This PDF file contains the front matter associated with SPIE Proceedings Volume 11443, including the Title Page, Copyright information, and Table of Contents.

The GRAVITY instrument has enabled major steps forward in infrared interferometry, by phase-referenced imaging at milli-arcsecond resolution, with a sensitivity increase by factor thousands, 30-100 micro-arcsecond astrometry, and few micro-arcsecond differential spectro-astrometry. We give an overview of the technology behind GRAVITY and highlight the game-changing results from the first three years of operation. Our presentation takes us from nearby exoplanets all the way to distant quasars, with special focus on the Galactic Center, the first precision tests of Einstein’s theory of General Relativity around massive black holes, and tests of the massive black hole paradigm on scales of 3-6 Schwarzschild radii.

The Gaia satellite was launched at the end of 2013 to collect data that will allow the determination of highly accurate positions, parallaxes, and proper motions for over one billion sources brighter than magnitude 20.7, from the solar system to our Milky Way and beyond. I will discuss the astrometric measurement concept and the design considerations and engineering challenges that follow. I will also review the problems faced in practice during the mission which however did not prevent its phenomenal success, as will be demonstrated with a few scientific highlights.

The NASA Engineering and Safety Center (NESC) was established in 2003 (after the Columbia accident) to provide an independent technical resource for the resolution of challenging technical problems (through the use of studies, analysis, tests, etc.) for NASA programs and projects. Since its inception, NESC has completed nearly 1000 technical assessments for NASA’s Human Exploration and Operation Mission Directorate (HEOMD), Science Mission Directorate (SMD), Space Technology Mission Directorate (STMD), and Aeronautics Research Mission Directorate (ARMD). Of the SMD related assessments, several were for the resolution of technical problems, analysis, or studies related to NASA’s astrophysics missions in various phases of the project from design to operation. Some of the recent examples of NESC technical support for NASA astrophysics missions have been for: Hubble Space Telescope (HST), Chandra X-ray Observatory (CXO), Fermi Gamma-ray Space Telescope, Kepler Space Telescope, Transiting Exoplanet Survey Satellite (TESS), James Webb Space Telescope (JWST), and Laser Interferometer Space Antenna (LISA). In this paper, we outline some of the technical challenges faced by these astrophysics missions and describe how NESC contributed to their resolution. The case studies cover a wide range of disciplines involving space telescopes, detectors, lasers, and attitude control systems. These efforts include innovative solutions for extending the life of the missions, technical resolution of challenging problems, strategies for risk mitigation, and failure investigations combined with lessons learned reports to advance discipline knowledge, enhance NASA capabilities, and avoid future problems.

The Herschel Space Observatory was the fourth Cornerstone mission of ESA’s Horizon 2000 programme, and a €1Bclass far infrared space observatory. The satellite and mission were developed over an approximately 10-year period before launch in 2009 and highly successful operation for approximately four years. A Post-Operations programme continued until 2017 (and with little resources even until 2019) in order to complete the data processing, calibration and documentation activities and to populate the Herschel Science Archive with the final data products and documentation. The Herschel Science Team, which oversaw the mission over a nearly 20-year period from late 1998 until its 61st and final meeting in late 2017, has conducted a comprehensive lessons learned review of the project from start to finish, encompassing all aspects of the endeavour – programmatics and management of the spacecraft, instrument consortia and ground segment; instrument development and testing; spacecraft implementation; ground segment and operations preparation pre-launch, in-flight operation and post-operations; science management and user support; and communications. Science is not addressed here except in general terms – this is not a scientific assessment. Focusing on generic features of the mission and its management, organisation, and technical design that have potential applications and relevance to future space projects, we have identified and assessed a number of aspects in which the Herschel experience can provide valuable lessons, both positive and negative, to aid the effective development and success of future missions, especially ones that are comparable in magnitude and complexity. We outline the main findings and conclusions of this Lessons Learned exercise.

We present a plan to address the calibration needs of the Wide Field Instrument (WFI) on the Wide Field Infrared Space Telescope (WFIRST), for on on-orbit observations and ground testing. The science mission of WFI is based on a combination of large surveys, a Guest Observer program, and a strong archival research program. The WFIRST Science Requirements Document delineates several data quality and calibration requirements for the Mission. The Calibration Plan aims to be prescriptive and predictive, discussing which observations will be needed and estimating the total time required to carry out such observations. We discuss these requirements from an instrumental perspective, and identify the measurements, observations, and analysis steps needed to achieve the desired calibration and data quality levels, especially in terms of on-orbit observations..

Euclid, an ESA mission designed to characterise dark energy and dark matter, passed its Mission Critical Design Review in November 2018. It was demonstrated that the project is ready to start integration and test of the main systems, and that it has the ability to fulfil its top-level mission requirements. In addition, based on the performances at M-CDR, the scientific community has verified that the science requirements can be achieved for the Weak Lensing and Galaxy Clustering dark energy probes, namely a dark energy Figure of Merit of 400 and a 2% accuracy in the growth factor exponent gamma. We present the status of the main elements of the Euclid mission in the light of the demanding high optical performance which is the essential design driver is the to meet the scientific requirements. We include the space segment comprising of a service module and payload module hosting the telescope and its two scientific instruments, and the ground segment, which encompasses the operational and science ground segment. The elements for the scientific success of the mission for a timely release of the data are shortly presented: the processing and calibration of the data, and the design of the sky survey. Euclid is presently on schedule for a launch in September 2022.

The Euclid mission, of which the spacecraft is the essential space segment, is being developed to undertake the challenges of mapping the dark energy and dark matter distribution in the Universe. As the launch date is approaching (2nd half of 2022), the development of the spacecraft has successfully passed critical milestones with the manufacturing and integration of the telescope, instruments and service module. Each sub-element of the spacecraft has been qualified and their performance assessed. The assembly of the complete payload and spacecraft is currently on-going. The integrated optical performance end to end of the payload module is currently being assessed based on the as-built knowledge of the parts of the telescope and instruments.

SPHEREx, the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and ices Explorer, is a NASA MIDEX mission planned for launch in 2024. SPHEREx will carry out the first all-sky spectral survey at wavelengths between 0.75µm and 5µm with spectral resolving power ~40 between 0.75 and 3.8µm and ~120 between 3.8 and 5µm At the end of its two-year mission, SPHEREx will provide 0.75-to-5µm spectra of each 6.”2x6.”2 pixel on the sky - 14 billion spectra in all. This paper updates an earlier description of SPHEREx presenting changes made during the mission's Preliminary Design Phase, including a discussion of instrument integration and test ow and a summary of the data processing, analysis, and distribution plans.

Cool stars, especially spectral-type M, are important probes across contemporary astrophysics, from the forma- tion history of the galaxy to the coalescence of rocky exoplanets. Main sequence M-dwarf stars are one of the most abundant stars in the galaxy, and evolved M-giant stars are some of the most distant stars that can be individually observed. The Emu sky survey, described here, will deliver critical stellar properties of these cool stars by inferring the oxygen abundance via measurement of the water band strength at 1.4 μm. A relatively wide field zenith-looking telescope with time delay integration capability can perform such a survey without active pointing but requires a fast and low-noise detector. Emu employs the paradigm-changing properties of the Leonardo SAPHIRA electron avalanche photodiode array, to provide these powerful new observations at the critical water absorption wavelength inaccessible to ground-based telescopes due to the Earth's own atmosphere. Here we will present Emu mission concept, science objectives, instrument details and simulation results.

The Astrometric Gravitation Probe mission is a modern version of the 1919 Dyson-Eddington-Davidson experiment, based on a space-borne telescope with a permanent built-in eclipse, provided by a coronagraphic system. The expected improvement on experimental bounds to General Relativity and competing gravitation theories is by at least two orders of magnitude. The measurement principle is reviewed, in particular the principle of Fizeau-like combination of a set of individual inverted coronagraphs simultaneously feeding a common high resolution telescope. Also, the payload has a dual field of view property, in order to support simultaneous observations of stellar fields either very close, or far away, from the Sun, i.e. fields affected by either high or low light bending. We discuss a set of solutions introduced in the optical design to improve on technical feasibility and robustness of the optical performance against perturbations, in particular induced by manufacturing and alignment tolerances, and launch stresses.

In the search for exoplanets, one of the most sought-after goals from the outset has been to survey nearby systems for Earth-mass planets in their habitable zones. Because of their relatively low mass and size, and their separation from their host stars, these most prized targets have been elusive so far. High precision astrometry is an indirect method that is complementary in its reach to those of the Doppler and photometric transit methods. The Micro-arcsecond Astrometry Small Satellite (MASS), is a concept astrometric mission utilizing a small space telescope and ultra-precise focal plane and field distortion calibration. In one version, recently proposed as a NASA mission of opportunity, MASS's performance was evaluated with a 35 cm primary mirror and a 150 Mpix scientific CMOS sensor, and was estimated to achieve a single-look accuracy of 6 µas. Even with this modest telescope, MASS would have the sensitivity needed to find a 1 Earth-mass planet at 1 AU orbit (scaled to solar luminosity) around the ~5 nearest FGK stars and 2 Earth-mass planets around an additional ~15 nearest stars. MASS would be able not only to measure masses of these exo-Earths but also characterize their orbits for follow- on direct detection missions such as HabEx or LUVOIR. In this presentation we describe the proposed mission, the precision astrometric technique, and the results from testbed demonstration of the technique.

High precision astrometry aims at source position determination to a very small fraction of the diffraction image size, in high SNR regime. One of the key limitations to such goal is the optical response variation of the telescope over a sizeable FOV, required to ensure that bright reference objects to any selected target. The issue translates into severe calibration constraints, and/or the need for complex telescope and focal plane metrology. We propose an innovative system approach derived from the established TMA telescope concept, extended to achieve high filling factor of an annular field of view around the optical axis of the telescope. The proposed design is a very compact, 1 m class telescope compatible with modern CCD and CMOS detectors (EFL = 15 m). We describe the concept implementation guidelines and the optical performance of the current optical design. The diffraction limited FOV exceeds 1.25 square degrees, and the detector occupies the best 0.25 square degree with 66 devices.

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) project is a dedicated satellite developed at the cooperation of China and France, aim to make prompt multi-band observations of Gamma-Ray Bursts (GRBs), the afterglows and other high-energy transient astronomical events. The Visible Telescope (VT) is one of the four payloads onboard the SVOM. VT is designed to observe the afterglows of GRBs both in the visible and near infrared bands simultaneously. The telescope can reach a limiting magnitude of +22.5Mv and provide the redshift indicators for high-Z (z<4) GRBs. VT is also designed to measure the Relative Performance Errors (RPEs) for the satellite attitude and orbit control system (AOCS), aiming to improve the pointing stability of the platform during observation. VT adopts a Ritchey-Chrétien (RC) catadioptric optical configuration with a 440mm aperture and uses the dichroic prism before the focal plane to split the incident light into blue (visible) and red (near infrared) band. Two Fine Guidance Sensor (FGS) CCDs are mounted beside the main CCD on the blue band focal plane of VT and provide sub-arcsecond pixel resolution. Fiber reinforced plastic (CFRP) composites is selected as the material of VT’s main structure to ensure enough stiffness and strength during launch. The electrical video processing circuit is carefully designed to make the readout noise below 6e-/pix (rms) in 100s exposure time. Active and passive thermal control are used together to ensure the optical performance and thermoelectric cooler (TEC) is adopted to control the main CCDs working temperature below -65°C to reduce the noise. This paper provides a comprehensive overview of the scientific requirements and the key instrument design aspects of optics, main structure, electrics, thermal control, performance test and validation results of VT.

The HiZ-GUNDAM (high-z Gamma-ray bursts for UNraveling the Dark Ages Mission) is a time-domain and multi-messenger astronomy mission by monitoring high-energy astronomical transient events such as gamma-ray bursts (GRBs). The HiZ-GUNDAM is designed to provide alerts of high-redshift GRBs with an ultra-wide field X-ray monitor and a co-onboard 30-cm telescope for immediate photometric follow-up observations in the visible and near-infrared. The HiZ-GUNDAM satellite automatically changes its attitude toward the discovered transient object, starts the follow-up observations with the telescope, and sends alert information including the detailed position, the apparent magnitude and photometric redshift of the transient object within one hour. This mission was selected as one of the mission concept candidates of the competitively-chosen medium-class mission of ISAS/JAXA in the mid-2020s. The basic design of the breadboard model of the telescope is undergoing, and the verification plan of it is studied. The optics are cooled down to 200 K by radiation cooling, and infrared detectors are additionally cooled down to 120 K by a mechanical cooler. All mirrors in the telescope are made of the same aluminum-alloy to reduce the alignment errors during cooling. The four-band simultaneous observation is realized by three beam splitters. The HgCdTe and HyViSi detectors are installed in this telescope. Basic technologies for these specifications are demonstrated by our other missions. In addition, the onboard detection algorithm of high-redshift GRBs by distinguishing them from nearby dusty galaxies in the orbit is also studied. In this paper, we introduce the current status of the development of the telescope onboard HiZ-GUNDAM.

The James Webb Space Telescope (Webb) is the largest space telescope realized to-date, with a 6.5 m segmented primary mirror that must be folded to fit within its Ariane 5 launcher fairing. This infrared telescope is passively cooled using a five-layer sunshield that will keep the optical telescope and its four science instruments in the shade throughout the lifetime of the mission in an L2 orbit. Webb's science instruments include near- and mid- infrared imagers and spectrometers that cover the spectral range from 0.6-28.5 μ.m The Webb mission has a long history with numerous first of its kind technology developments, ground support equipment innovations, and algorithmic characterization advances. This conference proceeding summarizes the technical progress over the past two years, from the Spacecraft Element environmental testing to the Observatory integration and testing, and the final Observatory test plans leading up to launch, on-orbit commissioning, and science operations.

This paper gives a status of the JWST Observatory and what has happened since the last conference in June of 2018

The James Webb Space Telescope (JWST) is going through final integration and testing and is planned to launch in 2021. The last remaining optical challenge for JWST is to fully align the observatory in flight to meet the optical requirements but this effort involves many system considerations to do this safely and efficiently and the entire effort will take several months. This talk will cover what it takes to deploy and optically commission the telescope including the many interactions and constraints of deployment, thermal, optical, attitude control and contamination properties of the observatory. The talk will cover the final optical requirements that the telescope will need to meet and will provide the roadmap of timelines, cooldown profiles, Wavefront Sensing and Control steps, system constraint considerations, and implementation of lessons learned from the ground test campaign that will result in meeting those optical requirements.

The James Webb Space Telescope (JWST) is a large (6.5 m) near- and mid-infrared telescope scheduled for launch in 2021. JWST will be used to explore fundamental questions in astrophysics and planetary science, including the evolution of galaxies, the first light of stars, the formation of stars and planets as well as the characterization of exoplanets. To achieve these scientific goals, NASA and its international partners, the Canadian Space Agency (CSA) and the European Space Agency (ESA), have developed four science instruments for JWST and have prepared detailed commissioning plans for each. The NASA Project Science team has also outlined activities to characterize the performance of the Observatory as a whole. These activities include: 1) monitoring of the instrument and telescope cooldown for contamination mitigation; 2) measurements of straylight and other backgrounds for validation of the JWST stray light models as well as instrument background subtraction algorithms; 3) characterization of optical thermal distortion between its hot and cold telescope pointings within the observable field of regard and 4) trending of observatory performance parameters. Each of these activities has been planned in close collaboration with the observatory wavefront, commissioning planning, and science instrument teams. Here we present the plans for these activities, the expected results and how they will impact future guest observer (GO) proposals and JWST science community.

The Atmospheric Remote-Sensing Infrared Exoplanet Large-survey, ARIEL, has been selected to be the next (M4) medium class space mission in the ESA Cosmic Vision programme. From launch in 2028, and during the following 4 years of operation, ARIEL will perform precise spectroscopy of the atmospheres of ~1000 known transiting exoplanets using its metre-class telescope. A three-band photometer and three spectrometers cover the 0.5 µm to 7.8 µm region of the electromagnetic spectrum. This paper gives an overview of the mission payload, including the telescope assembly, the FGS (Fine Guidance System) - which provides both pointing information to the spacecraft and scientific photometry and low-resolution spectrometer data, the ARIEL InfraRed Spectrometer (AIRS), and other payload infrastructure such as the warm electronics, structures and cryogenic cooling systems.

Ariel, the “atmospheric remote sensing infrared exoplanet large survey” mission, is the European Space Agency’s Cosmic Vision M4 (medium-class number 4) science mission. It has recently gone through an implementation approval (“adoption”), with a planned launch in 2029. Ariel, together with two other M4 candidate missions (THOR and XIPE), was recommended in June 2015 to enter an assessment study, consisting of a Phase 0 at the ESA internal Concurrent Design Facility study followed by a Phase A with parallel industrial studies. The Phase A was concluded in March 2018 with the selection of Ariel as the M4 mission endorsed by the ESA Science Programme Committee (SPC). Phase B1 was subsequently initiated, and was concluded by the Mission Adoption Review in mid-2020, followed by the formal adoption of Ariel in November 2020 by the SPC. Ariel is a survey-type mission dedicated to the characterisation of exoplanets by performing a chemical census. Using the differential technique of transit/eclipse spectroscopic observations, Ariel will obtain transmission and/or emission spectra of the atmospheres of a large (~1000) and diverse sample of known exoplanets covering a wide range of masses, densities, equilibrium temperatures, orbital properties and host-star characteristics. This will include hot Jupiters to warm Super-Earths, orbiting A to M spectral class host stars. This paper reports on the Ariel Phase 0/A/B1 study, including the conclusions of the reviews that were conducted in 2020 to close the study and support the adoption process.

PLATO (PLAnetary Transits and Oscillation of stars) is the ESA Medium size dedicated to exo-planets discovery and cataloguing, adopted in the framework of the Cosmic Vision 2015-2025. The PLATO launch is planned in 2026 and the mission will last at least 4 years in the Lagrangian point L2. The primary scientific goal of PLATO is to discover and characterize a large amount of exo-planets hosted by bright nearby stars. The PLATO strategy is to split the collecting area into 24(+2) identical 120 mm aperture diameter fully refractive cameras with partially overlapped Field of View delivering an overall instantaneous sky covered area of about >2100 square degrees. The opto-mechanical sub-system of each camera, namely Telescope Optical Unit (TOU), is basically composed by a 6 lenses fully refractive optical system, presenting one aspheric surface on the front lens, and by a mechanical structure made in AlBeMet. In this paper we will update on the current working status of the TOUs.

CHEOPS (Characterizing Exoplanets Satellite) is an ESA scientific mission devoted to the characterization of known exoplanets orbiting bright stars, achieved through the precise measurement of exoplanet radii using the technique of transit photometry. CHEOPS was selected in October 2012 as the first Small-class mission (S) within the Agency’s Scientific Programme, with an implementation cycle drastically shorter than for Medium-class (M) and Large-class (L) missions and strict cost-cap to ESA. Following the phase A/B1 study, CHEOPS was adopted for implementation in February 2014 as a partnership between the ESA Science Programme and Switzerland, with a number of other Member States delivering significant contributions to the instrument development and to operations. The CHEOPS payload is a high precision photometer, with an optical Ritchey-Chrétien telescope with 300 mm effective aperture and a large external baffle to minimize straylight. The CHEOPS spacecraft (280 kg mass, 1.5 m size) is based on a flight-proven platform and is now operating in a dawn-dusk Sun Synchronous Orbit at 700 km altitude. CHEOPS completed the Preliminary Design Review at the end of September 2014, passed the Critical Design Review in May 2016 and the Qualification and Acceptance review in February 2019. CHEOPS was launched on a shared Soyuz flight from the European Space Centre of Kourou on 18 December 2019 (VS23), completing the In-Orbit Commissioning in March 2020. The paper describes the CHEOPS launch campaign, the early operations phase and the In-Orbit Commissioning results, including instrument and spacecraft performance.

Although astronomers have confirmed the existence of 4,000 exoplanets to date, it is still difficult to directly compare exoplanets with the planets in our solar system because most of the known transiting exoplanets have an orbital period shorter than 1 year. Recent analyses of the 4-year data from the Kepler spacecraft revealed dozens of long-period transiting exoplanets and showed that their abundance is of order unity around Sun-like stars. However, the stars targeted by Kepler are too faint to conduct follow-up observations. The on-going all-sky survey mission TESS, with four 10.5 cm cameras with a field of view of 24 deg x 24 deg, is finding nearby transiting planets; however, the nominal observation period (1 month{1 year) is too short to find long-period planets with au-scale orbits. Herein, we propose using the LOng-period Transiting exoplanet sUrvey Satellite (LOTUS) mission, which employs a 7.5 cm wide-field (33 deg x 33 deg) camera placed on a nanosatellite, to continuously monitor the same sky region and find long-period planets transiting nearby bright stars. We present a conceptual design for the optics and bus system of LOTUS. Our optical system has a uniform point spread function over the entire field of view and a wide wavelength range (0.5{1.0 um). The bus system is designed to ensure that the pointing precision is sufficient to achieve the sub-percent photometry required for the detection of transiting exoplanets.

MARSU is a CubeSat mission designed to monitor transits of planetary systems around nearby M-dwarfs and young Sun-like stars, and characterize the magnetic activity of the host stars. As a dedicated infrared space photometer, MARSU is expected to be able to detect Earth-like planets in the habitable zone of M dwarfs. It will achieve continuous (duty cycle in excess of 90%) photometric monitoring in the YJH bands (1- 1.7 µm) for stars up to an H magnitude of 11, at a precision better than one mmag over continuous periods of up to 3 months. A heliosynchronous orbit is selected to ensure nearly continuous monitoring of stellar targets in the antisolar direction. MARSU will include a photometric telescope occupying 1x1x3U in a 6U platform. The payload features an 8.5cm dioptric telescope with an athermal optical system and a Short-Wave InfraRed (SWIR) type detector. End-to-end simulations have been carried out and confirm that the quality of photometric data will be consistent with the primary science goals and that the subsequent technical constraints (e.g., pointing stability) are consistent with the expected performance of a 6U CubeSat. MARSU will work in parallel with SPIRou and SPIP, which are twin ground-based infrared spectropolarimeters and velocimeters operated as new generation instruments for the Canada-France-Hawaii Telescope (CFHT, Maunakea Observatory, Hawaii) and Télescope Bernard Lyot (TBL, Pic du Midi, France) respectively. The multi-source data will be analyzed together to optimize the activity filtering and exoplanet characterization (mass from the ground, radius from space).

A notional space telescope without any mirrors or lenses is being investigated. DUET (Dual Use Exoplanet Telescope) has a gossamer membrane annular Gabor Zone Plate primary objective that is flat. Highly chromatic stellar imagery is disambiguated in a secondary also made from diffractive elements. The data acquired is intrinsically spectrographic and could (1) detect radial velocity below 5 cm/sec and (2) take direct spectra of a systems exoplanets. DUET is intended as a follow-up to a survey telescope, THE MOST, being developed in tandem which will identify target stellar systems with earth-like exoplanets. DUET observes one star at a time, integrating its light until the exoplanetary system is resolved. DUET utilizes a battery of coronographic methods including angular differential imaging, interferometric nulling, and phased Fraunhofer line subtraction. The potential performance has been given preliminary laboratory tests which are detailed in Conference AS11451-192.

We are developing a 2D programmable field masks for Mutli-Object Spectroscopy (MOS) in sparsely populated fields. The device is based on the microshutter array MEMS technology originally developed for JWST NIRSpec. A new fabrication process has been developed to actuate microshutter arrays electrostatically thus eliminating the need for the macroscopic mechanisms and improving the reliability and robustness of the device. The microshutters, made with silicon nitride membranes with a shutter pitch size of 100 μm x 200 μm, rotate on narrow torsion bars. The microshutters are actuated, latched, and addressed electrostatically by applying voltages to the electrodes on the microshutters and the adjacent walls of the array support grid. We have demonstrated the fabrication and operation of the pilot arrays and produced an integrated flight unit that was successfully used on the FORTIS (Far-UV Off Rowland-circle Telescope for Imaging and Spectroscopy) project for suborbital flight in 2019.

ExoSpec Project is a NASA Headquarters directed work package that links four different tasks at Goddard space flight center to enable future missions to more efficiently characterize directly imaged exoplanets. One of the tasks is the development of parabolic deformable mirrors to improve on the current state-of-the-art wavefront sensing and control implementations that are baselined to have two high actuator count flat deformable mirrors (DMs). To effectively control both amplitude and phase aberrations, the flat DMs need to have a large separation distance. This large separation poses packaging challenges to missions designed to image rocky exoplanets at larger angular separations. To eliminate this large separation, the parabolic DM architecture makes the off-axis imaging elements in the optical train are controllable. Simulations also show performance enhancements with the architecture change; larger bandwidths have been shown to be controllable with the parabolic DMs and the number of required actuators can be reduced. With a 32x32 pupil flat DM and two 16x16 parabolic DMs, we could dig a 5-12 λ/D dark hole at 35% bandwidth. In addition to addressing the packaging challenge faced by future coronagraph missions, reducing the number of actuators reduces both cost and risk of having the entire coronagraph instrument’s performance depend on two high-actuator count DMs. To test these simulations, Goddard is building a testbed and has a vendor working on manufacturing the parabolic DM. Here we present these simulations, the current testbed performance, and the development plan to incorporate and test the parabolic DMs.

CUBESPEC is an ESA in-orbit demonstration 6U CubeSat mission, currently in phase A/B. CUBESPEC will deliver months long series of high-resolution spectroscopy to study the structure of massive stars. The payload consists of a Cassegrain telescope with a rectangular primary mirror of 9 x 19 cm2 and a compact high-resolution echelle spectrograph. We aim at a 2023 launch demonstrating the CUBESPEC concept: providing the astronomical community with a generic solution for affordable space-based spectroscopy. The spectrograph design can be configured with minimal hardware changes for low spectral resolution (R = 50) up to high resolution (R ~ 50000) over a over wavelength ranges between 200–1000nm. CUBESPEC will use the KU Leuven ADCS for coarse pointing of the spacecraft, supplemented with a fine-guidance system using a fast steering mirror to center the source on the spectrograph slit. We present the CUBESPEC design and mission analysis, and give an update of the project status.

MAJIS (Moons And Jupiter Imaging Spectrometer) is one of the science instruments of the ESA L-Class mission JUICE (Jupiter ICy Moons Explorer) to be launched in 2022 with an arrival at Jupiter in 2030. MAJIS will perform imaging spectroscopy through two channels: VIS-NIR (0.50 um - 2.35 um) and IR (2.25 μm - 5.54 μm). The Royal Belgian Institute for Space Aeronomy (BIRA-IASB) and the Royal Observatory of Belgium (ROB) contribute to MAJIS with the characterization of the VIS-NIR Flight Model (FM) and Spare Model (SM) detectors, including the design, development and validation of the setup, and the data processing pipeline. Typical detector characterization measurements were performed during the campaigns but also calibrated measurements such as Quantum Efficiency (QE). Since some of the characterization measurements require different illumination conditions, temperature, beam uniformity, exposure time, and/or data acquisition procedure, the characterization setup is configurable for dark conditions, uniform light beam, and convergent beam with same focal ratio as MAJIS convergence optics. The thermal-vacuum characterization facility was completed at BIRA-IASB premises and was subjected to validation tests on late 2019 and early 2020. MAJIS VIS-NIR FM detector was delivered for its complete characterization in June 2020; SM characterization shall be performed after time of meeting. In this paper, we summarize the optical and thermal performances of the facility, the detector's mechanical integration method and its optical alignment into the setup, the security system implemented, the general operation of the setup during the characterization campaign, and FM preliminary result analyses.

High angular resolution astronomical observation in far-infrared better than one milli-arcsecond will open a new field of astronomy, such as imaging inner region of protoplanetary disk and broad line region of active galactic nuclei. We propose to apply intensity interferometry in far-infrared wavelengths for aperture synthesis imaging. Intensity interferometry is known by the Hanbury-Brown and Twiss experiment in 1950’s, but aperture synthesis imaging was not possible because of missing phase information. Modern fast electronics enable a usage of fast photon detectors, and delay time measurements of photon bunches enable aperture synthesis imaging. There are several merits using intensity interferometry in far-infrared wavelengths. First, high sensitivity direct detectors can be used to realize background limited observations from space, not limited by quantum noise of heterodyne receivers. Second photon signal can be recorded, and correlation analysis can be made in post data analysis, and there is no need for beam combining optics. These lead to flexible telescope configuration in space; number of telescopes is not limited, attitude control of satellite can be independent, and baseline configuration is flexible. We have demonstrated the delay time measurements in microwave, some simulation studies for aperture synthesis imaging were made and developing fast photon detectors in terahertz frequencies. Experimental setup for intensity interferometry is being prepared. Prospects of far-infrared intensity interferometers on ground and in space are discussed.

Starshades are a leading technology to detect and characterize Earth-like exoplanets. In this paper we report on optical experiments of sub-scale starshades that advance critical starlight suppression technologies in preparation for the next generation of space telescopes. These experiments were conducted at the Princeton starshade testbed, an 80 m long enclosure testing 1/1000th scale starshades at a flight-like Fresnel number. In this paper we summarize recent updates made to the starshade testbed and optical model. We present results from recent experiments testing two starshade masks with intentional perturbations built into their shape. One of the perturbed masks has three petals that are shifted radially outward by 7-11 microns and the other mask has two petals shifted radially outward plus two petal edge segments displaced from their nominal position. We show the model agrees with experiment to better than 25% accuracy. These results are placed into context with previous experiments on perturbed shapes and progress made towards satisfying a critical milestone in advancing starshade technology to TRL 5.

The Coronagraph Instrument (CGI) on the Nancy Grace Roman Space Telescope will demonstrate the highcontrast technology necessary for visible-light exoplanet imaging and spectroscopy from space via direct imaging of Jupiter-size planets and debris disks. This in-space experience is a critical step toward future, larger missions targeted at direct imaging of Earth-like planets in the habitable zones of nearby stars. This paper presents an overview of the current instrument design and requirements, highlighting the critical hardware, algorithms, and operations being demonstrated. We also describe several exoplanet and circumstellar disk science cases enabled by these capabilities. A competitively selected Community Participation Program team will be an integral part of the technology demonstration and could perform additional CGI observations beyond the initial tech demo if the instrument performance warrants it.

NASA’s Nancy Grace Roman Space Telescope (formerly known as WFIRST) is a flagship astrophysics mission planned for launch in 2025. The coronagraph instrument (CGI) on Roman will demonstrate the technology for direct imaging and spectroscopy of exoplanets around nearby stars. It will work with the 2.4-meter diameter telescope to achieve starlight suppression that is 2-3 orders of magnitude deeper than previous space-based and ground-based coronagraphs by using active wavefront control in space with deformable mirrors. CGI has passed its Preliminary Design Review (PDR) in September 2019 and is working toward the instrument Critical Design Review (CDR) in the spring of 2021. We describe the CGI engineering design going into CDR and the operational concept planned for CGI observations.

Optical diffraction and wavefront sensing and control (WFSC) models validated against the high-fidelity Roman Space Telescope Coronagraph Instrument (CGI) testbed play a key role in mask design selection and the verification of many requirements that cannot be accomplished until the observatory is in orbit. We have been steadily improving our model fidelity for the as-built CGI testbed system. We demonstrate recently good agreement between measurements and model predictions while validating the Hybrid Lyot Coronagraph’s (HLC) performance using the in-orbit high order wavefront sensing and control (HOWFSC) operational scenario. We present modeling and testbed validation results that explain the reason why many testbed WFSC iterations were needed for HLC in the past. A new, direct application of model-generated initial deformable mirror (DM) voltage pattern has since been successfully demonstrated on the testbed with significant speed and performance improvement. This opens up new model-based initial DM pattern WFSC approaches for CGI. This can greatly reduce flight risk from potentially insufficient ground DM pattern generation due to schedule or cost constraints or from unexpected post-delivery changes. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology under contract to NASA.

The Coronagraphic Debris Exoplanet Exploring Payload (CDEEP) is a Small-Sat mission concept for high contrast imaging of circumstellar disks. CDEEP is designed to observe disks in scattered light at visible wavelengths at a raw contrast level of 10-7 per resolution element (10-8 with post processing). This exceptional sensitivity will allow the imaging of transport dominated debris disks, quantifying the albedo, composition, and morphology of these low-surface brightness disks. CDEEP combines an off-axis telescope, microelectromechanical systems (MEMS) deformable mirror, and a vector vortex coronagraph (VVC). This system will require rigorous testing and characterization in a space environment. We report on the CDEEP mission concept, and the status of the vacuum-compatible CDEEP prototype testbed currently under development at the University of Arizona, including design development and the results of simulations to estimate performance.

A new era is expected to arrive around 2030 with a pool of exoplanets amounting to about ten thousand, including mainly small to medium-sized planets, and over a hundred habitable terrestrial rocky planets, thanks to the space-borne transit surveys by the Kepler, TESS and PLATO missions, and ground-based transit and radial-velocity (RV) surveys. The exoplanet community has proposed various missions for detailed characterization of the terrestrial planets, but it is quite technique-demanding and time-consuming especially for those with wide orbits. The currently proposed ESA mission ARIEL is a first step for this purpose, and it is powerful for the characterizations of planets down to warm super-Earths. The NASA HabEx and LUVOIR missions are mega projects to further tackle down to habitable rocky planets, and will be in operation after 2035 if approved. In the meanwhile, China is funding a concept study of a 4-6m space telescope named HABITATS ( HABItable Terrestrial planetary ATmospheric Surveyor). HABITATS will be dedicated for the characterization of habitable rocky planets around nearby stars, which aims to start its operation within the next 10-15 years and last for 5+ years. We describe briefly the preliminary concept study of this mission and propose a baseline telescope and instrument parameter values based on our simulation results. International collaborations from various institutes and research groups are welcome to join this ambitious effort in the aspects of science, instrumentation, platform, funding resources.

The Habitable Exoplanet Observatory (HabEx), was one of four candidate flagship missions studied in detail by NASA, which were submitted for consideration to the 2020 Decadal Survey in Astronomy and Astrophysics for possible launch in 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 sun-like 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 was designed to be the Great Observatory of the 2030s and beyond, with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR.

To achieve the ambitious goal of directly imaging exo-Earths with a coronagraph, future space-based astronomical telescopes will require wavefront stability several orders of magnitude beyond state-of-the-art. The Ultra-Stable Large Telescope Research and Analysis – Technology Maturation (ULTRA-TM) program will mature critical technologies for this new regime of “ultra-stable optical systems” through component-level hardware demonstrations. This paper describes the progress towards demonstrating performance of these technologies in the picometer regime and with flight-like properties – including active systems like segment sensing and actuation and thermal sensing and control, as well as passive systems like low distortion mirror mounts and composite structures. Raising the TRL of these technologies will address the most difficult parts of the stability problem with the longest lead times and provide significant risk reduction for their inclusion in future mission concepts.

Future large-scale exoplanet direct-imaging missions will be capable of discovering and confirming Earth-Like exoplanets. The community has traditionally used the fraction of planets occurring within the visible limits of a telescope to evaluate these telescope designs. However, using only the instrument's geometric constraints and assuming a limiting planet magnitude ignores integration time requirements and can lead to overly optimistic performance predictions. In this paper, we present a new method for evaluating the fraction of observable planets that accounts for integration time. We also provide analytical methods for calculating the planet-star separation extrema for any given planet and analytical methods describing the true anomaly values at which a planet has a given planet-star separation. This new completeness calculation method explains some of the differences in the HabEx final report between EXOSIMS exoplanet yield numbers and completeness based yield estimates and attributes them to the lacking capabilities of current completeness based telescope performance evaluations. Our methods demonstrate that traditional completeness methods used in the final report and other exoplanet yield estimates overestimate yield between 32% and 141% compared to integration time adjusted completeness depending on the instrument capabilities and target.

The mid/far infrared hosts a wealth of spectral information that allows direct determination of the physical state of matter in a large variety of astronomical objects, unhindered by foreground obscuration. Accessing this domain is essential for astronomers to much better grasp the fundamental physical processes underlying the evolution of many types of celestial objects, ranging from protoplanetary systems in our own milky way to 10-12 billion year old galaxies at the high noon of galaxy formation in our universe. The joint ESA/JAXA SPICA mission will give such access for the astronomical community at large, by providing an observatory with unprecedented mid- to far-infrared imaging, polarimetric and spectroscopic capabilities.

The ESA/JAXA SPICA mission is a candidate for the ESA Cosmic Vision Medium Class M5 opportunity. Since 2019 an Airbus Defence and Space team has been performing a trade-off study (on behalf of ESA) to establish a baseline telescope optical configuration and design, which can meet the mission scientific performance requirements. This paper describes the telescope baseline design selected, with first estimates of the expected optical performance. The optical design wavelength is 20 microns for an operating temperature of 8 K covering a total bandwidth of 12 to 420 microns over a 30 arc minutes field of view, with a total required collecting area of at least 4.0 m². The fundamental mission science driver is to achieve a sky background (astrophysical sources) limited performance. The telescope is designed to illuminate three instruments namely; SMI (JAXA - Japan), SAFARI (SRON - Netherlands) and B-BOP (CEA - France).

We present an overview of the cryogenic system of the next-generation infrared observatory mission SPICA. One of the most critical requirements for the SPICA mission is to cool the whole science equipment, including the 2.5 m telescope, to below 8 K to reduce the thermal background and enable unprecedented sensitivity in the mid- and far-infrared region. Another requirement is to cool focal plane instruments to achieve superior sensitivity. We adopt the combination of effective radiative cooling and mechanical cryocoolers to accomplish the thermal requirements for SPICA. The radiative cooling system, which consists of a series of radiative shields, is designed to accommodate the telescope in the vertical configuration. We present thermal model analysis results that comply with the requirements to cool the telescope and focal plane instruments.

The Space Infrared Telescope for Cosmology and Astrophysics (SPICA) mission is to be launched into orbit around the second Lagrangian point (L2) in the Sun-Earth system. Taking advantage of the thermal environment in L2, a 2.5m-class large IR telescope is cooled below 8K in combination with effective radiant cooling and a mechanical cooling system. SPICA adopts a cryogen-free system to prevent the mission operation lifetime being limited by the amount of cryogen as a refrigerant. Currently, the mechanical cooler system with the feasible solution giving a proper margin is proposed. As a baseline design, 4K / 1K-class Joule-Thomson coolers are used to cool the telescope and thermal interface for Focal Plane Instruments (FPIs). Additionally, two sets of double stage stirling coolers (2STs) are used to cool the telescope shield. In this design, nominal operation of FPIs can be kept when one mechanical cooler is in failure. In this paper, current baseline configuration of the mechanical cooler system and current status of mechanical coolers developments which need to satisfy the specific requirements of SPICA cryogenic system are presented.

The National Academies’ Decadal Survey telescope studies have produced mission design concepts that plot pathways into the future to follow on from Hubble, Spitzer, JWST and NGRST. Considering the results of the LUVOIR and HabEx studies in particular, it is clear that segmented mirrors will eventually be needed to provide very large apertures in space and that this architecture presents both a scientific opportunity and an engineering challenge. Furthermore, while HabEx and LUVOIR cover a great deal of spectrum, both fall short of the mid-IR region where general astronomy and astrophysics can be undertaken that would be impossible from terrestrial observatories and where there also exist spectral features of interest in the search for life. A telescope with similar capabilities to Habex/LUVOIR but also capable of exoplanet work in spectral regions up to 5 μm would largely bridge the gap between those proposals and TPF-I (which would have operated from about 7 μm upwards), and is therefore worthy of study. The Active Telescope for Space Astronomy (ATSA) design study presents a possible architecture and is moderately sized (6 m) to enable the use of both starshade and coronagraph technologies. While the segment gaps of a segmented primary mirror present a challenge for coronagraphy, the architecture does allow direct wavefront control at each segment of that mirror, enabling a great degree of control at the primary source of contrast degradation. While active systems (for example, deformable mirrors on WFIRST CGI) are being incorporated into telescope designs today, a fully active mirror system needs further development for a future mission. With this concept in mind, and intending to build on the LUVOIR and HabEx studies, we discuss the elements of a cooled telescope design enabling both general astrophysics and exoplanet studies from the near UV through to the near-IR.

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. Origins was designed to minimize complexity and provide natural background-limited sensitivity. The telescope is 5.9 m in diameter. The telescope and its three scientific instruments are cryocooled to 4.5 K. The instruments collectively cover wavelengths from 2.8 to 590 microns. Origins will make targeted observations and conduct wide-area surveys in a variety of spectroscopic and broadband imaging modes.

LiteBIRD, the Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection, is a space mission for primordial cosmology and fundamental physics. JAXA selected LiteBIRD in May 2019 as a strategic large-class (L-class) mission, with its expected launch in the late 2020s using JAXA's H3 rocket. LiteBIRD plans to map the cosmic microwave background (CMB) polarization over the full sky with unprecedented precision. Its main scientific objective is to carry out a definitive search for the signal from cosmic inflation, either making a discovery or ruling out well-motivated inflationary models. The measurements of LiteBIRD will also provide us with an insight into the quantum nature of gravity and other new physics beyond the standard models of particle physics and cosmology. To this end, LiteBIRD will perform full-sky surveys for three years at the Sun-Earth Lagrangian point L2 for 15 frequency bands between 34 and 448 GHz with three telescopes, to achieve a total sensitivity of 2.16 μK-arcmin with a typical angular resolution of 0.5° at 100 GHz. We provide an overview of the LiteBIRD project, including scientific objectives, mission requirements, top-level system requirements, operation concept, and expected scientific outcomes.

LiteBIRD is a JAXA-led Strategic Large-Class mission designed to search for the existence of the primordial gravitational waves produced during the inflationary phase of the Universe, through the measurements of their imprint onto the polarization of the cosmic microwave background (CMB). These measurements, requiring unprecedented sensitivity, will be performed over the full sky, at large angular scales, and over 15 frequency bands from 34 GHz to 448 GHz. The LiteBIRD instruments consist of three telescopes, namely the Low-, Medium-and High-Frequency Telescope (respectively LFT, MFT and HFT). We present in this paper an overview of the design of the Medium-Frequency Telescope (89{224 GHz) and the High-Frequency Telescope (166{448 GHz), the so-called MHFT, under European responsibility, which are two cryogenic refractive telescopes cooled down to 5 K. They include a continuous rotating half-wave plate as the first optical element, two high-density polyethylene (HDPE) lenses and more than three thousand transition-edge sensor (TES) detectors cooled to 100 mK. We provide an overview of the concept design and the remaining specific challenges that we have to face in order to achieve the scientific goals of LiteBIRD.

Millimetron is a cryogenically cooled 10-m aperture space observatory. The telescope of the observatory will be maintained at a temperature less than 10 K, enabling its unprecedented sensitivity gain and will operate from 50 µm to 10 mm, encompassing the far-infrared, submillimeter and millimeter wavelength ranges. Observatory has two modes of observations: as a single dish space telescope, and as an element of Space-Earth Very Large Baseline Interferometer (SVLBI). Scientific instrumentation includes four instruments with capabilities for imaging, spectroscopy (medium- and high-resolution) and polarimetry, as well as an instrument for space-earth interferometry. We describe the key science cases and progress of the MSO development.

Due to the limited number of photons, directly imaging planets requires long integration times. The wavefront must be stable on the same time scale which is often difficult in space due to thermal variations and vibrations. In this paper, we discuss the results of implementing a dark hole maintenance (DHM) algorithm (Pogorelyuk et. al. 2019)¹ on the High-contrast imager for Complex Aperture Telescopes (HiCAT) at the Space Telescope Science Institute (STScI). The testbed contains a pair of deformable mirrors (DMs) and a lyot coronagraph. The algorithm uses an Extended Kalman Filter (EKF) and DM dithering to predict the drifting electric field in the dark hole along with Electric Field Conjugation to cancel out the drift. The DM dither introduces phase diversity which ensures the EKF converges to the correct value. The DHM algorithm maintains an initial contrast of 8.5 x 10^-8 for 6 hrs in the presence of the DM actuator random walk drift with a standard deviation of 1:7 x 10^-3 nm/s..

For the disaster prevention and mitigation, large segmented Earth observation telescope in the geostationary orbit is studied in JAXA. In order to obtain diffraction limited performance with the segmented telescope, it is necessary to co-phase the segmented primary mirrors with sub-wavelength accuracy. And since the displacement of the mirrors induced by environmental stress occurs during launching and in orbit, the phasing sensor also need to cover the measurement range exceed tens of micrometers. In this paper, we propose a technique for the purpose and enable us to obtain piston errors of multiple segments simultaneously independent of the edge orientation. The optical scheme for the telescope model is presented and some fundamental experiments are described.

Development of a high-contrast imaging system, especially toward direct detection of habitable Earth-like exoplanets, would be one of the most challenging themes in modern astronomy. For direct detection of exo-Earth, coronagraphic devices are required for suppressing bright diffracted light from a parent star. In addition, residual stellar speckles, caused by imperfection of optical components, have to be also rejected by wavefront control such as the speckle nulling technique. It is important to construct a dedicated testbed at which we can comprehensively develop the high-contrast imaging system for future era of space coronagraphs aimed at searching for exo-Earths. Recently, we have started construction of a new testbed in Japan which is called EXIST (Exoplanet Imaging System Testbed). The EXIST is planned to be compatible with various types of coronagraphs, such as phase-mask coronagraphs based on the photoniccrystal technology, common-path visible nulling coronagraph, and so on. In addition, optimally designed pupil apodizers will be installed into the testbed for maximizing the performance of the phase-mask coronagraphs with arbitrary aperture telescopes. We plan to utilize a spatial light modulator (SLM) for conducting the speckle nulling control. Thanks to a large pixel format of the SLM, we expect that a huge dark hole can be created against the residual speckles. Here, we report our recent progress on the construction of the new testbed and results of some preparatory experiments related to the coronagraphs and the speckle nulling control using the SLM.

The vector vortex coronagraph is an instrument designed for direct detection and spectroscopy of exoplanets over a broad spectral range. Our team is working towards demonstrating contrast performance commensurate with imaging temperate, terrestrial planets orbiting solar-type stars using the High Contrast Imaging Testbed facility at NASA's Jet Propulsion Laboratory. To date, the best broadband performance achieved is ~10-8 raw contrast over a bandwidth of Δλ/λ=10% in the visible regime (central wavelengths of 550 nm-750 nm), while monochromatic tests yield much deeper contrast (~10-9 or better). In this study, we analyze the main performance limitations on the testbeds so far, focusing on the quality of the focal plane mask manufacturing. We measure the polarization properties of the masks and the residual electric field in the dark hole as a function of wavelength. Our results suggest that the current performance is limited by localized defects in the in the focal plane masks. A new generation of masks is under test that have fewer defects and promise performance improvements.

Achieving high levels of contrast over broad bandwidths with segmented aperture telescopes is a key requirement to maximize the scientific yield for future exoplanet imaging missions and ground-based extremely large telescopes. The High-Contrast Spectroscopy Testbed for Segmented Telescopes (HCST) in the Exoplanet Technology Laboratory (ET Lab) at Caltech is designed to proof test new technologies aimed at tackling some of the most pressing and challenging goals of exoplanet science, namely the imaging and spectroscopic characterization of small planets across a wide range of stellar host types, including temperature Earth-size planets. Here we report on the status of a key milestone: Demonstration of 20% bandwidth nulling experiments using single mode fibers wavefront control.

Here we describe scientific processing pipeline of ASPIICS. The ASPIICS coronagraph onboard the formation ying PROBA-3 mission will deliver unprecedented observations of the solar corona starting from 1:1Rꙩ with low straylight. The Science Operations Center (SOC) of ASPIICS, to be installed at the Royal Observatory of Belgium, is responsible for delivering the raw and radiometrically calibrated data products to the science community. Among other processes, the SOC hosts the ASPIICS science data pipeline. The science processing of the ASPIICS data is required to account for the optical and detector effects correctly, convert the data into physical units, merge individual exposures into full field of view images, and calculate the polarized and spectral data products. The general architecture of the SOC is discussed and a particular attention is paid to the science data pipeline.

The CLUPI (CLose-UP Imager) instrument is a high-resolution camera mounted onto the Drill of the ExoMars 2020 rover mission carried out by the European Space Agency (ESA) and Roscosmos. The CLUPI development is under the responsibility of Thales Alenia Space Switzerland whereas the Principal Investigator is Dr. Jean-Luc Josset from the Space Exploration Institute. In the frame of the development CLUPI instrument, the CSEM developed and delivered three models of a flexure-based Focus Mechanism. The CLUPI Focus Mechanism (CFM) design utilizes flexure guides to allow very accurate frictionless adjustment of the focal distance of the imager. Such design must also comply with very stringent requirement from the ExoMars mission, especially regarding the low Martian temperatures and the launch/landing load environment. This article presents the three main challenges encountered during the development of the mechanism and how these were addressed: resilience, performance and reliability. This article then draws the lessons learnt from this development including potential design improvements for a similar design and general rules to applicable to any development involving compliant mechanism.

The volume available on-board small satellites limit the optical aperture to a few centimetres, which limits the Ground- Sampling Distance (GSD) in the visible to approximately 3 m at 500 km. We present a performance analysis of the concept of a deployable CubeSat telescope. This payload will allow a tripling of the ground resolution achievable from a CubeSat imager, hence allowing very high resolution imaging from Low Earth Orbit (LEO). The project combines precision opto-mechanical deployment and cophasing of the mirrors segments using active optics. The payload has the potential of becoming a new off-the-shelf standardised system to be proposed for all high angular resolution imaging missions using CubeSats or similar nanosats. Ultimately, this technology will develop new instrumentation and technology for small satellite platforms with a primary mirror size equal or larger than 30 cm. In this paper, we present the breakdown of the different error sources that may affect the final optical quality and propose cophasing strategies. We show that the piston, tip and tilt aberrations may need to be as small as 15 nm RMS to allow for diffraction-limited imaging. By taking a co-conception approach, i.e. by taking into account the post-processing capability such as deconvolution, we believe these constraints may be somewhat released. Finally, we show numerical simulation of different solutions allowing the aberrations of the primary mirror segments.

The volume available on-board small satellites limit the optical aperture to a few centimetres, which limits the GroundSampling Distance (GSD) in the visible to approximately 3 m at 500 km. We present the latest development of a laboratory demonstrator for a deployable telescope that will triple the achievable ground resolution and quadruple the photometric capability from a CubeSat imager. In this paper, we present the overall opto-mechanical design of a Cassegrain telescope with a segmented primary mirror with a 30 cm baseline. The segments are folded for launch and unfold in space. To enable diffraction-limited imaging, piston, tip, and tilt (PTT) on each of the mirror segments should be below 12 nm RMS. The key challenge is to ensure phasing, and this precision level will require an active phasing stage. We present laboratory results of deployment and active phasing of the primary mirror segments. The initial deployment is performed using shaped memory alloy that deploy mirror segments. We demonstrate a repeatability below ±4.5 μm, enabling the four PSFs (one for each mirror segment) to be imaged on the detector simultaneously. An alignment step using compact and calibrated capacitive sensors allows for a control of the mirror positions in PTT below the wavelength. Finally, we investigate the sensitivity of misalignments of a deployable secondary mirror and show that it is well within reach of the technology developed in this study.

In the next decade, NASA envisions a large space-based telescope that will perform unprecedented astronomy focused on the detection and characterization of Earth-like exoplanets. Recent advances in optical coronography enable this mission, but the technology imposes challenging requirements on telescope dynamic stability and vibration isolation. An integrated non-contact pointing and vibration isolation system called the Disturbance Free Payload (DFP) provides a means to achieve this stability. This system provides an ideal non-contact state (with only residual coupling from power and data cables and actuator effects) while allowing for the necessary degree of rigid-body payload control to meet required telescope pointing and system line-of-sight (LOS) agility. A subscale demonstration of the DFP technology on a CubeSat operating in 6 degrees of freedom in the space environment is one of several developments needed to advance the DFP architecture to TRL 6. This paper describes the mission goals and the preliminary payload and experiment design.

Organized by the Turnbull Science Investigation Team (SIT), the 2019-2020 Roman Exoplanet Imaging Data Challenge (EIDC) launched in mid October 2019 and ran for eight months. This data challenge was a unique opportunity for exoplanet scientists of all backgrounds and experience levels to get acquainted with realistic Roman CGI (coronagraphic) simulated data with a new contrast regimes at 10^-8 to 10^-9 enabling to unveil planets down to the Neptune-mass in reflected light. Participating teams had to recover the astrometry of an exoplanetary system combining precursor radial velocity data (also simulated across 15 years) with two to six coronagraphic imaging epochs (HLC and Star Shade). They had to perform accurate orbital fitting and determine the mass of any planet hidden in the data. It involved PSF subtraction techniques, post-processing and other astrophysics hurdles to overcome such as contamination sources (stellar, extragalactic and exozodiacal light). We organized four tutorial "hack-a-thon" events to get as many people on-board. The EIDC proved to be an excellent way to engage with the intricacies of the first mission to perform wavefront control in space, as a pathfinder to future flagship missions. It also generated a lot of positive interactions between open source package owners and a whole new set of young exoplanet scientists running them. As a community we are a few steps closer to being ready to analyze real CGI data!

The Nancy Grace Roman Space Telescope Coronagraph Instrument (CGI) will be capable of characterizing exoplanets in reflected light and will demonstrate space technologies essential for future missions to take spectra of Earthlike exoplanets. As the mission and instrument move into the final stages of design, simulation tools spanning from depth of search calculators to detailed diffraction models have been created by a variety of teams. We summarize these efforts, with a particular focus on publicly available datasets and software tools. These include speckle and point-spread-function models, signal-to-noise calculators, and science product simulations (e.g. predicted observations of debris disks and exoplanet spectra). This review is intended to serve as a reference to facilitate engagement with the technical and science capabilities of the CGI instrument.

To create a high contrast field of view with a shaped pupil coronagraph (SPC), the telescope pupil is imaged onto the shaped pupil mask, the shaped pupil mask is designed and fabricated through a design optimization based on a given pupil wavefront, and deformable mirrors (DM) in the coronagraph are modulated according to a nonlinear optimization procedure. Both the mask design optimization and the DM optimization require accurate knowledge of the image of the pupil at the shaped pupil plane for the calculation of Jacobians, and the evaluation of alignment tolerances. The shaped pupil coronagraphs demonstrated in the high contrast imaging testbed (HCIT) at JPL has heretofore assumed perfect imaging of the pupil onto the shaped pupil mask. Similarly, the design and performance modeling of the WFIRST CGI instrument makes the same assumption. In this paper we estimate and compare the image of the pupil mask at the shaped pupil plane in the case of the coronagraph testbed, and the image of the telescope pupil at the shaped pupil plane for the WFIRST CGI instrument. The estimated pupil images include field curvature and aberrations resulting from the layout of the parabolic mirror imaging system, which is optimized for the source image, not the image of the pupil. We also show the results of direct measurement of the image of the pupil mask at the shaped pupil plane in the coronagraph testbed.

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 planets in the habitable zone around nearby sun-like stars. Additionally, HabEx will perform a broad range of general astrophysics science enabled by 115 to 1700 nm spectral range and 3x3 arc-minute FOV instruments. Critical to achieving its science goals is a large, ultra-stable UV/Optical/Near-IR (UVOIR) telescope. The baseline HabEx telescope is a 4-meter off-axis unobscured three-mirroranastigmatic, 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.

As part of its technology demonstration, the Nancy Grace Roman Space Telescope (RST) Coronagraph Instrument (CGI) will demonstrate point source spectroscopy and polarization measurements of disks. The specific implementation of spectroscopy is a zero-deviation Amici prism and a slit to be placed on the planet after high contrast has been achieved by CGI. The polarization optics are a set of Wollaston prisms so that orthogonal polarization states can be measured simultaneously. The CGI spectral characterization mode, being designed and built and Goddard Space Flight Center (GSFC), has a spectral resolution of R50 at its central wavelength and is designed to accommodate a 15% bandpass spanning 610􀀀785nm. In order to recover Stokes information, there are two sets of Wollaston prisms clocked 45 degrees with respect to one another with each measurement taken in series. The Wollaston design and optical elements are a contribution by the Japanese Aerospace Exploration Agency (JAXA), with final alignment and testing being done at GSFC. The spectroscopy mode is designed to target Methane absorption features around 730nm, keeping the spectral resolution as low as possible to improve the signal-to-noise ratio and hence reduce detection time. We highlight the requirements for these modes and address the challenge of on-orbit spectral calibration for a deployable slit in the presence of pointing drifts. Of unique interest is how the observatory error budget couples into good stellar spectrum calibration and subsequent speckle subtraction. We also provide further detail on the optomechanical design, its modeled performance, and operations concept. These performance metrics are simulated to demonstrate how a slit located at an arbitrary field point is homed onto the planet and converted to a calibrated spectrum.

This paper presents the setup for empirical validations of the Pair-based Analytical model for Segmented Telescope Imaging from Space (PASTIS) tolerancing model for segmented coronagraphy. We show the hardware configuration of the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed on which these experiments will be conducted at an intermediate contrast regime between 10^-6 and 10^-8. We describe the optical performance of the testbed with a classical Lyot coronagraph and describe the recent hardware upgrade to a segmented mode, using an IrisAO segmented deformable mirror. Implementing experiments on HiCAT is made easy through its top-level control infrastructure that uses the same code base to run on the real testbed, or to invoke the optical simulator. The experiments presented in this paper are run on the HiCAT testbed emulator, which makes them ready to be performed on actual hardware. We show results of three experiments with results from the emulator, with the goal to demonstrate PASTIS on hardware next. We measure the testbed PASTIS matrix, and validate the PASTIS analytical propagation model by comparing its contrast predictions to simulator results. We perform the tolerancing analysis on the optical eigenmodes (PASTIS modes) and on independent segments, then validate these results in respective experiments. This work prepares and enables the experimental validation of the analytical segment-based tolerancing model for segmented aperture coronagraphy with the specific application to the HiCAT testbed.

Coronagraph is a powerful instrumentation that can be used to realize direct exoplanet imaging. Because the stars are far brighter than the exoplanets, a very high requirement for extinction is raised to obtain a high contrast imaging. By optimizing the transmittance of the entrance pupil and the Lyot stop in Lyot Coronagraph, a sequential optimization procedure is proposed to obtain even higher contrast imaging. In this manuscript, the usually adopted joint optimization in the existing literatures is divided into two steps, which we call the sequential optimization procedure. First, the entrance pupil is optimized for maximum transmission while the contrast constraint is imposed on the focal plane of the lens behind it. Second, the Lyot stop is optimized for maximum transmission with the contrast constraint imposed on the imaging plane. Compared with the joint optimization procedure, the sequential one can provide additional advantages. In terms of performance, under the same conditions, an IWA(Inner working angle) of 1.53λ/D can be obtained while the IWA for joint one is 2.01λ/D. Moreover, the sequential optimization is much faster. Referring to practical applications, the optimum transmittance of Lyot stop in sequential case becomes binary and therefore easy to fabricate. However sequential optimization reduces the throughput approximately 36.81%, which is a drawback that should be compensated.

The JamesWebb Space Telescope (JWST) will probe circumstellar environments at an unprecedented sensitivity. However, the performance of high-contrast imaging instruments is limited by the residual light from the star at close separations (<2-3"), where the incidence of exoplanets increases rapidly. There is currently no solution to get rid of the residual starlight down to the photon noise level at those separations, which may prevent some crucial discoveries. JWST's launch is planned for October 2021 with a planned baseline science mission lifetime of only five years. Thus, it is crucial to start developing a solution to this problem before its launch. We are investigating an innovative approach of post-processing built on a Bayesian framework that provides a more robust determination of faint astrophysical structures around a bright source. This approach uses a model of high-contrast imaging instrument that takes advantage of prior information, such as data from wavefront sensing (WFS) operations on JWST, to estimate simultaneously instrumental aberrations and the circumstellar environment. With this approach, our goal is to further improve the contrast gain over the contrast that can be achieved with JWST instruments, starting with NIRCam direct imaging and coronagraphic imaging. This work will pave the way for the future space-based high-contrast imaging instruments such as the Nancy Grace Roman Space Telescope_ Coronagraph Instrument (Roman CGI). This technique will be crucial to make the best use of the telemetry data that will be collected during the CGI operations.

Modern coronagraph design relies on advanced, large-scale optimization processes that require an ever increasing amount of computational resources. In this paper, we restrict ourselves to the design of Apodized Pupil Lyot Coronagraphs (APLCs). To produce APLC designs for future giant space telescopes, we require a fine sampling for the apodizer to resolve all small features, such as segment gaps, in the telescope pupil. Additionally, we require the coronagraph to operate in broadband light and be insensitive to small misalignments of the Lyot stop. For future designs we want to include passive suppression of low-order aberrations and finite stellar diameters. The memory requirements for such an optimization would exceed multiple terabytes for the problem matrix alone. We therefore want to reduce the number of variables and constraints to minimize the size of the problem matrix. We show how symmetries in the pupil and Lyot stop are expressed in the complete optimization problem, and allow removal of both variables and constraints. Each mirror symmetry reduces the problem size by a factor of four. Secondly, we introduce progressive refinement, which uses low-resolution optimizations as a prior for higher resolutions. This lets us remove the majority of variables from the high-resolution optimization. Together these two improvements require up to 256x less computer memory, with a corresponding speed increase. This allows for greater exploration of the phase space of the focal-plane mask and Lyot-stop geometry, and easier simulation of sensitivity to Lyot-stop misalignments. Moreover, apodizers can now be optimized at their native manufactured resolution.

Many biologically produced chiral molecules such as amino acids and sugars show a preference for left or right handedness (homochirality). Light reflected by biological materials such as algae and leaves therefore exhibits a small amount of circular polarization that strongly depends on wavelength. Our Life Signature Detection polarimeter (LSDpol) is optimized to measure these signatures of life. LSDpol is a compact spectropolarimeter concept with no moving parts that instantaneously measures linear and circular polarization averaged over the field of view with a sensitivity of better than 10^-4. We expect to launch the instrument into orbit after validating its performance on the ground and from aircraft. LSDpol is based on a spatially varying quarter-wave retarder that is implemented with a patterned liquid-crystal. It is the first optical element to maximize the polarimetric sensitivity. Since this pattern as well as the entrance slit of the spectrograph have to be imaged onto the detector, the slit serves as the aperture, and an internal field stop limits the field of view. The retarder’s fast axis angle varies linearly along one spatial dimension. A fixed quarter-wave retarder combined with a polarization grating act as the disperser and the polarizing beam-splitter. Circular and linear polarization are thereby encoded at incompatible modulation frequencies across the spectrum, which minimizes the potential cross-talk from linear into circular polarization.

The exoplanet atmosphere characterization goals of future UV/Optical/Infrared flagship space missions will drive challenging design requirements for instrument wavefront controls, spatial and spectral sampling, spectral bandwidth, and detector performance. The new ExoSpec Project links four previously distinct research efforts at Goddard and Ames for enabling and enhancing the characterization of directly-imaged exoplanets. ExoSpec is comprised of three laboratory subsystem demonstrations: high-contrast integral field spectrographs, p-channel CCDs, and parabolic deformable mirrors. A fourth component, exoplanet spectral retrieval, is an iterative data simulation activity driven by the goal of optimizing the system-level instrument design for atmosphere retrieval metrics. The ExoSpec Project's emphasis on system-level spectroscopy performance complements the objectives of other technology demonstrations supported by NASA.

Accurate measurement of exoplanetary masses is a critical step in addressing key aspects of NASA's science vision. Measuring masses of Earth-analogs around FGK stars out to 10 pc requires sub-microarcsecond astrometric accuracy, which is not within the capabilities of current instrumentation. Thus, new technology will be required to build an astrometric instrument capable of achieving such performance. This will immediately empower the possibility for dedicated astrometric missions, and perhaps most enticing, it will enable astrometric observing modes to be added (with relatively low cost and impact) to any mission boasting a sufficiently stable direct imaging platform. In this paper, we provide an overview of the scientific goals and technology utilized on two of NASA's astrometry testbeds dedicated to advancing stellar astrometry for exoplanet detection. The first one, located at the Jet Propulsion Laboratory (JPL), is dedicated to imaging stellar astrometry on sparse fields. The goal of this testbed is to mature the Diffractive Pupil (DP) technology to TRL-5, demonstrating high-fidelity performance in a relevant environment. This testbed operates in a vacuum tank at the High Contrast Imaging Testbed (HCIT) at JPL. The second testbed, located at NASA Ames Research Center, is dedicated to advancing narrow angle relative astrometry to detect exoplanets around nearby binary stars. The key technology in this testbed is a DP specially designed to measure the angle between two sources on the sky. This testbed operates in air and aims to bring this technology to TRL-4.

The direct imaging and spectroscopic characterization of atmospheres of Earth-like exoplanets requires a starlight suppression system to detect a faint planetary signal at small angular separations. Future space telescopes will require segmentation which presents additional challenges for coroangraphy due to pupil discontinuities. We present compact designs that will feed into the Segmented Coronagraph Design and Analysis (SCDA) group's end-to-end models that studies the sensitivity of PIAA designs to segmented pupils such as those representative of the Large UV / Optical /Infrared (LUVOIR) mission concept.

In order to maximize the potential of the next-generation of large space-based observatory to detect and characterize Earth-like exoplanets, coronagraphs must be designed that can obtain high (~10^-10) contrasts in the presence of realistic low-order aberrations and finite stellar diameters. Unfortunately, for telescopes with central obstructions, maintaining aberration robustness for most coronagraph designs entails significant losses in either throughput or inner working angle. This has resulted in stringent limitations for exo-Earth yields on planned future on-axis telescopes, such as LUVOIR-A. We address this limitation with modified versions of apodized charge 6 and charge 8 vortex coronagraphs which use multiple stages of focal plane mask. These multi-stage apodized vortex coronagraphs (MSAVCs) produce dark holes with contrast <10^-10 and mitigate the flux due to tip/tilt offsets as large as 0.05 λ/D while obtaining core throughputs that are a factor of ~2 higher than similarly constrained single-stage apodized vortex coronagraphs. The MSAVCs we present are robust to several low-order aberrations, and we discuss the possibility of explicitly constraining low-order aberrations further. Furthermore, we demonstrate mitigating flux due to misalignment between focal plane masks, thus overcoming a significant hurdle in implementing multi-stage vortex designs. By using a parametric expression to estimate the yield of a charge 6 MSAVC for a 10% central obstruction relative to an off-axis charge 6 vortex coronagraph on an 8-m telescope, we estimate it may be possible to retain ~67% of the off-axis yield

Dichroic filters are used by instrument designers to split a field of view into different optical paths for simultaneous measurement of different spectral bands. Quantifying the polarization aberrations of a dichroic is relevant for predicting the incident polarization states downstream, which could affect the performance of diffraction limited systems. One important application is the fore-optics of exoplanet imaging coronagraphs. In this work, the polarization properties of the Edmund #69-205 650 nm roll-off dichroic are measured using a rotating retarder Mueller matrix imaging polarimeter. The polarization properties of this commercial dichroic are compared at normal and 45° angle of incidence. The normal incidence measurements verify the instrument calibration since no polarization aberrations were observed. Transmission measurements at 680 nm and 45° yield a 2.9 rad magnitude of retardance and 0.95 diattenuation. Effectively, at 630 nm the dichroic is a λ/4 waveplate with a horizontal fast-axis.

We designed and built a laboratory model of a sparse space telescope. The purpose of the model is to test various algorithmic, optical, and mechanical issues with such a telescope: how to achieve alignment after deployment that yields diffraction limited optical performance. Our model uses four non-redundant sparse sectors. Each segment has three degrees of freedom, with supplementary coarse focusing, so the search volume for a perfect image is quite large, ~10⁵¹. We tried stochastic searches, optimizing the point spread to its minimum, and are now testing different directed search algorithms, of volume order 10¹⁹ or less. This will cut the search time from one day to about one hour, with much less chance of actuator failure.

Imaging exo-Earths is an exciting but challenging task because of the 10-10 contrast ratio between these planets and their host star at separations narrower than 100 mas. Large segmented aperture space telescopes enable the sensitivity needed to observe a large number of planets. Combined with coronagraphs with wavefront control, they present a promising avenue to generate a high-contrast region in the image of an observed star. Another key aspect is the required stability in telescope pointing, focusing, and co-phasing of the segments of the telescope primary mirror for long-exposure observations of rocky planets for several hours to a few days. These wavefront errors should be stable down to a few tens of picometers RMS, requiring a permanent active correction of these errors during the observing sequence. To calibrate these pointing errors and other critical low-order aberrations, we propose a wavefront sensing path based on Zernike phase-contrast methods to analyze the starlight that is filtered out by the coronagraph at the telescope focus. In this work we present the analytical retrieval of the incoming low order aberrations in the starlight beam that is filtered out by an Apodized Pupil Lyot Coronagraph, one of the leading coronagraph types for starlight suppression. We implement this approach numerically for the active control of these aberrations and present an application with our first experimental results on the High-contrast imager for Complex Aperture Telescopes (HiCAT) testbed, the STScI testbed for Earth-twin observations with future large space observatories, such as LUVOIR and HabEx, two NASA flagship mission concepts.

In image-based wavefront sensing by phase retrieval, the sum-squared difference (SSD) of simulated and measured PSF intensities, i.e., the intensity error metric (IEM), suffers from noise model mismatch. The IEM assumes additive Gaussian noise, but the true noise model is mixed Poisson-Gaussian (PG). The generalized Anscombe transform (GAT) addresses this issue by transforming the noise model from mixed PG to approximately additive Gaussian. We developed a method that uses the bias and gain terms derived for the bias-and-gain-invariant (BGI) IEM to create a BGI GAT error metric (GEM) and a BGI SSD of field amplitudes, i.e., amplitude error metric (AEM). We performed simulations comparing the retrieval accuracy of the three BGI metrics for various amounts of mixed PG noise. We found that the BGI GEM performs comparable or better than the BGI IEM and AEM for all amounts of mixed PG noise. Therefore, the BGI GEM is a good general-use error metric that works well for any mixed PG noise.

In high-contrast imaging applications, such as the direct imaging of exoplanets, a coronagraph is used to suppress the light from an on-axis star so that a dimmer, off-axis object can be imaged. To maintain a high-contrast dark region in the image, optical aberrations in the instrument must be minimized. The use of phase-contrast-based Zernike Wavefront Sensors (ZWFS) to measure and correct for aberrations has been studied for large segmented aperture telescopes and ZWFS are planned for the coronagraph instrument on the Roman Space Telescope (RST). ZWFS enable subnanometer wavefront sensing precision, but their response is nonlinear. Lyot-based Low-OrderWavefront Sensors (LLOWFS) are an alternative technique, where light rejected from a coronagraph's Lyot stop is used for linear measurement of small wavefront displacements. Recently, the use of Deep Neural Networks (DNNs) to enable phase retrieval from intensity measurements has been demonstrated in several optical configurations. In a LLOWFS system, the use of DNNs rather than linear regression has been shown to greatly extend the sensor's usable dynamic range. In this work, we investigate the use of two different types of machine learning algorithms to extend the dynamic range of the ZWFS. We present static and dynamic deep learning architectures for single- and multi-wavelength measurements, respectively. Using simulated ZWFS intensity measurements, we validate the network training technique and present phase reconstruction results. We show an increase in the capture range of the ZWFS sensor by a factor of 3.4 with a single wavelength and 4.5 with four wavelengths.

We present the continued progress and laboratory results advancing the technology readiness of Multi-Star Wavefront Control (MSWC), a method to directly image planets and disks in multi-star systems such as Alpha Centauri. Because of the ubiquity of multistar systems, this method increases the science yield of many missions and concepts such as WFIRST, HabEx, LUVOIR, and potentially enables the detection of Earth-like planets (if they exist) around our nearest neighbor star, Alpha Centauri. We report on lab demonstrations of MSWC, including one at the Ames Coronagraph Experiment (ACE) laboratory, as well as with the SCExAO instrument. Our demonstrations include both sub- and super-Nyquist versions of MSWC, showing that active suppression of light from a binary is possible even when the star separation exceeds the outer outer working angle of the deformable mirror. We also use standard single-star speckle suppression techniques to isolate and quantify the gains of MSWC.

The MIRI instrument on the James Webb Space Telescope is equipped with detectors which are susceptible to signal disruption by the charge deposited from impacting cosmic rays. In order to quantify the degree to which the structure of MIRI will shield the detectors, we have used an opto-mechanical ray tracing approach, whereby the solid bodies in a detailed 3D model of the instrument are substituted with an absorptive glassy material. By importing this modified model into a ray tracing program (Tracepro) and then launching many rays from the detector, we have been able to generate a map of aluminium path length as a function of direction. We find that there is a minimum thickness of 2 to 3 mm over a few patches which subtend no more than 1.5 % of the sky for the worst case, imager detector. We discuss the performance of the shielding provided by the MIRI structure, concluding that this minimum thickness of aluminium is sufficient to suppress the impact of low energy protons below the level of the unavoidable flux due to high energy cosmic rays.

The James Webb Space Telescope features a powerful complement of focal-plane instruments: the Mid-Infrared Instrument (MIRI), the Near-Infrared Camera (NIRCam), the Near-Infrared Imager and Slitless Spectrograph (NIRISS), the Near-Infrared Spectrograph (NIRSpec), and the Fine Guidance Sensor (FGS). These instruments offer an exciting suite of scientific capabilities for imaging, high-contrast imaging, and spectroscopy. To bring these capabilities on-line after launch, a carefully scoped and sequenced set of commissioning activities has been developed. These activities will confirm the functionality of the instruments, characterize their performance (optimizing where possible), obtain initial calibrations at a level required to properly plan observations, and demonstrate essential operational sequences such as target acquisition. We present a high-level overview of these activities and the planned commissioning timeline to execute them.

ARIEL, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey mission1-3 was selected in early 2018 by the European Space Agency (ESA) as the fourth medium-class mission (M4) launch opportunity of the Cosmic Vision Program, with an expected launch in late 2028. It is the first mission dedicated to the analysis of the chemical composition and thermal structures of up to a thousand transiting exoplanets atmospheres, which will expand planetary science far beyond the limits of our current knowledge.

PLATO is an exoplanet hunting mission from the European Space Agency. It is a medium-class mission, with a launch foreseen in 2026. Its prime objective is to uncover Earth-sized planets residing in the habitable zone of their host star. The payload consists of 26 cameras with a very wide field-of-view. While the operational temperature of the cameras will be -80°C, the focal plane of each camera will be integrated with its telescope assembly (bearing the optics) at room temperature. The degradation of the optical quality at ambient, combined with the detector dark current and with the very high accuracy required from the alignment process bring a number of interesting challenges. In the present article, we review the alignment concept, present optical simulations of the measurements at ambient along with their analysis, and present an error budget for the optical measurements. The derivation of this error budget is easily applicable to all optical measurements to be performed during the alignment, i.e. the definition of the best image plane at the operational temperature and the optical alignment itself, at room temperature.

.We describe the main tasks of the Product Assurance process for the Telescope Optical Unit (TOU) of the ESA PLATO mission, that starts from the design phase and proceeds through all phases, up to the final product, with the aim of improving the likelihood of success of the mission. When dealing with the opto-mechanical components of the TOU, several aspects regarding safety and performance have to be analyzed and tracked. From the PA point of view, we focus in this paper on materials and processes selection that shall be suitable and robust enough for the space environment. Cleanliness and contamination control is needed to overcome loss of optical performance. Validations and qualifications on prototypes is fundamental to assess the reliability of the instrument for its purpose and for the lifetime of the mission.

PLATO is ESA's upcoming exoplanet-hunting mission. The spacecraft has 26 cameras equipped with a total of 104 individual CCDs, which together provide more than 2,000 megapixels, giving a combined optical sensitivity surface of 0.66m². This is more than twice as much detector area than on ESA's Gaia mission, the largest camera ever flown in space. To measure changes in stellar brightness, the CCDs are read out at a cadence of 25 seconds, resulting in a massive amount of data that has to be processed on-board. In a pre-reduction step, hundreds of thousands of small windows of the target stars, called imagettes, are extracted from the detector arrays. This reduction process decreases the data volume down from several gigabytes to 25 MiB per acquisition period. Following this step, the remaining science data are sent to the instrument control unit (ICU), where they are processed and compressed in a lossless manner. While some science data products, such as measured backgrounds and fluxes, can be processed in software, the number of imagettes to be compressed (90% of the total science data) exceeds the available CPU resources. To solve this critical problem, a specialised hardware data compressor logic was developed for an RTAX-2000 field-programmable gate array (FPGA). The implemented compression method decorrelates the data temporally by a running average, which has an exponential tail. This pre-encoding step results in an almost geometric distribution of the residuals, a suitable input for the successive Golomb encoder. The set of parameters that control the encoder are semi- adaptive, i.e., they self-adjust to the data at certain intervals. While in principle being quite straightforward, the implementation turned out to be very challenging with the required handling of the data streams in real-time. With our approach we are able to meet the high requirements and managed to process the imagette data lossless with a speed of 2 MBps at a compression ratio up to 3.2. This paper shows how the PLATO data compression concept works, which algorithms are involved in it, and discusses the specifics of the hardware and software implementation.

A fiber fed, wide beam collimator was developed as a tool to support the Assembly, Integration and Verification (AIV) tasks associated to the integration of the ESA-PLATO telescope unit (TOU) to the focal plane, for the 26 cameras that are going to be assembled at the Centre Spatial de Liége (CSL). This collimator will work as source for the alignment process at ambient temperature, providing a white light beam that must comply with a series of critical requirements, namely high spatial uniformity over an clear aperture of 150 mm (better than 85%), Wavefront Error associated to focus aberration at the level of λ/30 rms and high flux stability over time (2% in 24h). This paper will present the steps taken towards the development, manufacture and integration of this collimator, as well as the tests devised to evaluate requirements compliance.

PLATO is an M-class mission (M3) of the European Space Agency (ESA) whose launch is scheduled in 2026. The main aim of the mission is the detection and characterization of terrestrial exoplanets orbiting around bright solar-type star. The payload consists of 26 small telescopes: 24 “normal" cameras and 2 “fast" cameras. The huge amount of data produced by the PLATO telescopes is acquired and processed on-board by the Data Processing System (DPS) made up by various processing electronic units. The DPS of the PLATO instrument comprises the Normal and Fast DPUs (Data Processing Units) and a single ICU (Instrument Control Unit), are data routed through a SpaceWire network. The topic of this paper is the description of the architecture of the ICU and its role within the DPS, the status of the Avionic Validation Model (AVM) testing at the end of the Unit Preliminary Design Review (UPDR) performed by ESA and the results of the test of the first engineering model.

PLAnetary Transits and Oscillations of stars (PLATO) is a mission belonging to the European Space Agency Cosmic Vision program which objective is to find and study extrasolar planetary systems. PLATO is composed of 26 telescopes which will observe uninterruptedly Sun like stars in order to identify a periodic decrease of the star brightness indicating the possible transit of an exoplanet. The PLATO on-board Data Processing System (DPS) consists of an Instrument Control Unit (ICU) and several distributed Digital Processing Units (DPUs) connected together by a SpaceWire network. The ICU collects and compresses scientific data from the DPUs and it implements the main data interface towards the satellite for telemetry and telecommands. The focus of this paper is on the Boot Software (BSW) of the ICU. The BSW is executed on a LEON3FT processor to perform system initialization, hardware checks, telecommand/telemetry management and the start of the ICU Application Software (ASW) responsible of the PLATO sub-system management necessary for the mission objectives. ICU BSW is the only boot software on-board PLATO and its high criticality level requires stringent verification/validation activities and a high-quality control of the software product which is achieved through extensive quality plans, multi-level testing and static analysis of software code. This paper describes the BSW dependable architecture along with the methods used to achieve the required performances, including FDIR techniques. Two engineering models of the ICU are going to be developed and the foreseen functional and performance tests will be presented in this paper.

PLATO is an ESA mission to hunt for Earth-sized exoplanets in the habitable zone of their host star. The heart of the payload consists of 26 wide-field cameras. We develop a Common Electrical Ground Support Equipment (EGSE) framework for the testing and verification of these cameras. The focal planes are aligned to the telescope optics at ambient temperature and the performance verification is done at operational temperature in thermal-vacuum conditions in different facilities. The Common-EGSE system will guarantee that tests are executed via the same procedures and are analyzed identically, by providing a software framework that can be tuned for site-specific hardware and avoids duplicate developments. The Common EGSE provides commanding for the camera and the Ground Support Equipment (GSE), telemetry monitoring, logging, data storage, and data analysis. In addition, the design allows for sharing commanding and analysis scripts. We present the design of the system and the generic commanding scheme for test setup hardware.

A description of the Data Processing Unit’s (DPU) hardware and the Application Software (ASW) of the Near Infrared Spectro-Photometer (NISP) at EUCLID mission is given. NISP is composed by a focal plane of 16 H2RG HAWAII near infrared detectors (0.9÷2 μm) interfaced with 16 ASICs, both produced by Teledyne. The complete system is handled by two identical DPU units running in parallel and independently with the same ASW, and each governing 8 detector chains. Flight DPU units were used for validating the ASW as well as a single EQM model of the DPU (fully representative of the Flight model). Details of the DPU hardware components and its most relevant performances are described, focusing on the Digital Control Units’ handling of data coming from the ASICs. It is also described the ASW architecture emphasizing the onboard data pre-processing in which a series of on-line operations are performed to reduce the amount of data sent to ground, thus guaranteeing its consistency and quality (i.e. multi accumulation charge slope fit calculation, quality factor evaluation, reference pixel correction, saturation pixels flagging and lossless compression). Finally, a description of the latest NISP system’s test campaigns focusing on those for the Electromagnetic Compatibility, Susceptibility and Thermal Vacuum is provided; and a detail description of the results used to successfully validate the DPU ASW.

The total integrated emission from galaxies, known as the Extragalactic Background Light (EBL), is an important observable for understanding the history of star formation over the history of the universe. Spatial fluctuations in the infrared EBL as measured by the Cosmic Infrared Background ExpeRiment (CIBER), Spitzer and AKARI exceed the predicted signal from galaxy clustering alone. The CIBER-2 project seeks to extend CIBER observa- tions of the EBL throughout the near infrared into the optical, through measurements above Earth's atmosphere during a suborbital sounding rocket flight. The experiment has a LN2-cooled 28.5 cm Cassegrain telescope along with three optical paths and dichroic beamsplitters, which are used to obtain three wide-field images in six broad spectral bands between 0.5-2.0 μm. The three focal planes also contain linear variable filters (LVFs) which simultaneously take spectra with resolution R=20 across the same range. CIBER-2 is scheduled to y multiple times on a Black Brant IX sounding rocket from White Sands Missile Range in the New Mexico desert. For the first flight, scheduled for early 2021, we have completed a variety of pre-flight optical tests, which we use to make focus adjustments, spectral response measurements, and absolute photometric calibrations. In this paper, we describe the methods behind these tests and present their results for pre-flight performance evaluation. In particular, we present measurements of the PSF for each broad spectral band, along with absolute calibration factors for each band and the LVF. Through monochromator scans, we also measure the spectral responsivity of each LVF as a function of position.

In this paper we describe the final status of the application software (ASW) of the instrument control unit (ICU) of NISP, the Near-Infrared Spectro-Photometer of the Euclid mission, as the version for Flight has been tested and delivered to the industry for the next integration phases. This software is based on a real-time operating system (RTEMS) and will interface with all the subunits of NISP, as well as the command and data management unit (CDMU) of the spacecraft for telecommand and housekeeping management. We will describe in particular the final tests and the main obstacles which had to be faced in order to implement an efficient and reliable interface with all the NISP subsystems.

The Nancy Grace Roman Space Telescope will include, as one of its two instruments, the highest contrast coronagraph ever attempted, with sensitivity down to Jupiter class planets. With ux ratio below 1e-8, these planets will be exceedingly dim, so that signal rates are as low as 0.01 electrons per second at the imaging detector. These rates necessitate ultra-low noise detectors and methods. For its science imaging camera, the Roman Coronagraph will employ an electron multiplication CCD (EMCCD), to achieve near-zero read noise. EMCCD's, however, deliver the low read noise at the cost of amplification of all other noise, because of the stochastic nature of the electron multiplication process. To circumvent this next-order challenge, a thresholding technique called photon counting can be used. The resulting image has no read noise and no excess noise factor (ENF). The remaining challenge, for precision photometry, is to account for the undercount and overcount effects inherent to photon counting. These arise primarily from the inefficiency of thresholding itself, and coincidence loss, where multiple-electron events are not distinguished from single-electron ones. Here we present a detailed description of the photon counting algorithm and the corrections necessary to achieve photometric accuracy below 0.5%.

In this paper we describe the activities towards the design of a common framework for the Instrument Control and Data Processing Units for the three scientific payload instruments on board the joint ESA-JAXA SPICA mission, currently at the end of its phase A study. In this context, we started a program to assess modular architectures based on the use of a quad-core fault-tolerant LEON4 SPARC V8 processor on a SpaceWire network. We will describe the results of our initial tests using both Asymmetric Multi processing (AMP) and Symmetric Multi Processing (SMP) configurations. In addition, the possibility to adopt the RTEMS real time operating system, already space qualified on single core processors, will be evaluated both in terms of latency performances and of dynamical allocation of the resources. Finally, we will present the outline of the way forward for the next phases of the SPICA project.

Abstract for Program NASA is considering future missions to seek evidence of life on other worlds. These include a coronagraphic Large UV-Optical-IR (LUVOIR) Surveyor and a starshade-based Habitable Exoplanet Observatory (HabEx). Both would use “biosignatures” to assess habitability. Biosignatures are spectral features that are thought to indicate the possible presence of life. Unfortunately, biosignature characterization is photon starved. This motivates challenging detector requirements including zero read noise, negligible false count rate, good near-IR QE to detect H2O (940 nm), and excellent radiation tolerance for use in space. To meet these requirements, NASA Goddard Space Flight Center (GSFC) is partnered with Lawrence Berkeley National Laboratory to add high speed photon counting outputs to thick, fully depleted, p-channel CCDs. We present recent test results and discuss future plans. This project is a sub-package within the Exoplanet Spectroscopy (ExoSpec) Technologies Work Package at GSFC. undefined NASA is considering future missions to seek evidence of life on other worlds. These include a coronagraphic Large UV-Optical-IR (LUVOIR) Surveyor and a starshade-based Habitable Exoplanet Observatory (HabEx). Both would use “biosignatures” to assess habitability. Biosignatures are spectral features that are thought to indicate the possible presence of life. Unfortunately, biosignature characterization is photon starved. This motivates challenging detector requirements including zero read noise, negligible false count rate, good near-IR QE to detect H2O (940 nm), and excellent radiation tolerance for use in space. To meet these requirements, NASA Goddard Space Flight Center (GSFC) is partnered with Lawrence Berkeley National Laboratory to add high speed photon counting outputs to thick, fully depleted, p-channel CCDs. We present recent test results and discuss future plans. This project is a sub-package within the Exoplanet Spectroscopy (ExoSpec) Technologies Work Package at GSFC.

The Multi-spectral Visible Imaging Camera (MVIC) detector is a time-delay and integration (TDI) CCD with 4, 8, 16, 32, and 64 TDI modes. MVIC is scheduled to fly as part of the instrument suite on the Lucy mission to the Trojans launching in 2021. We present here the pre-delivery SwRI Detector Characterization Lab (SDCL) data of the Flight (FM) and Flight Spare (FS) from 370 to 925nm. The MVIC sensor consists of six broad-band top-hat filters on a single sapphire substrate developed by VIAVI Solutions and six CCDs on a single wafer developed by Semiconductor Technology Associates (STA). We have calibrated both the FS and FM for read noise, dark current, linearity, quantum efficiency, and total system throughput. The data were collected using standard Photon Transfer Curve techniques at strategically chosen wavelengths corresponding to center and edge of the bandpass filters. Each system was also calibrated for spuriously operational pixels and cosmetic defects. The pixel response function is mapped on a pixel-by-pixel basis for the 64 TDI mode.

LiteBIRD is a JAXA-led strategic Large-Class satellite mission designed to measure the polarization of the cosmic microwave background and cosmic foregrounds from 34 to 448 GHz across the entire sky from L2 in the late 2020's. The primary focus of the mission is to measure primordially generated B-mode polarization at large angular scales. Beyond its primary scientific objective LiteBIRD will generate a data-set capable of probing a number of scientific inquiries including the sum of neutrino masses. The primary responsibility of United States will be to fabricate the three flight model focal plane units for the mission. The design and fabrication of these focal plane units is driven by heritage from ground based experiments and will include both lenslet-coupled sinuous antenna pixels and horn-coupled orthomode transducer pixels. The experiment will have three optical telescopes called the low frequency telescope, mid frequency telescope, and high frequency telescope each of which covers a portion of the mission's frequency range. JAXA is responsible for the construction of the low frequency telescope and the European Consortium is responsible for the mid- and high- frequency telescopes. The broad frequency coverage and low optical loading conditions, made possible by the space environment, require development and adaptation of detector technology recently deployed by other cosmic microwave background experiments. This design, fabrication, and characterization will take place at UC Berkeley, NIST, Stanford, and Colorado University, Boulder. We present the current status of the US deliverables to the LiteBIRD mission.

We present a new concept of an unprecedentedly compact, 10 cm-sized (optics), IR high-resolution (λ~3μm, R~30,000) cross-dispersed spectrograph. The spectrograph has high-throughput and can cover an octave of wavelength in a single exposure without mechanisms and electric power, thus it is not only highly efficient but also stable and low power rather than existing IR high-resolution spectrometers for space application. The key technologies that make this possible are germanium (n~4) immersion grating with high diffraction efficiency and all-cordierite reflective optical system with diffraction-limited performances at 633 nm. In previous studies, we have successfully demonstrated that both systems work properly at cryogenic temperature. An immersion grating enables us to realize n-times smaller spectrographs than that with a classical reflective grating, and also it can offer the quasi-Littrow configuration without the white pupil. Cordierite is a low CTE ceramics and has higher specific stiffness and thermal conductivity than low CTE glasses. An optical system made entirely of this material enables us to utilize all the advantages of the reflective optical system (wide wavelength coverage, high throughput, correction of high-order aberrations, compact optical design, and constant optical path independent of environment conditions) without bothering about fabrication of mirrors of high surface accuracy and complex optical alignment demanded for the conventional reflective optical system. This CubeSat-class spectrograph could expand the opportunity of IR high-resolution remote-sensing spectroscopy of the Jupiter’s and Saturn’s moons for exploring molecules possibly related to prebiotic chemistry.

We consider the scientific benefits and technical feasibility of a 6-m, non-deployed, cold space telescope mission concept, covering the ultraviolet, visible, near-infrared, and mid-infrared wavebands, for direct imaging of exoplanets and a broad range of astronomical investigations. The concept uses the largest practical aperture size that can be launched without deployment, for lower risk and cost. An innovative, rigid outer barrel and sunshield control temperature and stray light in a compact, Spitzer-like configuration that provides a 100-K telescope. Additional active and passive thermal features provide millikelvin temperature stability. The ultraviolet and visible instruments are based on the suite developed for the Habitable Exoplanet Observatory concept. The cold telescope enables the scientifically important addition of mid-infrared imaging and spectroscopy modes, providing background-limited imaging to 5 um wavelength. The telescope uses actively-controlled mirrors to compensate for cool-down aberrations, other optical uncertainties, and tolerances or errors that may occur in manufacturing, assembly, launch, and on-orbit operations. A starshade provides high-dynamic-range imaging and spectroscopy of exoplanets, potentially augmented by a coronagraph for exoplanet search and orbit measurement. Special attention has been paid to contamination control, assessing the feasibility of UV imaging with a cryogenic telescope. The paper will provide design details and assessment of scientific yield and technology readiness, while addressing real and perceived issues for a space telescope capable of covering this wide wavelength range.

A process to converge on selection of the most efficient spaceborne mirror substrate material is described. While parametric descriptors of structural efficiency and resilience to transient response have been used for this purpose over decades, significant parameter revisions are now possible with heightened precision of measuring characteristics that dominate thermal stability, principally coefficient of thermal expansion. An updated parametric diagram of materials will be presented for initial evaluation in the context of space environments and prescribed optical performance. Other important material factors that next enter the selection are heritage, mirror or size, homogeneity, isotropy, fracture mechanics, richness of design data and of course schedule and cost. SCHOTT has established ZERODUR® fabrication facilities to provide newest CNC generation of a full range of optical surface forms, and to enable advanced lightweighting up to 4 meters diameter.

Space interferometry is the inevitable endpoint of high angular resolution astrophysics, and a key technology that can be leveraged to analyse exoplanet formation and atmospheres with exceptional detail. Here, we present a feasibility study into a small scale formation flying interferometric array, flying in Low Earth Orbit, that will aim to prove the technical concepts involved with space interferometry while still making unique astrophysical measurements. We will detail the design of the mission, as well as present orbital simulations that show that the array should be stable enough to perform interferometry with <50 m/s/year Δv and one thruster per spacecraft. We also conduct observability simulations to identify what parts of the sky are visible for a given orbital configuration. We conclude with optimism that this design is achievable, but a more detailed control simulation factoring in a metrology system is the next step to demonstrate full mission feasibility.

A starshade is a large flower-shaped screen designed to enable the direct imaging of exoplanets with a space telescope. The starshade perimeter is composed of sharp, precisely shaped edges to minimize the glint of sunlight into the telescope. Past work has focused on bare edges to minimize the terminal radius. This paper describes the broadband, wide-angle performance of edges coated with a thin multi-layer anti-reflection coating. This coating uses a combination of interference and absorption to reduce the surface reflectivity and to avoid the negative effects associated with a large cross-sectional area. A custom scattered light testbed has been developed to quantify the amount of light scattered from sample edges and to validate Finite-Difference Time-Domain (FDTD) models of the optical scatter. We show that optical edge samples with this coating significantly reduce the solar glint pattern compared to similar uncoated optical edges.

Extragalactic background light (EBL) consists of entire radiation emitted throughout the cosmic history and is one crucial observable quantity to study astrophysics in the early universe, such as first stellar objects or primordial black holes. In the visible and near-infrared, zodiacal light (ZL), sunlight scattered by interplanetary dust, is the brightest foreground for observer in the near-earth orbit and its uncertainty limits accuracy of the EBL measurement. To overcome this problem, observations from heliocentric distance beyond 5 au, where the ZL is negligible, is promising. To achieve the EBL observation in deep space, we have been developing EXo- Zodiacal Infrared Telescope (EXZIT) onboard a solar sail spacecraft to Jovian Trojans planned in Japan around 2030. According to our mission study, a three-mirror reflective telescope optics design with a 90mm × 50mm effective aperture and 16 deg × 8 deg field of view (FoV) followed by a focal plane array HAWAII-2RG with a linear variable filter makes available to detect the EBL at high significance in 0.4–1.6 μm with specific wavelength resolution of ∼ 20 . In the present study, we develop test optics to demonstrate optical performance in room temperature for the future observation. By adopting only mirrors of aspherical surface, we design the optics whose aberration is minimized to show point spread function (PSF) of approximately 3 pix × 3 pix on the focal plane. The mirrors are fabricated by machining aluminum alloy A6061 with a honeycomb processing on the back surface to reduce the mirror mass. After integrating and aligning the mirrors with support jigs, we measure the PSF on the focal plane by a visible camera by inserting collimated beam of different angle of incidence, covering the whole FoV. We evaluate the PSF size by analyzing encircled energy in comparison with that expected from the ray-trace simulation of the optics. Throughout the FoV of the optics, the measured PSF size is comparable to the simulation. The present study demonstrates the precision machining of the aspherical mirrors and the optical performance of the designed optics. As a next step, we plan to develop thermal structure of EXZIT to demonstrate the optical performance in low temperature.

LiteBIRD is JAXA Strategic Large Mission for the late 2020s that aims to observe the large-scale B-mode polarization pattern of the cosmic microwave background. One of its telescopes, the Low Frequency Telescope (LFT), has a crossed-Dragone design and observes at 34-161 GHz with a field of view of 18° x 9°. Because a miscalibration of the polarization angles mixes E- and B-mode polarization, we have measured the variation of the polarization angles in the field of view of a 1/4-scaled LFT antenna at 140-220 GHz, which corresponds to 35-55 GHz for the full-scale LFT, considering a scaling of the wavelength. We placed a collimated-wave source near the scaled-LFT aperture and rotated the polarization angle of the LFT feed. The measurements were explained well with a simple Jones matrix calculation, and the fitting errors of the polarization angles were less than 0.1’. We also measured the polarization angles by rotating the polarization direction in the scaled-LFT aperture, and the results were consistent with the angles measured by rotating the feed polarization at the ±10” level, except at the lowest frequencies. The polarization angle at the edges of the focal plane varied from that at the center by up to around a degree, with larger variation at lower frequencies. We evaluated the polarization angles for both Pol-X and Pol-Y feeds, and the results with Pol-Y showed a trend consistent with ray-tracing simulations. The results for Pol-X showed the opposite trend of the polarization rotation direction and larger angle variations.

We report on the laboratory experiments of a densified pupil spectrograph designed for mid-infrared transit spectroscopy of exoplanets. We developed a testbed consisting of a blackbody infrared light source, a densified pupil spectrograph, and a prototype JWST Si:As Impurity Band Conduction (IBC) detector array to simulate observations of a planet’s host star. In order to thermally stabilize the measurement system, we installed all of the components in a large cryogenic dewar and controlled the temperatures of the thermal source and the Si:As IBC detector. The characteristics of the spectrum formed on the detector were consistent with the designed values. The photometric precision of the densified pupil spectrograph was 14 ppm on average over the whole observing wavelength range of 8.5 to 10.5 μm. The systematic noise component of the spectrograph hidden behind the transit spectrograph was 11 ppm.

The electromagnetic interference (EMI) is becoming an increasingly important factor in the spacecraft design equipped with highly sensitive detectors. This is particularly the case for LiteBIRD, in which the TES bolometers are exposed to space through the optical path. A particular concern is radiative interference caused by the X-band transmission during the ground communication. As the end-to-end verification test will be conducted in a later phase of the development, we need to derisk the concern early using simulation. In this report, we present the result of the EMI effects in the 1-GHz frequency range based on the electromagnetic simulation using a finite difference time domain (FDTD) solver. We modeled the dominant large structures of the spacecraft, calculated the spatial transmission of the antenna power, and estimated the electric field strength at the detector focal plane. The simulation results helped constrain aspects of the LiteBIRD satellite, such as the forward/backward ratio of the transmission antenna, to reduce the coupling between the antenna and the detectors.

SMI (SPICA Mid-infrared Instrument) is one of the three focal-plane science instruments for SPICA. SMI is the Japanese-led instrument proposed and managed by a university consortium. SMI covers the wavelength range from 10 to 36 μm with four separate channels: the low-resolution (R = 60 – 160) spectroscopy function for 17 – 36 μm, the broad-band (R = 5) imaging function at 34 μm, the mid-resolution (R = 1400 – 2600) spectroscopy function for 18 – 36 μm, and the high-resolution (R = 29000) spectroscopy function for 10 – 18 μm. In this presentation, we will show the latest design and specifications of SMI as a result of feasibility studies.

The far infrared instrument SAFARI spectrometer on board the SPace Infrared telescope for Cosmology and Astrophysics (SPICA) provides moderate resolution spectra (R~300) with simultaneous coverage over 34 to 230 μm. With the high sensitivity TES detectors, the SAFARI can reach the sensitivity down to ~7×10^-20 W/m². In order to provide accurate calibration for the TES readout circuit, a calibration source assembly (CSA) is developed to provide a stable and absolute flux radiation to the spectrometer over the whole spectral range. The CSA has a primary function during observations to take periodic reference measurement to correct for drift, subtracting backgrounds, etc from the detector. The CSA is composed of three microlamps and one integrating sphere. The microlamps are made of resistance wires by microlithography to mimic square blackbody sources. By combining an 81K microlamp and a 24K microlamp, a reasonably flat spectrum can be produced at the output of the integrating sphere. The radiation to the transition edge sensor detector pixel is around 1×10^-16 W. The integrating sphere can also provide a uniform output to cover the size of SAFARI field of view including the target and sky pixels. In this paper, the CSA design and the prototype results of the microlamp and the integrating sphere are presented.

SPICA provided the next step in mid- and far-infrared astronomical research and was a candidate of ESA's fifth medium class Cosmic Vision mission. SAFARI is one of the spectroscopic instruments on board SPICA. The Focal Plane Unit (FPU) design and analysis represent a challenge both from the mechanical and thermal point of view, as the instrument is working at cryogenic temperatures between 4.8K and 0.05K. Being a large instrument, with a current best estimate of 148,7kg of mass, its design will have to be optimized to fit within the mission´s mass and volume budget. The FPU will also have to be designed for its modularity and accessibility due to the large number of subsystems that SAFARI had to accommodate, highlighting Fourier Transform Spectrometer Mechanism (FTSM) and the three grating-based point source spectrometer modules (GM) which operates at 1.7K in the FPU, the latter representing 60% of the total mass of the instrument

The Mid-Infrared Spectrometer (Camera) transit spectrometer (MISC-T) is one of the baseline instruments studied for the Origins Space Telescope. MISC-T employs a novel densified pupil optical design and achieves exquisite stability and precision (<5ppm in 2.8—11μm, <20ppm in 11—20μm). It provides the Origins with the capability to assess the habitability of nearby exoplanets and search for signs of life. An additional MISC Wide Field Imager (MISC-WFI) is studied as an upsope option for the Origins. MISC-WFI offers an imaging and low-resolution spectroscopic capability for 5—28μm. The MISC WFI also serves as the focal plane pointing and guiding for the observatory.

SPICA is a mid to far infra-red space mission to explore the processes that form galaxies, stars and planets. SPICA/SAFARI is the far infrared spectrometer that provides near-background limited observations between 34 and 230 micrometers. The core of SAFARI consists of 4 grating modules, dispersing light onto 5 arrays of TES detectors per module. The grating modules provide low resolution (250) instantaneous spectra over the entire wavelength range. The high resolution (1500 to 12000) mode is accomplished by placing a Fourier Transform Spectrometer (FTS) in front of the gratings. Each grating module detector sees an interferogram from which the high resolution spectrum can be constructed. SAFARI data will be a convolution of complex spectral, temporal and spatial information. Along with spectral calibration accuracy of < 1 %, a relative flux calibration of 1% and an absolute flux calibration accuracy of 10% are required. This paper will discuss the calibration strategy and its impact on the instrument design of SAFARI

We present the B-BOP instrument, a polarimetric camera on board the future ESA-JAXA SPICA far-infrared space observatory. B-BOP will allow the study of the magnetic field in various astrophysical environments thanks to its unprecedented ability to measure the linear polarization of the submillimeter light. The maps produced by B-BOP will contain not only information on total power, but also on the degree and the angle of polarization, simultaneously in three spectral bands (70, 200 and 350 microns). The B-BOP detectors are ultra-sensitive silicon bolometers that are intrinsically sensitive to polarization. Their NEP is close to 10E^-18 W/sqrt(Hz). We will present the optical and thermal architectures of the instrument, we will detail the bolometer design and we will show the expected performances of the instrument based on preliminary lab work.

This paper describes the end-to-end opto-mechanical design of the SAFARI instrument on SPICA and the analysis of the spectrometer optical performances. SAFARI instrument is a high sensitivity grating-based spectrometer operating in the 34-230 μm wavelength range. The scientific drivers lead to the implementation of two modes of operation. The Low- Resolution (LR) or nominal mode (R~300) and the High-Resolution (HR), that implies to include a Martin-Puplett Fourier Transform Spectrometer (MP-FTS) to achieve the required spectral resolution (R~2000-11000). The optical system is all-reflective and consists of three main modules. The input optics module (IOM) is an unobscured reflective Offner relay. In the IOM a Beam Steering Mirror (BSM) is included for spatial modulation and to allow efficient sky mapping. The Band and Mode Distributing Optics (BMDO) module splits the radiation band into the four different spectral bands and includes the MP-FTS. The field image existing at the output of the BMDO constitutes the entrance to the Grating Module Optics (GM). These modules provide spectral dispersion by means of linear and reflective diffraction gratings and the final image onto the detectors. Performances of the GMs are high demanding with a detector divided into 2 sub-bands with a different pixel size for each sub-band.

OSS on Origins is designed to decode the cosmic history of nucleosynthesis, star formation, and supermassive black hole growth with wide-area spatial-spectral 3-D surveys in the 30 to 670 micron band. Six wideband grating modules combine to cover the full band at R=300, each couples a long slit with at least 30 beams on the sky. Two high-resolution modes are provided: one incorporates an interferometer in front of the gratings providing R of more than 40,000 at 112 microns, the other adds an etalon for R>300,000 at 112 microns. The full system design is presented, including optics, detector arrays, readouts, and the thermal design.

We report the development of an optical encoder and its readout system for a cryogenically-cooled continuously rotating half-wave plate (HWP) polarization modulator unit (PMU) in the LiteBIRD low-frequency telescope. LiteBIRD is a cosmic microwave background polarization satellite mission to probe B-mode polarization, which originates from primordial gravitational waves, observing from the second Lagrange point (L2). LiteBIRD employs a continuously-rotating HWP to mitigate systematic effects. The knowledge of the position angle of the HWP is in a one-to-one relationship to the incident polarization angle. The required reconstruction accuracy is about 1 arcmin and the targeted rotational frequency stability is 1 mHz. A unique development constraint comes from a telemetry bandwidth limitation between the Earth and L2, and thus we implement a digital process to reduce the data volume assuming a future implementation of on-board processing of the encoder data before the downlink. The demonstrations were done experimentally using a breadboard model of the PMU: a readout system using FPGA (Spartan-6) and a rotational mechanism using a superconducting magnetic bearing and AC motor. We acquired the encoder data from the rotational mechanism operating under two conditions: liquid nitrogen at room pressure and below 10 K in a cryostat. We demonstrated the reconstruction of the position angle accuracy < 0.5 arcmin and the corresponding data volume of 0.12 GB/day, which is at least an order of magnitude smaller than the total data volume per day. We further discuss the sources of the position angle uncertainty and its implications to the observations.

The LiteBIRD mission is a JAXA strategic L-class mission for all sky CMB surveys which will be launched in the 2020s. The main target of the mission is the detection of primordial gravitational waves with a sensitivity of the tensor-to-scalar ratio δr<0.001. The polarization modulator unit (PMU) represents a critical and powerful component to suppress 1/f noise contribution and mitigate systematic uncertainties induced by detector gain drift, both for the high-frequency telescope (HFT) and for the mid-frequency telescope (MFT). Each PMU is based on a continuously-rotating transmissive half-wave plate (HWP) held by a superconducting magnetic bearing in a 5K environment. In this contribution we will present the design and expected performance of the LiteBIRD PMUs and testing performed on every PMU subsystem with a room-temperature rotating disk used as a stand-in for the cryogenic HWP rotor.

LiteBIRD is a JAXA strategic L-class mission devoted to the measurement of polarization of the Cosmic Microwave Background, searching for the signature of primordial gravitational waves in the B-modes pattern of the polarization. The onboard instrumentation includes a Middle and High Frequency Telescope (MHFT), based on a pair of cryogenically cooled refractive telescopes covering, respectively, the 89-224 GHz and the 166-448 GHz bands. Given the high target sensitivity and the careful systematics control needed to achieve the scientific goals of the mission, optical modeling and characterization are performed with the aim to capture most of the physical effects potentially affecting the real performance of the two refractors. We describe the main features of the MHFT, its design drivers and the major challenges in system optimization and characterization. We provide the current status of the development of the optical system and we describe the current plan of activities related to optical performance simulation and validation.

The Solar Disk Imager (SDI), one of the instruments of the Lyman-alpha Solar Telescope (LST), aims to obtain full-disk images of the Sun in the Lyman-alpha waveband with high spatial and temporal resolution. In order to obtain high quality scientific data, various calibrations (including dark current, flat-field, radiometry, optical geometry, etc.) are required both on ground and in-flight. As other solar imagers, the flat-field calibration of SDI generally adopts the so-called KLL method to derive the flat-field from a set of relatively displaced non-uniform solar images. The KLL method is suitable for flat-field calibration of telescopes working in white light and infrared wavebands. When the working wavelength is extended to ultraviolet (UV) or extreme ultraviolet (EUV) wavebands, many difficulties and uncertainties reduce the accuracy of the obtained flat-field. We use images taken by the Atmospheric Imaging Assembly (AIA) to simulate the input images for the flat-field computations with the KLL algorithm and different dither patterns to find a suitable one for the in-flight flat-field calibration of SDI. Our results show that a circular dither pattern with 21 offset positions properly arranged and images with reduced spatial resolution down to about 15" allow us to obtain flat-fields with required accuracy of 2% of SDI.

The STereo Imaging Channel (STC) is one of the three channels of the SIMBIO-SYS instrument on board the BepiColombo ESA spacecraft. The design of the camera consists in a double wide-angle camera with two sub-channels looking at ±20° with respect to the nadir direction. Each sub-channel can acquire three quasi-contiguous areas of the Mercury surface in different colours determined by the filters mounted on the detector. The filters are divided in two categories: 4 broad band filters (20 nm of bandwidth and centred at 420, 550, 750 and 920 nm respectively) necessary to the chemical analysis of the Hermean surface; 2 panchromatic (PAN) filters with 200 nm of bandwidth and centred at 600 nm, designed for the stereo acquisition. The nominal Field of View (FoV) of each sub-channel is 5:38°x4:8°. The in-flight stellar calibration will be performed during the nominal mission using stellar fields images. To effectively plan this calibration activity, two analyses have been performed: the first one consists in simulating the observation of stars having different apparent magnitude to derive the best integration time needed to reach a specific Signal to Noise Ratio. Considering the characteristics of the STC camera and of its CMOS detector, the threshold magnitude needed for a star to be detectable will also be determined. The second part consists in selecting the stellar fields from the ESA GAIA archive and Tycho stellar catalogue that contain a pre-defined minimum number of stars required to perform the in-flight geometrical calibration. This selection have been performed taking into account stars brighter than the threshold defined in the first part.

MAJIS is an imaging spectrometer operating in the visible and IR range which is part of the payload of the JUICE mission of ESA, dedicated to the study of the icy moons of Jupiter, Jupiter and the Jupiter environment, to be launched in June 2022. MAJIS implements two channels, one for the visible-near IR range (0.5 – 2.35 μm) and one for the IR range (2.25 – 5.52 μm). Each channel collects photons with a H1RG detector^1,2. The trajectory of the JUICE spacecraft in the Jupiter system crosses the radiation belts, in particular during flybys of Europa and Ganymede as well as during the orbiting phase around Ganymede (280 days). The Jupiter radiation belts are the most intense in the solar system, hence a combination of shielding and on-board processing has been implemented for handling the impact rate of high energy electrons, each generating large numbers of electrons (“spikes”) when impacting detector pixels. The de-spiking approach consists in splitting each acquisition into N = 2 to 8 sub-integrations, then sorting the resulting N values for each pixel, averaging a subset of the lowest values. This selective averaging approach effectively sort outs subintegrations impacted by a spike so as to meet a target of less than 1% corrupted pixels for each frame. This can be achieved by adjusting the sorting strategy to the local high energy electron flux, which strongly depends on the distance from Jupiter and on the latitude. Specific selective averaging strategies can also be implemented for mitigating possible instrumental artefacts.

EnVisS (Entire Visible Sky) is an all-sky camera specifically designed to fly on the space mission Comet Interceptor. This mission has been selected in June 2019 as the first European Space Agency (ESA) Fast mission, a modest size mission with fast implementation. Comet Interceptor aims to study a dynamically new comet, or interstellar object, and its launch is scheduled in 2029 as a companion to the ARIEL mission. The mission study phase, called Phase 0, has been completed in December 2019, and then the Phase A study had started. Phase A will last for about two years until mission adoption expected in June 2022. The Comet Interceptor mission is conceived to be composed of three spacecraft: spacecraft A devoted to remote sensing science, and the other two, spacecraft B1 and B2, dedicated to a fly-by with the comet. EnVisS will be mounted on spacecraft B2, which is foreseen to be spin-stabilized. The camera is developed with the scientific task to image, in push-frame mode, the full comet coma in different colors. A set of ad-hoc selected broadband filters and polarizers in the visible range will be used to study the full scale distribution of the coma gas and dust species. The camera configuration is a fish-eye lens system with a FoV of about 180°x45°. This paper will describe the preliminary EnVisS optical head design and analysis carried out during the Phase 0 study of the mission.

HYPSOS (Hyperspectral Stereo Observing System, patented) is a novel concept for a hyperspectral-stereo camera that combines the 3D information attainable by two stereo images, with the fine spectral sampling of a spectrograph. Planetary remote sensing represents an interesting application field for the HYPSOS concept. At the basis of HYPSOS there is the merge between two different approaches for studying the surface of a planet: the morphology of any feature analyzed by the geologist through the 3D images, and the composition of the same feature, through the hyperspectral data. In general, the merging of data provided by two different instruments may have problems due to co-registration and calibration, and the resolutions may be different requiring some interpolation. HYPSOS solves this problem by hardware: the images of the stereo channels are oriented in such a way that they are both placed along the same direction. In this way it is possible to use the same spectrometer for both channels, eventually leaving some space between the two channels to avoid signal contamination. This configuration is achieved by the placement of simple field rotating prisms along the optical paths of the two stereo-channels. A further advantage of this approach is that it does not require to limit the spectral range, which is otherwise necessary to avoid the superposition of spectra obtained by using two slits separated along track. In this paper we provide details on the configuration of the instrument, the optical layout of a possible implementation, and the resulting performances.

The Solar Corona Imager is an internally occulted coronagraph on board the ASO-S mission, which has the advantage of imaging the inner corona in H I Lyman-α (Lyα) and white-light (WL) wavebands. However, scattering of solar disk light by the primary mirror (M1) becomes the main source of stray light. To study the methods of stray light suppression, three scattering models are used to model M1 scattering in Zemax OpticStudio. The ratio of coronal emission to predicted stray light decrease along field of view in both channels. The stray light in Lyαchannel is generally lower than coronal emission, but the stray light in WL channel tends to be one order of magnitude higher than coronal signal at 2:5Rꙩ. Optimized parameter combinations that suppress the stray light to required level are obtained, which put some limitations on the M1 manufacture. Besides, K-correlation model is recommended to simulate surface scattering.

MAJIS is part of the science payload of the JUICE mission to be launched in 2022. BIRA-IASB and ROB contribute to MAJIS with the characterization of the VIS-NIR Flight Model (FM) and Spare Model (SM) detectors, including the design, development, and validation of the setup, as well as the data processing pipeline. The VIS-NIR detectors are thermalized within a temperature range from 125 K to 150 K during their characterization campaigns. Moreover, the temperature of their electronic units must always remain above 120 K to avoid any irreparable damage, and below 160 K for operative conditions. Likewise, to avoid any risk of contamination, the detector should preferably be operated below 10^-5 mbar of vacuum. To fulfill these requirements, a complete security system was developed; it includes redundant thermal control loops, alarms from every pressure and temperature monitoring devices in use, and a robust semi-automatic control system for the pumping and cryocooling equipment. Moreover, the security system is complemented by the Temperature Ground Support Equipment (TGSE), which provides a LabVIEW user-friendly interface to communicate the status of the detector and the vacuum chamber in real-time. This subsystem was successfully validated in May 2020, before the delivery of the FM detector in June 2020. In this paper, we summarize the design, implementation and validation tests of the security system as well as the thermal and vacuum performances of the facility. We also show the thermal behavior of the detector during acquisitions representative of typical MAJIS observations.

MAJIS is part of the science payload of the ESA L-Class mission JUICE to be launched in 2022 with an arrival at Jupiter in 2030. MAJIS will perform imaging spectroscopy through two channels: VIS-NIR (0.50 µm - 2.35 µm) and IR (2.25 µm - 5.54 µm). The Royal Belgian Institute for Space Aeronomy (BIRA-IASB) and the Royal Observatory of Belgium (ROB) contribute to MAJIS with the characterization and calibration of the VIS-NIR Flight Model (FM) and Spare Model (SM) detectors, including the design, development, and validation of the setup, as well as the data processing pipeline. The FM and SM detectors are characterized under different illumination conditions (along four decades of dynamical range), temperature (125 K - 144 K), beam uniformities, exposure times, and/or data acquisition rates. In this paper, we describe the optical performances of the facility, which can be configurable for dark conditions, uniform light beam, and convergent beam with same focal ratio as MAJIS convergence optics. We provide a relative radiometry scale for the typical characterization measurements, as well as a fully characterized flux that will allow us to perform characterization measurements in an absolute radiometry scale, such as quantum efficiency (QE). In addition, we describe the thermal performances provided by the bench reaching different temperature scenarios, including the expected operating temperature of the detector at 132 K. The characterization facility was completed and subjected to validation tests in early 2020. The MAJIS VIS-NIR FM detector was delivered for its complete characterization in June 2020.

We are at a crossroads today with large and complex missions, known as flagships: while much has been achieved to lower their size, weight, and power demands, there are science questions that cannot be answered but through the exquisite measurements characteristic of flagships. We need an approach to a resilient flagships program for science: 1) One, conduct an assessment of the fundamental science questions and concept feasibility study to define the core science requirements (those that, if not met, render the mission unnecessary), and the corresponding technology challenges. 2) Two, fund technologies to TRL 6, including systems engineering and system integration approaches, and also ways to determine the impact of science requirements on the mission concept (complexity, cost, schedule). 3) Three, mature the system concept prior to prototyping of manufacturing and test activities. 4) Four, review science requirements in light of systems level interactions that are driving complexity, cost and schedule, and re-scope accordingly. 5) Five, after the technology development is complete, develop a prototype of the system to resolve implementation issues. 6) Six, establish a not-to-exceed annual funding level that continues until a prototype is complete. As prototype development is nearing completion, provide a realistic estimate of the scope of remaining work. 7) Seven, obtain Congressional approval for all remaining development funds (similar to the approach for Navy capital ships). 8) Finally, develop and deploy the mission following an optimal funding profile. When evaluating contracting approaches, it is important to contemplate a NASA Center serving as prime and evaluate contractors’ abilities to execute one-off payload elements.

The Canadian astrophysics community is embarking on its decadal planning exercise for the 2020-2030 period to decide on Canadian priorities. Canada has contributed to missions such as Herschel, Planck, Astrosat, Hitomi and has delivered two instruments for the JWST and contributing to the XARM mission. Looking ahead, the Canadian Space Agency (CSA) is currently supporting developments for several new space astrophysics mission opportunities, such as for LiteBIRD and SPICA and concepts such as the wide-field UV-optical space telescope Current investments and new concepts for the next decade are summarized.