-resolution spectroscopy(Hirahara et al. 2010), we have conducted the “first light” astronomical observation of GIGMICS by the Kanata 1.5-m telescope at Higashi- Hiroshima Observatory from January to April, 2011. Toward many astronomical objects such as the Moon, Venus, Jupiter, circumstellar envelopes of late-type stars, proto-planetary nebulae, and interstellar molecular clouds in the vicinity of star-forming regions, we conducted spectroscopic observations in the N-band region.
An unobscured four spherical mirrors based collimator as a tradeoff solution for the Optical Ground Support Equipment (OGSE) of the High Resolution Camera (HRIC) of Simbio-Sys
Show abstract
The authors present the tradeoff and the merit criteria that lead to the selection of the M. Brunn [1]
"un obscured four mirrors based telescope" as the collimator of the Optical Ground Support Equipment in the
frame of the Assembly Integration and Verification (AIV) activities forecast for the optical characterization of
the High Resolution Camera (HRIC) on board of the Simbio-sys mission to Mercury, instrument currently
under development and manufacturing at Selex Galileo (SG) facilities in its Florence site. Several optical
configurations have been accounted for the design and manufacturing of the three meters focal length,
diffraction limited and wide field of view (0.4X0.6 degs) toolkit. From the classical un obscured systems such
as the aspheric solution based onto two hyperbolic mirror, working under an f - number of 13.6, the Brunn
solution revealed excellent optical quality free from coma, astigmatism and spherical aberration accomplished
by an ultra compact design in within a volume of 1.2x1.0 x0.5 cubic meters and other basic advantages such
as the relative easy way in aligning and manufacturing the mirrors.
Simulations and performances of AMICA at Dome C
Show abstract
Simulations of the expected performances of AMICA (Antarctic Multiband Infrared Camera) mounted on ITM (Infrared
Telescope Maffei, formerly IRAIT) at Dome C, Antarctica, are here presented. The computation has been carried out
through the analysis of images obtained by a focal plane simulator, here described, taking into account the telescope and
the imaging system characteristics (optics, read-out electronics and detectors) and the site properties. The evaluation of
the expected S/N ratio in various near- and mid-infrared pass-bands are fundamental to properly define the observational
plans and the scheduling of the robotic observatory.
Characterizing near-infrared sky brightness in the Canadian high arctic
Show abstract
We present the first measurements of the near-infrared (NIR), specifically the J-band, sky background in the Canadian High Arctic. There has been considerable recent interest in the development of an astronomical observatory in Ellesmere Island; initial site testing has shown promise for a world-class site. Encouragement for our study came from sky background measurements on the high Antarctic glacial plateau in winter that showed markedly lower NIR emission when compared to good mid-latitude astronomical sites due to reduced emission from the Meinel bands, i.e. hydroxyl radical (OH) airglow lines. This is possibly a Polar effect and may also be present in the High Arctic. To test this hypothesis, we carried out an experiment which measured the the J-band sky brightness in the High Arctic during winter. We constructed a zenith-pointing, J-band photometer, and installed it at the Polar Environment Atmospheric Research Laboratory (PEARL) near Eureka, Nunavut (latitude: 80° N). We present the design of our ruggedized photometer and our results from our short PEARL observing campaign in February 2012. Taken over a period of four days, our measurements indicate that the
J-band sky brightness varies between 15.5-15.9 mag arcsec2; with a measurement uncertainty of 0.15 mag. The
uncertainty is entirely dominated by systematic errors present in our radiometric calibration. On our best night, we measured a fairly consistent sky brightness of 15.8 ± 0.15 mag arcsec2. This is not corrected for atmospheric extinction, which is typically < 0.1 mag in the J-band on a good night. The measured sky brightness is
comparable to an excellent mid-latitude site, but is not as dark as claimed by the Antarctic measurements. We
discuss possible explanations of why we do not see as dark skies as in the Antarctic. Future winter-long sky
brightness measurements are anticipated to obtain the necessary statistics to make a proper comparison with
the Antarctic measurements.
AMICA at Dome C: results from the first year of automatic operation tests in Antarctica
Show abstract
Results from the first year of AMICA operations at Dome C are presented. AMICA is an astronomical camera for
imaging between 2 and 24 μm designed to work automatically at the extreme conditions of Antarctica. Except for the
cryostat, AMICA devices are hosted inside a rack whose operating conditions are automatically controlled.
120 days of environmental tests data have been obtained in 2011. The data concern the operating parameters of the
system. The results show an excellent performance. A quality factor is computed as a function of the external conditions
and a few critical correcting actions are described.
A new Nasmyth mirror mechanism increases the number of focal stations of the Mercator Telescope
Show abstract
Originally, the Mercator telescope (Roque de Los Muchachos Observatory, La Palma) only had one Cassegrain
and one Nasmyth focal station available. Both foci are currently occupied and the exploitation scheme of the
Mercator telescope does not allow regular instrument changes. To accommodate our new three-channel imager
MAIA and to allow
exible scheduling with rapid follow-up of transient phenomena, we have designed and built
a new mechanism for the Nasmyth mirror that enables the use of the second Nasmyth focal station and of two
compact intermediate foci at the front and the rear side of the telescope tube. This mechanism uses high-precision
gears, bearings and optical encoders to allow for
exible and very accurate positioning of the Nasmyth mirror
along the rotation and tilt axes. It is controlled by a programmable logic controller (PLC) that is the precursor
of a completely new PLC and OPC-UA based telescope control system. We present the design, the construction
and the performance of this new Nasmyth mirror mechanism.
LINC-NIRVANA, integration of an interferometric and cryogenic camera: first verification results
Show abstract
LINC-NIRVANA is an interferometric imaging camera, which combines the two 8.4 m telescopes of the Large
Binocular Telescope (LBT). The instrument operates in the wavelength range from 1.1 μm to 2.4 μm, covering the J, H and K-bands. The beam combining camera (NIRCS) offers the possibility to achieve diffraction limited images with the
spatial resolution of a 23 m telescope.
This camera, which combines the AO corrected beams of both telescopes, is designed to deliver a 10 arcsec x 10 arcsec
diffraction limited field of view. The optics and cryo-mechanics are designed for operation at 60 Kelvin. Equipped with a
HAWAII-2 detector mounted on a rotation stage in order to compensate for the sky rotation, a filter wheel and a dichroic
wheel to split the light into the science channel and the fringe tracking channel, the camera is fairly large and complex
and requires certain features to be considered and tested.
The verification of all these components follows a challenging AIV plan. We describe this AIV phase from initial
integration of individual units to the final verification tests of the complete system. We report the performance of the
cryogenic opto-mechanics and of the science detector. We also demonstrate the functionality of the cryo-mechanics and
the cryo-cooling at sub-system level, which represents the current state of integration. Finally, we discuss key elements
of our design and potential pros and cons.
KiwiSpec - an advanced spectrograph for high resolution spectroscopy: prototype design and performance
Show abstract
A new advanced high resolution spectrograph has been developed by Kiwistar Optics of Industrial Research
Ltd., New Zealand. The instrument, KiwiSpec R4-100, is bench-mounted, bre-fed, compact (0.75m by 1.5m
footprint), and is well-suited for small to medium-sized telescopes. The instrument makes use of several advanced
concepts in high resolution spectrograph design. The basic design follows the classical white pupil concept in
an asymmetric implementation and employs an R4 echelle grating illuminated by a 100mm diameter collimated
beam for primary dispersion. A volume phase holographic grating (VPH) based grism is used for cross-dispersion.
The design also allows for up to four camera and detector channels to allow for extended wavelength coverage at
high eciency. A single channel prototype of the instrument has been built and successfully tested with a 1m
telescope. Targets included various spectrophotometric standard stars and several radial velocity standard stars
to measure the instrument's light throughput and radial velocity capabilities. The prototype uses a 725 lines/mm
VPH grism, an off-the-shelf camera objective, and a 2k×2k CCD. As such, it covers the wavelength range from
420nm to 660nm and has a resolving power of R ≈ 40,000. Spectrophotometric and precision radial velocity
results from the on-sky testing period will be reported, as well as results of laboratory-based measurements. The
optical design of KiwiSpec, and the various multi-channel design options, will be presented elsewhere in these
proceedings.
A comparison of the mechanical design of fiber feeds for GRACES and GHOS
Show abstract
The instrument group of the Herzberg Institute of Astrophysics has been commissioned by the Gemini Observatory
to participate in a competitive conceptual design study for a new Gemini High-Resolution Optical Spectrograph
(GHOS). Concurrently this same group is working in partnership with both the Gemini and CFH Telescopes to
design the Gemini Remote Access to CFHT ESPaDOnS Spectrograph, (GRACES). Both these instruments will use
a fiber feed allowing light received by the Gemini telescope to be processed via remotely positioned instruments.
This paper will explore the similarities and differences in requirements, inherent challenges, concepts, design
solutions and areas of concept sharing.
Tools for DIY site-testing
Federico Flores,
Roberto Rondanelli,
Accel Abarca,
et al.
Show abstract
Our group has designed, sourced and constructed a radiosonde/ground-station pair using inexpensive opensource
hardware. Based on the Arduino platform, the easy to build radiosonde allows the atmospheric science
community to test and deploy instrumentation packages that can be fully customized to their individual sensing
requirements. This sensing/transmitter package has been successfully deployed on a tethered-balloon, a weather
balloon, a UAV airplane, and is currently being integrated into a UAV quadcopter and a student-built rocket.
In this paper, the system, field measurements and potential applications will be described. As will the science
drivers of having full control and open access to a measurement system in an age when commercial solutions
have become popular but are restrictive in terms of proprietary sensor specifications, “black-box” calibration
operations or data handling routines, etc. The ability to modify and experiment with both the hardware and
software tools is an essential part of the scientific process. Without an understanding of the intrinsic biases or
limitations in your instruments and system, it becomes difficult to improve them or advance the knowledge in
any given field.
Cryogenic mechanical design: SPIROU spectrograph
Show abstract
This paper presents an overview of the PDR level mechanical and opto-mechanical design of the cryogenic spectrograph
unit of the nIR spectropolarimeter (SPIROU) proposed as a new-generation instrument for CFHT. The design is driven
by the need for high thermo-mechanical stability in terms of the radial velocity (RV) of 1 m/s during one night, with the
requirement for thermal stability set at 1 mK/24 hours. This paper describes stress-free design of the cryogenic optical
mounts, mechanical design of the custom-build cryostat, mechanical design of the optical bench, and thermal design for
1 mK thermal stability. The thermal budget was calculated using lumped-mass model thermal analysis, implemented in
Modelica multi-domain modeling language. Discussion of thermal control options to achieve 1 mK thermal stability is
included.
On-sky operations and performance of LMIRcam at the Large Binocular Telescope
Show abstract
The L/M-band (3−5 μm) InfraRed Camera (LMIRcam) sits at the combined focal plane of the Large Binocular
Telescope Interferometer (LBTI), ultimately imaging the coherently combined focus of the LBT’s two 8.4-meter
mirrors. LMIRcam achieved first light at the LBT in May 2011 using a single AO-enabled 8.4-meter aperture.
With the delivery of LBT’s final adaptive secondary mirror in Fall of 2011, dual-aperture AO-corrected interferometric
fringes were realized in April 2012. We report on the performance of these configurations and characterize
the noise performance of LMIRcam’s HAWAII-2RG 5.3-μm cutoff array paired with Cornell FORCAST readout
electronics. In addition, we describe recent science highlights and discuss future improvements to the LMIRcam
hardware.
ISAS: interferometric stratospheric astrometry for solar system
Show abstract
The Interferometric Stratospheric Astrometry for Solar system (ISAS) project is designed for high precision
astrometry on the brightest planets of the Solar System, with reference to many field stars, at the milli-arcsec
(mas) level or better. The science goal is the improvement on our knowledge of the dynamics of the Solar System,
complementing the Gaia observations of fainter objects. The technical goal is the validation of basic concepts for
the proposed Gamma Astrometric Measurement Experiment (GAME) space mission, in particular, combination
of Fizeau interferometry and coronagraphic techniques by means of pierced mirrors, intermediate angle dual field
astrometry, smart focal plane management for increased dynamic range and pointing correction. We discuss
the suitability of the stratospheric environment, close to space conditions, to the astrometric requirements. The
instrument concept is a multiple field, multiple aperture Fizeau interferometer, observing simultaneously four
fields, in order to improve on the available number of reference stars. Coronagraphic solutions are introduced
to allow observation of internal planets (Mercury and Venus), as well as of external planets over a large fraction
of their orbit, i.e. also close to conjunction with the Sun. We describe the science motivation, the proposed
experiment profile and the expected performance.
Analysis of stellar radiance contamination in observed satellite spectra
Show abstract
Reflectance spectra of Earth orbiting satellites can be readily observed with small diameter telescopes (D < 1 m)
by utilizing a method known as slitless spectroscopy. Satellite spectra can be observed by simply placing a
transmission grating within the collimated optical path of the telescope without the need to image through a
slit. The simplicity of the slitless spectroscopy design makes it a promising alternative to spatially resolving
satellites with larger and more expensive diameter telescopes for applications of space situational awareness.
However, accurately observing satellite re
ectance spectra without imaging through a slit requires a dark and
homogeneous background. This requirement is frequently violated as background stars streak across the image
due to the slewing motion of the telescope during satellite tracking. Rather than throwing out all images with
noticeable stellar contamination, a principle component analysis of contaminated images from three geostationary
satellite observations showed that it may still be possible to assess and identify satellite characteristics depending
upon the amount of stellar contamination in the spectral region of interest. Additionally, a simple technique for
automatic removal of contaminated frames is proposed based on an outlier analysis using Gaussian statistics and
was found to successfully remove all signicantly contaminated frames.
Enhanced spectral resolution via externally dispersed interferometry
Show abstract
Externally dispersed interferometry (EDI) uses a hybrid spectrometer that combines a Michelson interferometer in series
with a grating spectrometer. EDI provides a means of deriving spectral information at a resolution substantially higher
than that provided by the grating spectrograph alone. Near IR observations have been conducted using the Triplespec
spectrometer mounted on the 5m Hale telescope. Spectra have been reconstructed at a resolution of ~27000 where the
resolution of Triplespec is ~2700. Progress in the development of the EDI technique is reported herein emphasizing
studies related to the accuracy of the reconstructed spectra.
Khayyam: a tunable spatial heterodyne spectrometer for observing diffuse emission line targets
Show abstract
We describe first 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 telescopes where significant observing time can be obtained. This instrument –Khayyam- is a tunable all-reflective spatial heterodyne spectrometer (SHS) that is mounted to a fixed focal plane shared by the 0.6m Coude auxiliary telescope and the 3m Shane telescope on Mt. Hamilton. Khayyam has an up to 78 arcmin input field of view, resolving power up to 176000, and a tunable bandpass from 350-700 nm. It is being field tested for initial use to study spatially extended solar system targets where high resolving power is necessary to separate multimodal signals, crowded molecular bands, and to sample low velocities (<10 km/s) and rapid temporal cadence is necessary to track physical evolution. Two of the best comet targets during next year is comet C/2011 L4 (PanSTARRS), and C/2011 F1 (LINEAR). Our goal is to sequentially measure isotopic ratios of 14N:15N and 12C:13C in CN, along with the production rate and the production rate ratios of varies daughter species, particularly C2, C3, NH2, OI, and CN, as a function of heliocentric distance and time.
Tips and tricks for aligning an image derotator
Show abstract
One possible key reference element in optical alignment is represented by the rotational stage, a mechanical bearing, or
any similar suitable device having enough accuracy and precision so that optical tolerances are reasonably relaxed wrt
imperfections in the rotational movement. This allows a safe, reliable, easy to reproduce, determination of both rays
parallel to the axis or to their centering within almost any plane. An image derotator, that in its simplest form is made up
by three flat mirrors arranged in a so called K-mirror layout, moving together on a precision rotating stage, seems to be
the most safe, strong, and self built-in alignment tool. Moreover you can use the mechanical part as well as the optical
one. Care has to be given when internally and externally aligning has to be accomplished within a certain degree of
precision. To further make the situation more complex, the technical overall requirements can be tight enough that the
distribution of the error budget among the various components (imperfect mechanical rotation, imperfect internal
alignment, flexures during rotations) is not due to a single item. In this case, in fact, a number of tips and tricks can be
useful to find out which is the best approach to follow. The specific case of the two K-mirrors on board LINCNIRVANA
is here illustrated in a few lessons.
A powerful ethernet interface module for digital camera control
Stephen M. Amato,
John C. Geary
Show abstract
We have found a commercially-available ethernet interface module with sufficient on-board resources to largely handle
all timing generation tasks required by digital imaging systems found in astronomy. In addition to providing a high-bandwidth
ethernet interface to the controller, it can largely replace the need for special-purpose timing circuitry.
Examples for use with both CCD and CMOS imagers are provided.
Posters: Multi-Object Instruments
Hermes: the engineering challenges
Show abstract
The Australian Astronomical Observatory is building a 4-channel VPH-grating High Efficiency and Resolution Multi
Element Spectrograph (HERMES) for the 3.9 meter Anglo-Australian Telescope (AAT). HERMES will provide a
nominal spectral resolving power of 28,000 for Galactic Archaeology with an optional high-resolution mode of 45,000
with the use of a slit mask.
HERMES is fed by a fibre positioning robot called 2dF at the telescope prime focus. There are a total of 784 science
fibres, which interface with the spectrograph via two separate slit body assemblies, each comprising of 392 science
fibers. The slit defines the spectral lines of 392 fibres on the detector. The width of the detector determines the spectral
bandwidth and the detector height determines the fibre to fibre spacing or cross talk. Tolerances that follow from this are
all in the 10 micrometer range.
The slit relay optics must contribute negligibly to the overall image quality budget and uniformly illuminate the
spectrograph exit pupil. The latter requirement effectively requires that the relay optics provide a telecentric input at the
collimator entrance slit. As a result it is critical to align the optical components to extreme precision required by the
optical design.
This paper discusses the engineering challenges of designing, optimising, tolerancing and manufacturing of very precise
mechanical components for housing optics and the design of low cost of jigs and fixtures for alignment and assembly of
the optics.
Detectors and cryostat design for the SuMIRe Prime Focus Spectrograph (PFS)
Show abstract
We describe the conceptual design of the camera cryostats, detectors, and detector readout electronics for the SuMIRe
Prime Focus Spectrograph (PFS) being developed for the Subaru telescope. The SuMIRe PFS will consist of four
identical spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each
spectrograph will have three channels covering wavelength ranges 3800 Å - 6700 Å, 6500 Å - 10000 Å, and 9700 Å -
13000 Å, with the dispersed light being imaged in each channel by a f/1.10 vacuum Schmidt camera. In the blue and red
channels a pair of Hamamatsu 2K x 4K edge-buttable CCDs with 15 um pixels are used to form a 4K x 4K array. For
the IR channel, the new Teledyne 4K x 4K, 15 um pixel, mercury-cadmium-telluride sensor with substrate removed for
short-wavelength response and a 1.7 um cutoff will be used. Identical detector geometry and a nearly identical optical
design allow for a common cryostat design with the only notable difference being the need for a cold radiation shield in
the IR camera to mitigate thermal background. This paper describes the details of the cryostat design and cooling
scheme, relevant thermal considerations and analysis, and discusses the detectors and detector readout electronics.
A spectrograph instrument concept for the Prime Focus Spectrograph (PFS) on Subaru Telescope
Show abstract
We describe the conceptual design of the spectrograph opto-mechanical concept for the SuMIRe Prime Focus
Spectrograph (PFS) being developed for the SUBARU telescope. The SuMIRe PFS will consist of four identical
spectrographs, each receiving 600 fibers from a 2400 fiber robotic positioner at the prime focus. Each spectrograph will
have three channels covering in total, a wavelength range from 380 nm to 1300 nm. The requirements for the instrument
are summarized in Section 1. We present the optical design and the optical performance and analysis in Section 2.
Section 3 introduces the mechanical design, its requirements and the proposed concepts. Finally, the AIT phases for the
Spectrograph System are described in Section 5.
MEGARA: the future optical IFU and multi-object spectrograph for the 10.4m GTC telescope
A. Gil de Paz,
E. Carrasco ,
J. Gallego ,
et al.
Show abstract
In these proceedings we give a summary of the characteristics and current status of the MEGARA instrument,
the future optical IFU and MOS for the 10.4-m Gran Telescopio Canarias (GTC). MEGARA is being built
by a Consortium of public research institutions led by the Universidad Complutense de Madrid (UCM, Spain)
that also includes INAOE (Mexico), IAA-CSIC (Spain) and UPM (Spain). The MEGARA IFU includes two
different fiber bundles, one called LCB (Large Compact Bundle) with a field-of-view of 12.5×11.3 arcsec2 and
a spaxel size of 0.62 arcsec yielding spectral resolutions between R=6,800-17,000 and another one called SCB
(Small Compact Bundle) covering 8.5×6.7 arcsec2 with hexagonally-shaped and packed 0.42-arcsec spaxels and
resolutions R=8,000-20,000. The MOS component allows observing up to 100 targets in 3.5×3.5 arcmin2. Both
the IFU bundles and the set of 100 robotic positioners of the MOS will be placed at one of the GTC Folded-Cass
foci while the spectrographs (one in the case of the MEGARA-Basic concept) will be placed at the Nasmyth
platform. On March 2012 MEGARA passed the Preliminary Design Review and its first light is expected to
take place at the end of 2015.
FOCCoS for Subaru PFS
Show abstract
The Fiber Optical Cable and Connector System (FOCCoS), provides optical connection between 2400
positioners and a set of spectrographs by an optical fibers cable as part of Subaru PFS instrument. Each positioner
retains one fiber entrance attached at a microlens, which is responsible for the F-ratio transformation into a larger one so
that difficulties of spectrograph design are eased. The optical fibers cable will be segmented in 3 parts at long of the
way, cable A, cable B and cable C, connected by a set of multi-fibers connectors. Cable B will be permanently attached
at the Subaru telescope. The first set of multi-fibers connectors will connect the cable A to the cable C from the
spectrograph system at the Nasmith platform. The cable A, is an extension of a pseudo-slit device obtained with the
linear disposition of the extremities of the optical fibers and fixed by epoxy at a base of composite substrate. The second
set of multi-fibers connectors will connect the other extremity of cable A to the cable B, which is part of the positioner's
device structure. The optical fiber under study for this project is the Polymicro FBP120170190, which has shown very
encouraging results. The kind of test involves FRD measurements caused by stress induced by rotation and twist of the
fiber extremity, similar conditions to those produced by positioners of the PFS instrument. The multi-fibers connector
under study is produced by USCONEC Company and may connect 32 optical fibers. The tests involve throughput of
light and stability after many connections and disconnections. This paper will review the general design of the FOCCoS
subsystem, methods used to fabricate the devices involved and the tests results necessary to evaluate the total efficiency
of the set.
The development of WIFIS: a wide integral field infrared
spectrograph
Show abstract
We present the current results from the development of a wide integral field infrared spectrograph (WIFIS). WIFIS offers an unprecedented combination of etendue and spectral resolving power for seeing-limited, integral field observations in the 0.9 - 1.8 μm range and is most sensitive in the 0.9 - 1.35 μ,m range. Its optical design consists of front-end re-imaging optics, an all-reflective image slicer-type, integral field unit (IFU) called FISICA, and a long-slit grating spectrograph back-end that is coupled with a HAWAII 2RG focal plane array. The full wavelength range is achieved by selecting between two different gratings. By virtue of its re-imaging optics, the spectrograph is quite versatile and can be used at multiple telescopes. The size of its field-of-view is unrivalled by other similar spectrographs, offering a 4.511x 1211 integral field at a 10-meter class telescope (or
2011 x 5011 at a 2.3-meter telescope). The use of WIFIS will be crucial in astronomical problems which require
wide-field, two-dimensional spectroscopy such as the study of merging galaxies at moderate redshift and nearby star/planet-forming regions and supernova remnants. We discuss the final optical design of WIFIS, and its predicted on-sky performance on two reference telescope platforms: the 2.3-m Steward Bok telescope and the
10.4-m Gran Telescopio Canarias. We also present the results from our laboratory characterization of FISICA.
IFU properties such as magnification, field-mapping, and slit width along the entire slit length were measured by our tests. The construction and testing of WIFIS is expected to be completed by early 2013. We plan to commission the instrument at the 2.3-m Steward Bok telescope at Kitt Peak, USA in Spring 2013.
OSIRIS tunable imager and spectrograph for the GTC: from design to commissioning
Beatriz Sánchez,
Marta Aguiar-González,
Roberto Barreto,
et al.
Show abstract
OSIRIS (Optical System for Imaging and low Resolution Integrated Spectroscopy) was the optical Day One instrument
for the 10.4m Spanish telescope GTC. It is installed at the Observatorio del Roque de Los Muchachos (La Palma, Spain).
This instrument has been operational since March-2009 and covers from 360 to 1000 nm. OSIRIS observing modes
include direct imaging with tunable and conventional filters, long slit and low resolution spectroscopy. OSIRIS wide
field of view and high efficiency provide a powerful tool for the scientific exploitation of GTC. OSIRIS was developed
by a Consortium formed by the Instituto de Astrofísica de Canarias (IAC) and the Instituto de Astronomía de la
Universidad Nacional Autónoma de México (IA-UNAM). The latter was in charge of the optical design, the manufacture
of the camera and collaboration in the assembly, integration and verification process. The IAC was responsible for the
remaining design of the instrument and it was the project leader. The present paper considers the development of the
instrument from its design to its present situation in which is in used by the scientific community.
BATMAN: a DMD-based MOS demonstrator on Galileo Telescope
Show abstract
Multi-Object Spectrographs (MOS) are the major instruments for studying primary galaxies and remote and faint objects.
Current object selection systems are limited and/or difficult to implement in next generation MOS for space and groundbased telescopes. A promising solution is the use of MOEMS devices such as micromirror arrays which allow the remote control of the multi-slit configuration in real time.
We are developing a Digital Micromirror Device (DMD) - based spectrograph demonstrator called BATMAN. We want
to access the largest FOV with the highest contrast. The selected component is a DMD chip from Texas Instruments in
2048 x 1080 mirrors format, with a pitch of 13.68μm. Our optical design is an all-reflective spectrograph design with F/4
on the DMD component.
This demonstrator permits the study of key parameters such as throughput, contrast and ability to remove unwanted
sources in the FOV (background, spoiler sources), PSF effect, new observational modes. This study will be conducted in
the visible with possible extension in the IR. A breadboard on an optical bench, ROBIN, has been developed for a
preliminary determination of these parameters.
The demonstrator on the sky is then of prime importance for characterizing the actual performance of this new family of
instruments, as well as investigating the operational procedures on astronomical objects. BATMAN will be placed on the
Nasmyth focus of Telescopio Nazionale Galileo (TNG) during next year.
The design of the MOONS-VLT spectrometer
Show abstract
MOONS is a new conceptual design for a multi-object spectrograph for the ESO Very Large Telescope (VLT)
which will provide the ESO astronomical community with a powerful, unique instrument able to serve a wide
range of Galactic, Extragalactic and Cosmological studies. The instrument foresees 1000 fibers which can be
positioned on a field of view of 500 square-arcmin. The sky-projected diameter of each fiber is at least 1 arcsec
and the wavelengths coverage extends from 0.8 to 1.8 μm.
This paper presents and discusses the design of the spectrometer, a task which is allocated to the Italian National
Institute of Astrophysics (INAF).
The baseline design consists of two identical cryogenic spectrographs. Each instrument collects the light from
over 500 fibers and feeds, through dichroics, 3 spectrometers covering the "I" (0.79-0.94 μm), "YJ" (0.94-1.35
μm) and "H" (1.45-1.81 μm) bands.
The low resolution mode provides a complete spectrum with a resolving power ranging from R'4,000 in the
YJ-band, to R'6,000 in the H-band and R'8,000 in the I-band. A higher resolution mode with R'20,000 is
also included. It simultaneously covers two selected spectral regions within the J and H bands.
MOHAWK: a 4000-fiber positioner for DESpec
Show abstract
We present a concept for a 4000-fibre positioner for DESpec, based on the Echidna ‘tilting spine’ technology. The DESpec focal plane is 450mm across and curved, and the required pitch is ~6.75mm. The size, number of fibers and curvature are all comparable with various concept studies for similar instruments already undertaken at the AAO, but present new challenges in combination. A simple, low-cost, and highly modular design is presented, consisting of identical modules populated by identical spines. No show-stopping issues in accommodating either the curvature or the smaller pitch have been identified, and the actuators consist largely of off-the-shelf components. The actuators have been prototyped at AAO, and allow reconfiguration times of ~15s to reach position errors 7 microns or less. Straightforward designs for metrology, acquisition, and guiding are also proposed. The throughput losses of the entire positioner system are estimated to be ~15%, of which 6.3% is attributable to the tilting-spine technology.
High resolution spectrograph for the 4MOST facility
Show abstract
4MOST (4-metre Multi-Object Spectrograph Telescope) is a wide field and high multiplex fibre-fed spectroscopic
facility continuously running a public survey on one of ESO's 4-metre telescopes (NTT or VISTA). It is currently
undergoing a concept study and comprises a multi-object (300) high resolution (20 000) spectrograph whose purpose is
to provide detailed chemical information in two wavelength ranges (395-456.5 nm and 587-673 nm). It will complement
the data produced by ESA's space mission Gaia to form an unprecedented galactic-archaeology picture of the Milky Way
as the result of the public survey. Building on the developments carried out for the GYES1 instrument on the Canada-
France-Hawaii Telescope in 2010, the spectrograph is intended as being athermal and not featuring any motorised parts
for high reliability and minimum maintenance, thereby allowing it to operate every night for five years. In addition to the
fixed configuration which allows fine-tuning the spectrograph to a precise need, it features a dual-arm architecture with
volume-phase holographic gratings to achieve the required dispersion at a maximum efficiency in each channel. By
combining high yield time-wise and photon-wise, the spectrograph is expected to deliver more than a million spectra and
make the most out of the selected 4-metre telescope.
M2FS: the Michigan/Magellan Fiber System
Show abstract
We describe the Michigan/Magellan Fiber System (M2FS) under construction for use on the Magellan/Clay telescope.
M2FS consists of four primary components including: (1) A fiber-fed double spectrograph (MSPec) in which each
spectrograph is fed by 128 fibers (for a total multiplexing factor of 256) and each is optimized in to operate from 370-
950 nm; (2) A fiber mounting system (MFib) that supports the fibers and fiber plug plates at the telescope f/11 Nasmyth
focal surface and organizes the fibers into ‘shoes’ that are used to place the fibers at the image surface of the MSpec
spectrographs;, (3) A new wide-field corrector (WFC) that produces high-quality images over a 30 arcmin diameter
field; (4) A unit (MCal) mounted near the telescope secondary that provides wavelength and continuum calibration and
that supports a key component in a novel automated fiber identification system. We describe the opto-mechanical
properties of M2FS, its modes of operation, and its anticipated performance, as well as potential upgrades including the
development of a robotic fiber positioner and an atmospheric dispersion corrector. We describe how the M2FS design
could serve as the basis of a powerful wide-field, massively multiplexed spectroscopic survey facility.
The metrology cameras for Subaru PFS and FMOS
Show abstract
The Prime Focus Spectrograph (PFS) is a new multi-fiber spectrograph on Subaru telescope. PFS will cover around 1.4
degree diameter field with ~2400 fibers. To ensure precise positioning of the fibers, a metrology camera is designed to
provide the fiber position information within 5 μm error. The final positioning accuracy of PFS is targeted to be less than
10 μm. The metrology camera will locate at the Cassegrain focus of Subaru telescope to cover the whole focal plan. The
PFS metrology camera will also serve for the existing multi-fiber infrared spectrograph FMOS.
A series of detector systems for MUSE
Show abstract
The 24 IFU from MUSE are equipped with 4K x 4K CCD detectors which are operated at cryogenic temperature around
160 K. The large size of the chip combined with a rather fast camera (F/2) impose strong positioning constrains. The
sensitive surface should remain in an angular envelope of less than 30 arc sec in both directions. The ambitious goal of
having the same spectrum format on every detector imposes also a very accurate positioning in the image plane. The
central pixel has to be located in a square smaller 50 microns relative to the external references.
The first part of the paper describes the mechanical design of the detector head. We concentrate on the various aspects of
the design with its very complex interfaces. The opto-mechanical concept is presented with an emphasis on the
robustness and reliability. We present also the necessary steps for the extreme optimization of the cryogenic performance
of this compact design driven with a permanent view of the production in series.
The techniques and procedures developed in order to meet and verify the very tight positioning requirements are
described in a second part. Then the 24 fully assembled systems undergo a system verification using one of the MUSE
spectrographs. These tests include a focus series, the determination of the PSF across the chip and a subsequent
calculation of the tip/tilt and shift rotation of the detector versus the optical axis.
VIRUS spectrograph assembly and alignment procedures
Show abstract
We describe the mechanical assembly and optical alignment processes used to construct the Visual Integral-Field
Replicable Unit Spectrograph (VIRUS) instrument. VIRUS is a set of 150+ optical spectrographs designed to support
observations for the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). To meet the instrument's
manufacturing constraints, a production line will be set up to build subassemblies in parallel. To aid in the instrument's
assembly and alignment, specialized fixtures and adjustment apparatuses have been developed. We describe the design
and operations of the various optics alignment apparatuses, as well as the mirrors' alignment and bonding fixtures.
Integrating BigBOSS with the Mayall Telescope
Show abstract
BigBOSS is a proposed ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the
growth of large scale structure. It consists of a fiber-fed multi-object spectrograph designed to be installed on the Mayall
4-meter telescope at Kitt Peak, Arizona. BigBOSS includes an optical corrector assembly and 5000-fiber-positioner
focal plane assembly that replace the existing Mayall prime focus hardware. 40-meter long optical fiber bundles are
routed from the focal plane, through the telescope declination and right ascension pivots, to spectrographs in the
thermally insulated FTS Laboratory, immediately adjacent to the telescope. Each of the ten spectrographs includes three
separate spectral bands. The FTS Laboratory also houses support electronics, cooling, and vacuum equipment. The
prime focus assembly includes mounts for the existing Mayall f/8 secondary mirror to allow observations with
Cassegrain instruments. We describe the major elements of the BigBOSS instrument, plans for integrating with the
Telescope, and proposed modifications and additions to existing Mayall facilities.
Hector: a high-multiplex survey instrument for spatially resolved galaxy spectroscopy
Show abstract
First light from the SAMI (Sydney-AAO Multi-object IFS) instrument at the Anglo-Australian Telescope (AAT) has
recently proven the viability of fibre hexabundles for multi-IFU spectroscopy. SAMI, which comprises 13 hexabundle
IFUs deployable over a 1 degree field-of-view, has recently begun science observations, and will target a survey of
several thousand galaxies. The scientific outputs from such galaxy surveys are strongly linked to survey size, leading the
push towards instruments with higher multiplex capability. We have begun work on a new instrument concept, called
Hector, which will target a spatially-resolved spectroscopic survey of up to one hundred thousand galaxies. The key
science questions for this instrument concept 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. One design option for Hector uses the existing 2 degree field-of view top end at the AAT, with 50 individual
robotically deployable 61-core hexabundle IFUs, and 3 fixed format spectrographs covering the visible wavelength range
with a spectral resolution of approximately 4000. A more ambitious option incorporates a modified top end at the AAT
with a new 3 degree field-of-view wide-field-corrector and 100 hexabundle IFUs feeding 6 spectrographs.
A fast new cadioptric design for fiber-fed spectrographs
Show abstract
The next generation of massively multiplexed multi-object spectrographs (DESpec, SUMIRE, BigBOSS, 4MOST,
HECTOR) demand fast, efficient and affordable spectrographs, with higher resolutions (R = 3000-5000) than current
designs. Beam-size is a (relatively) free parameter in the design, but the properties of VPH gratings are such that, for
fixed resolution and wavelength coverage, the effect on beam-size on overall VPH efficiency is very small. For alltransmissive
cameras, this suggests modest beam-sizes (say 80-150mm) to minimize costs; while for cadioptric
(Schmidt-type) cameras, much larger beam-sizes (say 250mm+) are preferred to improve image quality and to minimize
obstruction losses. Schmidt designs have benefits in terms of image quality, camera speed and scattered light
performance, and recent advances such as MRF technology mean that the required aspherics are no longer a prohibitive
cost or risk.
The main objections to traditional Schmidt designs are the inaccessibility of the detector package, and the loss in
throughput caused by it being in the beam. With expected count rates and current read-noise technology, the gain in
camera speed allowed by Schmidt optics largely compensates for the additional obstruction losses. However, future
advances in readout technology may erase most of this compensation.
A new Schmidt/Maksutov-derived design is presented, which differs from previous designs in having the detector
package outside the camera, and adjacent to the spectrograph pupil. The telescope pupil already contains a hole at its
center, because of the obstruction from the telescope top-end. With a 250mm beam, it is possible to largely hide a 6cm ×
6cm detector package and its dewar within this hole. This means that the design achieves a very high efficiency,
competitive with transmissive designs. The optics are excellent, as least as good as classic Schmidt designs, allowing
F/1.25 or even faster cameras. The principal hardware has been costed at $300K per arm, making the design affordable.
MEGARA spectrograph for the GTC: mechanical and opto-mechanical design
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 GTC 10.4m telescope. This contribution summarizes the current
mechanical design of the spectrograph and the adopted solutions for the mechanisms and the opto-mechanical
components.
The Dark Energy Spectrometer: a potential multi-fiber instrument for the Blanco 4-meter Telescope
Show abstract
We describe the preliminary design of the Dark Energy Spectrometer (DESpec), a fiber-fed spectroscopic instrument
concept for the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory (CTIO). DESpec would take
advantage of the infrastructure recently deployed for the Dark Energy Camera (DECam). DESpec would be mounted in
the new DECam prime focus cage, would be interchangeable with DECam, would share the DECam optical corrector,
and would feature a focal plane with ~4000 robotically positioned optical fibers feeding multiple high-throughput
spectrometers. The instrument would have a field of view of 3.8 square degrees, a wavelength range of approximately
500<<1000 nm, and a spectral resolution of R~3000. DESpec would provide a powerful spectroscopic follow-up
system for sources in the Southern hemisphere discovered by the Dark Energy Survey and LSST.λ
MIRADAS for the Gran Telescopio Canarias: system overview
Show abstract
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS, a near-infrared multi-object echelle
spectrograph operating at spectral resolution R=20,000 over the 1-2.5μm bandpass) was selected in 2010 by the Gran
Telescopio Canarias (GTC) partnership as the next-generation near-infrared spectrograph for the world's largest
optical/infrared telescope, and is being developed by an international consortium. The MIRADAS consortium includes
the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de
Canarias, Institut de Física d'Altes Energies, Institut d'Estudis Espacials de Catalunya and Universidad Nacional
Autonoma de Mexico, as well as probe arm industrial partner A-V-S (Spain). In this paper, we review the overall system
design for MIRADAS, as it nears Preliminary Design Review in the autumn of 2012.
MIRADAS control system
Show abstract
The Mid-resolution InfRAreD Astronomical Spectrograph (MIRADAS, a near-infrared multi-object echelle
spectrograph operating at spectral resolution R=20,000 over the 1-2.5μm bandpass) was selected in 2010 by the Gran
Telescopio Canarias (GTC) partnership as the next-generation near-infrared spectrograph for the world's largest
optical/infrared telescope, and is being developed by an international consortium. The MIRADAS consortium includes
the University of Florida, Universidad de Barcelona, Universidad Complutense de Madrid, Instituto de Astrofísica de
Canarias, Institut de Física d'Altes Energies, Institut d'Estudis Espacials de Catalunya and Universidad Nacional
Autónoma de México. This paper shows an overview of the MIRADAS control software, which follows the standards
defined by the telescope to permit the integration of this software on the GTC Control System (GCS). The MIRADAS
Control System is based on a distributed architecture according to a component model where every subsystem is selfcontained.
The GCS is a distributed environment written in object oriented C++, which runs components in different
computers, using CORBA middleware for communications. Each MIRADAS observing mode, including engineering,
monitoring and calibration modes, will have its own predefined sequence, which are executed in the GCS Sequencer.
These sequences will have the ability of communicating with other telescope subsystems.
MEGARA spectrograph optics
Show abstract
MEGARA is the next optical Integral-Field Unit (IFU) and Multi-Object Spectrograph (MOS) for Gran Telescopio
Canarias. The instrument offers two IFUs plus a Multi-Object Spectroscopy (MOS) mode: a large compact bundle
covering 12.5 arcsec x 11.3 arcsec on sky with 100 μm fiber-core; a small compact bundle, of 8.5 arcsec x 6.7 arcsec
with 70 μm fiber-core and a fiber MOS positioner that allows to place up to 100 mini-bundles, 7 fibers each, with 100
μm fiber-core, within a 3.5 arcmin x 3.5 arcmin field of view, around the two IFUs. The fibers, organized in bundles,
end in the pseudo-slit plate, which will be placed at the entrance focal plane of the MEGARA spectrograph. The large
IFU and MOS modes will provide intermediate to high spectral resolutions, R=6800-17000. The small IFU mode will
provide R=8000-20000. All these resolutions are possible thanks to a spectrograph design based in the used of volume
phase holographic gratings in combination with prisms to keep fixed the collimator and camera angle. The MEGARA
optics is composed by a total of 53 large optical elements per spectrograph: the field lens, the collimator and the camera
lenses plus the complete set of pupil elements including holograms, windows and prisms. INAOE, a partner of the GTC
and a partner of MEGARA consortium, is responsible of the optics manufacturing and tests. INAOE will carry out this
project working in an alliance with CIO. This paper summarizes the status of MEGARA spectrograph optics at the
Preliminary Design Review, held on March 2012.
Hyper Suprime-Cam: conceptual design to introduce spectroscopic mode
Show abstract
Hyper Suprime-Cam (HSC) is the wide-field CCD camera which is attached to the prime focus of Subaru
Telescope. It covers the field of view of 1.5 degree in diameter by 116 2k x 4k fully-depleted CCDs. In this
paper, we present the conceptual design of optics and mechanics how to introduce spectroscopic mode to this
simple imager HSC. The design is based on the idea that the optical elements such as collimeter, grisms and
camera lenses are integrated as a ’filter’ of HSC. The incident light is folded by pickup mirror at filter layer and
introduced to the filter space. After passing the slit, the incident light is collimated by the collimeter lens and
divided into three wavelength ranges by dichroic mirrors. The collimated beam in each wavelength range is fed
to the grism and dispersed. The dispersed beam is converged by the camera lens and folded by 45 degree mirror
to the direction parallel to the optical axis. The resultant spectra are imaged on the main CCDs on the focal
plane. The space allowed for filters is 600 mm in diameter and 42 mm thick, which is very tight but we are
able to design spectroscopic optics with some difficulties. The spectral resolution is designed to be more than
1000 and the wavelength coverage is targeted to be 370–1050 nm to realize medium-resolution spectroscopy for
various type of objects. We show the optical design of collimeter, grism and camera lenses together with the
mechanical layout of the spectroscopic optics.
MEGARA focal plane subsystems
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 GTC. The Fiber Units are placed at one Folded Cassegrain focus and
feed the spectrograph located on a Nasmyth-type platform.
This paper summarizes the status of the design of the MEGARA Folded Cassegrain Subsystems after the PDR (held on
March 2012), as well as the prototyping that has been carried out during this phase.
The MEGARA Fiber Unit has two IFUs: a Large Compact Bundle covering 12.5 arcsec x 11.3 arcsec on sky (100
microns fiber-core), and a Small Compact Bundle, of 8.5 arcsec x 6.7 arcsec (70 microns fiber-core), plus a Fiber MOS
positioner, able to place up to 100 mini-bundles 7 fibers each (100 microns fiber-core) in MOS configuration within a
3.5arcmin x 3.5arcmin FOV. A field lens provides a telecentric focal plane where the fibers are located. Microlens arrays
couple the telescope beam to the collimator focal ratio at the entrance of the fibers (providing the f/17 to f/3 focal ratio
reduction to enter into the fibers). Finally, the fibers, organized in bundles, end in the pseudo-slit plate, which will be
placed at the entrance focal plane of the MEGARA spectrographs.
The influence of motion and stress on optical fibers
Show abstract
We report on extensive testing carried out on the optical fibers for the VIRUS instrument. The primary result of
this work explores how 10+ years of simulated wear on a VIRUS fiber bundle affects both transmission and focal
ratio degradation (FRD) of the optical fibers. During the accelerated lifetime tests we continuously monitored
the fibers for signs of FRD. We find that transient FRD events were common during the portions of the tests
when motion was at telescope slew rates, but dropped to negligible levels during rates of motion typical for
science observation. Tests of fiber transmission and FRD conducted both before and after the lifetime tests
reveal that while transmission values do not change over the 10+ years of simulated wear, a clear increase in
FRD is seen in all 18 fibers tested. This increase in FRD is likely due to microfractures that develop over time
from repeated flexure of the fiber bundle, and stands in contrast to the transient FRD events that stem from
localized stress and subsequent modal diffusion of light within the fibers. There was no measurable wavelength
dependence on the increase in FRD over 350 nm to 600 nm. We also report on bend radius tests conducted
on individual fibers and find the 266 μm VIRUS fibers to be immune to bending-induced FRD at bend radii
of R 10 cm. Below this bend radius FRD increases slightly with decreasing radius. Lastly, we give details
of a degradation seen in the fiber bundle currently deployed on the Mitchell Spectrograph (formally VIRUS-P)
at McDonald Observatory. The degradation is shown to be caused by a localized shear in a select number of
optical fibers that leads to an explosive form of FRD. In a few fibers, the overall transmission loss through the
instrument can exceed 80%. These results are important for the VIRUS instrument, and for both current and
proposed instruments that make use of optical fibers, particularly when the fibers are in continual motion during
an observation, or experience repeated mechanical stress during their deployment.≥
An adjustable slit mechanism for a fiber-fed multi-object spectrograph
John I. Bailey III,
Mario L. Mateo,
Alan P. Bagish,
et al.
Show abstract
Fiber-fed multi-object spectrographs have greatly enhanced the spectroscopic capabilities of the world's premiere
telescopes, but their flexibility has typically been limited by a fixed effective slit size that constrains the available
resolving power. We present a novel mechanism that, for the first time, equips a fiber-fed spectrograph with
multiple discreet slits of different widths. In this paper, we detail the mechanical design of our variable slit
mechanism, which is capable of positioning any one of six slits in front of the fibers immediately prior to
injection into the spectrograph's optical train. Further, we present the details of related systems necessary to
achieve closed loop positioning of the slit mechanism given that no encoder is used. We also briefly discuss our
use of open source and open hardware projects in the design. Finally, we describe the control system we have
implemented for this subsystem.
Methods for evaluating the performance of volume phase holographic gratings for the VIRUS spectrograph array
Show abstract
The Visible Integral field Replicable Unit Spectrograph (VIRUS) is an array of at least 150 copies of a simple, fiber-fed integral field spectrograph that will be deployed on the Hobby-Eberly Telescope (HET) to carry out the HET Dark Energy Experiment (HETDEX). Each spectrograph contains a volume phase holographic grating as its dispersing element that is used in first order for 350 < λ(nm) < 550. We discuss the test methods used to evaluate the performance of the prototype gratings, which have aided in modifying the fabrication prescription for achieving the specified batch diffraction efficiency required for HETDEX. In particular, we discuss tests in which we measure the diffraction efficiency at the nominal grating angle of incidence in VIRUS for all orders accessible to our test bench that are allowed by the grating equation. For select gratings, these tests have allowed us to account for < 90% of the incident light for wavelengths within the spectral coverage of VIRUS. The remaining light that is unaccounted for is likely being diffracted into reflective orders or being absorbed or scattered within the grating layer (for bluer wavelengths especially, the latter term may dominate the others). Finally, we discuss an apparatus that will be used to quickly verify the first order diffraction efficiency specification for the batch of at least 150 VIRUS production gratings.
VIRUS-W: commissioning and first-year results of a new integral field unit spectrograph dedicated to the study of spiral galaxy bulges
Show abstract
In November and December 2010 we successfully commissioned a new optical fibre-based Integral Field Unit
(IFU) spectrograph at the 2.7m Harlan J. Smith Telescope of the McDonald Observatory in Texas. Regular science observations commenced in spring 2011. The instrument achieves a spectral resolution of λ/Δλ = 8700 with a spectral coverage of 4850Å – 5480Å and a spectacular throughput of 37% including the telescope optics.
The design is related to the VIRUS-P instrument that was developed for the HETDEX experiment, but was modified significantly in order to achieve the large spectral resolution that is needed to recover the dynamical properties of disk galaxies. In addition to the high resolution mode, VIRUS-W offers a stellar population mode with a resolution of λ/Δλ = 3300 and a spectral coverage of 4340Å – 6040Å. The IFU is comprised out of 267
150 μm-core optical fibers with a fill factor of 1/3. With a beam of f/3.65, the core diameter translates to 3.2" on sky and a large field of view of 105" x 55" that is ideally suited to study the bulge regions of local spiral galaxies. The large throughput is due to a design that operates close to the numerical aperture of the fibers, a
large 200mm aperture refractive camera with no central obscuration, highly efficient volume phase holographic gratings, and a high-QE CCD. We will discuss the design, the performance and briefly present an example for the very up-to-date science that is possible with such instruments at 2m class telescopes.
LUCI in the sky: performance and lessons learned in the first two years of near-infrared multi-object spectroscopy at the LBT
Show abstract
LUCI (former LUCIFER) is the full cryogenic near-infrared multi-object spectrograph and imager at the LBT. It presently allows for seeing limited imaging and multi-object spectroscopy at R~2000-4000 in a 4x4arcmin2 FOV from 0.9 to 2.5 micron. We report on the instrument performance and the lessons learned during the first two years on sky from a technical and operational point of view. We present the upcoming detector upgrade to Hawaii-2 RG arrays and the operating modes to utilize the binocular mode, the LBT facility AO system for diffraction limited imaging as well as to use the wide-field AO correction afforded by the multi-laser GLAO System ARGOS in multi-object spectroscopy.
The VIMOS upgrade programme
Show abstract
The high multiplex advantage of VIMOS, the VLT visible imager and multi-object/integral-field spectrometer, makes it
a powerful instrument for large-scale spectroscopic surveys of faint sources. Following community input and
recommendations by ESO's Science and Technology Committee, in 2009 it was decided to upgrade the instrument. This
included installing an active flexure compensation system and replacing the detectors with CCDs that have a far better
red sensitivity and less fringing. Significant changes have also been made to the hardware, maintenance and operational
procedures of the instrument with the aim of improving availability and productivity. Improvements have also been
made to the data reduction pipeline. The upgrade will end in 2012 and the results of the program will be presented here.
Integration status of the configurable slit unit for GTC-EMIR
Show abstract
The Configurable Slit Unit (CSU) is a key module of EMIR (wide field NIR multi-object spectrograph) which will be one of the key next generation instruments of the Gran Telescopio de Canarias (GTC). The CSU enables a multi-slit configuration, a long slit, or an imaging aperture in the 6’x6’ (340mm x 340mm) field of view. This is realized by 110 sliding bars which can be configured at cryogenic working temperature to create 55 slits with a position accuracy of 6 micron. The CSU incorporates a number of enabling technologies which have been developed, validated and matured as a part of the total development of the CSU. Dedicated actuator drive and position measurement technologies have been successfully developed. Also a selective surface treatment technology, to give detailed features on the same part opposite emissivity performances, has been developed. All these technologies are currently implemented in the realization of the unit. Manufacturing of components for the unit has challenged state of the art production equipment and skills to the limit due to the size, number, accuracy and complexity of the parts and features. Integration and verification of the CSU is advancing. Both mechanics as electronics have been tested at sub-module level. Ahead is the challenge of actual integration of the electronics and software in order to get the mechanical hardware to operate within specification. Control strategies are developed and tuned to guarantee robust operation of the unit in cryogenic working environment. As a final integration step all individual axes are calibrated with an external interferometer measurement system.
Vacuum and cryogenic system for the MUSE detectors
Show abstract
MUSE with its 24 detectors distributed over an eight square meter vertical area was requiring a well engineered and
extremely reliable cryogenic system. The solution should also use a technology proven to be compatible with the very
high sensitivity of the VLT interferometer. A short introduction reviews the various available technologies to cool these 24 chips down to 160 K. The first part of the paper presents the selected concept insisting on the various advantages offered by LN2. In addition to the purely vacuum and cryogenic aspects we highlight some of the most interesting features given by the control system based on a PLC.
4MOST spectral data simulation
Paola Sartoretti,
Nicolas Leclerc,
Jakob Walcher,
et al.
Show abstract
4MOST is a phase A study of a very high-multiplex, wide-field fibre-fed spectrograph system for the VISTA or
NTT telescope. The main stellar goal of the instrument is to complement and complete the informations on the
Milky Way, that Gaia will provide both on radial velocity and chemical analysis. Two resolution modes (about
5000 and 20000) are foreseen to operate at the same time.
We have developed a simulator of spectral data for the 4MOST spectrograph. This simulator produces mock
scientic spectra to be analyzed by the science team in order to constrain the feasibility of their requirements
and help refine the high-level specications of the instrument. We present here the spectra simulator and how
some of the simulation results are used to define the performances of 4MOST.
The measuring apparatus research for BigBOSS fiber-positioner
Show abstract
Throughput of a fiber-robot-based multi-object spectrograph depends on the accuracy and precision of the fiber position
system. An efficient and accurate method of quantifying the performance of an actuator is necessary during the design
iteration process, final design, and for post-production characterization. A CCD camera-based optical setup was
developed at the Lawrence Berkeley National Laboratory to test these parameters of fiber robot positioners. The setup is
described, as well as tests used to quantify distortion and cross-check measurement by smart scope.
Fore-optics of the MUSE instrument
Show abstract
MUSE (Multi Unit Spectroscopic Explorer) is a second generation VLT panoramic integral field spectrograph developed
for the European Southern Observatory (ESO), operating in the visible wavelength range (0.465-0.93 μm). The MUSE
instrument is currently under integration and the commissioning is expected to start at the beginning of year 2013. The
scientific and technical capabilities of MUSE are described in a series of 19 companion papers. The Fore-Optics (FO),
situated at the entrance of MUSE, is used to de-rotate and provide an anamorphic magnification (x 5 / x 2.5) of the 1 arc
minute square field of view from the F/15.2 VLT Nasmyth focal plane (Wide Field Mode, WFM). Additional optical
elements can be inserted in the optical beam to further increase the magnification by a factor 8 (Narrow Field Mode,
NFM). An atmospheric dispersion corrector is also added in the NFM. Two image stabilization units have been
developed to ensure a stabilization of the field of view (1/20 of a resolved element) for each observation mode.
Environmental values such as temperature and hygrometry are monitored to inform about the observation conditions. All
motorized functions and sensors are remote-controlled from the VLT Software via the CAN bus with CANOpen
protocol. In this paper, we describe the FO optical, mechanical and control/command electronic concept, development
and performance.
Initial results from VIRUS production spectrographs
Show abstract
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) uses a novel technique of replicated spectrographs (VIRUS) to measure dark energy at intermediate redshifts (2 < z < 4). VIRUS contains over 30,000 fibers and over 160 independent and identical channels. Here we report on the construction and characterization of the initial batch of VIRUS spectrograph cameras. Assembly of the first batch of 16 is in progress. A brief overview of the assembly is presented, and where available performance is compared to specification.
Development and performance of the MUSE calibration unit
Show abstract
The Multi-Unit Spectroscopic Explorer (MUSE), an integral-field spectrograph for the ESO Very Large Telescope, has
been built and integrated by a consortium of 7 European institutes. MUSE can simultaneously record spectra across a
field of view of 1 square arcminute in the wavelength range from 465nm to 930nm. The calibration unit (CU) for MUSE
was developed to provide accurate flat fielding, spectral, geometrical, image quality and efficiency calibration for both
the wide-field and AO-assisted narrow-field modes. This paper describes the performance of the CU and electronics,
from the subsystem validation to the integration, alignment and use in the MUSE instrument.
Performance of the main instrument structure and the optical relay system of MUSE
Show abstract
The foundation of the MUSE instrument with its high multiplexing factor of twenty-four spectrographs is formed
through its central main structure that accommodates all instrumental subsystems and links them with the telescope. Due
to instrument's dimension and complexity, the requirements on structural performance are demanding. How its
performance was tested and optimized through reverse engineering is addressed. Intimately mated with this central
structure is an optical relay system that splits the single telescopic field into twenty-four subfields. Each of those is
individually directed along three dimensions across the structure through a folding and imaging setup of an optical relay
system that at the end feeds one of the twenty-four spectrographs. This opto-mechanical relay system was tested when
mounted onto the main structure. The results obtained so far are given here.
MUSE instrument global performance test
Show abstract
MUSE (Multi Unit Spectroscopic Explorer) is a second generation instrument developed for ESO (European Southern
Observatory) and will be assembled to the VLT (Very Large Telescope) in 2013. The MUSE instrument can
simultaneously record 90.000 spectra in the visible wavelength range (465-930nm), across a 1*1arcmin² field of view,
thanks to 24 identical Integral Field Units (IFU). A collaboration of 7 institutes has partly validated and sent their subsystems
to CRAL (Centre de Recherche Astrophysique de Lyon) in 2011, where they have been assembled together.
The global test and validation process is currently going on to reach the Preliminary Acceptance in Europe in 2012. The
sharing of performances has been based on 5 main functional sub-systems. The Fore Optics sub-system derotates and
anamorphoses the VLT Nasmyth focal plane image, the Splitting and Relay Optics associated with the Main Structure
are feeding each IFU with 1/24th of the field of view. Each IFU is composed of a 3D function insured by an image slicer
system and a spectrograph, and a detection function by a 4k*4k CCD cooled down to 163°K. The 5th function is the
calibration and data reduction of the instrument. This article depicts the sequence of tests that has been completely
reshafled mainly due to planning constraints. It highlights the priority given to the most critical performances tests of the
sub-systems and their results. It enhances then the importance given to global tests. Finally, it makes a status on the
verification matrix and the validation of the instrument and gives a critical view on the risks taken.
The impact of surface-polish on the angular and wavelength dependence of fiber focal ratio degradation
Show abstract
We present measurements of how multimode fiber focal-ratio degradation (FRD) and throughput vary with levels
of fiber surface polish from 60 to 0.5 micron grit. Measurements used full-beam and laser injection methods at
wavelengths between 0.4 and 0.8 microns on 17 meter lengths of Polymicro FBP 300 and 400 μm core fiber.
Full-beam injection probed input focal-ratios between f/3 and f/13.5, while laser injection allowed us to isolate
FRD at discrete injection angles up to 17 degrees (f/1.6 marginal ray). We find (1) FRD effects decrease as grit
size decreases, with the largest gains in beam quality occurring at grit sizes above 5 μm; (2) total throughput
increases as grit size decreases, reaching 90% at 790 nm with the finest polishing levels; (3) total throughput
is higher at redder wavelengths for coarser polishing grit, indicating surface-scattering as the primary source of
loss. We also quantify the angular dependence of FRD as a function of polishing level. Our results indicate that
a commonly adopted micro-bending model for FRD is a poor descriptor of the observed phenomenon.
MUSE optical alignment procedure
Show abstract
MUSE (Multi Unit Spectroscopic Explorer) is a second generation VLT integral field spectrograph (1x1arcmin² Field of View) developed for the European Southern Observatory (ESO), operating in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently assembling and testing MUSE in the Integration Hall of the
Observatoire de Lyon for the Preliminary Acceptance in Europe, scheduled for 2013.
MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates
and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units
(IFU), that are mounted within a large monolithic instrument mechanical structure. Each IFU incorporates an image
slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and
cryogenic system. During 2011, all MUSE subsystems were integrated, aligned and tested independently in each
institute. After validations, the systems were shipped to the P.I. institute at Lyon and were assembled in the Integration
Hall
This paper describes the end-to-end optical alignment procedure of the MUSE instrument. The design strategy, mixing
an optical alignment by manufacturing (plug and play approach) and few adjustments on key components, is presented.
We depict the alignment method for identifying the optical axis using several references located in pupil and image
planes. All tools required to perform the global alignment between each subsystem are described. The success of this
alignment approach is demonstrated by the good results for the MUSE image quality.
MUSE commissioning at the VLT (Very Large Telescope) is planned for 2013.
Cryostat and CCD for MEGARA at GTC
Show abstract
MEGARA (Multi-Espectrógrafo en GTC de Alta Resolución para Astronomía) is the new integral field unit (IFU) and
multi-object spectrograph (MOS) instrument for the GTC. The spectrograph subsystems include the pseudo-slit, the
shutter, the collimator with a focusing mechanism, pupil elements on a volume phase holographic grating (VPH) wheel
and the camera joined to the cryostat through the last lens, with a CCD detector inside.
In this paper we describe the full preliminary design of the cryostat which will harbor the CCD detector for the
spectrograph. The selected cryogenic device is an LN2 open-cycle cryostat which has been designed by the
"Astronomical Instrumentation Lab for Millimeter Wavelengths" at INAOE. A complete description of the cryostat
main body and CCD head is presented as well as all the vacuum and temperature sub-systems to operate it. The CCD is
surrounded by a radiation shield to improve its performance and is placed in a custom made mechanical mounting which
will allow physical adjustments for alignment with the spectrograph camera. The 4k x 4k pixel CCD231 is our selection
for the cryogenically cooled detector of MEGARA. The characteristics of this CCD, the internal cryostat cabling and
CCD controller hardware are discussed. Finally, static structural finite element modeling and thermal analysis results are
shown to validate the cryostat model.
A wide field corrector concept including an atmospheric dispersion corrector for the ESO-NTT
Show abstract
An optical design for a wide field corrector (WFC) turning the ESO New Technology Telescope (NTT) into a powerful fiber coupled spectroscopic wide filed, multi object facility is presented. The design utilizes a three square degree (optional 5 square degrees are possible) field of view (FoV) and is designed for a 1.5 arcsec diameter fibre aperture. One of the three lenses of the corrector system is shifted laterally to achieve atmospheric dispersion correction. Image quality properties and a basic tolerancing analysis is shown with this paper.
The LAMOST low resolution spectrograph stability performance
Show abstract
One of the Large Sky Area Multi-Object Spectroscopic Telescope (LAMOST) scientific requirements require the ability
of the low resolution spectrograph(LRS) to measure velocities to a accuracy of 4km/s over the entire 5 degree field in 2
hours objects observation. This requirement results in the specification of image movement less than 0.6μm/hours
(0.05pixl/hours corresponding to the science detector).There are 16 spectrographs for LAMOST telescope, so we expect
the design aspects of the instrument directed towards achieving the stability goal. In this paper we present the last design
aspects of the instrument which enable meeting the 4km/s requirement, and the recent test results of the LRS’s Stability
Performance. The test results show that the stability performance of LAMOST-LRS can meet the the stability goal, the
image shift along the direction of dispersion is not influenced by the external factors, and the image shift along vertical
dispersion direction meet the technical requirements when the environmental temperature of the spectrograph room is in
control.
A fibre positioner solution for the 4MOST instrument
Show abstract
4MOST1 is a multi object spectrograph facility for ESO’s NTT or VISTA telescope. 4MOST is one of the two projects selected for a conceptual design study by ESO. The 4MOST instrument will be able to position < 1500 fibres in the focal plane and collect spectra in a high resolution (R=20000)2 and a low resolution (R=5000) mode (HRM, LRM). The spectral coverage for the LRM is 400-900 nm, the HRM covers 390-459 nm and 564-676 nm. We will present one of the possible positioner designs and first tests of some components for the focal plane array. The design follows the LAMOST3 positioner and has two rotational axes to move the fibre inside the patrol disc. Each axis consists of a stepper motor attached to micro harmonic drive (MHD). The small outer dimensions and high gear ratios of the MHD-stepper motor package, makes them perfectly suitable for our application. The MHD is also backlash free and self-locking what gives us the opportunity to minimize power consumption and heat dissipation during observation without loosing the position of the fibre on sky. The control electronics will also be miniaturized and part of the positioner unit.
Hyper Suprime-Cam: the control system
Yousuke Utsumi,
Satoshi Kawanomoto,
Philip Tait,
et al.
Show abstract
We introduce the detail of the control system of Hyper Suprime-Cam (HSC) and its performance. Although it
has almost 10 times as many CCDs (104) as existing camera (Suprime-Cam), it is controlled by the common
user interface, the Subaru Observation Software System (SOSS) with the Gen2 implementation through the
HSC local controller (OBCP). If we adopt parallel programming, the read-out time should be within 25 seconds
including 18.6 seconds of readout time which is comparable to the current Suprime-Cam.
Hyper Suprime-Cam: filter exchange unit and shutter
Show abstract
We have developed a filter exchange unit (FEU) and a shutter of Hyper Suprime-Cam (HSC). FEU consists of two parts; the alignment mechanism of the filter in the optical path and a jukebox of the filters. The alignment mechanism can guarantee 10 μm position stability with respect to the focal plane CCDs. On the exchange sequence, a motorized cart grabs and pushes the filter from the jukebox. Each jukebox has 3 slots and we have two identical jukeboxes. The operation is fully automated and the entire exchange sequence takes 16 minutes. Also, we developed the focal-plane shutter with 1,030 mm diameter envelope and 60 mm thickness while having 600 mm aperture. We report the detail of design and implementation of the shutter and FEU, and installation procedure of FEU.
VXMS: the VISTA extreme multiplex spectrograph
Show abstract
A study for a spectrograph delivering at least 10000 slits for galaxies and 20000 for stars over a 2.5 deg2 field have been
completed as an answer to the call for proposal for future VISTA MOS instrumentation. In a single night, 65000 galaxy
redshifts can be measured to z~0.7 and beyond for measuring the Baryon Acoustic Oscillation (BAO) scale and many
other science goals. The design features ten cloned spectrographs which give a smaller total weight and length than a
unique spectrograph to make it placable in the space envelope of the Cassegrain focus. The clones use a transparent
design including a grism in which all optics are about the size or smaller than the clone rectangular subfield so that they can be tightly packed with little gaps between subfields. Only low cost glasses are used; the variations in chromatic aberrations between bands are compensated by changing a box containing the grism and two adjacent lenses. Two bands cover the 550nm to 900nm wavelength range at resolution of 1100 for blue end and 3000 for red end while another cover the Calcium triplet at 5000. An optional box does imaging but we studied different innovative methods for acquisition without imaging. A new 2.3° corrector was designed that places the pupil before and relatively near the focal plane which permits to give more space at the back of the spectrographs by placing them in a hedgehog configuration. An offaxis field lens in each spectrograph permits to control the pupil position.
BigBOSS: a stage IV dark energy redshift survey
Show abstract
BigBOSS is a Stage IV dark energy experiment based on proven techniques to study baryon acoustic oscillations and the growth of large scale structure. The 2010 Astronomy and Astrophysics Decadal Survey labeled dark energy as a key area of exploration. BigBOSS is designed to perform a 14,000 square degree survey of 20 million galaxies and quasi-stellar objects. The project involves installation of a new instrument on the Mayall 4m telescope, operated by the National Optical
Astronomy Observatory. The instrument includes a new optical widefield corrector, a 5,000 fiber actuator system, and a multi-object spectrometer. Systems engineering flowdown from data set requirements to instrument requirements are discussed, along with the trade considerations and a pre-conceptual baseline design of the widefield optical corrector, spectrometer and fiber positioner systems.
The BigBOSS spectrograph
Show abstract
BigBOSS is a proposed ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the
growth of structure with a 14,000 square degree galaxy and quasi-stellar object redshift survey. It consists of a 5,000-
fiber-positioner focal plane feeding the spectrographs. The optical fibers are separated into ten 500 fiber slit heads at the
entrance of ten identical spectrographs in a thermally insulated room. Each of the ten spectrographs has a spectral
resolution (λ/Δλ) between 1500 and 4000 over a wavelength range from 360 - 980 nm. Each spectrograph uses two
dichroic beam splitters to separate the spectrograph into three arms. It uses volume phase holographic (VPH) gratings for
high efficiency and compactness. Each arm uses a 4096x4096 15 μm pixel charge coupled device (CCD) for the
detector. We describe the requirements and current design of the BigBOSS spectrograph. Design trades (e.g. refractive
versus reflective) and manufacturability are also discussed.
GMTNIRS (Giant Magellan Telescope Near-Infrared Spectrograph): structural-mechanical design
Show abstract
A near-infrared spectrograph (NIRS) has been designed and proposed for utilization as a first-light instrument on the
Giant Magellan Telescope (GMT). GMTNIRS includes modular JHK, LM spectrograph units mounted to two sides of a
cryogenic optical bench. The optical bench and surrounding, protective radiation (thermal) shield are containerized
within a rigid cryostat vessel, which mounts to the GMT instrument platform. A support structure on the secondary side
of the optical bench provides multi-dimensional stiffness to the optical bench, to prevent excessive displacements of the
optical components during tracking of the telescope. Extensive mechanical simulation and optimization was utilized to
arrive at synergistic designs of the optical bench, support structure, cryostat, and thermal isolation system. Additionally,
detailed steady-state and transient thermal analyses were conducted to optimize and verify the mechanical designs to
maximize thermal efficiency and to size cryogenic coolers and conductors. This paper explains the mechanical and
thermal design points stemming from optical component placement and mounting and structural and thermal
characteristics needed to achieve instrument science requirements. The thermal and mechanical simulations will be
described and the data will be summarized. Sufficient details of the analyses and data will be provided to validate the
design decisions.
Posters: Imaging Surveyors/Solar Instrumentation/Airborne Instrumentation
LSST camera optics design
Show abstract
The Large Synoptic Survey Telescope (LSST) uses a novel, three-mirror, telescope design feeding a camera system that
includes a set of broad-band filters and three refractive corrector lenses to produce a flat field at the focal plane with a
wide field of view. Optical design of the camera lenses and filters is integrated in with the optical design of telescope
mirrors to optimize performance. We discuss the rationale for the LSST camera optics design, describe the methodology
for fabricating, coating, mounting and testing the lenses and filters, and present the results of detailed analyses
demonstrating that the camera optics will meet their performance goals.
Wide-field photometry at 20 Hz for the TAOS II Project
Show abstract
The TAOS II Project requires high-speed differential photometry of 10-20 thousand stars over a telescope field of
154mm diameter with 16-micron spatial resolution and good noise performance. We are developing a custom CMOS
imager array to accomplish this task.
The PAU camera and the PAU survey at the William Herschel Telescope
Show abstract
The Physics of the Accelerating Universe (PAU) is a project whose main goal is the study of dark energy. For this purpose, a new large field of view camera (the PAU Camera, PAUCam) is being built. PAUCam is designed to carry out a wide area imaging survey with narrow and broad band filters spanning the optical wavelength range. The PAU Camera is now at an advance stage of construction. PAUCam will be mounted at the prime focus of the William Herschel Telescope. With the current WHT corrector, it will cover a 1 degree diameter field of view. PAUCam mounts eighteen 2k×4k Hamamatsu fully depleted CCDs, with high quantum efficiency up to 1 μm. Filter trays are placed in front of the CCDs with a technologically challenging system of moving filter trays inside the cryostat. The PAU Camera will use a new set of 42 narrow band filters ranging from ~4400 to ~8600 angstroms complemented with six standard broad-band filters, ugrizY. With PAUCam at the WHT we will carry out a cosmological imaging survey in both narrow and broad band filters that will perform as a low resolution spectroscopic survey. With the current survey strategy, we will obtain accurate photometric redshifts for galaxies down to iAB~22.5 detecting also galaxies down to iAB~24 with less precision in redshift. With this data set we will obtain competitive constraints in cosmological parameters using both weak lensing and galaxy clustering as main observational probes.
A 3 degree prime focus field for the AAT
Show abstract
The Anglo-Australian Telescope's 2° field 400 fiber prime focus feed for spectroscopy has been very successful. For a
new instrument proposal (known as Hector) to provide robotically deployed IFUs at the AAT prime focus, a corrector
giving a field 3° in diameter is required to make optimum use of as many as 100 IFUs. Having IFUs with individual
field diameters of 10 to 15 arcsec feeding spectrographs allows some relaxation in the tolerances to lateral chromatic
aberration and to atmospheric dispersion, since each can be compensated computationally without much loss in
efficiency. The AAT has four removable top ends, of which the original prime focus version could be recycled to carry a
much larger corrector. Its outer ring passes a field up to 3.3° diameter without vignetting and the dome slit has a little
more clearance. A very satisfactory optical design has been developed for a corrector providing 3° field diameter
without vignetting, having six elements with three non-spherical surfaces. The diameter of the largest element is 1250
mm. The corrector also works well for direct imaging on a flat field up to 1° diameter.
Assembly, alignment, and testing of the DECam wide field corrector optics
Show abstract
The DES project is a 5 year imaging survey of the southern sky using the 4m Blanco Telescope at the Cerro Tololo
International Observatory in Chile. A new wide field camera with a 2.2 degree diameter field of view has been built to
undertake this survey. The alignment of the large lenses for this camera poses a significant challenge as they have to be
aligned to a tolerance of ±50 micrometers. This paper presents the assembly and alignment process of the full optical system along with the test results. Also included is the predicted imaging performance from the as-built system.
Design of the KMTNet large format CCD camera
Show abstract
We present the design for the 340 Mpixel KMTNet CCD camera comprising four newly developed e2v CCD290-99
imaging sensors mounted to a common focal plane assembly. The high performance CCDs have 9k x 9k format, 10
micron pixels, and multiple outputs for rapid readout time. The camera Dewar is cooled using closed cycle coolers and
vacuum is maintained with a cryosorption pump. The CCD controller electronics, the electronics cooling system, and the
camera control software are also described.
T80Cam: the wide field camera for the OAJ 83-cm telescope
Show abstract
The Observatorio Astrofísico de Javalambre (OAJ) is a new astronomical facility located at the Sierra de Javalambre (Teruel, Spain) whose primary role will be to conduct all-sky astronomical surveys. The OAJ facility will have two wide-field telescopes: the JST/T250; a 2.55-m telescope with a 3° diameter field of view (FoV), and the JAST/T80; an 0.83-m telescope with a 2° diameter FoV. First light instrumentation is being designed to exploit the survey capabilities of the OAJ telescopes. This paper describes the T80Cam, a wide-field camera that will be installed at the Cassegrain focus of the JAST/T80. It is equipped with an STA 1600 backside illuminated detector. This is a 10.5k-by-10.5k, 9μm pixel, high efficiency CCD that is read from 16 ports simultaneously, allowing read times of ~20s with a typical read noise of 6 electrons (rms). This full wafer CCD covers a large fraction of the JAST/T80’s FoV with a pixel scale of ~0.50"/pixel. T80Cam will observe in the wavelength range 330-1000nm through a set of 12 carefully optimized broad-, intermediate- and narrow-band filters. The camera is intended for surveys with the JAST/T80 telescope, starting with the planned J-PLUS (Javalambre Photometric Local Universe Survey), a multi-band photometric all-sky survey that will be completed in about 2 years and will reach AB∼ 23 mag (5σ level) with the SDSS filters.
Transport and installation of the Dark Energy Survey CCD imager
Show abstract
The Dark Energy Survey CCD imager was constructed at the Fermi National Accelerator Laboratory and delivered to
the Cerro Tololo Inter-American Observatory in Chile for installation onto the Blanco 4m telescope. Several efforts are
described relating to preparation of the instrument for transport, development and testing of a shipping crate designed to
minimize transportation loads transmitted to the camera, and inspection of the imager upon arrival at the observatory.
Transportation loads were monitored and are described. For installation of the imager at the telescope prime focus,
where it mates with its previously-installed optical corrector, specialized tooling was developed to safely lift, support,
and position the vessel. The installation and removal processes were tested on the Telescope Simulator mockup at
FNAL, thus minimizing technical and schedule risk for the work performed at CTIO. Final installation of the imager is
scheduled for August 2012.
Square-core bundles for astronomical imaging
Show abstract
Optical fibre imaging bundles (hexabundles) are proving to be the next logical step for large galaxy surveys as they offer spatially-resolved spectroscopy of galaxies and can be used with conventional fibre positioners. Hexabundles have been effectively demonstrated in the Sydney-AAO Multi-object IFS (SAMI) instrument at the Anglo-
Australian Telescope[5]. Based on the success of hexabundles that have circular cores, we have characterised a bundle made instead from square-core fibres. Square cores naturally pack more evenly, which reduces the interstitial holes and can increase the covering, or filling fraction. Furthermore the regular packing simplifies the process of combining and dithering the final images. We discuss the relative issues of filling fraction, focal ratio degradation (FRD), and cross-talk, and find that square-core bundles perform well enough to warrant further development as a format for imaging fibre bundles.
KWFC: four square degrees camera for the Kiso Schmidt Telescope
Show abstract
The Kiso Wide Field Camera (KWFC) is a facility instrument for the 105-cm Schmidt telescope being operated by the
Kiso Observatory of the University of Tokyo. This camera has been designed for wide-field observations by taking
advantage of a large focal-plane area of the Schmidt telescope. Eight CCD chips with a total of 8k x 8k pixels cover a
field-of-view of 2.2 degrees x 2.2 degrees on the sky. The dewar window works as a field flattener lens minimizing an
image distortion across the field of view. Two shutter plates moving in parallel achieve uniform exposures on all the
CCD pixels. The KWFC is equipped with a filter exchanger composed of an industrial robotic arm, a filter magazine
capable of storing 12 filters, and a filter holder at the focal plane. Both the arm and the magazine are installed inside the
tube framework of the telescope but without vignetting the beam. Wide-field survey programs searching for supernovae
and late-type variable stars have begun in April 2012. The survey observations are performed with a management
software system for facility instruments including the telescope and the KWFC. This system automatically carries out
observations based on target lists registered in advance and makes appropriate decisions for implementation of
observations by referring to weather conditions and status of the instruments. Image data obtained in the surveys are
processed with pipeline software in real time to search for candidates of time-variable sources.
Spectrophotometric calibration system for DECam
Show abstract
We describe a spectrophotometric calibration system that is being implemented as part of the DES DECam project at the
Blanco 4 meter at CTIO. Our calibration system uses a 1nm wide tunable source to measure the instrumental response
function of the telescope optics and detector from 300nm up to 1100nm. This calibration will be performed regularly to
monitor any change in the transmission function of the telescope during the 5 year survey. The system consists of a
monochromator based tunable light source that provides illumination on a dome flat that is monitored by calibrated
photodiodes that allow us to measure the telescope throughput as a function of wavelength. Our system has a peak
output power of 2 mW, equivalent to a flux of approximately 800 photons/s/pixel on DECam.
Test benches facilities for PAUCam: CCDs and filters characterization
Show abstract
The PAUCam [1] is an optical camera with a 18 CCDs (Hamamatsu Photonics K.K.) mosaic and up to 42 narrow- and
broad-band filters. It is foreseen to install it at the William Herschel Telescope (WHT) in the Observatorio del Roque de
los Muchachos, Canary Islands, Spain. As required by the camera construction, a couple of test bench facilities were
developed, one in Madrid (CIEMAT) that is mainly devoted to CCDs read-out electronics development and filter
characterization [2], and another in Barcelona (IFAE-ICE) that has as its main task to characterize the scientific CCDs in
terms of Dark Current, CTE, QE, RON and many other parameters demanded by the scientific performance required.
The full CCDs characterization test bench layout, its descriptions and some optical and mechanical characterization
results are summarized in this paper.
Focus and alignment of the Dark Energy Camera using out-of-focus stars
Aaron Roodman
Show abstract
The active optics system of the Dark Energy Camera (DECam) at the CTIO 4 meter Blanco telescope, built
for the Dark Energy Survey, uses out-of-focus stars (donuts) to determine the camera's focus and alignment, as
well as provide a measure of the wavefront. In this paper, we describe the donut analysis algorithm and present
results on focus, alignment, and wavefront from a donut campaign conducted at the Blanco from 2010 to 2012,
using the previous wide-field camera.
Development of MIMIZUKU: a mid-infrared multi-field imager for 6.5-m TAO telescope
Show abstract
TAO (The University of Tokyo Atacama Observatory) is planned to be constructed at the summit of Co. Chajnantor (5640 m altitude) in Chile. MIMIZUKU (Mid-Infrared Multi-field Imager for gaZing at the UnKnown Universe) is a mid-infrared imager (Field of View: 1' x 1'- 2' x 2') and spectrometer (Δλ/λ: 60-230) for the 6.5-m TAO telescope, covering the wavelength range of 2-38 μm. The MIMIZUKU has a unique equipment called Field Stacker (FS) which enables the simultaneous observation of target and reference object. The simultaneity is expected to improve photometric accuracy and to realize long-term monitoring observations. The development status of the MIMIZUKU is reported in this paper. The FS and the cryostat of the MIMIZUKU have been fabricated and under testing. The cold optics (550 mm x 750 mm x 2 floors) with 28 mirrors has been constructed. The mirrors were aligned with the positional precision of 0.1 mm and the angular precision of 0.1 deg. The evaluated optical performance is that the diffraction-limited image at λ <8 μm and the enough compact image (r <2 pix=0.22") at 2 λ ~2μm can be obtained. In the cold optics, the drive systems with backlash-less gears are employed and work well even in cryogenic environment. The grisms made with silicon and germanium have been fabricated by ultraprecision cutting. It was found that their surface roughness, grating constant, and blaze angle almost measure up to the designed values.
Hyper Suprime-Cam: implementation and performance of the cryogenic dewar
Show abstract
Hyper Suprime-Cam (HSC) is a next generation wide field optical camera developed for F/2 prime focus of the 8.2 m
Subaru telescope. The focal plane is about 600 mm in diameter where 116 CCDs (2k4k 15 micron square each) are
arranged and cooled down to -100°C. The HSC CCD cryostat system design is presented by Komiyama et al. (2010).
Since then, we made detail designs of the components, manufactured them and assembled the dewar. This paper presents
the actual performance of the system including flatness and parallelism of the SiC cold plate, stability of its temperature,
the amount of out-gassing.
The test of the 10k x 10k CCD for Antarctic Survey Telescopes (AST3)
Show abstract
A 10k x 10k single-chip CCD camera was installed on the first Antarctic Survey Telescope (AST3-1) at Dome A,
Antarctica in January 2012. The pixel size is 9 μm, corresponding to 1 arcsec on the focal plane. The CCD runs
without shutter but in frame transfer mode, and is cooled by thermoelectric cooler (TEC) to take advantage
of the low air temperature at Dome A. We tested the performance of the camera in detail, including the gain,
linearity, readout noise, dark current, charge transfer efficiency, etc. As this camera is designed to work at Dome
A, where the lowest air temperature could go down to −80°C in winter, we tested to cool not only the CCD
chip but also the controller which usually is operated at normal temperatures for ground-based telescopes. We
found that the performance of the camera changes a little when the controller is cooled.
Commissioning and initial performance of the Dark Energy Camera liquid nitrogen cooling system
Show abstract
The Dark Energy Camera and its cooling system has been shipped to Cerro Tololo Inter-American Observatory in Chile
for installation onto the Blanco 4m telescope. Along with the camera, the cooling system has been installed in the Coudé
room at the Blanco Telescope. Final installation of the cooling system and operations on the telescope is planned for the
middle of 2012. Initial commissioning experiences and cooling system performance is described.
Multi-purpose grating spectrograph for the 4-meter European Solar Telescope
Show abstract
This communication presents a family of spectrographs designed for the European Solar Telescope. They can operate in
four different configurations: a long slit standard spectrograph (LsSS), two devices based on subtractive double pass
(TUNIS and MSDP) and one based on an integral field, multi-slit, multi-wavelength configuration. The combination of
them composes the multi-purpose grating spectrograph of EST, focused on supporting the different science cases of the
solar photosphere and chromosphere in the spectral range from 3900 Å to 23000 Å. The different alternatives are made
compatible by using the same base spectrographs and different selectable optical elements corresponding to specific
subsystems of each configuration.
Development and produce of ground-based reflecting coronagraph for solar applications
Show abstract
The ground-based 0.36m mirror coronagraph with super-polished off-axis parabolic primary mirror for solar
applications has developed and build now. Optical system design, technology of scattering level measurement of
primary mirror surface and the method of adjustment are described. Also presents the constructions of heat-stop, Lyot-stop
assemblies and truss. The kit of spectral equipment and detectors for actual solar astrophysics tasks is discussed.
Wide-field Solc-type birefringent filter
Valery I. Skomorovsky,
Galina I. Kushtal,
Valery P. Sadokhin
Show abstract
A 24-element wide-field Solc birefringent filter (WFSBF) has been produced and tested for the first time. WFSBF is a
second unit to the 3-unit BF designed for imaging solar magnetic fields in the FeI 6173 Å spectral line. WFSBF
passband full width at half maximum is 0.2 Å. The optical stage of the Solc BF is apodized. The main passband has a
two-peak profile, to increase BF transmittance in spectral line wings. The neighbouring passbands at 2 Å are cut off by
the first BF unit. To measure magnetic fields, a narrower passband of the third BF unit is to scan the spectral line wings
in the ±0.05Å positions, in accordance with two-peak positions of the Solc filter profile. The wide field of view (FOV) of
the Solc filter was reached with composite birefringent stages of 24 positive artificial paratellurite and 24 negative
natural calcite crystals. FOV of a composite stage is eleven times larger than that of the only-calcite one. The calculated
passband is compared to the experimental one. Technological aspects of the manufacture as well as devices for plate
orientation are discussed.
A broad band imager for the European Solar Telescope
Show abstract
We report on the results of the conceptual design study of a broad band imager for the European Solar Telescope (EST),
a joint project of several European research institutes to design and realize a 4-m class solar telescope. The EST broad
band imager is an imaging instrument whose function is to obtain diffraction limited images over the full field of view of
EST at multiple wavelengths and high frame rate. Its scientific objective is the study of fundamental astrophysical
processes at their intrinsic scales in the Sun’s atmosphere. The optical layout foresee two observational modes: a
maximum field of view mode and a high resolution mode. The imager will have a 2'x2' corrected field of view in the first
mode and an angular resolution better than 0.04" at 500nm in the latter mode. The imager will cover a wavelength range
spanning from 390nm to 900nm through a number of filters with bandpasses between 0.05nm and 0.5nm. The selected
optical layout is an all refractive design. To optimize optical performances and throughput there will be two arms
working simultaneously: a blue arm (covering the 380nm – 500nm range) and a red arm (600nm – 900nm). The blue arm
will have two channels while the red arm only one. Each channel will be divided in three subchannels: one will host
narrow band filters for chromospheric observations, another one, in focus wide band filters used as reference for speckle
reconstruction and photospheric observations, and the last one, out of focus wide band filters for phase diversity
reconstruction of photospheric observations.
Preliminary design of the visible spectro-polarimeter for the Advanced Technology Solar Telescope
Show abstract
The Visible Spectro-Polarimeter (ViSP) is one of the first light instruments for the Advanced Technology Solar
Telescope (ATST). It is an echelle spectrograph designed to measure three different regions of the solar spectrum in
three separate focal planes simultaneously between 380 and 900 nm. It will use the polarimetric capabilities of the ATST
to measure the full Stokes parameters across the line profiles. By measuring the polarization in magnetically sensitive
spectral lines the magnetic field vector as a function of height in the solar atmosphere can be obtained, along with the
associated variation of the thermodynamic properties. The ViSP will have a spatial resolution of 0.04 arcsec over a
2 arcmin field of view (at 600 nm). The minimum spectral resolving power for all the focal planes is 180,000. The
spectrograph supports up to 4 diffraction gratings and is fully automated to allow for rapid reconfiguration.
The S4I prototype: a beam-slicer system dedicated to the new generation multichannel subtractive double pass for EST imaging spectropolarimetry
Frédéric Sayède,
Pierre Mein,
Jean-Philippe Amans,
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 beam slicer prototype that will be
tested and validated on an optical bench and on existing telescopes.
The prototype called S4I (Spectral Sampling with Slicer for Solar Instrumentation) is under construction and tested at the
Observatoire de Paris. It validates the opto-mechanical feasibility of the new beam slicer. The manufacture is now
complete: we give a description of the whole system. We give also some results of the first tests.
Polarimeter with a high-speed rotating waveplate for the solar observation
Show abstract
We developed a polarimeter for the ground-based solar observation using a high-speed rotating waveplate (typically
12.5–25 revolutions s−1) and a high-speed camera (typically 200–400 frames s−1) with commercially available
devices. Fast polarization modulation is required for the ground-based solar polarimetry to avoid producing
seeing-induced false polarization signals. Modulation with a high-speed rotating waveplate realizes not only fast
full-Stokes modulation but also wide coverage of the wavelength range, and therefore, a polarimeter with a highspeed
rotating waveplate is most suitable for the simultaneous polarimetry observations at multi-wavelengths
with a spectrograph. A comprehensive description of the instrument and some results of the solar spectropolarimetry
with this polarimeter are given in this paper.
Design and status of an optical and near-infrared spectrometer for the IRSF 1.4m Telescope
Show abstract
We present our new optical and near-infrared (NIR) spectrometer for the IRSF 1.4m telescope. The concept
of it is an effective use of photons, and so we have designed it to obtain a spectrum of the 0.4-2.5μm range
simultaneously and have a small number of optical surfaces in order to reduce reflection loss. Light collected by
the telescope is separated into optical (0.45-0.90μm) and NIR (1.0-2.5μm) wavelengths by a dichroic entrance
window, and two spectrometers are prepared, one for the optical wavelengths and another for the NIR. We use a
sapphire prism in the NIR spectrometer, and a diffraction grating in the optical spectrometer. The optical design
is very simple and the number of optical surfaces is 9 for optical and 10 for NIR (not including the telescope
mirrors). A 1024×250 pixels CCD (optical) and a 1024×1024 HgCdTe detector array (NIR) are used. The
spectral resolution will be 470@0.70μm and 380@1.8μm with a 1” slit width. A NIR slit viewer with a 3’.5 ×
3’.5 field of view is also mounted. The development of the spectrometer will be complete by March 2013.
Design, testing, and performance 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 engineering development of a suite of
instruments located at prime focus of the upgraded HET. The Prime Focus Instrument Package (PFIP) contains
acquisition, guiding, and wave front sensing instrumentation [2], the fiber feeds for the facility spectrographs (VIRUS,
HRS, MRS, LRS2), and ancillary hardware. This paper reviews the design and functions of the PFIP and presents
details of the mechanical design, integration and testing.
An optical and near-infrared multipurpose instrument HONIR
Show abstract
We have developed an optical-infrared instrument HONIR (Hiroshima Optical and Near-InfraRed camera) to be attached to the 1.5-m Kanata telescope at Higashi-Hiroshima Observatory, Hiroshima University. HONIR is a three color (one optical and two near-infrared bands among 0.5–2.4 µm) simultaneous imager and spectrograph with a polarimetry function. The field of view of the imaging mode is 10 arcmin square with a spatial sampling of 0".29. Among the planned multipurpose functions, a two color (0.5–1.0 µm and 1.15–2.40 µm) simultaneous imaging function has been installed and operated so far. The remaining functions, spectroscopy and polarimetry, and the second near-infrared band arm, are under development and will be installed in the near future.
Preliminary design of a multi-slit image slicer for EST
Show abstract
Integral field spectroscopy is a modern technique used in Astronomy to obtain simultaneous spectral information of all
points in a bidimensional field of view. This communication presents the preliminary design of a multi-slit image slicer
to be coupled to the spectrographs of the 4 meters aperture European Solar Telescope. This integral field unit will
provide the observation of an 80 arcsec2 field of view, rearranged into 8 slits of 200 arcsec length by 0.05 arcsec width.
Different optical design alternatives with diffraction limited optical quality, as well as the design of a prototype for the
GREGOR solar telescope, are presented.
HELLRIDE: a new interferometric multiline instrument for the analysis of the solar atmosphere
Show abstract
We are developing a new etalon-based spectrometer 'HELLRIDE' for the Vacuum Tower Telescope (VTT), Tenerife. It
will offer improved performance over existing devices in a number of operational aspects. Primary development goal has
been increasing the number of spectral lines for the simultaneous recording of solar Doppler shifts. Observations may
cover a large field-of-view at high spatial and temporal resolution. New electromagnetic drive technologies are to be
implemented. A focus will be set to achieve thermal stability with respect to spectroscopic drifts and pointing precision.
All aspects of device operation are to be covered by a numerical model allowing for offline testing and offline
observations simulation. Remote operation options will be available for dedicated observational programs.
The new instrument is foreseen to be used for the analysis of energy transfers within the solar atmosphere. The
helioseismological and kinetic aspects of chromospheric and coronal heating are here of special interest. To allow for
synchronized observations of photospheric and coronal phenomena new procedures are under development to improve
co-alignment of ground-based and space-based telescopes.
HELLRIDE stands for HELioseismological Large Regions Interferometric DEvice.
PICARD SOL mission, a ground-based facility for long-term solar radius measurement
Show abstract
For the last thirty years, ground time series of the solar radius have shown different variations according to
different instruments. The origin of these variations may be found in the observer, the instrument, the atmosphere
and the Sun. These time series show inconsistencies and conflicting results, which likely originate from
instrumental effects and/or atmospheric effects. A survey of the solar radius was initiated in 1975 by F. Laclare,
at the Calern site of the Observatoire de la Cˆote d’Azur (OCA). PICARD is an investigation dedicated to the
simultaneous measurements of the absolute total and spectral solar irradiance, the solar radius and solar shape,
and to the Sun’s interior probing by the helioseismology method. The PICARD mission aims to the study of the
origin of the solar variability and to the study of the relations between the Sun and the Earth’s climate by using
modeling. These studies will be based on measurements carried out from orbit and from the ground. PICARD
SOL is the ground segment of the PICARD mission to allow a comparison of the solar radius measured in space
and on ground. PICARD SOL will enable to understand the influence of the atmosphere on the measured solar
radius. The PICARD Sol instrumentation consists of: SODISM II, a replica of SODISM (SOlar Diameter
Imager and Surface Mapper), a high resolution imaging telescope, and MISOLFA (Moniteur d’Images SOLaires
Franco-Alg´erien), a seeing monitor. Additional instrumentation consists in a Sun photometer, which measures
atmospheric aerosol properties, a pyranometer to measure the solar irradiance, a visible camera, and a weather
station. PICARD SOL is operating since March 2011. First results from the PICARD SOL mission are briefly
reported in this paper.
The visible tunable filtergraph for the ATST
Show abstract
The Kiepenheuer-Institut will develop for the Advanced Technology Solar Telescope (ATST) a narrowband tunable
filter system (Visible Tunable Filter, VTF) for imaging spectroscopy and spectropolarimetry based on large-format
Fabry Perot interferometers. A major challenge for the realization of this instrument is the development of large-format
Fabry-Perots with a free aperture of about 250 mm. The instrument will operate in the spectral range between 500 and
900 nm with access to a host of magnetically sensitive lines. The instrument is designed to match the diffraction limit of
the 4m-aperture ATST and will be able to observe processes on the sun at spatial scales of 35 km. Its multi-line
capability, together with a field of view of one arc minute, and the ability to measure polarization states of the incoming
light allow to probe different layers of the solar atmosphere within a couple of seconds. The instrument is capable to
vary the spectral sampling, the integration time, and the temporal cadence over a wide range without changing or
compromising the opto-mechanical setup. This versatility gives unique possibilities to apply different measurement
schemes to a variety of science questions. The ATST is a fully funded US project, with the VTF as the only non-US
contribution, and is ready to start construction at the Haleakala summit. The VTF is foreseen as one of the ATST’s firstlight
instruments and should become operational in 2018.
The chromosphere and prominence magnetometer
Show abstract
The Chromosphere and Prominence Magnetometer (ChroMag) is conceived with the goal of quantifying the intertwined dynamics and magnetism of the solar chromosphere and in prominences through imaging spectro- polarimetry of the full solar disk. The picture of chromospheric magnetism and dynamics is rapidly developing, and a pressing need exists for breakthrough observations of chromospheric vector magnetic field measurements at the true lower boundary of the heliospheric system. ChroMag will provide measurements that will enable scientists to study and better understand the energetics of the solar atmosphere, how prominences are formed, how energy is stored in the magnetic field structure of the atmosphere and how it is released during space weather events like flares and coronal mass ejections. An integral part of the ChroMag program is a commitment to develop and provide community access to the "inversion" tools necessary for the difficult interpretation of the measurements and derive the magneto-hydrodynamic parameters of the plasma. Measurements of an instrument like ChroMag provide critical physical context for the Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS) as well as ground-based observatories such as the future Advanced Technology Solar Telescope (ATST).
GREGOR Fabry-Pérot interferometer: status report and prospects
Show abstract
The GREGOR Fabry-P´erot Interferometer (GFPI) is one of three first-light instruments of the German 1.5-meter GREGOR
solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI allows fast narrow-band imaging and post-factum
image restoration. The retrieved physical parameters will be a fundamental building block for understanding the dynamic
Sun and its magnetic field at spatial scales down to 50 km on the solar surface. The GFPI is a tunable dual-etalon system
in a collimated mounting. It is designed for spectropolarimetric observations over the wavelength range from 530–860 nm
with a theoretical spectral resolution of R ≈ 250,000. The GFPI is equipped with a full-Stokes polarimeter. Large-format, high-cadence CCD detectors with powerful computer hard- and software enable the scanning of spectral lines in time spans equivalent to the evolution time of solar features. The field-of-view of 50′′×38′′ covers a significant fraction of the typical area of active regions. We present the main characteristics of the GFPI including advanced and automated calibration and observing procedures. We discuss improvements in the optical design of the instrument and show first observational results. Finally, we lay out first concrete ideas for the integration of a second FPI, the Blue Imaging Solar Spectrometer, which will explore the blue spectral region below 530 nm.
The Large-Scale Polarization Explorer (LSPE)
S. Aiola,
G. Amico,
P. Battaglia,
et al.
Show abstract
The LSPE is a balloon-borne mission aimed at measuring the polarization of the Cosmic Microwave Background (CMB)
at large angular scales, and in particular to constrain the curl component of CMB polarization (B-modes) produced by
tensor perturbations generated during cosmic inflation, in the very early universe. Its primary target is to improve the
limit on the ratio of tensor to scalar perturbations amplitudes down to r = 0.03, at 99.7% confidence. A second target is
to produce wide maps of foreground polarization generated in our Galaxy by synchrotron emission and interstellar dust
emission. These will be important to map Galactic magnetic fields and to study the properties of ionized gas and of
diffuse interstellar dust in our Galaxy. The mission is optimized for large angular scales, with coarse angular resolution
(around 1.5 degrees FWHM), and wide sky coverage (25% of the sky). The payload will fly in a circumpolar long
duration balloon mission during the polar night. Using the Earth as a giant solar shield, the instrument will spin in
azimuth, observing a large fraction of the northern sky. The payload will host two instruments. An array of coherent
polarimeters using cryogenic HEMT amplifiers will survey the sky at 43 and 90 GHz. An array of bolometric
polarimeters, using large throughput multi-mode bolometers and rotating Half Wave Plates (HWP), will survey the same
sky region in three bands at 95, 145 and 245 GHz. The wide frequency coverage will allow optimal control of the
polarized foregrounds, with comparable angular resolution at all frequencies.
NIMBUS: the Near-infrared Multi-Band Ultraprecise Spectroimager for SOFIA
Show abstract
We present a new and innovative near-infrared multi-band ultraprecise spectroimager (NIMBUS) for SOFIA. This design is capable of characterizing a large sample of extrasolar planet atmospheres by measuring elemental and molecular abundances during primary transit and occultation. This wide-field spectroimager would also provide new insights into Trans-Neptunian Objects (TNO), Solar System occultations, brown dwarf atmospheres, carbon chemistry in globular clusters, chemical gradients in nearby galaxies, and galaxy photometric redshifts. NIMBUS would be the premier ultraprecise spectroimager by taking advantage of the SOFIA observatory and state of the art infrared technologies.
This optical design splits the beam into eight separate spectral bandpasses, centered around key molecular bands from 1 to 4μm. Each spectral channel has a wide field of view for simultaneous observations of a reference star that can decorrelate time-variable atmospheric and optical assembly effects, allowing the instrument to achieve ultraprecise calibration for imaging and photometry for a wide variety of astrophysical sources. NIMBUS produces the same data products as a low-resolution integral field spectrograph over a large spectral bandpass, but this design obviates many of the problems that preclude high-precision measurements with traditional slit and integral field spectrographs. This instrument concept is currently not funded for development.
A coherent polarimeter array for the Large Scale Polarization Explorer (LSPE) balloon experiment
Show abstract
We discuss the design and expected performance of STRIP (STRatospheric Italian Polarimeter), an array of coherent receivers designed to fly on board the LSPE (Large Scale Polarization Explorer) balloon experiment. The STRIP focal plane array comprises 49 elements in Q band and 7 elements in W-band using cryogenic HEMT low noise amplifiers and high performance waveguide components. In operation, the array will be cooled to 20 K and placed in the focal plane of a ~0.6 meter telescope providing an angular resolution of ~1.5 degrees. The LSPE experiment aims at large scale, high sensitivity measurements of CMB polarization, with multi-frequency deep measurements to optimize component separation. The STRIP Q-band channel is crucial to accurately measure and remove the synchrotron polarized component, while the W-band channel, together with a bolometric channel at the same frequency, provides a crucial cross-check for systematic effects.
Development of a new calibration method for ground-based Paschen-alpha imaging data
Show abstract
ANIR (Atacama Near InfraRed camera) is a near infrared camera for the University of Tokyo Atacama 1.0m telescope installed at the summit of Co. Chajnantor (5640m altitude) in northern Chile. The high altitude and the extremely low water vapor (precipitable water vapor:PWV=0.5mm) of the site enables us to perform observation of hydrogen Paschen alpha (Paα) emission line at 1.8751 μm. Since the first light observation in June 2009, we have succesfully obtained Paα narrow-band images of Galactic objects and near-by Galaxies. However, as there are many atmospheric absorption features within the wavelength range of the narrow-band filters which vary temporally due to change of PWV, it is difficult to calibrate the emission line flux accurately. Therefore, we have developed a new method to restore Paα emission-line flux from ground-based narrow-band filter imaging observations. First, average atmospheric transmittance within the narrow-band filter is derived using 2MASS stars in a image. Second, PWV is then estimated by comparing the transmittance with that calculated by atmospheric transmittance model software, ATRAN. Finally, the atmospheric transmittance at the wavelength of Paα emission-line is obtained from the model atmosphere corresponding to the obtained PWV. By applying this method to the data of nearby Luminous Infrared Galaxies obtained by ANIR, the emission line strength is estimated within the accuracy of 10% relative to that observed by HST/NICMOS. In this paper, we describe details of the calibration method and its accuracy.
DiffRACT: differential remapped aperture coronagraphic telescope
Show abstract
We propose a new high dynamic imaging concept for the detection and characterization of extra-solar planets. DIFFRACT standing for DIFFerential Remapped Aperture Coronagraphic Telescope, uses a Wollaston prism to split the entrance pupil into two exit pupils. These exit pupils are then remapped with 2 apertures lenses of different diameters resulting in two separate rescaled focal images of the same star. Since the angular separation of a putative exoplanet orbiting around the star is independent of the angular resolution of the remapped output pupils they appear at the same linear location in the resulting images that differ in resolution proportional to the exit pupil sizes.
Exoplanet detection is obtained by numerically rescaling the images at the same angular resolution and substracting them, so that, under aberration and photon noise free conditions the planet twin images appear as two positive and negative Airy patterns. In real conditions however and depending on the exoplanet separation normalized to the angular resolution of the input telescope detection performances depend strongly on the adaptive optics performances and the collecting surface of the telescope. In this study we present the formal expression of DIFFRACT optics concept with a complet set of numerical experiments to
estimate the performances of the concept under real observing conditions including instrument and adaptive optics corrections.
Modified modular imaging system designed for a sounding rocket experiment
Show abstract
We present the design and system calibration results from the fabrication of a charge-coupled device (CCD) based
imaging system designed using a modified modular imager cell (MIC) used in an ultraviolet sounding rocket mission.
The heart of the imaging system is the MIC, which provides the video pre-amplifier circuitry and CCD clock level
filtering. The MIC is designed with standard four-layer FR4 printed circuit board (PCB) with surface mount and
through-hole components for ease of testing and lower fabrication cost. The imager is a 3.5k by 3.5k LBNL p-channel
CCD with enhanced quantum efficiency response in the UV using delta-doping technology at JPL. The recently released
PCIe/104 Small-Cam CCD controller from Astronomical Research Cameras, Inc (ARC) performs readout of the
detector. The PCIe/104 Small-Cam system has the same capabilities as its larger PCI brethren, but in a smaller form
factor, which makes it ideally suited for sub-orbital ballistic missions. The overall control is then accomplished using a
PCIe/104 computer from RTD Embedded Technologies, Inc. The design, fabrication, and testing was done at the
Laboratory for Astronomical and Space Instrumentation (LASI) at Arizona State University. Integration and flight
calibration are to be completed at the University of Colorado Boulder before integration into CHESS.
Posters: ELT Instruments
Key science drivers for MICHI: a mid-IR instrument concept for the TMT
Show abstract
A mid-infrared (MIR) imager and spectrometer is being investigated for possible construction in the early operation of the Thirty Meter Telescope (TMT). Combined with the MIR adaptive optics (AO) system (MIRAO), the instrument will afford ~15 times higher sensitivity and ~4 times better spatial resolution (0.07”) at 10μm compared to 8m-class telescopes. Additionally, through exploiting the large collection area of the TMT, the high-dispersion spectroscopy mode will be unrivaled by other ground- and space-based facilities. These combined capabilities offer the possibility for breakthrough science, as well as ‘workhorse’ observing modes of imaging and low/moderate spectral resolution. In this paper we summarize the primary science drivers that are guiding the instrument design.
Modelling complex phenomena in optical fibres
Show abstract
We
present
a
new
model
for
predicting
the
performance
of
fibre
systems
in
the
multimode
limit.
This
is
based
on
ray-‐tracing
but
includes
a
semi-‐empirical
description
of
Focal
Ratio
Degradation
(FRD).
We
show
how
FRD
is
simulated
by
the
model.
With
this
ability,
it
can
be
used
to
investigate
a
wide
variety
of
phenomena
including
scrambling
and
the
loss
of
light
close
to
the
limiting
numerical
aperture.
It
can
also
be
used
to
predict
the
performance
of
non-‐round
and
asymmetric
fibres.
MANIFEST instrument concept and related technologies
Show abstract
The Australian Astronomical Observatory (AAO) has recently completed a feasibility study for a fiber-positioner facility proposed for the Giant Magellan Telescope (GMT), called MANIFEST (the Many Instrument Fiber System). The MANIFEST instrument takes full advantage of the wide-field focal plane to efficiently feed other instruments. About 2000 individually deployable fiber units are envisaged, with a wide variety of aperture types (single-aperture, image- or pupil-slicing, IFU). MANIFEST allows (a) full use of the GMT's 20' field-of-view, (b) a multiplexed IFU capability, (c) greatly increased spectral resolution via image-slicing, (d) the possibility of OH-suppression in the near-infrared.
Modelling the application of integrated photonic spectrographs to astronomy
R. J. Harris,
J. R. Allington-Smith
Show abstract
One of the well-known problems of producing instruments for Extremely Large Telescopes is that their
size (and hence cost) scales rapidly with telescope aperture. To try to break this relation alternative new
technologies have been proposed, such as the use of the Integrated Photonic Spectrograph (IPS). Due to
their diraction limited nature the IPS is claimed to defeat the harsh scaling law applying to conventional
instruments. The problem with astronomical applications is that unlike conventional photonics, they are not
usually fed by diraction limited sources. This means in order to retain throughput and spatial information
the IPS will require multiple Arrayed Waveguide Gratings (AWGs) and a photonic lantern. We investigate
the implications of these extra components on the size of the instrument. We also investigate the potential
size advantage of using an IPS as opposed to conventional monolithic optics. To do this, we have constructed
toy models of IPS and conventional image sliced spectrographs to calculate the relative instrument sizes and
their requirements in terms of numbers of detector pixels. Using these models we can quantify the relative
size/cost advantage for dierent types of instrument, by varying dierent parameters e.g. multiplex gain and
spectral resolution. This is accompanied by an assessment of the uncertainties in these predictions, which
may prove crucial for the planning of future instrumentation for highly-multiplexed spectroscopy.
Multi-object spectroscopy with the European ELT: scientific synergies between EAGLE and EVE
Show abstract
The EAGLE and EVE Phase A studies for instruments for the European Extremely Large Telescope (E-ELT) originated
from related top-level scientific questions, but employed different (yet complementary) methods to deliver the required
observations. We re-examine the motivations for a multi-object spectrograph (MOS) on the E-ELT and present a unified
set of requirements for a versatile instrument. Such a MOS would exploit the excellent spatial resolution in the near-infrared envisaged for EAGLE, combined with aspects of the spectral coverage and large multiplex of EVE. We briefly
discuss the top-level systems which could satisfy these requirements in a single instrument at one of the Nasmyth foci of
the E-ELT.
Characterizing the red optical sky background fluctuations from narrow-band imaging
Show abstract
The detection and characterization of the physical properties of very distant galaxies will be one the prominent science case of all future Extremely Large Telescopes, including the 39m E-ELT. Multi-Object Spectroscopic instruments are potentially very important tools for studying these objects, and in particular fiber-based concepts. However, detecting and studying such faint and distant sources will require subtraction of the sky background signal (i.e., between OH airglow lines) with an accuracy of 1%. This requires a precise and accurate knowledge of the sky background temporal and spatial fluctuations. Using FORS2 narrow-band filter imaging data, we are currently investigating what are the fluctuations of the sky background at 9000A. We present preliminary results of sky background fluctuations from this study over spatial scales reaching 4 arcmin, as well as first glimpses into the temporal variations of such fluctuations over timescales of the order of the hour. This study (and other complementary on-going studies) will be essential in designing the next-generation fiber-fed instruments for the E-ELT.
Optomechanical design concept for GMACS: a wide-field multi-object moderate resolution optical spectrograph for the Giant Magellan Telescope (GMT)
Show abstract
We describe the conceptual optomechanical design for GMACS, a wide-field, multi-object, moderate-resolution optical
spectrograph for the Giant Magellan Telescope (GMT). GMACS is a candidate first-light instrument for the GMT and
will be one of several instruments housed in the Gregorian Instrument Rotator (GIR) located at the Gregorian focus. The
instrument samples a 9 arcminute x 18 arcminute field of view providing two resolution modes (i.e, low resolution, R ~
2000, and moderate resolution, R ~ 4000) over a 3700 Å to 10200 Å wavelength range. To minimize the size of the
optics, four fold mirrors at the GMT focal plane redirect the full field into four individual "arms", that each comprises a
double spectrograph with a red and blue channel. Hence, each arm samples a 4.5 arcminute x 9 arcminute field of view.
The optical layout naturally leads to three separate optomechanical assemblies: a focal plane assembly, and two identical
optics modules. The focal plane assembly contains the last element of the telescope's wide-field corrector, slit-mask,
tent-mirror assembly, and slit-mask magazine. Each of the two optics modules supports two of the four instrument arms
and houses the aft-optics (i.e. collimators, dichroics, gratings, and cameras). A grating exchange mechanism, and
articulated gratings and cameras facilitate multiple resolution modes. In this paper we describe the details of the
GMACS optomechanical design, including the requirements and considerations leading to the design, mechanism
details, optics mounts, and predicted flexure performance.
Sorption-based vibration-free cooler for the METIS instrument on E-ELT
Show abstract
METIS is the 'Mid-infrared ELT Imager and Spectrograph' for the European Extremely Large Telescope. This E-ELT
instrument will cover the thermal/mid-infrared wavelength range from 3 to 14 μm and will require cryogenic cooling of
detectors and optics. We present a vibration-free cooling technology for this instrument based on sorption coolers
developed at the University of Twente in collaboration with Dutch Space. In the baseline design, the instrument has four
temperature levels: N-band: detector at 8 K and optics at 25 K; L/M-band: detector at 40K and optics at 77 K. The latter
temperature is established by a liquid nitrogen supply with adequate cooling power. The cooling powers required at the
lower three levels are 0.4 W, 1.1 W, and 1.4 W, respectively. The cryogenic cooling technology that we propose uses a
compressor based on the cyclic adsorption and desorption of a working gas on a sorber material such as activated carbon.
Under desorption, a high pressure can be established. When expanding the high-pressure fluid over a flow restriction,
cooling is obtained. The big advantage of this cooling technology is that, apart from passive valves, it contains no
moving parts and, therefore, generates no vibrations. This, obviously, is highly attractive in sensitive, high-performance
optical systems. A further advantage is the high temperature stability down to the mK level. In a Dutch national research
program we aim to develop a cooler demonstrator for METIS. In the paper we will describe our cooler technology and
discuss the developments towards the METIS cooler demonstrator.
Design and development of SWIMS: a near-infrared multi-object spectrograph for the University of Tokyo Atacama Observatory
Show abstract
SWIMS (Simultaneous-color Wide-field Infrared Multi-object Spectrograph) is one of the first-generation instruments
for the University of Tokyo Atacama Observatory (TAO; P.I.: Yuzuru Yoshii) 6.5-m telescope which is
planned to be constructed at the world's highest site, the summit of Cerro Chajnantor (an altitude of 5,640
m or 18,500 ft) in northern Chile. By placing a dichroic mirror into the collimated beam, SWIMS is capable
of wide-field (φ 9'.6 with 0".126 pixel-1) two-color simultaneous imaging as well as multi-object spectroscopy
(MOS) using cooled multi-slit masks covering the entire near-infrared spectra between 0.9 and 2.5 μm in a single
exposure with low-to-medium spectral resolutions. Up to 20 user-defined slit masks as well as long slit masks are
available. The field of view is covered with four 2048 x 2048 pixel HgCdTe focal plane arrays (HAWAII-2RG).
Tests of the MOS slit mask exchanger motions have been completed successfully without any trouble under
cryogenic environment. Further MOS tests will be performed at various tilt and rotation angles of the instrument
using a telescope simulator. Also, a conceptual study of a compact and cryogenic wide-field integral field
spectroscopy unit handled by the slit mask exchanger is now being carried out. The part of the current designs is
optimized for installation on the Subaru Telescope for performance verification and early scientific observations
prior to the construction of the TAO 6.5-m telescope. In this paper, we present the design and development
status of the instrument.
Variation of the near-IR sky continuum background from long-slit spectroscopy
Show abstract
The amplitudes and scales of spatial variations of the sky continuum background can be a potential limit of the telescope performance, because the study of the extremely faint objects requires the subtraction accuracy below 1%. Thus, studying its statistical properties is essential for the design of next generation instruments, especially the fiber-fed instruments, as well as their observation strategies. Using ESO archive data of VLT/FORS2 long-slit observations, we analyzed the auto-correlation function of the sky continuum. As preliminary results, we find that the sky continuum background has multi-scale spatial variations at scales from 2" to 150" with total amplitude of ~0.5%, for an given exposure time of 900s. This can be considered as the upper limit of sky continuum background variation over a field-of-view of few arcmins. The origin of these variations need further studies.
VIENTOS: a feasibility study of innovative pupil systems for the new generation of instruments in the large telescopes
Show abstract
The goal of VIENTOS project is to analyze pupil innovative systems that could be used in the new generation of
instruments for the large telescopes. This study tries to identify the current scientific needs, to understand why some of
them have not been fulfilled yet (due to pre-conceived technical ideas or to managerial reasons) and to propose optomechanical
solutions for these pupil elements that could produce a qualitative leap in the performance of the instruments
to operate in the large telescopes. VIENTOS is currently on-going as a collaborative project between FRACTAL and the
University Complutense of Madrid (UCM) and is being partially funded by a CDTI grant under the program Industry for
Science. CDTI is the Development and Industrial Transfer Center from the Minister of Science and Innovation (Spain).
Among the different innovative systems that we have carried out, our team has explored potential solutions for narrow
band Imaging with tunable filters in the near-IR and a novel pupil system called sliced-pupil grating, a device designed
for increasing the spectral resolution in astronomical spectrographs, without changing the geometry of the main optics.
Nanotechnology customized filters to be applicable to astronomical systems are under study.
Posters: Planet Finders/High Resolution AO Instruments
Conceptual design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) for the Subaru telescope
Show abstract
Recent developments in high-contrast imaging techniques now make possible both imaging and spectroscopy of planets around nearby stars. We present the conceptual design of the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), a lenslet-based, cryogenic integral field spectrograph (IFS) for imaging exo-planets on the Subaru telescope. The IFS will provide spectral information for 140x140 spatial elements over a 1.75 arcsecs x 1.75 arcsecs field of view (FOV). CHARIS will operate in the near infrared (λ = 0.9-2.5μm) and provide a spectral resolution of R = 14, 33, and 65 in three separate observing modes. Taking advantage of the adaptive optics systems and advanced coronagraphs (AO188 and SCExAO) on the Subaru telescope, CHARIS will provide sufficient contrast to obtain spectra of young self-luminous Jupiter-mass exoplanets. CHARIS is in the early design phases and is projected to have first light by the end of 2015. We report here on the current conceptual design of CHARIS and the design challenges.
Very high-resolution spectroscopy: the ESPRESSO optical design
Show abstract
Resolving power of spectrographs for large telescopes is generally limited by the maximum dimension of the dispersion
gratings. To overcome this limit, innovative optical configurations have been designed, starting from the ideas proposed
for CODEX. By properly combining pupil slicing and anamorphic magnification, a R~63’000-210’000 spectrograph has
been designed. Many different solutions were proposed during the early design phases, and a detailed trade off study has
been carried out to improve efficiency, manufacturability, and reduce risks and costs of the preliminary designs. We
present a full description of the optical design of the spectrograph after preliminary design review, together with
expected performances.
The GRAVITY Coudé Infrared Adaptive Optics (CIAO) system for the VLT Interferometer
Show abstract
GRAVITY is a second generation instrument for the VLT Interferometer, designed to enhance the near-infrared
astrometric and spectro-imaging capabilities of VLTI. Combining beams from four telescopes, GRAVITY will
provide an astrometric precision of order 10 micro-arcseconds, imaging resolution of 4 milli-arcseconds, and low
and medium resolution spectro-interferometry, pushing its performance far beyond current infrared interferometric
capabilities. To maximise the performance of GRAVITY, adaptive optics correction will be implemented
at each of the VLT Unit Telescopes to correct for the e_ects of atmospheric turbulence. To achieve this, the
GRAVITY project includes a development programme for four new wavefront sensors (WFS) and NIR-optimized
real time control system. These devices will enable closed-loop adaptive correction at the four Unit Telescopes
in the range 1.4-2.4 μm. This is crucially important for an e_cient adaptive optics implementation in regions
where optically bright references sources are scarce, such as the Galactic Centre. We present here the design of
the GRAVITY wavefront sensors and give an overview of the expected adaptive optics performance under typical
observing conditions. Bene_ting from newly developed SELEX/ESO SAPHIRA electron avalanche photodiode
(eAPD) detectors providing fast readout with low noise in the near-infrared, the AO systems are expected to
achieve residual wavefront errors of 400 nm at an operating frequency of 500 Hz.≤
PlanetCam UPV/EHU: a simultaneous visible and near infrared lucky-imaging camera to study solar system objects
Agustin Sanchez-Lavega,
J. F. Rojas,
R. Hueso,
et al.
Show abstract
PlanetCam is a two-channel camera designed primarily to observe the atmospheres of the planets (Venus, Mars, Jupiter,
Saturn, Uranus and Neptune) and the satellite Titan simultaneously at visible (0.4-1 microns) and NIR (1-2.5 microns)
wavelengths with high temporal and spatial resolution. This is accomplished by means of a dichroic beam splitter that
separates both beams directing them into two different detectors (visible and NIR channels). Each detector has filter
wheels including broad filters and narrow band filters centered in absorption bands characteristic of each planetary
atmosphere. Images are acquired and processed using the "lucky imaging" technique.
NESSI: an optimized Near-Infrared (NIR) Multi-Object Spectrograph (MOS) for exoplanet studies
Show abstract
NESSI: the New Mexico Tech Extra(solar)planet Spectroscopic Survey Instrument is a ground-based multi-object
spectrograph that operates in the near-infrared and is being deployed this fall at the Magdalena Ridge Observatory 2.4 m
telescope. When completed later this year, it is expected to be used to characterize the atmospheres of transiting
exoplanets with unprecedented ground-based accuracies down to about K = 9 magnitude. The superior capabilities of
NEESI for this type of work lay, in part, in the design philosophy used for the instrument which is well-focused on the
exoplanet case. We report here on this design philosophy, detail and status of the design and assembly, and preparation
for first light in the fall of 2012.
Conceptual study for a sub-pupil instrument having 4 high order adaptive optics path for parallel multi-wavelength high contrast imaging, and medium resolution spectrometry
Show abstract
We present the concept of an instrument that will create 4 circular sub-pupils of 3 m in diameter. Each sub-pupil path
will be corrected by a high order adaptive optics system (SR~80% in H) without spider and M2 obstruction. These four
independent channels, obviously all pointed towards the same field, allows the possibility of covering totally different
parts of the electromagnetic spectrum simultaneously without compromising Signal to Noise Ratio. Each channel can be
dedicated to very specialized but complementary purposes: high contrast imaging, pseudo-wide field imaging, high
precision multi-color photometry, medium-resolution spectroscopy, polarimetry and sparse-aperture masking.
An echelle spectrograph for precise radial velocity measurements in the near IR
Show abstract
We present the optical concept and design of a fiber-fed echelle spectrograph for precise radial velocity measurements in the near-infrared. The spectrograph is designed to achieve a nominal resolution λ/Δλ of the order of 40000 and to cover the range from 0.9μm to 1.7μm in a single exposure. This spectrum is to be recorded on a 2048×2048 infrared detector. The instrument is designed to be mounted at 1 to 2 m class telescopes for survey purposes. We present in the optical design and the instrument capability. We do emphasis particularly on optical aberrations and thus discuss the instrument expected limitations from the optical viewpoint.
Progress on multi-object exoplanet search spectral interferometer
Show abstract
It's a very important point that fully open up power of Gou Shoujing telescope (LAMOST) in exoplanet detection field
by developing a multi-exoplanet survey system. But it's an indisputable truth in the present astronomy that a traditional
type of multi-object high resolution spectrograph is almost impossible to be developed. External Dispersed
Interferometry is an effective way to improve the radial velocity measuring accuracy of medium resolution spectrograph.
With the using of this technique, Multi-object Exoplanet Search Spectral Interferometer (MESSI) is an exploratory
system with medium measuring accuracy based on LAMOST low resolution spectrograph works in medium-resolution
mode (R=5,000 - 10,000). And it's believed that will bring some feasible way in the future development of multi-object
medium/high resolution spectrograph. After prototype experiment in 2010, a complete configuration is under the
development, including a multi-object fixed-delay Michelson interferometer, an iodine cell with multi-fiber optical
coupling system and a multi-terminal switching system in an efficient fiber physical coupling way. By some effective
improvement, the interferometer has smaller cross section and more stable interference component. Moreover, based on
physical and optical fiber coupling technique, it's possible for the iodine cell and the switching system to simultaneously
and identically coupling 25 pairs of fibers. In paper, all of the progress is given in detail.
Optical design of new generation compact, high resolution and high Doppler precision optical spectrograph
Show abstract
We report optical design of new generation compact, high resolution, high throughput and high Doppler precision optical
spectrograph. This spectrograph uses cross-dispersed echelle design with white pupils and also takes advantage of a fiber
image slicer to slice one 2 arcsec telescope input fiber image (80 micron at f/4 at the KPNO 2.1 meter telescope) into
four 1 arcsec images (40 micron). The small sliced images coupled with slow optics play a key role in achieving high
spectral resolution within very compact instrument design to substantially reduce construction cost while increasing the
instrument stability for high Doppler precision over a long time. This optical spectrograph is called EXtremely high
Precision ExtrasolaR planet Tracker III (EXPERT-III). The coupling of the fiber sliced images with an R4 echelle with a
98mm diameter pupil produces R=110,000 in the entire optical wavelength region. It also uses a two-prism
cross-disperser to produce nearly homogeneous spectral order coverage while taking advantage of the anamorphic
magnification of the prisms to allow large wavelength coverage (380nm-900nm) in a single exposure with a 4kx4k CCD
detector. This very high resolution mode is designed to reach extremely high Doppler precision for radial velocity
measurements of bright solar type stars. The spectrograph is also directly coupled with an 80 micron telescope fiber-fed
image to obtain high throughput with R=60,000 for stellar spectroscopy. Details about the optical design and
performance are reported.
Optical design of a versatile FIRST high-resolution near-IR spectrograph
Show abstract
We report the update optical design of a versatile FIRST high resolution near IR spectrograph, which is called Florida IR Silicon immersion grating spectromeTer (FIRST). This spectrograph uses cross-dispersed echelle design with white pupils and also takes advantage of the image slicing to increase the spectra resolution, while maintaining the instrument throughput. It is an extremely high dispersion R1.4 (blazed angle of 54.74°) silicon immersion grating with a 49 mm diameter pupil is used as the main disperser at 1.4μm -1.8μm to produce R=72,000 while an R4 echelle with the same pupil diameter produces R=60,000 at 0.8μm -1.35μm. Two cryogenic Volume Phase Holographic (VPH) gratings are used as cross-dispersers to allow simultaneous wavelength coverage of 0.8μm -1.8μm. The butterfly mirrors and dichroic beamsplitters make a compact folding system to record these two wavelength bands with a 2kx2k H2RG array in a single exposure. By inserting a mirror before the grating disperser (the SIG and the echelle), this spectrograph becomes a very efficient integral field 3-D imaging spectrograph with R=2,000-4,000 at 0.8μm-1.8μm by coupling a 10x10 telescope fiber bundle with the spectrograph. Details about the optical design and performance are reported.
The SED Machine: a dedicated transient IFU spectrograph
Show abstract
The Spectral Energy Distribution (SED) Machine is an Integral Field Unit (IFU) spectrograph designed specifically to classify transients. It is comprised of two subsystems. A lenselet based IFU, with a 26" × 26" Field of View (FoV) and ∼ 0.75" spaxels feeds a constant resolution (R∼100) triple-prism. The dispersed rays are than imaged onto an off-the-shelf CCD detector. The second subsystem, the Rainbow Camera (RC), is a 4-band seeing-limited imager with a 12.5' × 12.5' FoV around the IFU that will allow real time spectrophotometric calibrations with a ∼ 5% accuracy. Data from both subsystems will be processed in real time using a dedicated reduction pipeline. The SED Machine will be mounted on the Palomar 60-inch robotic telescope (P60), covers a wavelength range of 370 − 920nm at high throughput and will classify transients from on-going and future surveys at a high rate. This will provide good statistics for common types of transients, and a better ability to discover and study rare and exotic ones. We present the science cases, optical design, and data reduction strategy of the SED Machine. The SED machine is currently being constructed at the Calofornia Institute of Technology, and will be comissioned on the spring of 2013.
Simulations of a near-infrared precision radial velocity spectrograph for finding planets around M dwarfs
Show abstract
We describe the development of a software simulator to support development of the Habitable Zone Planet Finder
Spectrograph (HPF), currently being designed to search for planets around M dwarf stars. HPF is a near infrared
R 50,000 cross-dispersed radial velocity spectrograph using a HAWAII-2 RG (H2RG) NIR array, is cooled to
200K, is fiber-fed, and operates in the Y and J bands. This instrument is funded and is in the design phase,
and will be commissioned on the 10m Hobby-Eberly Telescope in 2015. Our simulations process high-resolution
stellar spectra through models of the instrument, detector, and a simple extraction pipeline. Our objective is to
create a a fully functional simulation of the entire HPF system, which can be used to guide spectrograph design
and to aid in observation planning. We describe the fundamental design of these simulations and the tests we
have performed, which verify that the simulator code is stable with inclusion of simple detector effects, and is
ready for expansion to account for more complex factors such as order curvature.
KiwiSpec - an advanced spectrograph for high resolution spectroscopy: optical design and variations
Show abstract
The KiwiSpec R4-100 is an advanced high resolution spectrograph developed by KiwiStar Optics, Industrial
Research Ltd, New Zealand. The instrument is based around an R4 echelle grating and a 100mm collimated beam
diameter. The optical design employs a highly asymmetric white pupil design, whereby the transfer collimator
has a focal length only 1/3 that of the primary collimator. This allows the cross-dispersers (VPH gratings) and
camera optics to be small and low cost while also ensuring a very compact instrument. The KiwiSpec instrument
will be bre-fed and is designed to be contained in both thermal and/or vacuum enclosures. The instrument
concept is highly
exible in order to ensure that the same basic design can be used for a wide variety of science
cases. Options include the possibility of splitting the wavelength coverage into 2 to 4 separate channels allowing
each channel to be highly optimized for maximum eciency. CCDs ranging from smaller than 2K2K to larger
than 4K4K can be accommodated. This allows good (3-4 pixel) sampling of resolving powers ranging from
below 50,000 to greater than 100,000. Among the specic design options presented here will be a two-channel
concept optimized for precision radial velocities, and a four-channel concept developed for the Gemini High-
Resolution Optical Spectrograph (GHOST). The design and performance of a single-channel prototype will be
presented elsewhere in these proceedings.
Experimental results on wavefront correction using the self-coherent camera
Show abstract
The Self-Coherent Camera is dedicated to the direct detection of exoplanets. This instrument can be used as a focal plane wavefront sensor to measure static aberrations that induce speckles on the detector, which prevents the detection of faint companions. The Self-Coherent Camera creates a reference beam in the Lyot stop pupil plane in order to spatially modulate the speckle pattern with Fizeau fringes. We can then estimate for wavefront aberrations upstream of the coronagraphic mask and correct for them using a deformable mirror. Currently, the Self-Coherent Camera is combined with a deformable mirror located in the pupil plane upstream of a Four-Quadrant Phase Mask Coronagraph. In this paper, we present the formalism that explains how the Self-Coherent Camera encodes speckles and how we estimate the wavefront aberrations directly from the science image. We present numerical simulation results on speckle suppression in the focal plane. Then, we give experimental results on wavefront correction on our optical bench using a 32x32 actuators deformable mirror. We show that we can improve the contrast in the focal plane by a factor of more than 100 in the PSF wings up to 12/λD.
Buckling failure of the automated planet finder spectrometer determinate spaceframe
Show abstract
The Ken and Gloria Levy Spectrometer is now operational at a new 2.4 meter telescope on Mt. Hamilton. Together the
spectrometer and telescope comprise the Automated Planet Finder (APF), a radial velocity instrument. A catastrophic
failure occurred during transit as the instrument was being shipped to the observatory. Several struts buckled in the space
frame that supported the echelle grating. This event has caused UCO/Lick to re-evaluate design methodology and how
engineering safety factors apply to this type of structure. This paper describes the shipping container design, events
during shipment, the failure mechanism, testing and analysis of a remedy, and its implementation. We also suggest
design changes to prevent similar failures in the future.
Coronagraphic focal plane wave-front estimation for exoplanet detection : application to the Roddier & Roddier coronagraph
Show abstract
The final performance of current and future instruments dedicated to exoplanet detection and characterisation (such as SPHERE on the VLT, GPI on Gemini North or EPICS on E-ELT) 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 are the quasi-static aberrations introduced upstream of the coronagraphic mask. In order to reach the final detectivity, these aberrations have to be estimated and compensated for. Some of these aberrations are not seen by the wave-front sensor of the AO loop but only by the scientific instruments. In order to measure and compensate for these aberrations, we have recently proposed a dedicated focal-plane sensor called COFFEE (for COronagraphic Focal-plane wave-Front Estimation for Exoplanet detection), based on an analytical model for coronagraphic imaging. In this communication, we first present a thorough characterisation of COFFEE’s performance, by means of numerical simulations. We additionally present an experimental validation of COFFEE for low orders aberrations using an in-house Adaptive Optics Bench and an apodized Roddier and Roddier phase mask coronagraph.
Dark hole and planet detection: laboratory results using the self-coherent camera
Show abstract
Direct imaging and low-resolution spectroscopy of extrasolar planets are exciting but challenging scientific applications of coronagraphy. While the angular separation is well within the reach of actual telescope in the
near IR or visible, the planet-star contrast (from 10−6 to 10−10) requires wavefront quality and stability hard to reach even with a well-polished space telescope. Several solutions have been proposed to tackle the speckle noise introduced by the residual optical defects. While some concepts rely only on active wavefront correction
using deformable mirror, other techniques are based on post-processing and subtract a reference image recorded
sometimes simultaneously with the science image. One interesting solution is to choose a concept that allows
both active correction and post-processing of high contrast coronagraphic images. This is the case of the Self
Coherent Camera (SCC), which has been proposed for the project of space coronagraph SPICES and for the
ground-based planet finder EPICS studied for the European Extremely Large Telescope. After recalling the SCC
principle, we present both monochromatic and modest bandwidth (2%) experimental results of Dark Hole in the
focal plane using a SCC. Example of a post-processing result with SCC is also given to emphasize the interest
of combining it with active correction.
Laboratory test of a polarimetry imaging subtraction system for the high-contrast imaging
Show abstract
We propose a polarimetry imaging subtraction test system that can be used for the direct imaging of the reflected light
from exoplanets. Such a system will be able to remove the speckle noise scattered by the wave-front error and thus can
enhance the high-contrast imaging. In this system, we use a Wollaston Prism (WP) to divide the incoming light into two
simultaneous images with perpendicular linear polarizations. One of the images is used as the reference image. Then
both the phase and geometric distortion corrections have been performed on the other image. The corrected image is
subtracted with the reference image to remove the speckles. The whole procedure is based on an optimization algorithm
and the target function is to minimize the residual speckles after subtraction. For demonstration purpose, here we only
use a circular pupil in the test without integrating of our apodized-pupil coronagraph. It is shown that best result can be
gained by inducing both phase and distortion corrections. Finally, it has reached an extra contrast gain of 50-times
improvement in average, which is promising to be used for the direct imaging of exoplanets.
A passive cost-effective solution for the high accuracy wavelength calibration of radial velocity spectrographs
Show abstract
Today, the RV technique has pushed the planet detection limits down to super-earths but the reach the precision
required to detect earth-like planets it is necessary to reach a precision around 1cm s-1. While a significant part of
the error budget is the incompressible photon noise, another part is the noise in the wavelength calibration of the
spectrograph. In the past 3 years the Observatory of Geneva has designed, built and tested an commissioned 2
wavelength calibrator systems based on a Fabry-Perot (FP) interferometer with great success. The calibrator
system demonstrated 10 cm s-1 stability over one night and 1 m s-1 over 60 days. By improving the system injecting
the calibration light into the calibration fiber of the spectrograph we are aiming at 1 m s-1 repeatability over the
long term. This technique is now being extended to cover the near infrared to the K band in the frame of the
SPIROU project.
Near-infrared calibration systems for precise radial-velocity measurements
Show abstract
We present work done to prepare two new near-infrared calibration sources for use on high-precision astrophysical
spectrographs. Uranium-neon is an atomic calibration source, commercially available as a hollow-cathode lamp,
with over 10 000 known emission lines between 0.85 and 4 μm. Four gas cells — containing C2H2, H13CN, 12CO, and 13CO, respectively—are available as National Institute of Standards and Technology (nist) Standard Reference Materials (SRMs), and provide narrow absorption lines between 1.5 and 1.65 μm. These calibration sources may prove useful for wavelength-calibrating the future near-infrared high-precision radial-velocity spectrometers, including the Calar Alto high-Resolution search for M dwarfs with Exo-earths with a Near-infrared Echelle Spectrograph (CARMENES),1 the SpectroPolarimetre InfraROUge (SPIRou)∗, and the Habitable-Zone Planet Finder (HPF).2
Development of the Savart-plate lateral-shearing interferometric nuller for exoplanet (SPLINE)
Show abstract
The Savart-Plate Lateral-shearing Interferometric Nuller for Exoplanet (SPLINE) is a stable and fully achromatic nulling
interferometer proposed for direct detection of extrasolar planets with segmented-mirror telescopes like the Thirty Meter
Telescope (TMT). The SPLINE uses a Savart plate, a kind of polarizing beam splitter, to split a light beam into two
orthogonally polarized ones with a lateral shift. The Savart plate placed between crossed polarizers causes fully
achromatic destructive interference for an on-axis star light. On the other hand, planetary light from an off-axis direction
does not destructively interfere due to the lateral shift. The SPLINE provides a stable interferometric output because of
its simple common-path optical design without an optical-path difference control system. We carried out laboratory
demonstrations of the SPLINE to evaluate its stability, achromaticity, and achievable contrast. As a result, a high
contrast of >104 (peak-to-peak contrast) is achieved using a broadband light source as a star model. In addition, we also
propose to apply a differential imaging technique to the SPLINE for improving achievable contrast. We report our recent
activities and show the results of the laboratory demonstrations.
A slitless spectrograph for observing transient events with
small telescopes
Show abstract
A slitless UBVR spectrograph was designed and built to be used on small telescopes. Tests and observations with this
instrument attached to the 60-cm telescope have shown that it is an effective tool for the study of transient events. A
number of features have been incorporated into the construction of the configuration to optimize its operations and data
processing. It is capable of registering the continuous spectrum in the wavelength range 3500 – 9000 Å. The wavelength
scale after calibration is accurate to about 30 Å. The grating spectrum has a resolution of R ≈ 100 around 4800 Å. The
spectrograph provides a moderate signal-to-noise ratio for stars up to magnitude 16. Equivalent widths of non blended
lines can be measured down to 0.7 Å. To identify intrinsic activity in spectra, a special software based on the theory of
count statistics was developed; it is enabling us to detect the relative power of fluctuations down to (10-5 – 10-6).
Observational data obtained with the aid of the spectrograph made it possible to discover new fine-scale features and
flare-triggered phenomena in flaring red dwarfs, as well as a low-amplitude rapid variability in spectra of
chromospherically active stars.
Optical fiber modal noise in the 0.8 to 1.5 micron region and implications for near infrared precision radial velocity measurements
Show abstract
Modal noise in fibers has been shown to limit the signal-to-noise ratio achievable in fiber-coupled, high-resolution
spectrographs if it is not mitigated via modal scrambling techniques. Modal noise become significantly more important
as the wavelength increases and presents a risk to the new generation of near-infrared precision radial spectrographs
under construction or being proposed to search for planets around cool M-dwarf stars, which emit most of their light in
the NIR. We present experimental results of tests at Penn State University characterizing modal noise in the far visible
out to 1.5 microns and the degree of modal scrambling we obtained using mechanical scramblers. These efforts are part
of a risk mitigation effort for the Habitable Zone Planet Finder spectrograph currently under development at Penn State
University.
A diamond AGPM coronagraph for VISIR
Show abstract
In recent years, phase mask coronagraphy has become increasingly efficient in imaging the close environment of stars,
enabling the search for exoplanets and circumstellar disks. Coronagraphs are ideally suited instruments, characterized by
high dynamic range imaging capabilities, while preserving a small inner working angle. The AGPM (Annular Groove
Phase Mask, Mawet et al. 20051) consists of a vector vortex induced by a rotationally symmetric subwavelength grating. This technique constitutes an almost unique solution to the achromatization at longer wavelengths (mid-infrared). For this reason, we have specially conceived a mid-infrared AGPM coronagraph for the forthcoming upgrade of VISIR, the
mid-IR imager and spectrograph on the VLT at ESO (Paranal), in collaboration with members of the VISIR consortium.
The implementation phase of the VISIR Upgrade Project is foreseen for May-August 2012, and the AGPM installed will
cover the 11-13.2 μm spectral range. In this paper, we present the entire fabrication process of our AGPM imprinted on a
diamond substrate. Diamond is an ideal material for mid-infrared wavelengths owing to its high transparency, small
dispersion, extremely low thermal expansion and outstanding mechanical and chemical properties. The design process
has been performed with an algorithm based on the rigorous coupled wave analysis (RCWA), and the micro-fabrication
has been carried out using nano-imprint lithography and reactive ion etching. A precise grating profile metrology has
also been conducted using cleaving techniques. Finally, we show the deposit of fiducials (i.e. centering marks) with
Aerosol Jet Printing (AJP). We conclude with the ultimate coronagraph expected performances.
The IFS of SPHERE: integration and laboratory performances
Show abstract
SPHERE is an exo-solar planet imager, which goal is to detect giant exo-solar 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, 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) Y,
J, H and Ks bands (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) which works in the near IR (0.95≤λ≤1.6 μm), an ideal wavelength range for
the detection of planetary features. The IFS is based on a new conception microlens array (BIGRE) of 145X145 lenslets
designed to reduce as low as possible the contrast. The IFU will cover a field of view of about 1.7 x 1.7 square arcsecs
reaching a contrast of 10-7, giving an high contrast and high spatial resolution "imager" able to search for planet well
inside the star PSF. In the last year it has been integrated onto the huge optical bench of SPHERE and fully tested.
Calibration of an echelle spectrograph with an astro-comb: a laser frequency comb with very high repetition rate
Show abstract
Searches for extrasolar planets using precision radial velocity (PRV) techniques are approaching Earth-like planet sensitivity, however require an improvement of one order of magnitude to identify earth-mass planets in the habitable zone of sun-like stars. A key limitation is spectrograph calibration. An astro-comb, an octave-spanning laser frequency comb and a Fabry-Pérot cavity, producing evenly spaced frequencies with large wavelength coverage, is a promising tool for improved wavelength calibration. We demonstrate the calibration of a high-resolution astrophysical spectrograph below the 1 m/s level in the 8000-9000 Å and 4200 Å spectral bands.
Development of a new, precise near-infrared Doppler
wavelength reference: a fiber Fabry-Perot interferometer
Show abstract
We present performance reports of a new near-infrared (NIR) Fiber-Fabry Perot Interferometer (FFP) as a precise Doppler radial velocity (RV) wavelength reference.
FFPs are monolithic single-mode fiber devices that create emission spectra by interfering light traversing separate delay paths. The resulting interference spectrum provides a rich distribution of narrow lines, ideal for use as a precise spectrograph reference. The FFP has the advantages that the uniform density of emission lines gives a much wider bandwidth over which RV measurements are possible, and the finesse and bandwidth can be optimized for the specific application.
Design and performance of a new generation, compact, low cost, very high Doppler precision and resolution optical spectrograph
Show abstract
This paper is to report the design and performance of a very high Doppler precision cross-dispersed
echelle spectrograph, EXtremely high Precision ExtrasolaR planet Tracker III (EXPERT-III), as part of a
global Exoplanet Tracker (ET) network. The ET network is designed to hunt low mass planets, especially
habitable rocky planets, around GKM dwarfs. It has an extremely high spectral resolution (EHR) mode of
R=110,000 and a high resolution (HR) mode of R=56,000 and can simultaneously cover 0.38-0.9 μm
with a 4kx4k back-illuminated Fairchild CCD detector with a single exposure. EXPERT-III is optimized
for high throughput by using two-prisms cross-disperser and a large core diameter fiber (2 arcsec on sky,
or 80 μm at f/4) to collect photons from the Kitt Peak National Observatory (KPNO) 2.1m telescope. The
average overall detection efficiency is ~6% from above the atmosphere to the detector for the EHR Mode
and about 11% for the HR mode. The extremely high spectral resolution in a compact design (the
spectrograph dimension, 1.34x0.8x0.48 m) is realized by coupling the single input 80 μm telescope fiber
into four 40 μm fibers and re-arranging the four small core diameter fibers into a linear fiber slit array (a
one-to-four fiber image slicer). EXPERT-III is operated in a vacuum chamber with temperature controlled
to ~2 milli-Kelvin rms for an extended period of time. The radial velocity (RV) drift is controlled to
within 10 meters/second (m/s) over a month. EXPERT-III can reach a photon noise limited RV
measurement precision of ~0.3 m/s for a V=8 mag GKM type dwarf with small rotation (vsini =2 km/s) in
a 15 min exposure. EXPERT-III’s RV measurement uncertainties for bright stars are primarily limited by
the Thorium-Argon (ThAr) calibration source (~0.5 m/s). EXPERT-III will serve as an excellent public
accessible high resolution optical spectroscope facility at the KPNO 2.1m telescope.
Extreme Doppler precision with octagonal fiber scramblers
Show abstract
The detection of Earth analogs with radial velocity requires long-term precision of 10 cm/s. One of the factors
limiting precision is variation in instrumental profile from observation to observation due to changes in the
illumination of the slit and spectrograph optics. Fiber optics are naturally efficient scramblers. Our research is
focused on understanding the scrambling properties of fibers with different geometries. We have characterized
circular and octagonal fibers in terms of focal ratio degradation, near-field and far-field distributions. We have
characterized these fibers using a bench-mounted high-resolution spectrograph: the Yale Doppler Diagnostics
Facility (YDDF).
Stop-less Lyot coronagraph for exoplanet characterization
Show abstract
The characterization of directly-imaged exoplanets at very small angular separations requires high-contrast spec-troscopic capabilities. For this purpose, the new generation of instruments dedicated to direct imaging of massive exoplanets at large orbital radii, such as VLT/SPHERE and Gemini/GPI, includes integral field spectroscopy (IFS) and/or long slit spectroscopy (LSS) coupled with coronography. LSS is particularly challenging since observations will be stronly limited by quasi-static speckles and diffraction residuals that need to be removed with a posteriori data analysis methods. It is therefore necessary to limit as much as possible the influence of diffraction in the data. In this work we compare the use of the classical Lyot coronagraph (CLC) and the stop- less Lyot coronagraph (SLLC) with LSS for the characterization of exoplanets. SLLC uses a grey apodization to suppress the diffraction above 4.53 λ/D and does not require the use of any Lyot stop, offering a convenient implementation. We show that this apodized long slit spectroscopy (ALSS) improves notably the performance at small angular separations (0.3"-0.4"), allowing the spectral analysis of colder planets.
Performance of the integral field spectrograph for the Gemini Planet Imager
Show abstract
We present performance results, from in-lab testing, of the Integral Field Spectrograph (IFS) for the Gemini Planet Imager (GPI). GPI is a facility class instrument for the Gemini Observatory with the primary goal of directly detecting young Jovian planets. The GPI IFS is based on concepts from the OSIRIS instrument at Keck and utilizes an infrared transmissive lenslet array to sample a rectangular 2.8 x 2.8 arcsecond field of view. The IFS provides low-resolution spectra across five bands between 1 and 2.5μm. Alternatively, the dispersing element can be replaced with a Wollaston prism to provide broadband polarimetry across the same five filter bands. The IFS construction was based at the University of California, Los Angeles in collaboration with the Université de Montr eal, Immervision and Lawrence Livermore National Laboratory. During its construction, we encountered an unusual noise source from microphonic pickup by the Hawaii-2RG detector. We describe this noise and how we eliminated it through vibration isolation. The IFS has passed its preship review and was shipped to University of California, Santa Cruz at the end of 2011 for integration with the remaining sub-systems of GPI. The IFS has been integrated with the rest of GPI and is delivering high quality spectral datacubes of GPI's coronagraphic field.
Green astro-comb for HARPS-N
Show abstract
Searches for Earth-like exoplanets using the stellar radial velocity measurements require accuracy <10 cm/s over years.
To achieve such high accuracy requires a wavelength reference that provides many calibration lines with fractional
frequency accuracy of 10-10 in the visible spectral range. We have developed a green astro-comb that generates ~6000 lines equally spaced by ~0.15 Å over 1000-Å bandwidth (centered at 5500 Å). The frequency of each line is directly locked to a frequency standard with fractional accuracy of 10-12 over decades. We plan to bring this green astro-comb to the HARPS-north spectrograph at the TNG telescope for tests in 2012.
Tests of the demodulating CCDs for the SPHERE / ZIMPOL imaging polarimeter
Show abstract
The imaging polarimeter ZIMPOL is one of three focal plane instruments of the SPHERE / VLT planet finder. ZIMPOL
measures the linear polarization based on a fast modulation – demodulation principle using a charge-shifting technique
on a masked CCD for separating the photons with opposite polarization direction. This paper describes the on-chip
demodulation and the different detector read-out modes which are implemented for the ZIMPOL polarimeter. Test
results are presented which allow an evaluation of the performance of the ZIMPOL CCD detectors. The achievable
polarization efficiency is close to expectation and the charge trap correction with the two-phase demodulation mode
works well. Other detector effects like bias level variations and read-out patterns can be corrected in the data reduction
process. The tests demonstrate that the demodulating CCDs fulfill the requirements for the SPHERE project.
Fiber scrambling for precise radial velocities at Lick and Keck Observatories
Show abstract
The detection of Earth analogs with radial velocity requires extreme Doppler precision and long term stability.
Variations in the illumination of the slit and of the spectrograph optics occur on time scales of seconds and
minutes, primarily because of guiding, seeing and focusing. These variations yield differences in the instrumental
profile (IP). In order to stabilize the IP, we designed a fiber feed for the Hamilton spectrograph at Lick and for
HIRES at Keck. Here, we report all results obtained with these fiber scramblers. We also present the design of
a new double scrambler/pupil slicer for HIRES at Keck.
Polarimetric performance of the Gemini Planet Imager
Show abstract
We report on preliminary results from laboratory calibration of the Gemini Planet Imager (GPI) polarimetry mode. Utilizing a linear polarizer and a quarterwave plate in a telescope simulator testbed, we inject a set of 15 Stokes states into GPI that sample the Poincaré sphere. Calibration of the known and measured Stokes parameters allows us to determine the Mueller matrix of the instrument, from which we find that crosstalk from Stokes I to (Q,U) is < 1.5%. This is well within the acceptance test plan requirement that instrumental linear polarization be. However, instrumental circular polarization is 15%. Further testing is needed to identify the source of the significant circular polarization in the system to mitigate its effect on data quality. We find the instrument is sensitive enough to identify stress birefringence of the last lens in the telescope simulator testbed, and we measure it to have a retardance of 0.030 waves.
A testbed for simultaneous measurement of fiber near and far-field for the evaluation of fiber scrambling properties
Show abstract
To improve our understanding of fiber scrambling properties a test bed where fiber near-field and far-field can be measured simultaneously is described. A variety of measurements has been conducted with a selection of fibers from different vendors, including state-of-the-art octagonal and hexagonal fibers. After characterization of the test bench with respect to stability and resolution, scrambling measurements have been conducted using LEDs with central wavelengths ranging between 465-635 nm. The dependence on wavelength regarding to photometrical scrambling has been initially demonstrated. Moreover, two mechanical combined fiber cables have been analyzed that were made from octagonal-circular and hexagonal-octagonal fiber sections. In this context an apparatus for focal ratio degradation (FRD) measurements was assembled to compare different shaped fibers and fiber combinations. Finally, all these preliminary investigations will help in choosing a fiber with good radial scrambling performance for the next generation fiber-link of the fiber optic coupled Cassegrain echelle spectrograph FOCES intended to be operated at the 2.0m Fraunhofer Telescope at the Wendelstein Observatory.
SPHERE / ZIMPOL: characterization of the FLC polarization modulator
Show abstract
ZIMPOL is an imaging polarimeter for the high-contrast SPHERE/VLT "planet finder" instrument using fast
polarization modulation and demodulating CCD detectors. The polarimetric performance of the ZIMPOL instrument
depends on the polarimetric alignment and quality of the polarization components. This paper gives an overview on the
polarimetric concept and the calibration plan of ZIMPOL. We discuss in particular the alignment of the polarimetric
calibration components and the polarimetric properties of the ferro-electric liquid crystal (FLC) modulator package used
in ZIMPOL. Our measurements demonstrate the good broad-band performance of the modulator. Faint targets, like
extra-solar planets, require mainly a high polarimetric efficiency while for detailed studies of bright targets a good
characterization of the modulator package is essential. Therefore we quantify in detail the wavelength dependence of the
polarimetric efficiency and the cross-talk effects which have to be taken into account in the calibration and data
reduction process of high S/N measurements.
Two Fabry-Perot interferometers for high precision wavelength calibration in the near-infrared
Show abstract
The most frequently used standard light sources for spectroscopic high precision wavelength calibration are
hollow cathode lamps. These lamps, however, do not provide homogeneous line distribution and intensities.
Particularly in the infrared, the number of useful lines is severely limited and the spectrum is contaminated by
lines of the filler gas. With the goal of achieving sub m/s stability in the infrared, as required for detecting
earthlike extra-solar planets, we are developing two passively stabilized Fabry-Perot interferometers for the red
visible (600-1050nm) and near infrared wavelength regions (900-1350nm). Each of the two interferometers can
produce ~15,000 lines of nearly constant brightness. The Fabry-Perot interferometers aim at a RV calibration
precision of 10cm/s and are optimized in line shape and spacing for the infrared planet hunting CARMENES
spectrograph that is currently being built for the Calar Alto 3.5m telescope. Here we present the first results of
our work.
Investigating spectrograph design parameters with the Yale Doppler diagnostic facility
Show abstract
The detection of earth-like exoplanets with the Doppler technique requires extreme precision spectrographs stable over
timescales of years. The precision requirement of 10 cm/s is equivalent to a relative uncertainty of 3x10-10, and, with the typical dispersion of the Echelle spectrographs used for this purpose, translates to a shift of a few nanometers of the spectrum on the detector. Consequently, the instrument must be well understood and optimized in every component and detail. We describe the Yale Doppler diagnostic facility (YDDF), a dedicated bench mounted Echelle spectrograph in
our lab at Yale University, which will be used to systematically study the influence of different components at this
precision level. The spectrograph bench allows for a flexible optical configuration, high resolution and sampling, and
wide spectral coverage. Further, we incorporated a turbulence and guiding simulator to realistically reproduce the
situation at the telescope, enabling end-to-end tests of important parameters.
High-resolution Fourier transform spectrograph for characterization of echelle spectrograph wavelength calibrators
Show abstract
Wavelength calibrators are a critical component of high precision and accuracy radial velocity measurements. An order of magnitude improvement of the state-of-the-art of calibration of echelle spectrographs is amongst the requirements needed to achieve detection of earth-mass planets around sun-like stars in the habitable zone. We present studies of calibrators using a custom Fourier Transform Spectrograph (FTS) optimized for characterizing broadband, high repetition-rate laser frequency combs ("astro-combs") as well as other calibration sources including Th:Ar lamps and white-light etalons.
Alignment of the SPHERE-ZIMPOL imaging polarimeter
Show abstract
ZIMPOL is the high contrast imaging polarimeter subsystem of the ESO SPHERE instrument. ZIMPOL is dedicated to
detect the very faint reflected and hence polarized visible light from extrasolar planets. ZIMPOL is located behind an
extreme AO system (SAXO) and a stellar coronagraph. SPHERE is foreseen to have first light at the VLT early 2013.
ZIMPOL is currently integrated in the SPHERE system and in testing phase.
We describe the alignment strategy and the results of the ZIMPOL system and the related alignment of ZIMPOL into
SPHERE by the aid of an alignment unit. The field selecting tip/tilt mirror alignment and it’s requirement for
perpendicularity to the two detectors is described. The test setup of the polarimetric components is described.
SPHERE is an instrument designed and built by a consortium consisting of IPAG, MPIA, LAM, LESIA, Fizeau, INAF,
Observatoire de Genève, ETH, NOVA, ONERA and ASTRON in collaboration with ESO.
SPHERE-IRDIS assembly, integration and testing: from bits and metal to a planet-hunting machine
Show abstract
SPHERE, a second-generation instrument for the VLT, is currently under performance validation before shipping to
Chile. The IRDIS sub-system, an Infra-Red Dual-Imager and Spectrograph, was integrated on the SPHERE bench last
December, and this paper tells the story of the 12 months preceding this milestone: the Assembly, integration and Tests
(AIT) performed at Laboratoire d'Astrophysique de Marseille (LAM). Key points of the AIT strategy are then presented,
and the successes and failures---human, technical, and managerial---of this adventure are discussed. We also report on
the excellent optical quality achieved, paramount to guarantee ultimate performance of the SPHERE instrument, thanks
to high-quality optical manufacture and a successfully applied alignment strategy.
First laboratory results of SPHERE/IRDIS dual-band imaging and long slit spectroscopy modes
Show abstract
IRDIS is one of the science sub-systems of VLT/SPHERE dedicated to the detection and characterization of giant exoplanets at large orbital radii with high-contrast direct imaging. It offers a unique set of observational modes including dual-band imaging (DBI) with very low differential aberrations, and long slit spectroscopy (LSS) coupled with a classical Lyot coronograph that will be used to obtain spectra at low (R = ~50) and medium (R = ~500) resolution. During the past year, IRDIS has been integrated and tested in laboratory in a standalone configuration, and it has recently been integrated on the full SPHERE bench including the calibration unit, the common path optics and the extreme AO system. We present the first analysis of data obtained during laboratory tests of IRDIS in the DBI mode, both in standalone and with the full SPHERE bench, but without simulated seeing and AO correction. We show the first performance estimates of spectral differential imaging with IRDIS in H-band, which is used to attenuate the speckle noise induced by the instrumental aberrations. Similarly, for the LSS mode we present the first application of the spectral deconvolution data analysis method to attenuate the speckle noise on IRDIS data. Finally we compare these results to simulations that were performed during the development phase of the instrument.
Scientific design of a high contrast integral field spectrograph for the Subaru Telescope
Show abstract
Ground-based telescopes equipped with adaptive-optics (AO) systems and specialized science cameras are now capable of directly detecting extrasolar planets. We present the expected scientific capabilities of CHARIS, the Coronagraphic High Angular Resolution Imaging Spectrograph, which is being built for the Subaru 8.2 m telescope of the National Astronomical Observatory of Japan. CHARIS will be implemented behind the new extreme adaptive optics system at Subaru, SCExAO, and the existing 188-actuator system AO188. CHARIS will offer three observing modes over near-infrared wavelengths from 0.9 to 2.4 μm (the y-, J-, H-, and K-bands), including a low-spectral-resolution mode covering this entire wavelength range and a high-resolution mode within a single band. With these capabilities, CHARIS will offer exceptional sensitivity for discovering giant exoplanets, and will enable detailed characterization of their atmospheres. CHARIS, the only planned high-contrast integral field spectrograph on an 8m-class telescope in the Northern Hemisphere, will complement the similar instruments such as Project 1640 at Palomar, and GPI and SPHERE in Chile.
ESPRESSO front end opto-mechanical configuration
Show abstract
This paper presents the Espresso Front End mechanical and optical conguration. ESPRESSO, Echelle SPectro-graph for Rocky Exoplanets and Stable Spectroscopic Observations, will combine the efficiency of modern echelle
spectrograph design with extreme radial-velocity precision. It will be installed on ESO's VLT and it is expected
to achieve a gain of two magnitudes with respect to its predecessor HARPS. The instrumental radial-velocity
precision will also be improved to reach cm/s level. The Front End is a modular subsystem that collects the
light coming from the Coude Trains of all the Four Telescope Units (UT), provides Field and Pupil stabilization
via piezoelectric tip tilt devices and inject the beam into the Spectrograph fiber. The Front End will also inject
the calibration light coming from the calibration unit. There will be four Front End modules, one per UT.
A rotary Stage will provide the toggling between different observation mode: Single UT Ultra High resolution
(SUT-UHR), Single UT High resolution (SUT-HR) and multiple UTS Mid Rsolution (MUT-MR). The field and
pupil guiding is obtained through a reimaging system that elaborates the halo of the light out of the Injection
Fiber and a telescope pupil beacon. A dedicated guiding algorithm has been studied in order to provide proper
image stability even with faint objects (mv=20).
Laboratory demonstration and characterization of
phase-sorting interferometry
Show abstract
Non-common path (NCP) errors that lie downstream from the wavefront sensor (WFS) in an AO setup can’t
be directly corrected by the WFS and end up altering the science images by introducing quasi-static speckles.
These speckles impose limits to the direct imaging of exoplanets, debris disks and other objects for which we
require high contrast. Phase-sorting interferometry (PSI) uses WFS residuals as interferometric probes to the
speckles. With the retrieved amplitude and phase the deformable mirror can be adjusted to remove the speckles.
Previously PSI has been demonstrated to correct -to first order- the non-common path error on-sky at the MMTO
in Arizona. We present an AO laboratory testbed and the techniques used to determine the properties of PSI;
the influence of the time synchronisation between WFS and science camera, the achromacity of the atmosphere
and other limiting factors. Furthermore we test the performance of the PSI method when coronagraphs such
as apodizing phase plates, Lyot masks and 4QPMs are introduced to the setup. Lastly this setup enables us to
rapidly prototype high-contrast imaging techniques.
Mechanical design of NESSI: New Mexico Tech extrasolar spectroscopic survey instrument
Show abstract
NESSI: the New Mexico Tech Extrasolar Spectroscopic Survey Instrument is a ground-based multi-object
spectrograph that operates in the near-infrared. It will be installed on one of the Nasmyth ports of the
Magdalena Ridge Observatory (MRO) 2.4-meter Telescope. NESSI operates stationary to the telescope
fork so as not to produce differential flexure between internal opto-mechanical components during or
between observations. In this paper we report on NESSI's detailed mechanical and opto-mechanical design,
and the planning for mechanical construction, assembly, integration and verification.
The extreme polarimeter: design, performance, first results and upgrades
Show abstract
Well over 700 exoplanets have been detected to date. Only a handful of these have been observed directly. Direct observation is extremely challenging due to the small separation and very large contrast involved. Imaging polarimetry offers a way to decrease the contrast between the unpolarized starlight and the light that has become linearly polarized after scattering by circumstellar material. This material can be the dust and debris found in circumstellar disks, but also the atmosphere or surface of an exoplanet.
We present the design, calibration approach, polarimetric performance and sample observation results of the Extreme Polarimeter, an imaging polarimeter for the study of circumstellar environments in scattered light at visible wavelengths.
The polarimeter uses the beam-exchange technique, in which the two orthogonal polarization states are imaged simultaneously and a polarization modulator is swaps the polarization states of the two beams before the next image is taken. The instrument currently operates without the aid of Adaptive Optics. To reduce the effects of atmospheric seeing on the polarimetry, the images are taken at a frame rate of 35 fps, and large numbers of frames are combined to obtain the polarization images.
Four successful observing runs have been performed using this instrument at the 4.2 m William Herschel Telescope on La Palma, targeting young stars with protoplanetary disks as well as evolved stars surrounded by dusty envelopes. In terms of fractional polarization, the instrument sensitivity is better than 10−4. The contrast achieved between the central star and the circumstellar source is of the order 10−6. We show that our calibration approach yields absolute polarization errors below 1%.
A spectro-polarimetric integral field spectrograph for EPICS-EPOL
Show abstract
Imaging polarimetry offers a way to increase the contrast of light scattered from circumstellar material, enabling
direct observation of exoplanets –possibly rocky– with the E-ELT. To actually characterize these planets, some
spectral resolution is essential. With sufficient resolution –both spectral and spatial– the spectral differential
imaging technique can be used in addition to the polarimetry to detect circumstellar point sources. We present
the concept for a spectro-polarimetric integral field spectrograph for the EPICS-EPOL instrument and our
current efforts to demonstrate this concept with our existing imaging polarimeter ExPo.
FRD and scrambling properties of recent non-circular fibres
Show abstract
Optical fibres with octagonal, square and rectangular core shapes have been proposed as alternative to the circular fibres
to link the telescopes to spectrographs in order to increase the accuracy of radial velocity measurements. Theoretically
they offer better scrambling properties than their circular counterparts. First commercial octagonal fibres provided good
near field scrambling gains. Unfortunately the far field scrambling did not show important figures.
This article shows test results on new fibres from CeramOptec. The measurements show substantial improvements of the
far field scrambling gains. In addition, evaluation of their focal ratio degradation (FRD) shows much better performances
than previous fibres.
High efficiency inexpensive 2-slices image slicers
Show abstract
Image slicers are widely used in astronomical instrumentation to increase the resolving power of spectrographs with the
maximum throughput. However, the manufacturing costs are usually significant. This paper describes new image slicer
simple designs. They provide only two slices but with high throughput and low cost manufacture process. Two
prototypes have been evaluated and their performances are reported.
Mechanical design and integration of the support structure for the Reionization And Transients InfRared Instrument RATIR
Show abstract
In this article we present the mechanical design and the manufacturing of the support structure for the Reionization And
Transients InfraRed (RATIR) camera. The instrument is mounted at the f/13 Cassegrain focus of the 1.5-meter Harold
Johnson telescope of the Observatorio Astronómico Nacional at San Pedro Mártir (OAN/SPM) in Mexico. We describe
the high-level requirements and explain their translation to the mechanical specifications and requirements. We describe
the structural finite-element analysis and the boundary conditions, loads, and general assumptions included in the
simulations. We summarize the expected displacements, rotations and stresses. We present the optomechanical
components and the elements used to attach the instrument to the telescope. Finally, we show the instrument installed on
the telescope.
A new method for correcting fibre barycentre displacements in high resolution spectroscopy
Show abstract
Unpredictable displacements in the photocentre of an optical feed at the entrance slit of a spectrograph produce
corresponding barycentre offsets that impose limits to very high resolution schemes. These limitations not only apply to
direct light from a science object, but also light relayed via an optical fibre or image slicer. Several mitigation strategies
are in development or are currently in use, however these all have potentially restrictive idiosyncrasies.
An alternative approach is proposed to remove displacement effects from the spectra by nulling barycentre offsets.
Correction is achieved by time-integrating at the detector a sequence of multiple normal and 180-degree inverted images
of the input aperture, thus eliminating optical asymmetries about the axis of inversion, which is aligned orthogonal to the
spectral direction. The flip is generated with a path-length compensated, non-dispersive ‘reversion prism’, driven on a
high precision translation stage. The prism is periodically chopped in and out of the beam, and the resulting time-averaged
image thus has an imposed central axis regardless of barycentre shifts.
The method works regardless of the specifics of the spectrograph feed (fibre, multiple fibres, slit, slicer etc.) With a
relatively simple and inexpensive scheme it should be possible to stabilise an image to better than one part in 104 potentially permitting detection down to cms-1 regimes.
The concept is currently at a very early stage of development, so this paper outlines the basic principles and details a
practical reversion component that is currently under development at Durham CfAI. There then follows a description of
how the component will be implemented in a laboratory prototype scheme. The paper concludes with a proposed test
plan and suggests the focus for future work.