This PDF file contains the front matter associated with SPIE Proceedings Volume 11115, including the Title Page, Copyright Information, Table of Contents, and the Author and Conference Committee lists.

The Wide Field Infrared Survey Telescope (WFIRST), NASA’s next decadal astrophysics observatory, will enable advances in astrophysics by providing a large-scale survey capability in infrared wavelengths. The observatory is designed to capture data that will allow astronomers to unlock the mysteries of the universe, answering high-priority scientific questions related to the evolution of the universe and the habitability of exoplanets. Using a 2.4 m (7.9 ft) primary mirror, WFIRST will capture comparable quality images to the Hubble Space Telescope, but with more than 100 times the field of view, enabling the observatory to conduct comprehensive and efficient surveys of the infrared sky. Scientists estimate WFIRST has the potential to examine a billion galaxies over the course of its mission. Ball Aerospace was selected as NASA’s partner to design and develop the Wide Field Instrument (WFI) Opto-Mechanical Assembly for the WFIRST mission. The optical-mechanical assembly, which includes the optical bench, thermal control system, precision mechanisms, optics, electronics, and the relative calibration system, provides the stable structure and thermal environment that enables the wide-field, high quality observations of WFI. Ball's innovative design uses heritage hardware to unfold the incoming light, providing cost and schedule savings to the mission. In this paper, we present an overview of the WFI design, which completed its preliminary design review in June 2019. The overview includes a discussion of the design process, including several of the trade studies completed that led to the unfolded optical path architecture for the instrument design. The current state of the design is shown.

We have presented the optical design and early test result of WFIRST grism spectrometer in previous SPIE conferences. This paper reports the follow-on activity of the spectral and radiometric calibrations, including the calibration methods, experiment designs, and the light source and detector calibration. The real grism calibration includes the throughput versus wavelength, which is largely determined by the diffraction efficiency of the two diffractive surfaces. It also includes spectral resolution, point spread function, and encircle energy measurements. The measured data are presented. The comparisons between the test data and the simulation from theory, or optical model, are also presented.

The Cosmic Evolution Through UV Surveys (CETUS) concept has three UV instruments to achieve its science goals that work in the near ultraviolet (NUV) and far ultraviolet (FUV). The NUV multi-object spectrograph (MOS) and the NUV/FUV Camera operate simultaneously with their separate field of views. The key enabling technologies will be discussed including the micro-shutter array, detectors, and optical coatings. The NUV MOS can target up to 100 objects at a time which will allow over 100,000 galaxies to be observed during the mission lifetime. The UV Camera has the capability to image from the FUV to the NUV at the same time the MOS is operating at 180-350 nm. The UV Camera has a selection of bandpass filters, longpass filters, and two separate detectors to optimize observing in either the FUV or the NUV utilizing a sealed CsI solar blind micro-channel plate and a 4Kx4K CCD respectively. Both instruments have a tip/tilt/focus mechanism on one of their optics allowing independent focus correction and dithering of the image at the focal plane.

Raman Laser Spectrometer (RLS) is one of the Pasteur Payload instrument of the ExoMars 2020 mission, within the ESA’s Aurora Exploration Program. RLS is mainly composed by SPU (Spectrometer Unit), iOH (Internal Optical Head), and ICEU (Instrument Control and Excitation Unit), and will analyse Mars surface and sub-surface crushed samples by Raman spectroscopy. For the RLS Flight Model (FM) verification campaign, an end-to-end quick functional test was developed to evaluate the instrument performances stability. This test consists on a comparison of the centre pixel and the FWHM (Full Width at Half Maximum) of a set of Ne calibration lamp peaks, and was decided to be done before and after ever risky activity (transport, thermal tests, etc.) In the course of the end-to-end functional test carried out on RLS FM as part of the pre-delivery checks, an increment on the FWHM calibration lamp peaks was observed. Such performance variation was also noted to be dependent on the way the SPU thermal strap was assembled and the environmental conditions (P and T) in which the spectra were acquired. For that reason, a new SPU thermal strap assembly procedure was decided to be designed in order to ensure no extra negativeeffect was going to appear during the RLS FM installation on the ALD (Analytical Laboratory Drawer) and the instrument flight operation. In this paper, a deep exploration of the conditions in which such “de-focus” (probably due to an excessive thermal gradient between SPU structure and CCD) appears is carried out, demonstrating that the new thermal strap assembly procedure minimizes an incidental extra de-focus appearance during RLS installation on the ALD.

The 2.5~5um infrared band is an important waveband in infrared astronomy research. Infrared sky brightness monitoring is an important part of ground-based infrared astronomical observations. The measurement of infrared sky brightness and the characteristics of the infrared observation conditions of an area, especially the average intensity and variation parameters of infrared radiation will provide an important reference for future design of infrared telescopes and other observation instruments. We designed a sky brightness spectrograph for 2.5-5um continuous infrared spectroscopy using an InSb detector and conduct a test measurement of the sky brightness radiation intensity with L band whose center wavelength is 3.77um.

In the frame of the ESA Sentinel-5 mission, as part of the Copernicus program, Airbus is the prime contractor for the S5 Instrument. As part of the S5 instrument, which is using the METOP SG satellite as a platform, Leonardo is developing the Short-Wave Infrared Spectrometer (SWIR-SS), comprising two parallel channels covering the wavelength ranges of 1589÷1676 nm (SWIR 1) and 2304÷2386 nm (SWIR 3). Major objective of the S5 is the monitoring of the Earth atmosphere by taking measurements of trace gases and aerosols impacting air quality and climate, with a swath width of ca. 2670 Km providing daily coverage of Earth atmosphere at an unprecedented resolution of 7x7 Km2 at nadir. Main characteristic of the SWIR-SS compared to other spectrometers is the high spectral position one orbit stability less than 1um and high spectral pixel resolution of 0.1nm. High stability and optical quality requires accurate optical elements mounting design and high resolution is reached by using new developments regarding Immersed Grating (grating immersed on a prism) and the implementation of a cutting edge 3D Slit Homogenizer system, positioned on the object plane of the spectrometer, to mitigate radiometric errors arising from scene heterogeneity. In order to demonstrate the system performance the optical design has been validated by means of flight representative optical assemblies. These breadboards are representing all relevant optical elements of the system. This paper presents the tests, which have been performed on the flight representative optical elements and the test results. As the Optical Element Mounting, the Slit Homogenizer and the Immersed Grating are major elements to fulfil mission requirements the development approach is described. Special emphasis for Lens mounting is put on the stability and WFE, for the Slit Homogenizer is put on the requirements regarding the slit width variation and the quality of the entrance edge while the major design driver for the Immersed grating is the optical quality. This paper presents the development approach of these two major optical elements and the validation test results.

PLATO, PLAnetary Transits and Oscillation of stars, is an ESA mission mainly devoted to survey the Galaxy searching for and characterizing Earth-like exoplanets, and their host stars. This will be achieved using continuous and extremely accurate photometry for both exoplanetary transits and asteroseismology analysis. Current design plans to mount 26 cameras in the same instrument bench in order to cover a large field of view with the highest possible photon statistics. Each PLATO camera consists of the telescope (TOU, Telescope Optical Unit), the focal plane assembly (FPA), and the detector and camera read out electronics (FEE). Four CCDs (Charge Coupled Devices) will be included in each FPA, which implies a really delicate assembly and integration verification (AIV) process due to the stringent scientific requirements breakdown into hard engineering ones (among others, CCDs co-alignment in terms of tip and tilt and roll with respect to the optical axis). In the following lines, the FPA current opto-mechanical design is briefly presented and an integration process conceptual proposal is reported on, discussing the error budgets associated to the main requirements to be verified during FPAs AIV, and the main results obtained during the prototype first AIV round.

New optical fibre spectroscopic imaging devices for astronomy are being developed with very high throughput and excellent optical performance. Hector is a new generation multi-object Integral Field Spectroscopy (IFS) instrument that will utilise these high-performance fibre imaging devices called hexabundles". They are being developed in the Sydney Astrophotonic Instrumentation Laboratories (SAIL) at the University of Sydney. Hector is planned to be using these hexabundles on-sky by 2020 to carry out one of the world largest IFS galaxy surveys at the Anglo-Australian Telescope (AAT). The hexabundles contain up to 169 multi-mode Ceramoptec WF103/123um fibres per device, subtending a 26 arcseconds view with a spectrum at each fibre position for each galaxy. For astronomical instruments, optical fibres give significant flexibility in configuring a focal plane, but focal ratio degradation (FRD) can affect the performance of the optical fibres and directly influence the efficiency of any galaxy survey observed. Breakthroughs in glass fibre processing at SAIL have enabled hexabundles with minimal FRD - and therefore optimal performance. We will present the new developments in the SAIL labs and the resulting performance of new hexabundle devices for Hector and for other future applications.

In this study, we characterized the S13360-3050CS Multi-Pixel Photon Counter (MPPC), a silicon photomultiplier (SiPM) manufactured by Hamamatsu Photonics K.K.. Measurements were obtained inside a light tight dark box using 365 nm, 400 nm, 525 nm, 660 nm, 720 nm, 810 nm, and 900 nm light-emitting diodes (LED) and the Citiroc 1A front-end evaluation system manufactured by Weeroc. At a 2.95V over voltage, we measured a dark count rate of 5.07×10⁵ counts per second at 26°C, crosstalk probability of 8.7%, photon detection efficiency of 36% at 400 nm, linear range of 1.8×10⁷ photons per second, and saturation at 5×10⁸ photons per second. The S13360- 3050CS MPPC is a candidate detector for the Ultra-Fast Astronomy (UFA) telescope which will characterize the optical sky in the millisecond to nanosecond timescales using two SiPM arrays operated in coincidence mounted on the 0.7 meter Nazarbayev University Transient Telescope at the Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) located near Almaty, Kazakhstan. One objective of the UFA telescope will be to search for optical counterparts to fast radio bursts (FRB) that can be used to identify the origins of FRB and probe the epoch of reionization and baryonic matter in the interstellar and intergalactic mediums.

I will present on-going detector developments in our joint NASA/CNES balloon-borne UV multi-object spectrograph, FIREBall-2, the Faint Intergalactic Redshifted Emission Balloon. FIREBall-2 is a path finding mission to test new technology (EMCCDs) and make new constraints on the temperature and density of this gas. This instrument has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies (z ~ 0.7). One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (< 1 electron). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with a NuVu CCD Controller for Counting Photons (CCCP). This optimisation also includes methods for reducing dark current, via cooling, and exploring substrate voltage levels. I will present some of our dark current results from laboratory testing. We recently launched FIREBall-2 from Fort Sumner, New Mexico on September 22nd, 2018. This was the first time an EMCCD has been used for UV/optical observations in flight! I will present performance data from the flight including cosmic ray rate measurements, and some of our preliminary on-sky UV results using our data reduction.

The Charge Coupled Device (CCD) has often been the imaging detector of choice for satellite missions. The space environments these camera systems operate in is abundant with highly energetic radiation. It is impossible to fully protect the CCD from the radiation environment, understanding the impact of radiation damage at a fundamental level is essential to characterise and correct the degradation on the image or spectrum. Here we study the properties of individual traps, with particular attention paid to the silicon divacancy, one of the major trap species found in n-channel CCDs caused by radiation damage that can effect image readout. Through the use of the trap pumping technique it is possible to observe individual traps and their properties in high detail with sub-pixel accuracy. Previous studies using the trap pumping technique have focused on proton irradiated CCDs to characterise the resulting defects. In addition to proton irradiated devices, the use of a ⁶⁰Co source allows the study of traps resulting from gamma irradiation and through this analysis a comparison can be made.

CSTAR2 is a new telescope array which consists of two telescopes with 145mm-aperture and an equatorial mount, which was planned to update the CSTAR (Chinese Small Telescope Array) installed at Dome A, Antarctica in 2008. Since the previous camera was out of product, a brand new CCD camera with 1K*1K pixels was developed for CSTAR2, which was tested function well at -80℃ to prove the ability to work at Antarctica in a long period. The camera has a well performance and the readout noise is as low as 3.99e-_rms. An equatorial mount made by NIAOT (Nanjing Institute of Astronomical Optics & Technology) can rotate the telescope to point almost entire sky area. In order to control CSTAR2 in an efficient way, a multi-level software control system was developed which contains three main layers: device control layer, coordinating operation layer, user interface layer. The whole system was planned to achieve automatic observation and remote operation under the conditions of poor satellite-link network.

Pursuing ground breaking science in a cost and funding constrained environment presents new challenges to the development of future space astrophysics missions. Within the conventional cost models for large observatories, executing a flagship “mission after next” appears to be unstainable. To achieve our nation’s space astrophysics ambitions requires new paradigms in program design, system design, development and manufacture. Implementation of this new paradigm requires that the space astrophysics community adopt new answers to a new set of questions. This paper continues our discussion the origins of these new questions and the steps to their answers.

This paper presents NPS Sparse Aperture Testbed development to demonstrate sparse aperture concept. The testbed has a sparse aperture array consisting of three 2-inch diameter F/20 spherical mirrors. Each mirror is connected to a separate 6 axis ThorLabs stage to simulate motion in satellite formation. The beam combining platform employs three 1-inch diameter flat mirrors mounted on the correcting PI tip/tilt/piston actuated stages to provide coherent beam combining capabilities. For metrology, the system uses Zygo 9 single-axis displacement measuring interferometers. Transformation matrix between the aperture motion measured by the metrology and required motion by the correcting piston and tip/tilt stages was determined. The mirrors were moved continuously representing satellite formation errors and the motion was measured by laser metrology and using transformation matrix, the correcting stages were commanded, resulting in coherent combination of images from three apertures.

In this paper we examine several contrast-degrading static signature sources present in current terrestrial exoplanet Lyot Coronagraph/Telescope optical systems. These are: - Unnecessary optical surfaces, which increase cost, absorption, scatter, wavefront control and alignment issues. A suggested solution is to make every effort to investigate innovative solutions to reduce the number of optical surfaces during the early design phase. Consider free-form optics. - Diffraction from secondary support systems and classical hexagon segmented apertures, which masks the low IWA terrestrial exoplanets. A suggested mitigation is to investigate curved secondary support systems and a pinwheel architecture for the deployable primary aperture. - Polarization Fresnel and form birefringence aberrations, which distort the system PSF, introduce absorption, scatter and wavefront control issues. Mitigation is to reduce all ray-angles of incidence to a minimum, investigate zero-loss polarization compensation wavefront technology, and investigate metal thin film deposition processes required to minimize form birefringence in large-area high-reflectivity coatings. - Small-angle specular or resolved angle scattered light, which places a narrow halo of incoherent light around the base of the PSF. There is no requirement on mirror smooth-surface scatter. Investigate the physical source of the small angle scatter and develop mirror polishing and thin film deposition processes to minimize scatter.

Newton did not have a telescope in mind when he ran his dual prism experiment, but he did notice that the colors after the secondary prism changed with any change in the angle of the first. When applied to astronomical observation, a Newtonian dual dispersion architecture allows for an enormous improvement in field-of-view over a conventional mirror telescope. Combined with a stretched length of a primary objective grating as viewed from a fixed angle of grazing exodus, étendue AΩ can be shown to reach the tens of thousands. We have designed a telescope based on this architecture that takes very high resolution spectra of every object in a line of right ascension over the course of an observational cycle. Embodiments on the ground, airborne, in space and on the moon are discussed. Unlike all prior proposals for diffractive primaries, THE MOST, The High Étendue Multiple Object Spectrographic Telescope is not limited to a narrow spectral band or narrow field-of-view while enjoying the low mass and potentially low cost that was anticipated with recent investigations into diffraction primary objective telescopes.

Future space observatory missions require controlling wave front error and system alignment stability to picometer scale. Picometer stability performance demands precision knowledge of the mirror and metering structure materials to the same level. A high-speed electronic speckle pattern interferometer was designed and built to demonstrate measurements of both static and dynamic responses of picometer level amplitudes in mirror and structural materials subjected to very low energy disturbances. This paper summarizes the current status of tests to impart a dynamic disturbance of picometer scale and measure the response of specular and diffuse materials. The results show that subpicometer scale effects can be accurately measured in an open test environment outside a vacuum chamber.

The LISA mission concept has been selected by the European Space Agency (ESA) as its third large-class mission within the Cosmic Vision programme. LISA, which stands for “Laser Interferometer Space Antenna”, is a space-based gravitational wave observatory, consisting of three spacecraft in a triangular formation providing access to the milli-Hertz frequency band of the gravitational wave spectrum. The distance between the freely floating test masses housed within the spacecraft is monitored over arm-lengths of 2.5 million km at the picometer level by laser interferometry. First ideas for such a mission emerged long before the turn of the century and the concept has evolved over several decades culminating in the proposal of LISA in its current form in 2016. LISA is currently developed with contributions from the ESA member states and NASA as an international partner with an envisaged launch date before 2034. In this talk, we present the mission concept and its current state of development as well as the technological challenges, especially in the optical metrology chain. We address developments on the telescope, on the optical bench, lasers, and on the interferometric measurement.

The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffractionlimited at 0.4 μm and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument.

Since the 2010 Decadal Survey, the technologies needed for direct imaging of exoplanets advanced significantly. NASA investment in these technologies, prioritized in the 2010 Decadal Survey, have ripened to a maturity to enable direct imaging of earthlike exoplanets. For the first time since the discovery of exoplanets, a direct imaging mission can be conceived to start in less than ten years, possibly as soon as five years. The HabEx Observatory Concept design utilizes technologies that are state of the art or near to state of the art with clear paths of development. The philosophy of the design favors as high a Technology Readiness Level (TRL) as possible to minimize risk. We discuss the HabEx technology challenges and assess the TRL expected by the submission of the Final Report in 2019. Many of the enabling technologies are at, or expected to be at, TRL 5 by 2019, and the remaining technologies are at TRL 4. We update the technology maturity roadmap with technology advances in the past year and expand it to include an Architecture option which is a 3.2 m diameter on-axis segmented aperture with a starshade only. The starshade suppresses starlight before it enters the telescope, allowing the telescope optical performance and stability to be significantly looser than for a coronagraph, thus enabling a segmented primary mirror design that can meet stability requirements with minimal advancement from the state of the art. We assess the exoplanet-driven technologies of HabEx, including starshades, coronagraphs, deformable mirrors, wavefront control, 4 m aperture mirrors, jitter mitigation, segmented mirror stability, and low-noise detectors.

The Large UV/Optical/Infrared (LUVOIR) Surveyor is a concept for a powerful general-purpose observatory spanning the far-UV to the near-infrared. Two variants are being studied: LUVOIR-A (15-m diameter primary mirror) and LUVOIR-B (8-m mirror). These powerful and flexible observatories will enable revolutionary new studies in astrophysics and planetary science. LUVOIR is being designed to take the next great leap in exoplanet studies, with direct images and spectra of rocky Earthsized exoplanets in the habitable zones of other stars. These data will allow a wide range of investigations, including analysis of terrestrial planet atmospheres, discovery of potentially habitable exoplanets, and searches for evidence of global biospheres. A key goal for LUVOIR is to conduct these studies on a set of candidate habitable exoplanets large enough to constrain the frequency of habitable conditions (dozens of rocky planets orbiting solar-type stars). LUVOIR will also provide revolutionary advances in a broad range of astrophysics — from the epoch of reionization, through galaxy formation and evolution, to star and planet formation. The observatory could also enable powerful remote sensing observations of Solar System bodies. The LUVOIR-A architecture offers up to 25 km resolution at Jupiter, enabling sensitive, high resolution observations over long time baselines and a broad wavelength range. Finally, perhaps LUVOIR's most important scientific capability is its ability to address not only the science questions of today, but those of the 2040s and beyond that we have not yet thought to ask.

The Large Ultraviolet / Optical / Infrared Surveyor (LUVOIR) is one of four large mission concepts being study by NASA in preparation for the 2020 Decadal Survey in Astronomy and Astrophysics. Over the past three and a half years, the LUVOIR Science and Technology Definition Team (STDT) and Study Office at NASA’s Goddard Space Flight Center have developed a broad, compelling science case for LUVOIR, and detailed engineering point designs to achieve it. In this paper, we provide an overview of the two LUVOIR concepts: LUVOIR-A, a 15-m segmented, obscured aperture observatory, and LUVOIR-B, an 8-m segmented, unobscured aperture observatory. Both versions of LUVOIR cover a broad spectral range between 100 nm and 2.5 μm with a suite of imagers and spectrographs, including the High Definition Imager (HDI), the LUVOIR Ultraviolet Multi-object Spectrograph (LUMOS), and the Extreme Coronagraph for Living Planetary Systems (ECLIPS). LUVOIR-A will carry an additional fourth instrument, Pollux, a high-resolution UV spectropolarimeter being studied by the Centre National d’Etudes Spatiales (CNES). Both versions of LUVOIR are also designed to be serviceable and upgradeable. We will also provide a summary of the LUVOIR technology development program, which identifies critical enabling technologies, enhancing technologies, and a development plan to mature those technologies to TRL 6.

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of Herschel, the largest telescope flown in space to date. After a 3 ½ year study, the Origins Science and Technology Definition Team will recommend to the Decadal Survey a concept for Origins with a 5.9-m diameter telescope cryocooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (MISC-T) will measure the spectra of transiting exoplanets in the 2.8 – 20 μm wavelength range and offer unprecedented sensitivity, enabling definitive biosignature detections. The Far-IR Imager Polarimeter (FIP) will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer (OSS) will cover wavelengths from 25 – 588 μm, make wide-area and deep spectroscopic surveys with spectral resolving power R ~ 300, and pointed observations at R ~ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The telescope has a Spitzer-like architecture and requires very few deployments after launch. The cryo-thermal system design leverages JWST technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural backgroundlimited sensitivity.

To meet the ambitious science goal of characterizing exo-Earths via direct imaging and spectroscopy, future space-based astronomical telescopes will have requirements for optical stability at least several orders of magnitude beyond the current state of the art. Mission concepts requiring stability on the order of picometers include the Large UV/Optical/Infrared (LUVOIR) Surveyor and the Habitable Exoplanet (HabEx) Observatory, which use large primary mirrors and internal coronagraphs to perform high contrast imaging. The Ultra-stable Large Telescope Research and Analysis (ULTRA) Program is a system study performed by an industry consortium led by Ball Aerospace to evaluate potential architectures, perform trade studies, and identify technology gaps that must be addressed to enable picometerlevel optical stability in space. This paper will describe the results of the study, including identification and prioritization of technology gaps and a development roadmap to raise the technology readiness level (TRL) of key enhancing/enabling technologies.

For the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) to perform high-contrast direct imaging of habitable exoplanets using a coronagraph instrument, the system must maintain extremely low system dynamic wavefront error (on the order of 10 picometers RMS over the spatial frequencies corresponding to the dark-hole region of the coronagraph) over a long time wavefront control sampling interval (typically 10 or more minutes). Meeting this level of performance requires a telescope vibration isolation system that delivers a high degree of dynamic isolation over a broad frequency range. A non-contact pointing and isolation system called the Vibration Isolation and Precision Pointing System (VIPPS) has been baselined for the LUVOIR architecture. Lockheed Martin has partnered with NASA to predict the dynamic wavefront error (WFE) performance of such a system, and mature the technology through integrated modeling, subsystem test and subscale hardware demonstration. Previous published results on LUVOIR dynamic WFE stability performance have relied on preliminary models that do not explicitly include the effects of a segmented Primary Mirror. This paper presents a study of predicted dynamic WFE performance of the LUVOIR-A architecture during steady-state operation of the coronagraph instrument, using an integrated model consisting of a segmented primary mirror, optical sensitivities, steering mirror and non-contact isolation, and control systems. The design assumptions and stability properties of the control system are summarized. Principal observatory disturbance sources included are control moment gyroscope and steering mirror exported loads. Finally, observatory architecture trades are discussed that explore tradeoffs between system performance, concept of operation and technology readiness.

This paper, written in the form of an open letter to the Flagship systems designers of the future, conveys the main lessons learned by the authors from their tenures on Chandra, JWST and the current studies of decadal missions. These lessons will discuss the interaction of technology, architecture and design, requirements development, modeling and verification. Application of these lessons will be a key part of any future flagship’s effort to control cost, schedule and risk.

The Habitable Exoplanet Observatory Mission (HabEx) is one of four missions under study for the 2020 Astrophysics Decadal Survey. Its goal is to directly image and spectroscopically characterize planetary systems in the habitable zone around nearby sun-like stars. Additionally, HabEx will perform a broad range of general astrophysics science enabled by 100 to 2500 nm spectral range and 3 × 3 arc-minute FOV. Critical to achieving its the HabEx science goals is a large, ultrastable UV/Optical/Near-IR (UVOIR) telescope. The baseline HabEx telescope is a 4-meter off-axis unobscured threemirror- anastigmatic, diffraction limited at 400 nm with wavefront stability on the order of a few 10s of picometers. This paper summarizes the opto-mechanical design of the HabEx baseline optical telescope assembly, including a discussion of how science requirements drive the telescope’s specifications, and presents analysis that the baseline telescope structure meets its specified tolerances.

The HabEx mission concept is intended to directly image planetary systems around nearby stars, and to perform a wide range of general astrophysics and solar system observations. The baseline HabEx design would use both a coronagraph and a starshade for exoplanet discovery and characterization. We describe a lower-cost alternative HabEx mission design, which would only use a starshade for exoplanet science. The starshade would provide excellent exoplanet science performance, but for a smaller number of detected exoplanets of all types, including exoEarth candidates, and a smaller fraction of exoplanets with measured orbits. The full suite of HabEx general astrophysics and solar-system science would be supported.

The Habitable Exoplanet Imaging Mission (HabEx) is one of the four large mission concepts being studied by NASA as input to the upcoming 2020 Decadal Survey. The mission implements two world-class General Astrophysics instruments as part of its complement of instrumentation to enable compelling science using the 4m aperture. The Ultraviolet Spectrograph has been designed to address cutting edge far ultraviolet (FUV) science that has not been possible with the Hubble Space Telescope, and to open up a wide range of capabilities that will advance astrophysics as we look into the 2030s. Our paper discusses some of those science drivers and possible applications, which range from Solar System science, to nearby and more distant studies of star formation, to studies of the circumgalactic and intergalactic mediums. We discuss the performance features of the instrument that include a large 3’x3’ field of view for multi-object spectroscopy, and some 20 grating modes.

The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is a large-scale space telescope being submitted for review to the 2020 Decadal Survey in Astronomy and Astrophysics. Its science objectives include both direct imaging and spectral characterization of habitable exoplanets around sun-like stars, the study of planet, star, and galaxy formation, the transfer of matter between different galaxies, and the remote sensing of objects within the Solar System. Two architectures have been designed: a 15 m diameter on-axis telescope (LUVOIR-A) and an 8 m off-axis telescope (LUVOIR-B). This paper discusses the opto-mechanical design of the three LUVOIR instruments: the High Definition Imager (HDI), the LUVOIR UV Multi-object Spectrograph (LUMOS), and the Extreme Coronagraph for Living Planetary Systems (ECLIPS). For both the LUVOIR-A and LUVOIR-B variants of each instrument, optical design specifications are presented including first-order constraints, packaging requirements, and optical performance metrics. These factors are used to illustrate the final design of each instrument and LUVOIR as a whole. While it is desirable to have the two variants of each instrument be as similar to one another as possible to reduce engineering design time, this was not possible in a number of instances which are described in this paper along with the resulting tradeoffs. In addition to the optical designs, mechanical models are presented for each instrument showing the optical mounts, mechanisms, support structure, etc.

The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is a multi-wavelength observatory commissioned by NASA as one of four large mission concept studies for the Astro2020 Decadal Survey. Two concepts are under study which bound a range of cost, risk, and scientific return: an 8-meter diameter unobscured segmented aperture primary mirror and a 15- meter segmented aperture primary mirror. Each concept carries with it an accompanying suite of instruments. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is a near-ultraviolet (NUV)/optical/near-infrared (NIR) coronagraph; the LUVOIR Ultraviolet Multi-object Spectrograph (LUMOS) provides multi-object imaging spectroscopy in the 100-400 nanometer ultraviolet (UV) range; and the High Definition Imager (HDI) is a wide field-of-view near-UV/optical/near-IR camera that can also perform astrometry. The 15-meter concept also contains an additional instrument, Pollux, which is a high-resolution UV spectro-polarimeter. While the observatory is nominally at a 270 Kelvin operational temperature, the requirements of imaging in both IR and UV require separate detectors operating at different temperature regimes, each with stringent thermal stability requirements. The change in observatory size requires two distinct thermal designs per instrument. In this current work, the thermal architecture is presented for each instrument suite. We describe here the efforts made to achieve the target operational temperatures and stabilities with passive thermal control methods. Additional discussion will focus on how these instrument thermal designs impact the overall system-level architecture of the observatory and indicate the thermal challenges for hardware implementation.

A novel seldom used, thermal analysis approach for system-level thermal design is developed that leverages frequencybased techniques and metrics common in structural dynamics modeling. The ULTRA study, which is assessing technological capabilities for a 15-meter telescope requiring sub nanometer optical stability was the foundation for the initial thermal math model and requirements design space discussed in this paper. For such a large, space-based system under tight tolerances, a typical thermal analysis approach will not generate a meaningful understanding of which effects drive the thermal management design. To address this issue, a perturbance-based thermal modeling approach, which is more suited to generating an understanding of the bulk system-level sensitivities, was used instead. The model developed begins by running discrete sensitivities over a range of input perturbance frequencies. The output quantifies the system response to the various sources of thermal energy input. Results are gathered and combined to from Bode plots to quantify the effect of the system perturbances. These plots can quickly characterize the impact of certain thermal designs in relation to a frequency-based wave front error budget. Resulting sensitivities at the system / sub-system scale and the process for producing such results for the LUVOIR thermal math model utilized in the Ultra study are presented. Thermal stability is key to achieving coronographic missions with 10 E-10 contrast.

The large ultraviolet optical infrared surveyor (LUVOIR) study process has brought to fruition an extremely exciting scientific mission concept. The 3.5 year LUVOIR study duration enabled an unprecedented level of scientific, engineering, and technology thoroughness prior to the Astro2020 Decadal. This detail also shed light on many technical and programmatic challenges for efficiently developing a mission of this scale within the context of NASA’s flagships cost and schedule performances to date. While NASA’s flagships perform exquisitely once onorbit, there is understandable growing frustration in their development cost and schedule overruns. We felt it incumbent upon ourselves to ask how we could improve on delivering LUVOIR (or any of NASA’s future flagships) on schedule and on budget, not just for the next mission, but for all NASA large strategic missions to come. We researched past and current NASA flagship’s lessons learned publications and other large government projects that pointed to some systemic challenges that will only grow with larger and more complex strategic missions. Our findings pointed us to some ways that could potentially evolve NASA’s current flagship management practices to help improve on their development cost and schedule performance despite their growing complexity. This paper briefly comments on the motivations for NASA’s flagships and on the science motivations for a LUVOIR-like mission. We argue the incentives for improving NASA’s flagships development cost and schedule performance. We review the specific additional challenges of NASA’s flagships to acknowledge their specific issues. We then examine the most repeated systemic challenges we found from previous NASA flagships and other large government projects lessons learned/observed. Lastly, we offer recommendations to tackle these repeated systemic challenges facing NASA’s flagships. The recommendations culminate into a proactive integrated development and funding framework to enable improving the execution of NASA’s future flagship’s cost and schedule performance.

As the optical performance requirements of space telescopes get more stringent, the need to analyze all possible error sources early in the mission design becomes critical. One large telescope with tight performance requirements is the Large Ultraviolet / Optical / Infrared Surveyor (LUVOIR) concept. The LUVOIR concept includes a 15-meter-diameter segmented-aperture telescope with a suite of serviceable instruments operating over a range of wavelengths between 100nm to 2.5um. Using an isolation architecture that involves no mechanical contact between the telescope and the host spacecraft structure allows for tighter performance metrics than current space-based telescopes being flown. Because of this separation, the spacecraft disturbances can be greatly reduced and disturbances on the telescope payload contribute more to the optical performance error. A portion of the optical performance error comes from the disturbances generated from the motion of the Fast Steering Mirror (FSM) on the payload. Characterizing the effects of this disturbance gives insight into FSM specifications needed to achieve the tight optical performance requirements of the overall system. Through analysis of the LUVOIR finite element model and linear optical model given a range of input disturbances at the FSM, the optical performance of the telescope and recommendations for FSM specifications can be determined. The LUVOIR observatory control strategy consists of a multi-loop control architecture including the spacecraft Attitude Control System (ACS), Vibration Isolation and Precision Pointing System (VIPPS), and FSM. This paper focuses on the control loop containing the FSM disturbances and their effects on the telescope optical performance.

This paper discusses the optical design of the Origins Space Telescope. Origins is one of four large missions under study in preparation for the 2020 Decadal Survey in Astronomy and Astrophysics. Sensitive to the mid- and far-infrared spectrum (between 2.8 and 588 μm), Origins sets out to answer a number of important scientific questions by addressing NASA’s three key science goals in astrophysics. The Origins telescope has a 5.9 m diameter primary mirror and operates at f/14. The large on-axis primary consists of 18 ‘keystone’ segments of two different prescriptions arranged in two annuli (six inner and twelve outer segments) that together form a circular aperture in the goal of achieving a symmetric point spread function. To accommodate the 46 x 15 arcminute full field of view of the telescope at the design wavelength of λ = 30 μm, a three-mirror anastigmat configuration is used. The design is diffraction-limited across its instruments’ fields of view. A brief discussion of each of the three baselined instruments within the Instrument Accommodation Module (IAM) is presented: 1) Origins Survey Spectrometer (OSS), 2) Mid-infrared Spectrometer, Camera (MISC) transit spectrometer channel, and 3) Far-Infrared Polarimeter/Imager (FIP). In addition, the upscope options for the observatory are laid out as well including a fourth instrument: the Heterodyne Receiver for Origins (HERO).

The STereoscopic imaging Channel (STC) is one of the three channels of SIMBIO-SYS instrument, whose goal is to study the Mercury surface in visible wavelength range. The SIMBIO-SYS instrument is on-board of ESA Bepicolombo spacecraft. STC is a double wide angle camera designed to map in 3D the whole Mercury surface. The detector of STC has been equipped with six filters: two panchromatic and four broad band. The panchromatic filters are centred at 700 nm with 200 nm of bandwidth, while the broad band ones have bandwidth of 20 nm and are centred at 420, 550, 750 and 920 nm, respectively. In order to verify the relative spectral response of each STC sub-channel, a spectral calibration has to be performed during the on-ground calibration campaign. The result consists in the transmissivity curve of each filter of STC as function of wavelength. The camera has been illuminated with a monochromator coupled with a diffuser and a collimator. The images have been acquired by changing the wavelength of the monochromator in the range correspondent to the filter bandwidth. The background images have been obtained by covering the light source and have been used to calculate and subtract the dark signal, fixed pattern noise (FPN) and ambient effects.

We report results of the impact of fiber fusion splicing on Focal Ratio Degradation and transmission loss. Experiment use formed beam methods at wavelengths between 400 and 1000nm of Polymicro fiber. We test at five input f-ratio (f/2.5, f/3.75, f/5, f/75, f/10) conditions, the influence of fiber fusion splicing on FRD respectively, and test at f/5 input fratio condition, the influence of fiber fusion splicing on fiber transmission loss. A precision test system was designed to reduce the system error and human error. The measurement accuracy of the system reaches micron scale. The fiber end surface was prepared by large core fiber cutter, grinder and fusion splicing workstation. The fiber surface roughness is less than 1 micron and the surface angle is less than 0.5 deg. By optimize the cutting and polish process, adjusted the fusion parameters, a satisfactory results of optical fiber fusion obtained in the laboratory. The maximum transmission increase caused by the fiber fusion is less than 2%, average value is less than 1%; while the maximum FRD increase is less than 0.16 degrees. Our results indicate that fiber fusion technology can be adopted for repair failure optical fiber, replace the fiber clips and astronomical instrument construction.

LAMOST is a special Schmidt telescope with 16 spectrographs. Through these spectrographs, it can detect 4000 stellar spectra via optical fibers. Before the year of 2017 LAMOST’s spectrograph only work on low resolution spectrograph(LRS) mode, and recently we have finished the update of optical, mechanical structure and control system of these 16 spectrographs which could switch working mode between low resolution and middle resolution spectrograph(MRS) to meet the needs of LAMOST Phase II Sky Survey. Due to the strict optical performance requirements and the close arrangement of the optical equipment on the spectrograph platform, the control system must be quite accurate, stable and reliable. In this paper, we mainly describe the design and improvements of the spectrograph control system of the LAMOST’s spectrographs, including shutter sub-system control, back-illuminate sub-system control, LRS/MRS switch sub-system control, camera lens electric focus sub-system control, and some other sub-systems in LAMOST’s spectrograph control system. What’s more, there are also some connections between different sub-systems. As a result, we use FPGA chip as the main spectrograph controller, and make some improvements not only on host-computer software program, but also on slave-FPGA controller software and hardware design. The FPGA controller does some logical judgements according to the feedback information provided by the position sensor and the working mode designed to suit for different working condition. In this way, we make the spectrograph work more accurate and stable, and make it more safety and reliable especially on switching between LRS mode and MRS mode. Through those design and improvements on spectrograph’s control system mentioned in this paper, LAMOST could get more high-quality star spectral data from its 16 spectrographs.

We successfully rapid-prototyped a mostly off-the-shelf, partially 3D-printed pathfinder version of an integral field spectrograph (IFS) in order to compress the design/build/test schedule of a final, mostly-custom IFS, by accelerating the start date of data pipeline development, thus allowing this development to progress in parallel with the design, procurement, fabrication, and alignment of the final IFS version. This parallel-path development schedule enabled us to successfully design, build, align, test, and extract a data cube from the new IFS within only 1 year, even in the face of several design setbacks. We have begun using the now-functional IFS for development of IFS sensing and control algorithms, and have also begun implementing motorized alignment upgrades that enable the systematic characterization of the tolerance (or required compensation) of its data cube extraction to misaligned images, in support of NASA’s WFIRST and PISCES IFS.

The SwRI Detector Characterization Lab (SDCL) was established in order to facilitate the rapid calibration of large numbers of detector arrays for upcoming ground and space missions. The SDCL is equipped with a McPherson monochromator with exchangeable gratings and light sources enabling wavelength coverage from 0.3 to 5.0 micron at sub nanometer resolution. The SDCL also has cryostats capable of maintaining thermal control of detector subassemblies and transfer optics to a precision of 0.1K at 77K and 0.01K at 4K. Using this calibration system, we have calibrated the EEM and ETU detector for read noise, dark current, modulation transfer function, quantum efficiency, cross talk, and total system throughput. The data were collected using standard Photon Transfer Curve techniques at the various wavelengths corresponding to the MVIC filter bandpasses. Here, we will present the data for the engineering unit, the methodology used to perform the calibration, and the steps forward for calibration of the flight unit.

Future observatories capable of detecting Earth-like planets around other stars will have to be large and exquisitely stable, a so-called ultra-stable system (USS). The stability requirements for a USS are orders of magnitude greater stability than current systems. The analysis, design and verification of these systems will require detailed knowledge of all the factors that affect its performance. At performance levels measured in picometers, forces and effects that are negligible for current systems can become important actors. To assure there are no bad actors waiting in the wings to spoil the performance of a future ultra-stable system, a systematic and comprehensive study has been carried out to assess the impact to system performance for many of these small and typically ignored effects. The work presented includes the effects of system self-interactions and system interaction with the environment and the impact of both on the stability of the figure in a spatial and temporal sense.

Future space missions seeking evidence of life on exoplanets will demand better visible and near-infrared detectors than exist today. The desired detectors are both photon counting (to detect faint exoplanets) and radiation tolerant (for use in space). To address this, a team at NASA Space Flight Center and Lawrence Berkeley National Laboratory (LBNL) is adding photon counting output amplifiers to LBNL's thick, fully depleted, p- channel CCDs and characterizing them for space astrophysics. We are developing two photon counting CCD concepts: (1) hole multiplying CCDs and (2) Skipper CCDs. This paper is the companion article to an SPIE conference poster. It closely follows the poster, although we have expanded the narrative somewhat to make it stand alone.