This PDF file contains the front matter associated with SPIE Proceedings Volume 12180, including the Title Page, Copyright information, Table of Contents, and Conference Committee listings.

The James Webb Space Telescope (JWST)—a joint enterprise of NASA, the European Space Agency and the Canadian Space Agency—is the most complex and in some ways the most powerful telescope ever built. It’s history--which includes a near-death experience at the hands of a U.S. congressional committee in 2011 when there was an effort to kill the project--raises a range of important issues, as well as lessons for the future of space astronomy. In this talk, Dr. Robert W. Smith will discuss several key moments in JWST’s history.

JWST Project Scientist Jonathan Gardner presents an overview of JWST commissioning activities, highlighting observatory performance, followed by more detailed discussion of the individual science instruments.

Pathways to Discovery in Astronomy and Astrophysics for the 2020s has recommended a Great Observatory Maturation Program (GOMaP) to invest in co-maturation of mission concepts and technologies to inform an Analysis of Alternatives (AOA) study for an approximate 6-meter off-axis inscribed telescope to sample atmospheric spectra of ~25 potentially habitable exoplanets using UV, visible and Nir-IR wavelengths and to be launched in the early 2040s with a total cost of less than $11B including 5 years of operation. The history of past missions indicates that technology development is critical for enabling missions, the robustness, breadth, and duration of concept/technology co-maturation is important for mission success, and NASA has not ‘exactly’ implemented Decadal missions as recommended.

This paper examines how a choice programmatic architecture might enable re-use in design to speed up the development of the three flagship missions identified in the Astro 2020 survey. The paper begins with a review of the current milieu of Flagship developed, namely unique bespoke designs. Two program management architectures are introduced, the status quo, stand alone programs and the portfolio oriented Great Observatories Program Office, charged with completing all three missions in the more timely and efficient manner. Under the latter architecture, re-use of designs and hardware becomes a requirement. It is show that this can save many years is getting all three missions to launch and operation. The paper concludes with the recommendation that the ideas introduced here be further explored as part of the nascent Great Observatories Maturation Program currently being formulated.

Due to the continuous trend towards higher resolution, future large optical missions for both Astronomy and Earth Observation (telescopes, interferometry,...) are facing new challenges in terms of enabling technologies fighting adverse effects linked to the payload size (manufacturing issues, alignment and integration, in-orbit effects,...). We present here an updated overview of our R&D activities in this field as well as perspectives on the way-forward to technological maturity and implementation within future ESA mission concepts.

CubeSpec is an in-orbit demonstration CubeSat mission in the ESA technology programme, developed and funded in Belgium. The goal of the mission is to demonstrate high-spectral-resolution astronomical spectroscopy from a 6-unit CubeSat. The technological challenges are numerous. The telescope and echelle spectrometer have been designed to fit in a 10×10×20cm volume. The fast telescope focus and spectrometer alignment is achieved via an athermal design. Shielding from the Sun and Earth infrared flux is achieved via deploying Earth and Sun shades. Arcsecond-level pointing stability is achieved using a performant 3-axis wheel stabilised attitude control system with star tracker augmented with a fine beam steering mechanism. CubeSpec is now starting the implementation phase, with a planned launch in 2024. A qualification and a flight model will be constructed and tested in the next 2 years. In this contribution we will give an overview of the mission, its technologies and qualification status.

We present the CuRIOS project (*Cu*beSats for *R*apid *I*nfrared and *O*ptical *S*urveys), which is a constellation of CubeSats that monitors all-sky, all-the-time at ~1 minute cadence. CuRIOS is aimed at studying the death and afterlife of stars: white dwarfs, neutron stars, and black holes. Each CubeSat would have a roughly 10 deg x 10 deg field of view with ~3'' spatial resolution and a limiting magnitude of I=19 (vega) in 15 min with SNR=10. Hundreds of CubeSats would be required to fully tile the entire sky. The CuRIOS project is now possible thanks to demonstrated economies of scale that already deployed satellite constellations have demonstrated. Build costs may drop by 50x between the first few satellites and the later >20 satellites. We will present a conceptual design for CuRIOS and describe the CuRIOS survey, which will observe transient phenomena originating from black holes and neutron stars in the Milky Way and beyond.

Observations of standard stars and calibration sources are critical to most astronomical observations. Many of the scientific goals and questions recently highlighted in the Decadal Survey on Astronomy and Astrophysics 2020 require more precise calibration of telescopes and instruments than is possible with current methods. We present the Calibration Satellite for Traceable Astrophysical Radiometric Standards (CSTARS) mission concept. CSTARS is a small space telescope and spectroradiometer, whose absolute spectral response is traceable to NIST standards with an uncertainty of < 0.3%. CSTARS will be able to characterize and monitor the absolute spectral energy distribution of dozens of stars, including the white dwarfs commonly used to calibrate the Hubble Space Telescope and the most stable G-type dwarfs found so far. Once characterized, these targets may be used to calibrate a wide range of astronomical telescopes and instruments, on the ground and in space.

POET is a proposed Canadian Microsatellite mission designed to characterize and discover transiting exoplanets. A 20-cm all-reflective telescope will feed a trio of detectors to obtain simultaneous, high duty-cycle, photometry in the u (300-400 nm), Visible Near-Infrared (VNIR) (400-900 nm) and Short Wave Infrared (SWIR (900- 1700 nm) bands to make precision measurements of exoplanet transits for atmospheric characterization and to detect transiting Earth-sized planets. POET was selected as a high priority for a Microsatellite mission by the Canadian community as part of the CASCA Long Range Plan 2020. Advancement of the payload concept and technology development for the optical telescope assembly (OTA) are currently being carried out through the Space Technology Development Program of the Canadian Space Agency. POET is a collaboration between Bishop’s University, Western University, ABB and SFL-UTIAS.

Today, the combination of high angular resolution and high revisit rate is not readily available from space, at least not at a reasonable cost. Many applications in the science, civil or defense domains would benefit from having access to detailed images of the ground as often as possible, in order to study temporal evolutions of specific events. The high angular resolution requires large optics hence large platforms, whereas the revisit rate requires constellations of multiple satellites and therefore small and affordable platforms. We proposed the concept of a deployable telescope onboard a CubeSat, called AZIMOV [1, 3, 5], to address this specific gap. Reaching a diameter of 30 cm once deployed, this concept gives access to a meter resolution on the ground from a Low Earth Orbit, or to a 70 cm resolution on Mars surface from a 400 km polar orbit. We study in this paper the performance of such a telescope in the aggressive thermal environment of space, with respect to the tight optical requirements of the system.

Pandora is a low-cost space telescope designed to measure the composition of distant transiting planets. The Pandora observatory is designed with the capability of measuring precision photometry simultaneously with nearinfrared spectroscopy, enabling scientists to disentangle stellar activity from the subtle signature of a planetary atmosphere. The broad-wavelength coverage will provide constraints on the spot and faculae covering fractions of low-mass exoplanet host stars and the impact of these active regions on exoplanetary transmission spectra. Pandora will subsequently identify exoplanets with hydrogen- or water-dominated atmospheres, and robustly determine which planets are covered by clouds and hazes. Pandora observations will also contribute to the study of transit timing variations and phase curve photometry. With a launch readiness date of early-2025, the Pandora mission represents a new class of low-cost space missions that will achieve out-of-this-world science.

The Contemporaneous LEnsing Parallax and Autonomous TRansient Assay (CLEoPATRA) space mission concept is designed to provide variable-baseline simultaneous microlensing parallax measurements for NASA’s flagship Roman Space Telescope mission and for terrestrial telescopes. We here describe the design of the mission, including discussion of our efforts to develop the means to greatly reduce the data downlink bandwidth using artificial intelligence and modern fanless GPUs, FPGAs and Tensor Processing Units. We demonstrate a reduction of data downlinked by a factor of up to 28,000 permitting communications between Earth and a small, power-limited craft in deep space. We describe radiation testing of inferencing hardware, functionality of our artificial intelligence code, compressive sensing applied to photometric lightcurves and the implementation of new, integrated optics to permit a 20cm baffled telescope to fit fully inside a small scientific spacecraft.

DRACO is the only instrument on the Double Asteroid Redirection Test (DART) spacecraft. DRACO is a narrow angle camera designed to provide final images of the Didymos system at less than 0.50 m/px ground scale as well as provide images to be used for the Small-body Maneuvering Autonomous Real Time Navigation (SMARTNav) targeting system on board the DART spacecraft. DRACO includes an F/12.6, 2625mm focal length Ritchey-Chrétien telescope with a field-flattening lens. Images are taken with a 6.5um CMOS image sensor, the BAE CIS2521F, by the DRACO Focal Plane Electronics (FPE) and transferred to the spacecraft. Images are then processed for blobs and centroids for use in SMARTNav and either downlinked in real-time or recorded on the spacecraft for later playback. DRACO is thermally isolated and operated at -80°C to -20°C. Alignment was completed at room temperature, with additional checks after vibration testing and a focus shim was added for operation at cold temperature. Performance is near-diffraction limited and in-flight performance matches well with ground measurements. The BAE CIS2521 is measured to have very low read noise (< 2 e-) and negligible dark current. DRACO was integrated on the DART spacecraft in June 2021 after a successful instrument development and test campaign. DRACO is currently in use on the DART spacecraft after a successful commissioning. It will be used as the primary guidance sensor for the DART impact in September 2022 and provide high-resolution images of the Didymos system.

The Martian Moons eXploration (MMX) mission led by JAXA will conduct remote sensing of both Martian moons Phobos and Deimos and in-situ observations and return samples from Phobos. A small rover will be operating on Phobos’ surface and perform scientific measurements, in particular with its Raman Spectrometer for MMX (RAX). The instrument is jointly developed by DLR with partners from Spain (INTA, University of Valladolid) and Japan (JAXA, University of Tokyo). With its more than 20 optical elements (e.g. laser, lenses, mirrors, grating, dichroic beam-splitters, spectral filters), the optical alignment and integration of this very compact Raman spectrometer was one of the biggest challenges of the instrument development at DLR. This article will cover the different steps of alignment with 1) the integration of the lenses in each individual lens group, 2) the alignment and integration of each lens group to build the spectrometer, and 3) the global alignment verification of the end-to-end instrument. The main goal was to integrate the optical elements in RAX’s mechanical housing providing maximized scientific performance. This meant for example that the detector’s sensitive surface had to be precisely placed at the focal plane surface of the imaging objective to optimize the spectral resolution, but also that the confocality of the laser output (and image on Phobos’ surface) with the spectrometer slit had to be very accurately adjusted to optimize the Signal to Noise Ratio of the Raman features. Aligning and integrating a state-of-the art Raman spectrometer in a very compact volume of less than 10x10x10 cm³ and a mass lower than 1.5 kg was challenging but successful. The different tests performed on the instrument presented here also showed the robustness of the design and demonstrated that RAX can perform excellent scientific measurements on Phobos.

MAJIS (Moons And Jupiter Imaging Spectrometer) is the VIS-IR imaging spectrometer of the ESA/JUICE mission that will explore the Jovian system. It covers the spectral range 0.5 to 2.35 μm and 2.26 to 5.56 μm using two channels. The MAJIS Optical Head (OH) consists in a TMA telescope shared between the two channels, as well as a slit and collimator, then a dichroic filter that splits the light between the channels, each one being equipped with its own grating and focusing lens. The same type of detector is used for both spectrometers (apart from the order sorting filter), being a 400 pixels × 508 spectels with 36 µm pitch. We will present the characterization of the OH performed at Leonardo Company at cold operational temperatures (from 110K to 150K). The test set-up with a specific emphasis of the Optical Ground Support Equipment (OGSE) used during that characterization campaign will be shortly described. Then, the main performances (spatial, spectral) of the OH will be presented and a comparison with the requirements will be provided.

The GALA (Ganymede Laser Altimeter) is one of eleven scientific instruments of the ESA mission JUICE (Jupiter Icy Moons Explorer) with the goal of exploring the icy moons of Jupiter, with a special interest in Ganymede. By its atmosphere, magnetic field, and water abundance, Ganymede is similar to Earth [1]. GALA is a laser altimeter that generates a surface profile with a resolution of < 15 cm based on an emitted laser pulse that is reflected by the surface of the moon 500 km away [2]. The mechanical development of the receiver telescope with an extremely thin-walled primary mirror (thickness 4-8 mm; diameter ~ 300 mm) was driven by tough boundary conditions. These are a small envelope and mass budget with high mechanical loads, such as a quasi-static acceleration of 120 g during rocket launch and a temperature range from -50 °C up to 150 °C, at the same time. The athermal design is based on the use of a silicon particle reinforced aluminum compound (AlSi40) and an amorphous nickel-phosphorous plating to allow various shape correction and polishing processes. Another challenge was the high radiation load of 10¹² protons/cm² @ 10 MeV. Fraunhofer IOF developed and qualified a gold HR coating based on nanolaminate with R < 98% @ 1064 nm and high resistance. Thus, almost all process steps from development through manufacturing to integration and characterization could be carried out at Fraunhofer IOF. With a shape deviation of 27 nm RMS of the primary mirror and 8 nm RMS of the secondary mirror, a system performance of 90% encircled energy could be achieved with a pupil radius of 38 µm. The telescope was handed over to HENSOLDT in spring 2020 and will start its eight-year journey to Jupiter in 2023.

The Compact Doppler Magnetograph (CDM) is a space-qualified, miniaturized Doppler magnetograph, tailored to the requirements of a solar polar mission, and designed to provide photospheric line-of-sight magnetic field and Doppler velocity measurements of the solar surface. CDM is derived from the proven GONG (Global Oscillations Network Group) instrument design (Harvey et al., 1988, 1996), with a space qualified prototype developed for the Solaris solar polar MIDEX mission (Hassler et al., 2020). CDM has roughly 1/3 the mass of current state-of-the-art Doppler magnetographs (e.g., SOHO/MDI, SDO/HMI, SolO/PHI), with greatly increased sensitivity to the magnetic field (B) and Doppler velocity (v) and the capability to perform over an expanded spacecraft orbital velocity range, which is required to fit within the mission design constraints of currently feasible high latitude solar polar missions.

The advent of photonic integrated circuits (PICs) will allow the replacement of the large aperture of an optical telescope by a dense array of small apertures combined interferometically. The light coming from aperture pairs can be combined by a PIC in order to extract interferogram characteristics known as complex visibilities, from which the observed object can then be reconstructed. In such a compact interferometric imager, the optical components dedicated to image formation in a regular telescope are no longer necessary. In particular, such a concept is relevant for space missions where weight and size are critical. To date, the proposed concepts are made of one-dimensional arrays radially disposed in a circular instrument. The way of combining the apertures defines the optical transfer function of the instrument, which is key to the imaging performance. In this communication, our goal is to optimize the aperture configuration. Signal-to-noise considerations suggest using each aperture once and only once in order to avoid splitting the flux received on each aperture. Moreover, non-redundant configurations allow a broader spatial frequency coverage. We study aperture configurations based on these two conditions. We describe this problematic formally and we apply results from combinatorial theory to prove the existence of solutions to some problems of aperture configuration optimization, and to exhibit some explicit solutions. Firstly, we suggest new aperture configurations leading to a dense spatial frequency coverage. Secondly, we use these results to propose an optimal frequency coverage for a SPIDER-like design. Then, by complementing the latter instrument with a monolithic telescope, we propose a new aperture configuration that extends the spatial frequency coverage. Lastly, additional strategies to further extend the cut-off spatial frequency are explored and presented.

The Event Horizon Explorer (EHE) is a mission concept to extend the Event Horizon Telescope via an additional space-based node. We provide highlights and overview of a concept study to explore the feasibility of such a mission. We present science goals and objectives, which include studying the immediate environment around supermassive black holes, and focus on critical enabling technologies and engineering challenges. We provide an assessment of their technological readiness and overall suitability for a NASA Medium Explorer (MIDEX) class mission.

The number of terrestrial exoplanets accessible to high-contrast coronagraphic imaging with large telescopes is limited by the smallest angular offset from bright stars at which coronagraphs can observe. However, it is possible to reach inside a telescope’s coronagraphic regime by employing nulling interferometry across a telescope’s pupil. Indeed, “cross-aperture” nulling interferometry can observe significantly closer to stars than typical coronagraphs, enabling observations even within the stellar diffraction core. Identifying an optimal nulling coronagraph, i.e., one with both a very small IWA and a high throughput for exoplanet light, would thus be of great interest. A systematic examination of available nulling options has therefore been carried out, which has led to three things. The first is a topological overview that unites both multiaperture nulling interferometers and single-aperture phase coronagraphs into a common geometrical framework. The second is a new type of phase-mask coronagraph that has emerged from a gap in this framework, called here the “splitring” coronagraph. The third is a clear identification of the optimal configuration for a nulling coronagraph, which turned out to be an aperture-plane phase knife, i.e., an achromatic π-radian phase shift applied to half the telescope pupil prior to focusing the telescope’s point spread function (PSF) into a single-mode fiber. The theoretical peak efficiency of the phaseknife fiber coronagraph, 35.2% for a circular telescope aperture, is found to be almost twice that of the next most efficient case, the vortex fiber nuller, at 19.0%.

This paper will present an overview of the LISA (Laser Interferometer Space Antenna) optical bench and discuss the innovative methods developed to analyse and mitigate significant engineering challenges. There are two optical benches for each of the three LISA spacecraft. The optical bench consists of numerous components which form the paths of the interferometers used to measure the displacement changes caused by gravitational waves. Given each spacecraft is separated by 2.5 million Km, a laser beam sent from one to another arrives with a significantly lower irradiance than on departure. It is in part because of this that various engineering challenges are faced by the LISA OB. This is alongside the extremely demanding nature of measuring gravitational waves at a sensitivity of pico-meters per root-Hertz.

The James Webb Space Telescope (Webb) is a large, infrared space telescope that recently completed its on-orbit commissioning activities and has now embarked on its first year of approved science. Its architecture includes many first-of-its kind innovations for space, including a segmented primary mirror that is 6.6 m in diameter and a 5-layer sunshield used to passively cool the telescope and its four science instruments. Although Webb had an extensive test program, the system-level performance often relied on predictions based on integrated modeling, using conservative factors for the model uncertainties and primarily focusing on evaluating the performance at the end of life. A set of commissioning activities were designed for a system-level characterization of the performance. This proceeding will provide the status of the mission, including a discussion of the major events, on-orbit system performance, and early science highlights.

The long-awaited launch of the James Webb Space Telescope on December 25, 2021, initiated a complex commissioning campaign which successfully brought the observatory to readiness for carrying out its scientific observing program by early July, 2022. Commissioning began by bringing online the various spacecraft systems and executing a series of mission-critical deployments. The next few months involved a complex interplay of cooling toward the final cryogenic operating temperatures of the telescope and instruments, aligning the segmented, deployable telescope, bringing online Webb’s four scientific instruments (plus Fine Guidance Sensors), and beginning the process of preparing their many powerful observing modes for scientific use. We provide an overview of the process and timeline for executing the commissioning campaign and then focus on its final stages: for each instrument, acquiring the numerous pieces of performance data and carrying out the operational verifications that ultimately led to confirmation of each observing mode’s readiness for scientific operations.

Backgrounds observed by JWST will be a critical parameter for overall observatory sensitivity. JWST’s background, sensitivity and other performance requirements drove the observatory’s open architecture, sunshield geometry, orbit at L2 and other unique characteristics. These requirements were verified by analysis, to be measured for the first time on-orbit. Modeling JWSTs backgrounds is complex, as JWST backgrounds have multiple components including: backgrounds from in-field sources (such as Zodiacal Light) and stray light from scattering of sky sources outside the field; thermal selfemission of optical surfaces; and scattering of thermal self-emission from other Observatory surfaces. The unbaffled telescope design allows stray light paths from multiple directions. The 5-layer sunshield passively cools and shades the telescope and science instruments; however, there are thermal paths that may affect thermal performance. In-field backgrounds and stray light from sky sources can depend on the telescope’s pointing and observation date. The thermal emission contributions will depend on the Observatory’s sun orientation and recent history. The JWST Background Tool (JBT) uses the stray light models, in-field backgrounds, and thermal models to predict the expected backgrounds. Onorbit, several positions were measured at multiple wavelengths with NIRCam and MIRI to probe JWST’s backgrounds and validate model predictions. These results may be used to update the JWST Exposure Time Calculator in preparation for the Cycle 2 proposal call. This conference proceeding will provide a summary of the modeling backgrounds and report on the measured on-orbit backgrounds.

The direct characterization of exoplanetary systems with high contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximise the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55-hour Early Release Science Program that will utilize all four JWST instruments to extend the characterisation of planetary mass companions to ∼15-20 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative datasets that will enable a broad user base to effectively plan for general observing programs in future cycles.

The James Webb Space Telescope (JWST) launched on December 25th, 2021. The observatory was deployed and commissioned during its first six months. The Optical Telescope Element includes both large deployments of the Deployable Tower Assembly, Secondary Mirror Support Structure and the Primary Mirror Wings and it includes the deployment and alignment of the 18 primary mirror segments and the secondary mirror. The initial phase included cooldown and ice mitigation efforts followed by telescope deployments, mirror deployment and wavefront sensing and control. This paper will discuss the entire OTE commissioning from deployment through alignment including a discussion of results and lessons learned.

The James Webb Space Telescope (JWST) is a segmented deployable telescope, currently operating at L2. The telescope utilizes 6 degrees of freedom for adjustment of the Secondary Mirror (SM) and 7 degrees of freedom for adjustment of each of its 18 segments in the Primary Mirror (PM). After deployment, the PM segments and the SM arrived in their correct optical positions to within a ~1 mm, with accordingly large wavefront errors. A Wavefront Sensing and Controls (WFSC) process was executed to adjust each of these optical elements in order to correct the deployment errors and produce diffraction-limited images across the entire science field. This paper summarizes the application of the WFSC process.

NASA’s James Webb Space Telescope has completed the commissioning phase and optical performance evaluation. The size, architecture, and scope of Webb required new approaches to optical performance verification leveraging modeling and simulation. This effort was managed using system engineering processes with emphasis on model validation and statistical management of risks via error budgeting. At this time, this approach can be evaluated and understood given the process used for commissioning including tradeoffs of schedule, performance and risk. The lessons learned and approach are reviewed to assess the approach for future missions. To this end, this paper compares the predicted performance with that achieved on-orbit.

The Near-Infrared Spectrograph (NIRSpec) is one of the four focal plane instruments on the James Webb Space Telescope which was launched on Dec. 25, 2021. We present an overview of the as-run NIRSpec commissioning campaign, with particular emphasis on the sequence of activities that led to the verification of all hardware components of NIRSpec. We also discuss the mechanical, thermal, and operational performance of NIRSpec, as well as the readiness of all NIRSpec observing modes for use in the upcoming JWST science program.

To achieve its ambitious scientific goals, the Near-Infrared Spectrograph, NIRSpec, on board the Webb Space Telescope, needs to meet very demanding throughput requirements, here quantified in terms of photon-conversion efficiency (PCE). During the calibration activities performed for the instrument commissioning, we have obtained the first in-flight measurements of its PCE and also updated the modeling of the light losses occurring in the NIRSpec slit devices. The measured PCE of NIRSpec fixed-slit and multi-object spectroscopy modes overall meets or exceeds the pre-launch model predictions. The results are more contrasted for the integral-field spectroscopy mode, where the differences with the model can reach −20%, above 4 μm, and exceed +30%, below 2 μm. Additionally, thanks to the high quality of the JWST point-spread function, our slit-losses, at the shorter wavelength, are significantly decreased with respect to the pre-flight modeling. These results, combined with the confirmed low noise performance of the detectors, make of NIRSpec an exceptionally sensitive spectrograph.

The NIRSpec instrument for the James Webb Space Telescope (JWST) is a highly versatile near-infrared spectrograph that can be operated in various observing modes, slit apertures, and spectral resolutions. Obtaining dedicated calibration data for all possible combinations of aperture and disperser is an intractable task. We have therefore developed a procedure to derive a highly realistic model of the instrument’s optical geometry across the entire field of view, using calibration data acquired through only a subset of NIRSpec apertures, which nevertheless allows the light paths within the spectrograph to be accurately computed for all apertures and all observing modes. This parametric instrument model thus provides the basis for the extraction of wavelengthcalibrated spectra from any NIRSpec exposure, regardless of observing mode or aperture used. Optimizing the NIRSpec instrument model and deriving its final wavelength and astrometric calibration was one of the most crucial elements of the NIRSpec commissioning phase. Here, we describe the process of re-fitting the NIRSpec instrument model with in-orbit commissioning data, and present its final performance in terms of wavelength accuracy and astrometric calibration.

When observing with the slitless Low Resolution Spectroscopic (LRS) mode of the MIRI instrument on board the James Webb Space Telescope (JWST), photons at wavelengths shorter than the nominal wavelength range (5 μm - 12 μm) can reach the detector. In this paper, we study the impact of such photons in terms of opportunity to get spectral information below the nominal cut on, and in terms of possible contamination of the nominal spectrum by those photons. First, we present new laboratory measurements done to characterize the transmission and dispersion of the LRS disperser element, a Double Prisms Assembly (DPA), in the 3-5 μm wavelength range. We confirm a transmission peak at the level of about 30% around 3.7 μm and validate the dispersion optical model. We use the information to simulate how the short wavelengths will impact the spectroscopic images obtained during slitless LRS observations of bright stars; we see a bright spot at the pixel corresponding to the 3.7 μm. Such a spot has indeed been seen in the spectral images obtained during the commissioning of MIRI in May-June 2022; the level of the observed spot is lower than predicted. Such a feature could be useful when observing exoplanets, as it can bring addition information on the exoplanet atmosphere. The effect of spectral contamination is difficult to assess precisely; but, according to the modelisation we did, it is low: at most 7 % in the 5 - 6 μm range and negligible at longer wavelengths.

Ariel (Atmospheric Remote-Sensing Infrared Exoplanet Large Survey) is the adopted M4 mission in the framework of the ESA “Cosmic Vision” program. Its purpose is to conduct a survey of the atmospheres of known exoplanets through transit spectroscopy. Launch is scheduled for 2029. Ariel scientific payload consists of an off-axis, unobscured Cassegrain telescope feeding a set of photometers and spectrometers in the waveband between 0.5 and 7.8 µm and operating at cryogenic temperatures (55 K). The Telescope Assembly is based on an innovative fully-aluminum design to tolerate thermal variations avoiding impacts on the optical performance; it consists of a primary parabolic mirror with an elliptical aperture of 1.1 m of major axis, followed by a hyperbolic secondary that is mounted on a refocusing system, a parabolic re-collimating tertiary and a flat folding mirror directing the output beam parallel to the optical bench. An innovative mounting system based on 3 flexure-hinges supports the primary mirror on one side of the optical bench. The instrument bay on the other side of the optical bench houses the Ariel IR Spectrometer (AIRS) and the Fine Guidance System / NIR Spectrometer (FGS/NIRSpec). The Telescope Assembly is in phase B2 towards the Preliminary Design Review to start the fabrication of the structural model; some components, i.e., the primary mirror, its mounting system and the refocusing mechanism, are undergoing further development activities to increase their readiness level. This paper describes the design and development of the ARIEL Telescope Assembly.

AIRS is the infrared spectroscopic instrument of ARIEL: Atmospheric Remote‐sensing Infrared Exoplanet Large‐survey mission selected in March 2018 as the Cosmic Vision M4 ESA mission and planned to be launched in 2029 by an Ariane 6 from Kourou toward a large amplitude orbit around L2 for a 4 year mission. Within the scientific payload, AIRS will perform transit spectroscopy of over a 1000 of exoplanets to complete a statistical survey, including gas giants, Neptunes, super-Earths and Earth-size planets around a wide range of host stars. All these collected spectroscopic data will be a major asset to answer the key scientific questions addressed by this mission: what are the exoplanets made of? How do planets and planetary system form? How do planets and their atmospheres evolve over time? The AIRS instrument is based on two independent channels covering the CH0 [1.95-3.90] µm and the CH1 [3.90-7.80] µm wavelength range with prism-based dispersive elements producing spectrum of low resolutions R<100 in CH0 and R<30 in CH1 on two independent detectors. The spectrometer is designed to provide spectrum Nyquist-sampled in both spatial and spectral directions to limit the sensitivity of measurements to the jitter noise and intra pixels pattern during the long (10 hours) transit spectroscopy exposures. A full instrument overview will be presented covering the thermal mechanical design of the instrument functioning in a 60 K cold environment, up to the detection and acquisition chain of both channels based on 2 HgCdTe detectors actively cooled down below 42 K. This overview will present updated information of phase B2 studies in particular with the early manufacturing of prototype for key elements like the optics, focal-plane assembly and read-out electronics as well as the results of testing of the IR detectors up to 8.0 μm cut-off.

Within this paper, we describe architecture and functionality of the Fine Guidance Sensor (FGS), one of two instruments on-board ESA ARIEL mission. We present a conceptual design, development models, related challenges, and opportunities as seen at iPDR milestone.

The Atmospheric Remote-Sensing Infrared Exoplanet Large Survey (Ariel) is the M4 mission adopted by ESA’s ”Cosmic Vision” program. Its launch is scheduled for 2029. The purpose of the mission is the study of exoplanetary atmospheres on a target of ∼ 1000 exoplanets. Ariel scientific payload consists of an off-axis, unobscured Cassegrain telescope. The light is directed towards a set of photometers and spectrometers with wavebands between 0.5 and 7.8 µm and operating at cryogenic temperatures. The Ariel Space Telescope consists of a primary parabolic mirror with an elliptical aperture of 1.1· 0.7 m, followed by a hyperbolic secondary, a parabolic collimating tertiary and a flat-folding mirror directing the output beam parallel to the optical bench; all in bare aluminium. The choice of bare aluminium for the realization of the mirrors is dictated by several factors: maximizing the heat exchange, reducing the costs of materials and technological advancement. To date, an aluminium mirror the size of Ariel’s primary has never been made. The greatest challenge is finding a heat treatment procedure that stabilizes the aluminium, particularly the Al6061T651 Laminated alloy. This paper describes the study and testing of the heat treatment procedure developed on aluminium samples of different sizes (from 50mm to 150mm diameter), on 0.7m diameter mirror, and discusses future steps.

A space mission called “Earth 2.0 (ET)” is being developed in China to address a few of fundamental questions in the exoplanet field: How frequently habitable Earth-like planets orbit solar type stars (Earth 2.0s)? How do terrestrial planets form and evolve? Where did floating planets come from? ET consists of six 30 cm diameter transit telescope systems with each field of view of 500 square degrees and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees. The ET transit mode will monitor ~1.2M FGKM dwarfs in the original Kepler field and its neighboring fields continuously for four years while the microlensing mode monitors over 30M I< 20.6 stars in the Galactic bulge direction. ET will merge its photometry data with that from Kepler to increase the time baseline to 8 years. This enhances the transit signal-to-noise ratio, reduce false positives, and greatly increases the chance to discover Earth 2.0s. Simulations show that ET transit telescopes will be able to identify ~17 Earth 2.0s, about 4,900 Earth-sized terrestrial planets and about 29,000 new planets. In addition, ET will detect about 2,000 transit-timingvariation (TTV) planets and 700 of them will have mass and eccentricity measurements. The ET microlensing telescope will be able to identify over 1,000 microlensing planets. With simultaneous observations with the ground-based KMTNet telescopes, ET will be able to measure masses of over 300 microlensing planets and determine the mass distribution functions of free-floating planets and cold planets. ET will be operated at the Earth-Sun L2 orbit with a designed lifetime longer than 4 years.

An innovative Chinese space mission, the Earth 2.0 (ET) mission, is being developed to combine the transit and microlensing method together to search for Earth-sized exoplanets in the Galaxy, including the most precious ones—Earth 2.0s, i.e., habitable Earth-sized (0.8-1.25 Earth radii) planets orbiting solar type stars, cold and free-floating low-mass planets. ET’s 6 transit telescopes will monitor a FoV of 500 square degrees (covering the Kepler field) continuously for at least four years and generate a huge database containing high-cadence and ultra-high photometry precision light curves of 1.2 million FGKM dwarfs. With such a high value database in hand, many unsolved issues in the exoplanet field and even stellar sciences will be well addressed. Besides looking for Earth 2.0s and constraining its occurrence rate, ET will be dedicated to map a much wider radius-period diagram of terrestrial-like exoplanets than ever and reveal how it depends on the stellar properties and environments. With the 4-yr legacy data of Kepler, ET will observe some planet systems for up to 8 years and catch additional components in a multi-planet system, e.g. cold Giant, cold sub-Earths, exomoons, exorings and even exocomets. Are exomoons and exocomets common in a planet system? What’s the favorite number of planets in a multi-planet system? What’s the most common orbital configuration of planet systems? With these new data, ET will deepen our understandings on how unique our Solar system is and how do multi-planet systems evolve. In addition to exoplanet sciences, ET’s time series data will also benefit the studies in asteroseismology, archeology in the Galaxy, time-domain astrophysics and black hole science.

The Earth 2.0 (ET) mission is a Chinese next-generation space mission to detect thousands of Earth-sized terrestrial planets, including habitable Earth-like planets orbiting solar type stars (Earth 2.0s), cold low-mass planets, and freefloating planets. To meet the scientific goals, the ET spacecraft will carry six 30 cm diameter transit telescopes with each field of view of 500 square degrees, and one 35 cm diameter microlensing telescope with a field of view of 4 square degrees, monitor ~1.2M FGKM dwarfs in the original Kepler field and its neighboring fields continuously while monitoring over 30M stars in the Galactic bulge direction. The high precision transit observations require high photometry precision and pointing stability, which is the key drive for the ET spacecraft design. In this paper, details of the overall mission modeling and analysis will be presented. The spacecraft orbit, pointing strategy, stability requirements are presented, as well as the space-ground communication analysis. The ET spacecraft adopts an ultra-high photometry precision & high stable platform, largely inherited from other space science missions. The preliminary design of spacecraft which meets mission requirements is introduced, including the spacecraft overall configuration, observation modes, avionics architecture and development plan, which pays great attention to the pointing stability and huge volume science telemetry download.

The Earth 2.0 (ET) mission is a Chinese next-generation space mission aiming at detecting thousands of terrestrial-like planets, including habitable Earth-like planets orbiting solar type stars (i.e., Earth’s 2.0s), cold low-mass planets, and free-floating planets. The ET mission will use six 300 mm diameter wide field telescope arrays to continuously monitor 1.2 million FGKM dwarf stars in the original Kepler field and its adjacent regions for four consecutive years to search for new planets including Earth 2.0s using the transit technique. The six telescopes have the same configuration, point to the same sky area, and constitute the main scientific payload. Each telescope has an effective aperture of 300 mm with a very wide field of view (FOV) of 500 square degrees and a wavelength coverage of 450-900 nm. Each telescope is equipped with a focal plane mosaic camera. The mosaic camera is composed of 2×2, 9k×9k CMOS detectors with pixel size of 10μm. The optical design results in the diameter of the 90% encircled energy (EE90%) less than 40μm (or 4 pixels) over the entire FOV. About 20% vignetting at the edge of the FOV is introduced to provide good throughput for the entire FOV while keeping optics size and weight down to reduce manufacturing risk and scientific payload within the mass and volume limit. In this paper, we will present the optical design details, including influence analysis of various factors on image quality, e.g., glass material, detector flatness, manufacturing and assembly tolerances. In addition, we will describe temperature stability analysis of the telescope on image quality and photometry measurements.

PLATO (PLAnetary Transits and Oscillations) mission is a space-based optical multi-camera photometer mission of the European Space Agency to identify and characterize exoplanets and their hosting stars using two main techniques: planetary transit and asteroseismology. The PLATO spacecraft is composed of a Service Module and a Payload Module. The Service Module comprises all the conventional spacecraft subsystems and the sun shield with attached solar arrays. The Payload Module consists of a highly stable optical bench, equipped with 26 optical imagers/cameras covering a global field of view of > 2232 deg2. The design includes two types of cameras: 24 Normal Cameras (N-CAMs) with measurement cadences of 25s and 2 Fast Cameras (F-CAMs) with a cadence of 2.5s. The PLATO spacecraft data is complemented by ground based observations and processed by a dedicate Science Ground Segment. We describe the mission and spacecraft architecture and provide a view of the current status of development.

PLATO (Planetary Transits and Oscillations of stars) is the Cosmic Vision Programme M3 mission selected by the Science Programme Committee (SPC) for launch in 2026. The main goal of the PLATO mission is to detect terrestrial exoplanets in the habitable zone of solar-type stars and to characterize their bulk properties. The PLATO payload includes 26 nearly identical cameras (6 lenses dioptric design) with broadband sensitivities down to 500nm and up to 1000 nm to achieve of total field of view larger than 1,000 square degrees. We provide an overview of the design and performance verification activities conducted on the Camera Engineering Model (EM) and present an overview of the performance results. We also provide an overview of the Manufacturing, Assembly, Integration and Verification (MAIV) approach that was defined for the small series production and delivery of the 26 Flight Cameras. Impact of using 3 independent facilities for TVAC activities is also discussed.

PLATO (PLAnetary Transits and Oscillations of stars) is the third medium-class mission (M3), selected by the European Space Agency (ESA) in 2014 and adopted in 2017 for the Cosmic Vision 2015-2025 scientific program. The launch is scheduled in 2026 from the French Guiana (Kourou) for a nominal in-orbit lifetime of 4 years plus up to 4 years of possible extension. The main purpose of the mission is the discovery and preliminary characterization of many different types of exoplanets down to rocky terrestrial planets orbiting around bright solar-type stars. The PLATO spacecraft will operate from a halo orbit around L2 (the Sun-Earth 2nd Lagrangian Point), a virtual point in space, 1.5 million km beyond Earth as seen from the Sun and its Payload will consist of 26 small telescopes (24 normal and 2 fast), pointing at the same target stars, that provide images every 25 seconds with the normal camera and every 2.5 seconds for the two fast cameras, operating in a close loop with the AOCS (S/C Attitude and Orbit Control System). Each camera (consisting of a telescope, the Focal Plane Assembly and its Front-End Electronics) will host four CCDs producing 20.3 megapixels images adding up to 81.4 megapixels per normal camera and 2.11 gigapixels for the overall Payload (P/L). This huge amount of data cannot be transmitted to the ground and need to be processed on-board by the P/L Data Processing System (DPS) made up of 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), in charge of HW and SW lossless data compression and managing the P/L through a SpaceWire (SpW) network. In this paper we will review the status of the Instrument Control Unit (ICU) after its Critical Design Review (CDR) process, performed by ESA and PMC (PLATO Mission Consortium), the results of the performance test preliminary run on the Engineering Model (EM), waiting for the following Engineering and Qualification Model (EQM) and Proto-Flight Model (PFM), and the status of the early models development (Engineering Models 1 and 2, Mass and Thermal Dummy - MTD) that, along with the Boot SW (BSW) burning in PROM readiness, will enable the EQM manufacturing.

PLATO (PLAnetary Transits and Oscillation of stars) is the ESA M-size mission aimed to the discovery of exo-planets hosted by bright, nearby stars. The launch of PLATO spaceship is scheduled for 2026. It will orbit Sun-Earth L2 for 4 years, looking towards deep space and covering a wide (2132 deg ² total) area of space. To do so, PLATO will use 26 fully dioptric designed cameras, each composed of a telescope optical unit (TOU) and a focal plane array (FPA). For manufacturing purposes, the FPA will be assembled at ambient temperature, although the best image plane (BIP) of the TOU will be determined during test at cryo-vacuum conditions (-80°C). This poses a metrology challenge at TOU manufacturing and testing and at FPA integration facilities. To this extent, the procedures for the precise characterization and localization of the BIP during TOU tests are presented. In order to circumvent the thermal effects of contraction of the fixture, which in part operate at ambient and in part are cooled at -80°C (operation temperature), the final measurement will be derived by the repeated assessment of the coordinates of a set of fiducials at ambient and operation temperature. Compliance with a strict error budget is achieved by using a combination of sensors (confocal, focusvariation), mounted on very precise and repeatable hexapods. Hartmann masks are also used to co-register the position and orientation of mounting of the FPA between facilities.

PLATO (PLAnetary Transits and Oscillations of stars) is a European Space Agency medium class mission, whose launch is foreseen for 2026. Its primary goal is to discover and characterise terrestrial exoplanets orbiting the habitable zone of their host stars. This goal will be reached with a set of 26 wide field-of-view cameras mounted on a common optical bench. Here we show some results of the first cryogenic vacuum test campaign made on the Engineering Model (EM) of one PLATO camera, performed at the Netherlands Institute for Space Research (SRON). In particular we present the search for the best focus temperature, which was done first by using a Hartmann mask, and then by maximizing the ensquared energy fractions of the point spread functions (PSFs) on the entire field of view taken at different temperature plateaus. Furthermore we present the PSF properties of the EM at the nominal focus temperature over all the field of view, focusing on the ensquared energy fractions. The Engineering Model camera was successfully integrated and validated under cryo-vacuum tests, allowing the mission to pass ESA’s Critical Milestone, and confirming the mission is on track for launch in 2026.

The Fast Front End Electronic (F-FEE) is a unit of the payload for the PLATO ESA mission. PLATO aims at finding and characterising a large number of extra solar planetary systems. In order to achieve its scientific objectives, PLATO relies on the analysis of continuous time series of high precision photometric measurements of stellar fluxes. The scientific payload of PLATO is based on a multi-telescope approach, involving a set of 24 ”normal” cameras working at a cadence of 25 s optimized to monitor stars fainter than magnitude 8 (photometry on saturated stars down to magnitude 4 will be possible), plus two ”fast” cameras working at a cadence of 2.5 s, and observing stars in the V range from 4 to 8. Beside providing star brightness measurements for bright stars, the ”fast” cameras also work as fine guidance sensors for the attitude control system of the Spacecraft. Each ”fast” camera is equipped with 4 CCDs with 4510 × 2255 light sensitive pixels each, working in frame transfer mode. In view of the instrument development an Engineering Model (EM) of the F-FEE has been manufactured, assembled and tested. The performance tests have been conducted using artificially generated CCD signals as well as real CCDs, proving the capability of the electronics to satisfy the demanding requirements to fine guidance but also science requirements of the PLATO mission.

High-precision astrometry well beyond the capacities of Gaia will provide a unique way to achieve astrophysical breakthroughs, in particular on the nature of dark matter, and a complete survey of nearby habitable exoplanets. In this contribution, we present the scientific cases that require a flexibly-pointing instrument capable of high astrometric accuracy and we review the best mission profiles that can achieve such observations with the current space technology as well as within the boundary conditions defined by space agencies. We also describe the way the differential astrometric measurement is made using reference stars within the field. We show that the ultimate accuracy can be met without drastic constrains on the telescope stability.

The concept of a 3 lines of sight telescope for space astrometry is evaluated in terms of implementation feasibility and some science applications. The beam combination by pupil splitting exploits the Hipparcos concept, extending it to true large bidimensional angle. The PSF symmetry provides equivalent astrometric performance and immediate field identification on the common detector. Operation aspects are investigated in terms of field identification and observing strategy, in particular pointing constraints and sky density of reference bright stars. The approach, based on flat mirrors mounted on a pyramidal structure, provides a simple geometric framework, with immediate mechanical materialization and clear interface to metrology. The geometric arrangements considered place the lines of sight either along the (x, y, z) Cartesian axes, or in a planar layout for a Gaia-like astrometric mission. The application to a single head, multiple boresight star tracker is also outlined.

Since the publication of the HIPPARCOS catalog in 1997, and with its successor Gaia in operational phase since 2013 having already published 3 data releases, global astrometry has earned itself a prominent role in the field of astrophysics. Both missions rest on the well-established concepts of one-dimensional (or nearly one-dimensional) observations performed by a telescope that is continuously scanning the sky following a predefined scanning law. Moreover, Gaia heavily relies also on the concept of self-calibrating instrument. In this work we explore the possibility of exploiting two-dimensional observations performed by a pointed mission, discussing the feasibility of this concept, and its possible advantages.

GREX-PLUS (Galaxy Reionization EXplorer and PLanetary Universe Spectrometer) is a new mission concept for ISAS/JAXA’s strategic L-class mission program in the 2030s. With a 1.2 m aperture, a 50 K cryogenic space telescope will have a < 1, 400 arcmin² wide-field camera with 6 bands in the 2–10 μm wavelength range and a high-dispersion spectrometer with a wavelength resolution of < 30, 000 in the 10–18 μm band. The cryogenic infrared mission concept of GREX-PLUS is based on SPICA, exploiting the technical resources so far studied and developed, such as an active cooling system. The high-dispersion spectrometer of GREX-PLUS is based on the high-dispersion channel of the SPICA Mid-Infrared Instrument (SMI). The wide-field camera of GREX-PLUS is also based on previous concept studies for the ISAS/JAXA’s WISH mission concept. GREX-PLUS is a concept proposal for a Japan-led mission but international collaborations are also welcome.

SPHEREx is a NASA Medium Explorer mission planned for launch in early 2025. It will produce an all-sky near infrared spectral survey from 0.75µm to 5µm with 6.2”x 6.2” pixels and spectral resolving power ranging between R=35 and R=130. Each focal plane assembly (FPA) comprises three 2048x2048 H2RG detector arrays. The H2RG detector is paired with a Linear Variable Filter, placed just above the detector, that defines a spectral response that varies over the detector along one spatial direction. Two FPAs view the sky through a dichroic beamsplitter, where the short-wave FPA uses three 2.5µm cutoff H2RGs and the mid-wave FPA uses three 5.3µm cutoff H2RGs. We developed a novel laboratory setup to carry out spectral response measurements of every pixel by coupling a cryogenic Winston Cone and integrating spheres to a grating spectrometer which allows us to measure the full 2x3.5°x11.3° field of view simultaneously. This presentation will present the design of the test apparatus and results.

The NISP (Near Infrared Spectrometer and Photometer) is one of the two Euclid instruments (see ref [1]). It operates in the near-IR spectral region (950-2020nm) as a photometer and spectrometer. The instrument is composed of: - a cold (135K) optomechanical subsystem consisting of a Silicon carbide structure, an optical assembly, a filter wheel mechanism, a grism wheel mechanism, a calibration unit and a thermal control system - a detection system based on a mosaic of 16 H2RG with their front-end readout electronic. - a warm electronic system (290K) composed of a data processing / detector control unit and of an instrument control unit that interfaces with the spacecraft via a 1553 bus for command and control and via Spacewire links for science data This paper presents: - the final architecture of the flight model instrument and subsystems - the performances and the ground calibration measurement done at NISP level and at Euclid Payload Module level at operational cold temperature.

ESA’s mission Euclid while undertaking its final integration stage is fully qualified. Euclid will perform an extra galactic survey (0<z<2) using visible and near-infrared light. To detect the infrared radiation is equipped with the Near Infrared Spectro-Photometer (NISP) instrument with a sensitivity in the 0.9-2 μm range. We present an illustration of the NISP Data Processing Unit’s Application Software, highlighting the experimental process to obtain the final parametrization of the on-board processing of data produced by an array of 16 Teledyne’s HAWAII-2RG (HgCdTe) - each of 2048×2048 px², 0.3 arcsec/px, 18 μm pixel pitch; using data from the latest test campaigns done with the flight configuration hardware - complete optical system (Korsh anastigmat telescope), detectors array (0.56 deg² firld of view) and readout systems (16 Digital Control Units and Sidecar ASICs). Also, we show the outstanding Spectrometric (using a Blue and two Red Grisms) and Photometric (using Y_E 0.92-1.15μm, J_E 1.15-1.37μm, and H_E 1.37-2.0 μm filters) performances of the NISP detector derived from the end-to-end payload module test campaign at FOCAL 5 - CSL; among them the Photometric Point Spread Function (PSF) determination, and the Spectroscopic dispersion verification. Also the performances of the onboard processing are presented. Then, we describe the solution of a major issue found during this final test phase that put NISP in the critical path. We will describe how the problem was eventually understood and solved thanks to an intensive coordinated effort of an independent review team (tiger team lead by ESA) and a team of NISP experts from the Euclid Consortium. An extended PLM level campaign in ambient in Liege and a dedicated test campaign conducted in Marseille on the NISP EQM model, with both industrial and managerial support, finally confirmed the correctness of the diagnosis of the problem. Finally, the Euclid’s survey is presented (14000 deg² wide survey, and ∼40 deg² deep-survey) as well as the global statistics for a mission lifetime of 6 years (∼1.5 billion Galaxy’s shapes, and ∼50 million Galaxy’s spectra).

The Nancy Grace Roman Space Telescope (“Roman”) is NASA’s next flagship observatory. Launching in 2027, it will test theories of the accelerated expansion of the universe, as well as expand the census of exoplanets in our galaxy. These science objectives are enabled by Roman’s large field of view, agile survey capabilities, and excellent stability. The Roman optical system comprises an optical telescope assembly (OTA) and two instruments: the primary science wide-field instrument (WFI), and a technology demonstration coronagraph instrument (CGI). This paper will describe the optical system configuration and associated performance requirements and expectations, including summary results from Monte Carlo simulations of the end-to-end alignment, launch, and commissioning operations. We will describe the optical test and verification program, including stray light analysis and verification. We will also describe the use of focus-diverse phase retrieval during both test and commissioning ph

The Nancy Grace Roman Space Telescope (RST) is a Hubble-class telescope with a large field of view for large surveys of the sky, cold temperatures for enabling near infrared imaging, and controlled temperature stability for long exposures and coronagraphy. The OTA includes the primary mirror, secondary mirror, and aft optics for guiding light into the Wide Field Instrument and the Coronagraph Instrument. The testing of the optical assemblies and structures are nearly complete in preparation for telescope integration. Pictures and descriptions of the assemblies are provided, followed by performance results measured at these level of assemblies. The assemblies are nearly complete as they are tested through thermal cycling to cold temperatures for infrared operation, mechanical strength and vibration, and optically testing. Optical surface figure error results are shown for all the optical surfaces.

The Nancy Grace Roman Space Telescope will enable advances in astrophysics by providing a large-scale survey capability in infrared wavelengths. The observatory is designed to provide data that will allow astronomers to unlock mysteries of the universe, answering high-priority scientific questions related to the evolution of the universe and the habitability of exoplanets. Using a 2.4 m (7.9 ft) primary mirror, Roman will capture comparable quality images to Hubble, but with more than 200 times the field of view of Hubble’s near-infrared channel, enabling the observatory to conduct comprehensive and efficient surveys. The Wide Field Instrument (WFI) features a 300-megapixel mosaic focal plane assembly with 18 H4RG detectors. WFI includes filters that provide an imaging mode covering 0.48 - 2.0 μm and two slitless spectroscopy modes. To meet scientific objectives, WFI requires a stable structural and cryogenic environment. NASA designs and develops the WFI science data signal chain and selected Ball Aerospace as their partner to design and develop the WFI Opto-Mechanical Assembly. In this paper, we present a WFI design evolution overview from early phases of the project through the critical design review. Innovations that increased performance, improved testability, and reduced mass and power will be discussed. Moving the third telescope mirror from the instrument to the heritage telescope assembly, eliminating the cryocooler by converting from an active to passive thermal design, unfolding the optical path to eliminate the mirror in the instrument design, and changing the plane of the serviceable latch configuration to ensure a kinematic mount are presented.

With the recent Astro2020 report, a NASA-led cryogenic far-IR probe has emerged as the primary opportunity for sensitive measurements between the 28-micron cutoff of JWST and the onset of ground-based windows in the submillimeter. The probe will provide new tools for topics ranging from star formation in the earliest galaxies, to the cosmic history of heavy elements, to the formation of stars and planets. We will present our work optimizing the scientific return from this powerful yet cost-capped mission. The instrumentation emphasizes spectrophotometry and spectroscopy, both wide-field and pointed. It will provide high-fidelity maps and unbiased redshift-resolved surveys, as well as rich, high-sensitivity spectra of targets of interest. Paramount among the design trades is that of spatial multiplexing vs spectral resolving power; this optimization is conducted in light of the multiple science goals, and within the constraints of realistic detector sensitivity and array format.

OASIS (Orbiting Astronomical Satellite for Investigating Stellar Systems) is a space-based, MIDEX mission concept that employs a 14 meter inflatable aperture and cryogenic heterodyne receivers to perform high resolution (R<10⁶) observations at terahertz frequencies. OASIS targets far-infrared transitions of H₂O and its isotopologues, as well as HD and other molecular species from 660 to 63 μm that are otherwise obscured by the Earth’s atmosphere. OASIS will have <10x the collecting area and <4x the angular resolution of Herschel and complements the short wavelength capabilities of JWST. With its large collecting area and suite of terahertz heterodyne receivers, OASIS will have the sensitivity to follow the water trail from galaxies to oceans. OASIS represents a paradigm shift in the realization of large space apertures. Our paper will focus on how the development work for OASIS can be leveraged to realize a new generation of space telescopes.

We present a far-infrared polarimetric camera for future space observatories. The instrument will allow the study of the magnetic field in various astrophysical environments thanks to its unprecedented ability to measure the linear polarization. The maps produced by the instrument will contain not only information on total power, but also on the degree and the angle of polarization, simultaneously in six spectral bands (between 70 and 500 microns). The detectors are ultra-sensitive silicon bolometers that are intrinsically sensitive to polarization. We will present the optical and thermal architectures of the instrument and we will show the expected performances based on preliminary lab work.

LiteBIRD is a JAXA-led international project aimed to make high sensitivity measurements of the primordial B-modes through cosmic microwave background (CMB) polarization observations. LiteBIRD is expected to launch in the late 2020s. The Low Frequency Telescope (LFT) has a 400 mm diameter aperture and will observe at 34-161 GHz. The LFT is an optimized crossed Dragone reflective telescope with high order correction terms in the reflector shapes to maximize its diffraction-limited throughput across a 18° x 9° FOV. We will report on the development of the LFT optics design and assess the optical tolerances for potential misalignments and reflector deformations.

LiteBIRD is a JAXA-led international project that aims to test representative inflationary models by performing an allsky cosmic microwave background radiation (CMB) polarization survey for 3 years at the Sun-Earth Lagrangian point L2. We aim to launch LiteBIRD in the late 2020s. The payload module (PLM) is mainly composed of the Low-Frequency Telescope (LFT), the Mid-Frequency Telescope and High-Frequency Telescope (MHFT), and a cryo-structure. To conduct the high-precision and high-sensitivity CMB observations, it is required to cool the telescopes down to less than 5 K and the detectors down to 100 mK. The high temperature stability is also an important design factor. It is essential to design and analyze the cryogenic thermal system for PLM. In this study, the heat balance, temperature distribution, and temperature stability of the PLM for the baseline design are evaluated by developing the transient thermal model. The effect of the Joule-Thomson (JT) coolers cold tip temperature variation, the periodical changes in subK Adiabatic Demagnetization Refrigerator (ADR) heat dissipation, and the satellite spin that generates the variable direction of solar flux incident are implemented in the model. The effect of contact thermal conductance in the LFT and the emissivity of the V-groove on the temperature distribution and heat balance are investigated. Based on the thermal analysis, it was confirmed that the PLM baseline design meets the requirement of the temperature and the cooling capability of the 4K-JT cooler. In addition, the temperatures of the V-groove and the LFT 5-K frame are sufficiently stable for the observation. The temperature stability of the Low Frequency Focal Plane (LF-FP) is also discussed in this paper.

The Nancy Grace Roman Space Telescope (formerly WFIRST) will be launched in the mid-2020s with an onboard Coronagraph Instrument which will serve as a technology demonstrator for exoplanet direct imaging. The Roman Coronagraph will be capable of detecting and characterizing exoplanets and circumstellar disks in visible light at an unprecedented contrast level of ~10^-8 or better at small separations. Such a contrast level, which is 2 to 3 orders of magnitude better than state-of-the-art visible or near-infrared coronagraphs, raises entirely new challenges that will be overcome using a combination of hardware, calibration and data processing. In particular, the Roman Coronagraph will be the first space-based coronagraphic instrument with active low- and high-order wavefront control through the use of largeformat (48x48) deformable mirrors, and its electron-multiplying Charge Coupled Device (EMCCD) detector will enable faint signal detection in photon-counting mode. The Roman Coronagraph successfully passed its critical design review in April 2021 and its system integration review in June 2022. It is now well on its path to demonstrate many core technologies at the levels required for a future exo-Earth direct imaging mission.

The Nancy Grace Roman Space Telescope is NASA’s flagship astrophysics mission planned for launch in 2026. 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 and point source detection limits that are 2–3 orders of magnitude deeper than previous space-based and groundbased coronagraphs by using active wavefront control with deformable mirrors. CGI has passed its Critical Design Review (CDR) in April of 2021, and System Integration Review (SIR) in June of 2022. We describe the status of CGI’s development and plans for the upcoming integration and testing phase.

The Coronagraphic Instrument (CGI) of the Roman Space Telescope NASA space mission is a demonstrator of critical technologies for future space coronagraphs aiming at imaging and spectroscopy of exoplanets and debris disks. Extremely high optical performances are required in term of optical quality of the components inside this instrument. The Stress Mirror Polishing (SMP) technique have been developed for several decades at Laboratoire d’Astrophysique de Marseille (LAM). SMP allows reaching exquisite optical quality on the optics demonstrated through very low Surface Figure Errors (SFE): <5nm RMS on low frequencies, <2nm RMS on middle frequencies (from 3 to 10 cycles per pupil), an extremely low level of high frequencies (no ripples) and micro-roughness < 5Å RMS. In the frame of a scientific international collaboration between NASA and CNES, the French space agency, LAM is selected for the manufacturing of all Off-Axis Parabolas (OAP) for the WFIRST-CGI. LAM has delivered 17 models including one prototype, 8 flight models in July 2021 and 8 flight spares delivered in May 2022. In this paper, we give an overview of the SMP process, from design to manufacturing and verification tests validating the performance. We will present the performance obtained on the first models that have been manufactured compared to theoretical calculations based on requirements for these OAPs.

NASA’s next flagship mission, the Nancy Grace Roman Space Telescope, is a 2.4-meter observatory set to launch no later than May 2027. Roman features two instruments: the Wide Field Imager and the Coronagraph Instrument. The Roman Coronagraph is a Technology Demonstration that will push the current capabilities of direct imaging to smaller contrast ratios (∼10⁻⁹) and inner-working angles (3 λ/D). In order to achieve this high precision, Roman Coronagraph data must be calibrated to remove as many potential sources of error as possible. Here we present a detailed overview of the current plans for the Nancy Grace Roman Space Telescope Coronagraph Instrument Observation Calibration Plan, including identifying potential sources of error and how they will be mitigated via on-sky calibrations.

The Astro2020 Decadal Survey recommended as the next strategic astrophysics mission a 6 m class space telescope capable of high-contrast direct imaging of Earth-size exoplanets in about one hundred habitable zones of nearby sun-like stars. The expected number of imageable exoplanets for such a telescope depends on the architecture and the metrics used to evaluate those architectures. In this paper, we assess the yield of notional coronagraph-only, starshade-only, and hybrid starshade/coronagraph architectures for several metrics. We evaluate the exoplanet yield for a 20% bandwidth, SNR=5, R=70 water search metric; a 20% bandwidth, SNR=8.5, R=140 oxygen search metric; and a 4x20% bandwidth metric, SNR=8.5, R=7 for 450-700 nm and R=140 for 700-1000 nm, which is tailored for a coronagraph’s sequence of 20% bandwidth sub-spectra. We bound the number of expected exoplanets by considering three cases of a priori knowledge: the case of no prior knowledge that requires a photometric blind search for exoplanets; the theoretical case of perfect prior knowledge that skips the photometric blind search and performs only spectral characterizations using realistic mission scheduling constraints (this approach shows the upper bound and when target exhaustion is reached); and a case of partial prior knowledge via a hypothetical, future extreme precision radial velocity instrument with 3 cm/s sensitivity. This work is an initial study of the potential exoplanet science return for the Decadal-recommended large infrared/optical/UV Great Observatory (IROUV).

Future space missions such as LUVOIR and HabEx require large apertures and coronagraphs with active wavefront control to image and characterize faint exoplanets. ECLIPS is the coronagraph instrument on LUVOIR, an 8-15m segmented telescope. The Apodized Pupil Lyot Coronagraph is the baselined mask technology to enable the required 10e−10 contrast for observations in the habitable zones of nearby stars. Its performance depends on wavefront sensing and control to compensate for dynamic and static aberrations induced by beam shear, segment, and global wavefront errors. Here we present how these aberrations are simulated and evaluate the ExoEarth yield in different scenarios.

The Planetary Imaging Concept Testbed Using a Recoverable Experiment - Coronagraph (PICTURE-C) mission will directly image debris disks and exozodiacal dust around nearby stars from a high-altitude balloon using a vector vortex coronagraph. The first flight of PICTURE-C launched from the NASA Columbia Scientific Balloon Facility (CSBF) in Ft. Sumner, NM on September 28, 2019. This flight successfully demonstrated many key technologies for exoplanetary direct imaging missions and all hardware components for the second, sciencefocused flight of PICTURE-C, which had been scheduled for the fall of 2021, but was delayed due to inclement weather until 2022. We present laboratory demonstrations of the flight 2 coronagraph, which uses a high-order 952 actuator MEMS deformable mirror to create a high-contrast dark zone at the 10^-7 level. The performance of the low-order and high-order wavefront control systems is demonstrated and compared with model predictions.

Radial velocity method can not only provide basic planetary parameters to characterize exoplanets, but also help to improve the detection efficiency of other detection methods such as transit and direct imaging. Space nearinfrared radial velocity detection could support future habitable exoplanets detection missions with its unique observational advantage. This paper introduces two kinds of spatial-modulated Fourier transform spectrometer for space-based near-infrared radial velocity detection.

The unparalleled theoretical performance of an ideal vector vortex coronagraph makes it one of the most promising technologies for directly imaging exoplanets with a future, off-axis space telescope. However, the image contrast required for observing the light reflected from Earth-sized planets (∼ 10⁻¹⁰) has yet to be demonstrated in a laboratory setting. With recent advances in the manufacturing of liquid crystal vector vortex waveplates as well as system-level performance improvements on our testbeds, we have achieved raw contrast of 1.57×10⁻⁹ and 5.86×10⁻⁹ in 10% and 20% optical bandwidths, respectively, averaged over 3-10 λ/D separations on one side of the pseudo-star. The former represents a factor of 10 improvement over the previously reported performance. We will show experimental comparisons of the contrast achieved and a function of spectral bandwidth. We provide estimates of the limiting error terms and discuss the improvements needed to close the gap in contrast performance required for future exoplanet imaging space telescopes.

Coronagraphs are an important technology to directly image and characterize exoplanets. Their efficiency has steadily been improving over the past several decades, but has not yet reached fundamental limits. In particular, the expected exoplanet yield for missions such as the Astro2020-recommended “IR/O/UV Flagship” can still be improved by factors of at least 2-3. One possible architecture that can enable at least a part of this improvement is the Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC). It features high throughput, small inner working angle (IWA), and almost no loss in PSF sharpness, and natively supports obstructed and segmented apertures. Historically, key disadvantages of PIAA have been poor tolerance to stellar angular sizes and maturity, but latest designs and demonstrations have made significant strides in this respect. We present the current status of our program to mature the PIAACMC technology. We first present our PIAACMC designs for LUVOIR-A and B, which resulted in improved expected yield of Exo-Earths relative to the baselines for both mission concepts. In particular, for LUVOIR-B, the yield improves from 28 to 42 due to improved tolerance to stellar angular size in our design. Our and vacuum demonstrations for the LUVOIR-A aperture at JPL’s High Contrast Imaging Testbed (HCIT) include: 1.9e-8 raw contrast in 10% broadband light between 3.5 and 8 l/D; 4.1e-8 and 1.6e-9 coherent contrasts in monochromatic light between 2-4 and 4-8 l/D, respectively. We also present measurements and analysis of sensitivity to tip/tilt jitter and stellar angular size and compare our test results to models.

We present recent laboratory results demonstrating high-contrast coronagraphy for the future space-based large IR/Optical/Ultraviolet telescope recommended by the Decadal Survey. The High-contrast Imager for Complex Aperture Telescopes (HiCAT) testbed aims to implement a system-level hardware demonstration for segmented aperture coronagraphs with wavefront control. The telescope hardware simulator employs a segmented deformable mirror with 37 hexagonal segments that can be controlled in piston, tip, and tilt. In addition, two continuous deformable mirrors are used for high-order wavefront sensing and control. The low-order sensing subsystem includes a dedicated tip-tilt stage, a coronagraphic target acquisition camera, and a Zernike wavefront sensor that is used to measure and correct low-order aberration drifts. We explore the performance of a segmented aperture coronagraph both in “static” operations (limited by natural drifts and instabilities) and in “dynamic” operations (in the presence of artificial wavefront drifts added to the deformable mirrors), and discuss the estimation and control strategies used to reach and maintain the dark-zone contrast using our low-order wavefront sensing and control. We summarize experimental results that quantify the performance of the testbed in terms of contrast, inner/outer working angle and bandpass, and analyze limiting factors.

High-contrast imaging techniques are essential for future space missions aimed at directly detecting and characterizing exoplanets. We constructed a new testbed called the facility for coronagraphic elemental technologies (FACET) for the development of high-contrast imaging techniques. FACET has three optical paths (A, B, and C). Path A is used for developing focal-plane phase mask (FPM) coronagraphs. Currently, we have been developing photonic-crystal multi-layer phase masks for suppressing stellar light over a broad wavelength range. In path B, we demonstrate high-contrast observation combining FPM coronagraphs with a dark hole (DH) control technique. A spatial light modulator (SLM) is used as a wavefront control device. We are developing DH control techniques that take advantage of the large pixel format of the SLM. In path C, we demonstrate DH control for detecting exoplanets not only around single stars but also around binary-star systems. We install the SLM into the common-path visible nulling coronagraph to test the multiple-star DH control. We report details of FACET and recent progress of our activities at FACET. We have recently made significant progress with the demonstration of observation for a single star for which we achieved a monochromatic contrast of 2.9 × 10⁻⁹ at path C.

Detecting and characterizing the atmospheres of terrestrial exoplanets is a primary goal of the proposed nextgeneration IR/O/UV mission recommended by Astro2020 decadal survey. Achieving this goal with direct imaging depends critically on developing coronagraph technology that maximizes the exoEarth yield. Stringent tradeoffs between low-order aberration sensitivity, inner working angle, and throughput have been one of the main limiting factors affecting the yield of coronagraph technologies for telescopes with complex apertures. We present preliminary hybrid PIAA-vortex coronagraph designs for obstructed apertures. PIAA-vortex designs can be used to close the yield gap between on-axis and off-axis telescopes, which in turn has the potential to translate to significant yield gains for future space missions. In our forthcoming publication, we will present further analysis of the PIAA-vortex along with the formalism for optimizing 2-D mirror shapes in the geometric-optics regime.

The vector vortex coronagraph is an ideal choice for the future space-based mission that is proposed by Astro2020. However, it requires polarization filtering and every observing band requires a different VVC. The triple-grating vector vortex coronagraph (TGVVC) aims to mitigate these limitations. In this paper, we present the first laboratory results of a TGVVC prototype using the High Contrast Imaging Testbed facility at NASA’s Jet Propulsion Laboratory. We describe the design and manufacturing, study the coronagraphic performance, the impact of polarization filtering on the dark zone contrast, and the appearance and impact of half-orders.

A majority of Sun-like stars have at least one stellar companion that can introduce additional noise into the field of view of any high-contrast imaging instrument, limiting the achievable contrast. These include high-quality target stars such as the A and B components of Alpha Centauri, our nearest stellar neighbor. Enabling direct imaging of binary stars has the potential to increase the scientific yield for coronagraphic instruments planned on NASA’s future space missions including the Roman Space Telescope and the next IR/O/UV flagship recommended by Astro2020. Multi-Star Wavefront Control (MSWC) is a wavefront-control technique that simultaneously removes the (mutually incoherent) stellar leakage from both stellar components, enabling direct imaging of planets in many binary star systems. We present the latest testbed and numerical results obtained towards MSWC experiments as part of the technology development effort to demonstrate compatibility with existing high-contrast imaging platforms for this technique. In particular, we present experimental and modeling results from the Occulting Mask Coronagraph (OMC) testbed at JPL demonstrating Super-Nyquist Wavefront Control. During this testing window, the MSWC mask design has been inserted into the testbed and SNWC-based control generated a dark zone between 79-83 λ/D around the 2nd diffraction order reaching 5.1e-8 contrast. The OMC is configured with a shaped pupil mask with the same design as the MSWC mask on the Roman Space Telescope’s coronagraph instrument with the goal of using validated models to demonstrated MSWC operation at contrast levels relevant to the Roman coronagraphic instrument.

Directly imaging exoplanets requires long integration times when using a space-based coronagraphic instrument due to the small number of photons. Wavefront stability on the same timescale is of the utmost importance; a difficult feat in the presence of thermal and mechanical instabilities. In this paper, we demonstrate that dark zone maintenance (DZM) functions in the low signal-to-noise (SNR) regime similar to that expected for the Roman Space Telescope (RST) and the “large (∼6 m aperture) infrared/optical/ultraviolet (IR/O/UV) space telescope” recommended by the 2021 decadal survey. We develop low-photon experiments with tunable noise properties to provide a representative extrapolation. The experiments are performed on the High-contrast Imager for Complex Aperture Telescopes (HiCAT) at the Space Telescope Science Institute (STScI). High-order wavefront error drifts are injected using a pair of kilo-deformable mirrors (DMs). The drifts are corrected using the DMs via the DZM algorithm; note that the current limiting factor for the DZM results is the air environment. We show that DZM can maintain a contrast of 5.3 × 10⁻⁸ in the presence of DM random walk drift with a low SNR.

The technology to manufacture main reflectors of satellite-mounted telescopes using CFRP (Carbon Fiber Reinforced Plastics) was studied. CFRP has high specific rigidity and zero thermal expansion which are required for space telescopes. However, the difficulty of high precision machining of CFRP and the fiber print-through appeared on the surface have prevented CFRP from achieving high accuracy and surface smoothness required for the mirrors. We studied the replica technology and process conditions in detail. The replica technology was improved not only to eliminate the fiber print-through on the CFRP surface, but also to achieve high shape accuracy of the mirrors. At the moment, shape accuracy of 0.6 μm and surface roughness of 3 nm were obtained. The area density of the CFRP mirrors was lighter than one-fifth of the conventional mirrors made of zero expansion glass which are machined for mass reduction. The lightweight and thermally stable CFRP mirrors are expected for reflectors of large aperture, and will improve the resolution of space telescopes.

Imaging of an earth analog is a major milestone for the exoplanet science and the instrumentation community. Coronagraphs relay on the DM resolution and stability to be able to achieve contrast of 1e10 at an angular separation of a fraction of an arcsecond. In this paper we describe our experience working with DMs and show that the device resolution and stability are defined by the electronics performance instead of the properties of the DM itself. We describe our effort to advance the DM electronics to achieve 19-bit resolution and long term stability with the goal of overcoming any coronagraph contrast limitations imposed by the driving electronics.

The Far InfraRed Spectroscopic Surveyor (FIRSS) is a novel concept for an astrophysics satellite mission that will revolutionise our understanding of the life cycle of the ISM and its role in the onset of star formation in our Galaxy and external galaxies. FIRSS will carry out large scale spectroscopic surveys in a number of discreet spectroscopic channels centred on important atomic, ionic and molecular species not accessible from the ground that will allow us to study the phase structure of the ISM. The FIRSS concept uses a multi-terahertz heterodyne payload and a ~2 m primary antenna to scan the infrared/submm sky from L2.

In many astrophysical instruments, optical elements and absorbers are extensively used and can alter the status of input polarized light. In particular in mm-wave experiments the lack of knowledge of material properties is becoming the most critical issue in controlling systematic effects. We developed a pipeline of test and analysis to characterize absorbing materials through the measurement of reflectance and transmittance spectra over a broad range of frequencies (from 200 GHz to 800 GHz) and incident angles (up to 70°). Spectra were acquired with a Martin-Puplett interferometer, coupled with a cryogenic bolometer detector. The setup is characterized by using a Neoprene sample (1 mm thick). The aliasing, the reproducibility and the incidence angle error are analyzed to evaluate the impact on the measurements. Individual one-day sessions ensure the capability to characterize transmittance/reflectance with high signal-to-noise: error < 0.5% in the 300-800 GHz band and ∼ 2% in the 200-300 GHz. A Monte Carlo-based fitting method is used to retrieve the physical properties of the sample. The thickness 1.005±0.016 mm is compatible with the one measured with calipers. The measured refractive index at 200 GHz is n=2.416±0.032.

Some concepts for a future large IR/O/UV space telescope include a James Webb Space Telescope (Webb) style sunshade for thermal stability. This will bias the telescope cold and complicate one key advantage that a 6m high-contrast imaging telescope could have: operating and testing at room temperature. Early concepts of LUVOIR-B, a segmented, off-axis 8-meter aperture concept developed the Large Mission Concept Study Teams, predict more than 5kW of heat would be needed to bring the telescope to operating temperature. These room-temperature telescopes invite configurations that could take more advantage of solar heating. This paper explores architecture options and identifies some technologies, their maturation requirements, and risks.

We present a novel approach to quantify wavefront stability of large observatories in space, based on the science goals of coronagraph instrument aimed at imaging and characterizing earth-analog candidates. We developed this method in the context of the Astro 2020 recommendation for technology trades studies towards the maturation of a flagship IR\O\UV. We apply this method to quantify the observatory requirements of a series of possible future IR\O\UV mission architectures -primary geometry, coronagraph and wavefront sensor. We discuss similarities and differences between monolithic and segmented architectures. For segmented ones, we highlight the importance of tuning the modal content of primary segments instabilities so they lie as much as possible in the null-space space of the coronagraph.

The recently released Astro2020 Decadal Survey recommends a large IR/O/UV space telescope that can observe potentially habitable exoplanets. Achieving this goal requires a telescope with wavefront stability on the order of picometers in some modes. The Ultra-Stable Large Telescope Research and Analysis – Technology Maturation (ULTRATM) program has matured key component-level technologies for this new regime of “ultra-stable optical systems,” including active components like segment edge sensors, actuators and thermal sensing and control hardware, as well as passive components like low distortion mirror mounts and stable composites for structures. Hardware testbeds have demonstrated component performance in the desired regime and with path-to-flight properties and simulations have applied those results to the flight system. These component level demonstrations are a critical step to enable subsequent subsystem and system level demonstrations of an ultra-stable telescope.

The Ultraviolet/Optical/Infrared (UVOIR) flagship astrophysics architectures proposed by the Astro2020 Decadal Survey fundamentally challenge the current test-like-you-fly approach to space systems, because of their physical scale, multiple stages of on-orbit deployment, and extremely stringent optical performance requirements unique to visible-light coronagraphy. These limitations elevate the importance of integrated control, structural dynamics, and optical modeling, particularly in early system architecture studies. A unique non-contact observatory control architecture called Disturbance Free Payload (DFP) for next-generation large astrophysics observatories involves physically isolating the segmented telescope structure from the supporting spacecraft by means of a non-contact interface. In this control architecture, rigidbody telescope pointing is achieved by actuating the payload with non-contact voice coil actuators and maintaining positive interface gaps using spacecraft inertial actuators and interface non-contact sensors. This architecture presents distinct advantages over current state-of-the-art spacecraft vibration isolation approaches, particularly for large flexible spacecraft, but also introduces unique disturbance and coupling mechanisms that must be analyzed. In this paper, development of an integrated model is described, consisting of a 6.7-meter inscribed segmented optical system, and an unobscured telescope with 55 primary mirror segments. The paper starts with an overview of the models that directly predict time-domain lineof-sight and wavefront error dynamic stability (optics, dynamics, control system, error sources). Next, key dynamic stability performance metrics for coronagraph contrast performance are described and a systematic methodology for realizing an accurate but computationally feasible truncated modal model is presented. Finally, an exemplar point design that is compliant to 10-picometer RMS wavefront error is developed, and the necessary component errors to achieve this performance are presented.

The Astro 2020 Decadal Survey has recommended technology and pre-formulation efforts for a 6-meter class Ultraviolet Optical Infrared telescope which is stable for high contrast observations of Exoplanets and general astrophysics. Here we report on progress on an ultra-stable test system and a series of picometer scale metrology demonstrations using High Speed Interferometry to achieve new levels of thermal control and new methods of calibration along with small scale demonstrations of mirror and structure components. Here we review the history of these efforts and recent ultra-stable measurements of a glass test article including thermal control and optical stability. We will summarize the challenge and progress of making drift measurements and report on recent progress in thermal control and glass ultrastability control that could have implications for future systems. We will close with a discussion of implications of these results to future efforts.

The Astro2020 report recommended that NASA’s next flagship have direct imaging of rocky, Earthlike exoplanets as its core science mission. At present, the starshade is the only high contrast imaging technique that has demonstrated broadband contrast at levels suitable for imaging exo-Earths in the laboratory. A starshade is an occulter positioned to cast a shadow of an exoplanet’s host star onto the telescope aperture, and narrow enough that the nearby exoplanet remains visible to the telescope. The starshade has a precise shape tailored to suppress diffraction of the starlight into the shadow. Starshade-based observations also have other advantages compared to coronagraphic observations. These include: no effective limit to the outer working angle, higher throughput for the exoplanet light, dramatically simpler requirements on the telescope optics, and the ability to provide high contrast at ultraviolet wavelengths. These advantages come at the price of needing a separate spacecraft to fly the starshade in formation with the telescope, and the consequent costs in fuel and time required for stationkeeping and retargeting. We describe work being done to mature starshade technology to technology readiness level 5 (TRL 5) in NASA’s S5 activity. This work includes optical measurements of a starshade’s ability to suppress light at levels required for a flagship mission, laboratory demonstrations of position sensing and control methods for starshade formation flying, and manufacture and test of flight-like starshade mechanical assemblies that can deploy accurately and stably to the precise shape required for starlight suppression in space.

Following the results of Starshade Milestone 1 in which we demonstrated broadband contrast better than 10⁻¹⁰, we have performed model validation experiments to show that diffraction models accurately predict the contrast due to perturbations representing the building blocks of the instrument error budget. The perturbations include the displacement of petal edge segments, sinusoidal petal edge shape deformations, global petal position errors, and random petal radial placement errors. We also show that the model accurately predicts the combined effects of two errors. The experiments result in a measured Model Uncertainty Factor (MUF) that is then applied to the starshade instrument contrast error budget.

The Near-Infrared Spectrograph (NIRSpec) is one the four focal plane instruments on the James Webb Space Telescope (JWST) which was launched on December 25, 2021. We present the in-flight status and performance of NIRSpec’s detector system as derived from the instrument commissioning data as available at the time of the conference. The instrument features two 2048 × 2048 HAWAII-2RG sensor chip assemblies (SCAs) that are operated at a temperature of about 42.8 K and are read out via a pair of SIDECAR ASICs. NIRSpec supports “Improved Reference Sampling and Subtraction” (IRS2) readout mode that was designed to meet NIRSpec’s stringent noise requirements and to reduce 1/f and correlated noise. In addition, NIRSpec features subarrays optimized for bright object time series observations, e.g. for the observation of exoplanet transit around bright host stars. We focus on the dark signal as well as the read and total noise performance of the detectors.

We have built an ultra-stable laboratory spectrometer, called MIRASET (Mid-IR Array Spectrometer demonstration for Exoplanet Transits), that will demonstrate a new method to extract mid-infrared spectral lines observed in the atmospheres of transiting planets around M-stars. Those lines potentially indicate the presence of life on the planet. This goal is achieved by using a black body source as a calibration reference, which in the laboratory experiment also simulates the emission of the M-star. The black body emission source will be tuned to dissipate the equivalent power on the detectors that would be observed from Proxima Cen B and Trappist-1 if they were observed with a space-based observatory such as ORIGINS or a dedicated MIR exoplanet mission such as MIRECLE. Furthermore, we use a laser that simulates a spectral line from the planet. We constantly monitor the temperature of the black body with high precision by using a photodiode measuring the black body in the visible. We will demonstrate the ability to monitor the black body emission over a several hour period, superimposed with a laser-generated spectral line, down to a photometric precision of 5ppm, while demonstrating the spectral stability of the spectrometer. This precision constitutes the requirement for the detection of important atmospheric lines from earth-like planets around M-stars.

The JWST Mid-Infrared Instrument (MIRI) detector arrays are Si:As blocked impurity band devices, direct descendants of the Spitzer/IRAC long wavelength arrays. Similarly to the IRAC row-column effect, analysis of flightlike MIRI detector data has shown that columns and rows in which source signals are located can suffer from pull up (brightness increase) or pull down (brightness decrease) in the flux image. Here we present results from the JPL MIRI detector characterisation campaigns dedicated to understanding this row-column effect as well as the first results showing the effect in the flight detectors for MIRI. We show the effect is flux dependent and confirm that the effect manifests differently for rows versus columns. We discuss the origin of the flux offset, which is related to a change in the signal output in time that distorts the input ramp as a function of the saturation level of illuminated pixels. We conclude by discussing the row-column effect in the context of different MIRI instrument modes and present preliminary proposals to mitigate and/or correct the effect in MIRI data.

We describe the commissioning and operation of a 25 element Transition-Edge Sensor (TES) cryogenic detector array system for use in the far-infrared band of the electromagnetic spectrum. This detector system, supplied by QMC Instruments Limited, is an integral component to the development of a spatial/spectral double Fourier laboratory-based interferometer testbed instrument within the Astronomical Instrumentation Group laboratories at the University of Lethbridge, Canada. The 5x5 rectangular grid of TES elements is feedhorn-coupled and operates at ∼6K within a dedicated cryostat providing both optical and thermal shielding. Cryogenic cooling of ∼0.5W is provided by a CryoMech PT405RM/CP2850 pulse-tube cooler/compressor suite. The detector readout system uses time-division multiplexing controlled by a dedicated National Instruments field-programmable gate array board and computer interface. This paper describes the characterization and optimization of this detector system, including the evaluation and validation of the readout electronics, hardware, software, detector noise properties, the multiplexing parameter space, optical sensitivity, and the integration of this system within a laboratory testbed interferometer instrument.

Pandora is a SmallSat mission, designed to study the atmospheres of exoplanets using transmission spectroscopy and to investigate the impact that stellar contamination and variability has on observing the spectra of these worlds. Pandora’s initial science operation lifetime is one year, so optimizing the science return is critical. Here we present two tools created to assist in the design process. The first is a 2-D spectrum simulator being developed to help refine target selection, optimize observation strategies, and assist in the creation of a data reduction pipeline. The second is a pseudo-retrieval framework that provides a quantifiable method for comparing potential targets against a handful of exoplanetary atmospheric parameters important to the Pandora mission. Preliminary results show Pandora will place tighter constraints on atmospheric properties like water abundance compared to HST and answering its mission objectives will help to inform targets for missions like JWST.

SkyHopper is a proposed CubeSat mission to simultaneously observe 4 bands in the wavelength range from 0.8 to 1.7 micron. The light is captured by a telescope with a 100 mm × 200 mm primary and a field of view of 0.6° × 2.6°. A preliminary definition (phase B) of the optical telescope assembly for the mission is now completed. It is designed to make high precision intensity measurements of every object in the field of view. This brought a series of constraints to avoid stray light. Different optical designs were studied. A Kösters prism is used to split the light into 4 bands on a 2k x 2k detector. The telescope design is based on a 3 mirror anastigmat with additional lenses to provide good image quality in the final focal plane for all bands and also in the intermediate focal plane and the pupil plane where cold stops are needed. Aberrations and vignetting of the prism had to be removed. Science applications include exoplanet transits in front of low-mass stars, rapid Infrared follow-up of Gamma Ray Bursts and exploring the Cosmic Infrared Background.

CubeSpec is an ESA in-orbit-demonstration mission, based on a 6U CubeSat, targeting high-resolution astronomical spectroscopy. It is developed and funded in Belgium and scheduled for launch at the end of 2024. The CubeSpec payload consists of an off-axis Cassegrain telescope with a rectangular aperture (186x82mm2 ) and a prism cross-dispersed echelle spectrograph. The telescope aperture almost completely covers the surface area of 2 CubeSat units and the entire optical system fits in 4 units (10x20x20cm) of the spacecraft. CubeSpec delivers a spectral resolution of R=55000 and covers the wavelength range from 420 to 620 nm. Furthermore, it is equipped with a fine-guidance system based on a fast beam-steering mirror and a fine-guidance sensor that provide accurate centering of the source image on the spectrograph slit to compensate for spacecraft pointing jitter. In this contribution, we present the optical design of the CubeSpec payload.

CubeSpec is an in-orbit CubeSat mission aiming to demonstrate high-spectral-resolution astronomical spectroscopy with a 10 × 20cm² aperture telescope. A robust calibration system is crucial for CubeSpec’s spectrograph to operate reliably and autonomously. Typically, flat-field illumination defines order locations, while a line source ties wavelength values to detector pixels. The main challenge is to fit everything into a 10 × 10 × 20cm³ volume without forfeiting quality and control. This work proposes Calibration Unit for CUbespec (CUCU). CUCU offers a compact, energy-efficient calibration solution for space-borne spectrograph platforms, miniaturizing both calibration stages. A blue and white LED coupled into one fiber produce the continuum light source, spanning the spectrograph’s operational range of 420nm to 620nm. The line standards emerge from injecting collimated LED light into a solid Fabry-P´erot etalon. To satisfy the mission requirements, CUCU should deliver calibration exposures with an SNR of 200. Throughput measurements estimate calibration exposures to take no longer than 0.5s.

Available volumes of nanosats such as CubeSats impose physical limits to the telescope diameter, limiting achievable spatial resolution and photometric capability. For example, a 12U CubeSat typically only has sufficient volume to host a 20 cm diameter monolithic telescope. In this paper, we present recent advances in deployable optics to host a 30 cm+ diameter telescope in a 6U CubeSat, with a volume of 4U dedicated to the payload and 2U to the satellite bus. To reach this high level of compactness, we fold the primary and secondary mirrors for launch, which are then unfolded and aligned in space. Diffraction-limited imaging quality in the visible part of the spectrum is achieved by controlling each mirror segment in piston, tip, and tilt. In this paper, we first describe overall satellite concept, we then report on the optomechanical design of the payload to deploy and adjust the mirrors. Finally, we discuss the automatic phasing of the primary to control the final optical quality of the telescope.

∂Lux is a newly developed optical modelling framework deigned to harness the tools underpinning the modern machine learning revolution and directly apply them to optics. Both neural networks and optical systems map an input vector to some output vector employing a series of intermediary linear transformations and nonlinear matrix operations. This isomorphism allows for optical models to be directly constructed within existing automatic differentiation libraries. ∂Lux exploits this relationship harnessing automatic differentiation libraries to create a naively end-to-end fully differentiable optical modelling framework. This may precipitate a paradigm shift in the power and utility of these optical models, opening the possibility to entirely novel algorithms and approaches. This manuscript explores some of the many ways to harness the potential of these codes, particularly focusing on the application example provided by the Toliman space telescope mission.

With a focus on off-the-shelf components, Twinkle is the first in a series of cost competitive small satellites managed and financed by Blue Skies Space Ltd. The satellite is based on a high-heritage Airbus platform that will carry a 0.45 m telescope and a spectrometer which will provide simultaneous wavelength coverage from 0.5–4.5 μm. The spacecraft prime is Airbus Stevenage while the telescope is being developed by Airbus Toulouse and the spectrometer by ABB Canada. Scheduled to begin scientific operations in 2025, Twinkle will sit in a thermally-stable, sun-synchronous, low-Earth orbit. The mission has a designed operation lifetime of at least seven years and, during the first three years of operation, will conduct two large-scale survey programmes: one focused on Solar System objects and the other dedicated to extrasolar targets. Here we present an overview of the architecture of the mission, refinements in the design approach, and some of the key science themes of the extrasolar survey.

For space-based Earth Observations and solar system observations, obtaining both high revisit rates (using a constellation of small platforms) and high angular resolution (using large optics and therefore a large platform) is an asset for many applications. Unfortunately, they prevent the occurrence of each other. A deployable satellite concept has been suggested that could grant both assets by producing jointly high revisit rates and high angular resolution of roughly 1 meter on the ground. This concept relies however on the capacity to maintain the phasing of the segments at a sufficient precision (a few tens of nanometers at visible wavelengths), while undergoing strong and dynamic thermal gradients. In the constrained volume environment of a CubeSat, the system must reuse the scientific images to measure the phasing errors. We address in this paper the key issue of focal-plane wave-front sensing for a segmented pupil using a single image with deep learning. We show a first demonstration of measurement on a point source. The neural network is able to identify properly the phase piston-tip-tilt coefficients below the limit of 15nm per petal.

In order to characterize and calibrate the Metimage spectro-radiometer instrument response in Solar Spectral Bands, an Optical Ground Support Equipment (OGSE), a sun simulator has been designed and developed at CSL. This Sun Simulator (SUSI) is designed for wavelength ranging from 400 nm to 2300 nm. In order to reach radiance and both spatial and angular homogeneity requirements a specific design allowing mixing up to 4 plasma lamp sources has been designed and implemented. This mixing and homogenizing device is placed at the focal plane of an Off Axis parabolic mirror which will produce an 0.5° full divergence beam over a pupil of 350 mm. First the design and its challenges will be given. Simulation of SUSI performances are then proposed. Finally, experimentally measured performances of the OGSE are presented.

EnVisS (Entire Visible Sky) is a space camera aboard the Comet Interceptor ESA mission. This is the first F-class space mission, a new generation of fast ESA missions, and it is scheduled for launch in 2029. Comet Interceptor aims to study, by means of in situ observations, a dynamically new comet, or interstellar object, that enters the Solar System for the first time. Approaching the comet, three modules will detach: spacecraft A will provide remote sensing and communications, while spacecraft B1 and B2 will cross the coma and fly-by the nucleus. EnVisS is a fish-eye camera with a field of view (FOV) of 180° × 45°. It is mounted on B2, which is spin stabilized; the spin provides the scanning motion for the camera allowing imaging the whole sky (180° × 360°) including the comet. The EnVisS optical head is composed of ten lenses; the collected visible light passes through a three-strip filter assembly before reaching the detector. The central filter strip is a broadband filter, while the sides filter strips are linear polarizers, with the aim of studying the polarization state of the light reflected by both the comet coma and its core. The optical performance of EnVisS has been evaluated through ray tracing analyses. In this paper, the ghost study will be described and ghost images will be shown. This analysis, performed in the ZEMAX OpticStudio®, highlights which optical element causes the most intense ghost images and shows their distribution over the detector.

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 April 2023. 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). H1RG detectors from Teledyne where selected for these two channels. The specific constraints of MAJIS (very wide dynamic range, windowing, on-board de-spiking) required very significant adjustments to readout microcodes provided by Teledyne. The de-spiking approach implemented by MAJIS relies on on-board processing of series of consecutive sub-integrations5 . For reaching optimum performance, possible biases between successive CDS readouts of the same signal needed to be lower than the total noise. The first of the two detector readouts required for CDS had to be implemented very shortly after reset so as to benefit from the full well depth for dynamic range. This required coping with the reset anomaly which is specific to the HxRG family of detectors. The MAJIS team selected an approach based on drop frames and dark subtraction which minimized microcode adjustments so as to limit development and schedule risks. Detector characterization then instrument calibration showed that this approach was quite successful in terms of performances with no impact on the duty cycle for observations with short integration times.

We describe the IR focal plane filters of the MAJIS imaging spectrometer for the JUICE mission to the Jupiter System. The focal plane filters provided by Viavi Solutions are integrated into a filter holder placed above the IR channel focal plane array, enclosed in a baffle and cooled to cryogenic temperatures. The filters comprise two segments bonded together on a sapphire substrate: a broad-band, low-pass filter and a narrow-band linear variable filter (LVF) in the MWIR. We present the justification for using such filters, their architecture, the measurement facilities that were implemented for assessing their performances and the derived optical performances. The filters have been fully qualified and integrated into MAJIS and are within the performance specifications.

The JUICE (JUpiter ICy moons Explorer) mission by ESA aims to explore the emergence of habitable worlds around gas giants and the Jupiter system as an archetype of gas giants. MAJIS (Moons and Jupiter Imaging Spectrometer) is the visible to near-infrared imaging spectrometer onboard JUICE which will characterize the surfaces and exospheres of the icy moons and perform monitoring of the Jupiter atmosphere. The launch is scheduled for 2023 with the first MAJIS observations inside the Jovian system occurring more than 8 years later. The MAJIS optical head is equipped with two Teledyne H1RG detectors, one for each of the two spectrometer channels (VIS-NIR and IR). This paper describes the characterization of the VIS-NIR Focal Plane Unit. These detectors will be operated in a non-standard way, allowing near/full-frame retrieval over short integration times (<< 1 sec) while maintaining good noise performance. After a quick description of the characterization strategy that was designed to evaluate the performances of the VIS-NIR detector according to the MAJIS operational specifications, the paper will address the data analyses and the main results of the characterization campaign. The major performance parameters such as dark current, linearity, noise, quantum efficiency, and operability will be presented and compared with the requirements.

We describe the IR focal plane unit of the MAJIS imaging spectrometer for the JUICE mission to the Jupiter Sys tem. Optical light from the telescope and spectrometer is focalized on the IR Focal plane unit which compris es a Teledyne Imaging Sensors H1RG detector overlain by a Viavi Solutions filter assembly. Both components are baffled and work at cryogenic temperatures. We describe the IR focal plane architecture, the measurement facilities and the main performance-critical specifications. The IR channel of MAJIS offers strong versatility with the capability to acquire high resolution spectra from the Jupiter atmosphere to organic matter on icy moon surfaces, over a wide spectral and dynamical range.

There is currently a growing interest for the in-situ robotic and human exploration of the Moon’s surface and subsurface. In particular, several mission concepts foresee the exploration of lunar caves and underground structures like e.g. the lava tubes, (i.e. conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow) and other depressed morphologies such as permanently shadowed craters which could present in situ resources such as water ice. Given the limited onboard resources of these missions and extreme illumination conditions ranging from sunlight to complete darkness, the cameras might be capable of operating without the support of any artificial illumination system. This paper studies the radiance properties of a set of different lunar cave pits as illuminated uniquely by the sunlight for different Sun elevations above the Moon horizon and permanently shadowed craters such as Shackleton’s interior. This is as an endmember for complete darkness of extreme importance because it could be a cold trap for volatiles and a potential future human exploration target. The simulations are carried out using the OpticStudio ray tracing software and a Lambertian scattering model of the cave pit walls. The radiance maps within the caves can be used by the scientific community to estimate the typical Signal to Noise Ratio (SNR) of the required observations with optical cameras deployed on the lunar surface. This is accomplished both for directly illuminated, penumbra and umbra regions of the cave pit. We believe that the proposed investigations are of wide interest for the future missions to the Moon and its robotic and manned exploration.

The Solar Radiation and Climate Experiment (SORCE) recorded daily Solar Spectral Irradiance (SSI) measurements from 2003 to 2020, overlapping with the Total and Spectral Irradiance Sensor (TSIS1) for ∼2 years (Mar. 2018 - Feb. 2020). We use data from the Spectral Irradiance Monitors (SIM), spanning 704 days and 554 time-matched observations, to compare absolute irradiance calibrations in a truly unique space-based UV-IR spectroscopic overlap study. This 200–2400 nm comparison was conducted during the Solar Cycle 24 minimum, so observed differences are likely instrumental. We find peak-to-peak (maximum) absolute scale differences of 12% with a mean fractional difference of 0.7 ± 2.9%. A multiplicative scale correction factor (STICR) has been developed to reconcile the TSIS1 and SORCE SIM irradiance differences. Applying this correction to the SORCE-SIM V27 dataset, we provide a re-calibrated dataset known as the TSIS1-SIM Adjusted Values (TAV). We discuss the challenges in the creation of STICR and TAV, and lessons learned about using temporally overlapping space observatories to provide a continuous solar observation record.

Metis is the coronagraph on board the Solar Orbiter ESA/NASA mission, it is designed to study the solar corona by providing an artificial solar eclipse. Metis features two channels: the ultraviolet H I (121.6 nm) and the visible light (580-640 nm). This work is focalised on the latter. Radiometric performances have been tested on-ground using a flatfield panel (uniform illumination), and the in-flight stability can be verified through the light reflected from the instrument door. When the Sun light impacts on the spacecraft shield, a fraction is reflected in the direction of the door, which then partly reflects it inside Metis. The analysis of the door images confirms its integrity and that of its subsequent optical components, since the reflected intensity follows as expected a 1/r² law, r being the Sun-spacecraft distance. Further analysis is being performed on such images to verify the operating status of various elements of Metis. Complementary ray-tracing simulation studies on the door retro-reflectivity properties are also in progress.

The High Resolution Telescope (HRT) of the Polarimetric and Helioseismic Imager (SO/PHI) on-board the Solar Orbiter mission (SO) provides near diffraction limited observations of the solar surface. The HRT Refocus Mechanism (HRM) allows for acquiring calibration data in flight which are used in post processing on ground to estimate the image quality of SO/PHI-HRT data products and its dependence on the SO-Sun distance. Our aim is to characterise the wavefront aberrations in the optical path of SO/PHI-HRT and consequently the image quality in the focal plane of the telescope. We use calibration data taken during the Near Earth Commissionning Phase (NECP) and the second Remote Sensing Check-out Window (RSCW2) of Solar Orbiter’s Cruise Phase (CP). In particular, we apply a Phase Diversity (PD) analysis to estimate the low-order wavefront aberrations. The restoration with the retrieved Point Spread Function (PSF) from the PD analysis increases the RMS contrast of the solar granulation in the visible continuum from 4 % to 10−11%.

White light observations of the solar corona are crucial for understanding large-scale coronal structures and examining the evolution of solar transients, such as coronal mass ejections (CMEs), which have important space weather impacts. We seek to develop technology for producing high-resolution, wide-FOV maps of the white light corona with reduced instrument size and complexity. With conventional optical designs, scanning the corona with a small instantaneous FOV or accommodating a telescope on a spinning or non-solar centered spacecraft would require large/complex gimbaled systems. To avoid these complex systems, conventional heliospheric imagers are designed with a wide FOV, sacrificing spatial resolution and throughput for coverage. To address this need, we have designed a visible light telescope which uses novel achromatic metasurface Risley prisms (MRPs) to create high-resolution, wide-FOV maps of the solar corona in a small form factor: the Coronal and Heliospheric imaging with Achromatic Metasurfaces Pathfinder (CHAMP). MRPs enable rapid mapping of a large FOV with a small instantaneous FOV, and features of interest (e.g., CMEs, comets, etc.) can be tracked using optimized scanning patterns. Here we present the preliminary concept and optical design for CHAMP.

The ACS-NIR spectrometer on board the Trace Gas Orbiter is currently being used to probe the atmosphere of Mars. When ACS-NIR is pointed at the Sun, it detects the spectral signature of atmospheric components present on its line of sight (LOS) as it passes through the atmosphere. The solar spectrum is directly measured when the LOS is above the atmosphere. Special observations were therefore made to construct the solar spectrum in the 0.7-1.7 μm domain. This is mainly useful for ACS-NIR calibrations and for other experiments. The observations consist in recording all the diffraction orders of ACS-NIR by continuously varying the frequency of its AOTF. Here we will present how to process this data to obtain the solar spectrum. We will first show how we get the flat field for image correction. Next, we will present how to overcome order contamination using a geometric method. We will then show how to correct the order intensity variations to obtain the solar spectrum. We will end by showing some results.

MAJIS (Moons And Jupiter Imaging Spectrometer) is the visible and infrared imaging spectrometer of the ESA L-Class mission JUICE (JUpiter Icy moons Explorer). MAJIS plays a major role for achieving the JUICE main scientific objectives, which include the compositional study of the Galilean moons, their past and present activity, and its relation with observed surface features. It will also study the composition, structure, chemistry and dynamics of the Jovian atmosphere. MAJIS is composed of two spectral channels: the VIS-NIR (0.5µm-2.35µm), and the IR (2.25µm-5.54µm). Both channels are equipped with a Focal Plane Unit (FPU) mainly including a Teledyne H1RG Focal Plan Array (FPA), one Focal Plane electronics (FPE) and one filter. A dedicated facility was developed at the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) for the characterization of the Flight (FM) and Spare (SM) models of the MAJIS VIS-NIR FPU. The radiometric capabilities of the facility include: (1) the tuning of the monochromatic flux provided to the detector over a four-decade range of intensity, (2) optical configurations for dark conditions, uniform light beam or convergent light beam with the same focal ratio as MAJIS, and (3) relative and absolute radiometric scales at the FPA plane. This work describes the radiometric characterization campaign of the MAJIS VIS-NIR SM FPU and the respective data analysis methods used to derive some of the detector key parameters such as the gain, the dark current, the linearity, the full-well capacity and the operability. A comparison with the performances of the FM VIS-NIR FPU is also provided.

The advent of photonic integrated circuits (PICs) will allow the replacement of the large aperture of an optical telescope by a dense array of small apertures combined interferometically. The light coming from aperture pairs can be combined by a PIC in order to extract interferogram characteristics known as complex visibilities, from which the observed object can then be reconstructed. In such a compact interferometric imager, the optical components dedicated to image formation in a regular telescope are no longer necessary. In particular, such a concept is relevant for space missions where weight and size are critical. In this communication, we study such an instrument concept, focusing on signal-to-noise considerations. We recall the design basis for the field and the spatial resolution, and we show that the spectral resolution must be no less than the field to resolution ratio. Then, we analyze the signal-to-noise ratio of this concept, assuming that each spatial frequency is recorded only once, and compare the signal-to-noise ratio with that of a monolithic telescope. We perform the comparison in Fourier space for an identical number of recorded photons. We show that the noise propagation of the interferometric imager is identical to that of a monolithic telescope that would have a flat Modulation Transfer Function with a level roughly given by the ratio of the small apertures’ diameter to the maximum baseline. We conclude that the noise propagation in low and medium spatial frequencies is unfavorable for the interferometric imager.

In this paper, facing the high-contrast, high-resolution and high-sensitivity technical difficulties that need to be solvedfordirect detection of habitable exoplanets, we research on the high-precision simulation method of spatial distributedsynthetic aperture optical interference system, which is one of the main ways to achieve this detection goal, by ZEMAXsoftware. We have built the simulation model of optical system for Michelson-type synthetic aperture telescope. It isverified from the principle and simulation analysis in ZEMAX software that the simulation precision of the optical system can achieve a high-contrast better than 10^-7, and the simulation results of the distribution and variationof theinterference fringes are correct. Finally, we analyze the influence of factors such as band width and optical systemerroron the key index of the fringe visibility. The research in this paper can provide the necessary foundationfor theparameter decomposition and optimization design of the future spatial distributed synthetic aperture optical interferencesystem in habitable exoplanets.

Atmospheric retrieval studies are essential to determine the science requirements for future generation missions, such as the Large Interferometer for Exoplanets (LIFE). The use of heterogeneous absorption cross-sections might be the cause of systematic effects in retrievals, which could bias a correct characterization of the atmosphere. In this contribution we quantified the impact of differences in line list provenance, broadening coefficients, and line wing cut-offs in the retrieval of an Earth twin exoplanet orbiting a Sun-like star at 10 pc from the observer, as it would be observed with LIFE. We ran four different retrievals on the same input spectrum, by varying the opacity tables that the Bayesian retrieval framework was allowed to use. We found that the systematics introduced by the opacity tables could bias the correct estimation of the atmospheric pressure at the surface level, as well as an accurate retrieval of the abundance of some species in the atmosphere (such as CO₂ and N₂O). We argue that differences in the line wing cut-off might be the major source of errors. We highlight the need for more laboratory and modeling efforts, as well as inter-model comparisons of the main radiative transfer models and Bayesian retrieval frameworks. This is especially relevant in the context of LIFE and future generation missions, to identify issues and critical points for the community to jointly work together to prepare for the analysis of the upcoming observations.

Space borne nulling interferometry in the mid-infrared waveband is one of the most promising techniques for characterizing the atmospheres of extra-solar planets orbiting in the habitable zone of their parent star, and possibly discovering life markers. One of its most difficult challenges is the control of free-flying telescope spacecrafts moving around a central combiner in order to modulating the planet signal, within accuracy better than one micrometer at least. Moreover, the whole array must be reconfigured regularly in order to observe different celestial targets, thus increasing the risk of loosing one or more spacecrafts and aborting the mission before its normal end. In this paper is described a simplified optical configuration where the telescopes do not need to be rotated, and the number of necessary array reconfigurations is minimized. It allows efficient modulation of the planet signal, only making use of rotating prisms or mirrors located into the central combiner. In this paper the general principle of a nulling interferometer with a fixed telescope array is explained. Mathematical relations are established in order to determining the planet modulation signal. Numerical simulations are carried out for three different arrangements of the collecting telescopes. They confirm that nulling interferometry in space does not require a rotating telescope array.

The James Webb Space Telescope (JWST) will revolutionize the field of high-contrast imaging and enable both the direct detection of Saturn-mass planets and the characterization of substellar companions in the mid-infrared. While JWST will feature unprecedented sensitivity, angular resolution will be the key factor when competing with ground-based telescopes. Here, we aim to characterize the performance of several extreme angular resolution imaging techniques available with JWST in the 3–5 µm regime based on data taken during the instrument commissioning. Firstly, we introduce custom tools to simulate, reduce, and analyze JWST NIRCam and MIRI coronagraphy data and use these tools to extract companion detection limits from on-sky NIRCam round and bar mask coronagraphy observations. Secondly, we present on-sky JWST NIRISS aperture masking interferometry (AMI) and kernel phase imaging (KPI) observations from which we extract companion detection limits using the publicly available fouriever tool. Scaled to a total integration time of one hour and a target of the brightness of AB Dor (W1 ≈ 4.4 mag, W2 ≈ 3.9 mag), we find that NIRISS AMI and KPI reach contrasts of ∼ 7–8 mag at ∼ 70 mas and ∼ 9 mag at ∼ 200 mas. Beyond ∼ 250 mas, NIRCam coronagraphy reaches deeper contrasts of ∼ 13 mag at ∼ 500 mas and ∼ 15 mag at ∼ 2 arcsec. While the bar mask performs ∼ 1 mag better than the round mask at small angular separations ≲ 0.75 arcsec, it is the other way around at large angular separations ≳ 1.5 arcsec. Moreover, the round mask gives access to the full 360 deg field-of-view which is beneficial for the search of new companions. We conclude that already during the instrument commissioning, JWST high-contrast imaging in the L- and M-bands performs close to its predicted limits and is a factor of ∼ 10 times better at large separations than the best ground-based instruments operating at similar wavelengths despite its < 2 times smaller collecting area.

Similarly to other spectroscopic instruments operating in the infrared wavelength range, the observations of the Mid-Infrared Instrument (MIRI) on-board the James Webb Space Telescope (JWST) are subject to fringing. The different layers in the detectors act as Fabry-P´erot etalons, causing fringes up to 30% in depth. The depth and phase of these detector fringes is not constant for all source geometries on the sky, and depends on the illumination of the MIRI pupil. This means that point sources will show a different fringe pattern from semi-extended sources and extended sources. In fact, it has been found that a smooth change in depth and phase occurs depending on what part of the point spread function (PSF) is sampled. Here, we aim to use the predictable change in fringe pattern to find evidence for the presence of an additional body in what is seemingly a single point source. To do this, we create a forward model of the PSF including fringes and insert this into a Bayesian retrieval loop. The Bayesian loop finds the coordinates on the detector for one or more point sources that best fits the data of two point sources added together. We find that the code is able to identify the along-slice coordinates of the two point sources, but there is less of a dependency on the fringes with the across-slice coordinate. Using commissioning and Cycle 1 data, we will be able to better characterise the fringes, and improve the forward models.

JWST is a world class space observatory that will add profound knowledge of the universe that Hubble began. Within the observatory there are four scientific instruments and a precision guider. During the commissioning phase,1 the primary instrument that will be used to align the mirrors and measure pupil shear will be the Near InfraRed Camera (NIRCam). The NIRCam instrument has two modules each including a focal plane positioned at the final image plane of the instrument. NIRCam2 can also use its focal planes to image the OTE pupil by using a deployable lens known as the Pupil Imaging Lens (PIL). When the PIL is deployed, NIRCam can image the pupil with the focal plane and the data can be analyzed to determine the amount of pupil shear between the Optical Telescope Element (OTE) and NIRCam. At various points in the commissioning process, the PIL is deployed and the alignment between NIRCam and the OTE is measured. Other commissioning activities measure the relative photometry and infer whether the signal is vignetted. Like NIRCam, MIRI can measure pupil shear of the system. MIRI, the Mid-Infrared Instrument comprises both a wide-field imager (5-28μm) and a medium resolution spectrograph (R 1500 to 3500)3 Unlike NIRCam which uses a deployable lens to measure the pupil, the Imager channel uses a filter wheel located at the pupil plane between the MIRI pick-off mirror and the imager detector. It has 18 filters and mask elements which can be selectively commanded into the science path. One of these elements, called the ALignment Lens (AL) or Filterwheel Lens (FLENS) projects a shadow onto the MIRI imager focal plane. The OTE shadow through the FLENS allows MIRI to serve as a cross-check to NIRCAm on pupil shear. This paper details the MIRI pupil shear analysis process used by the JWST team throughout commissioning.

In a cold and stable space environment, the James Webb Space Telescope (JWST or ”Webb”) reaches unprecedented sensitivities at wavelengths beyond 2 microns, serving most fields of astrophysics. It also extends the parameter space of high-contrast imaging in the near and mid-infrared. Launched in late 2021, JWST underwent a six month commissioning period. In this contribution we focus on the NIRCam Coronagraphy mode which was declared ”science ready” on July 10 2022, the last of the 17 JWST observing modes. Essentially, this mode enables the detection of fainter/redder/colder (less massive for a given age) self-luminous exoplanets as well as other faint astrophysical signal in the vicinity of any bright object (stars or galaxies). Here we describe some of the steps and hurdles the commissioning team went through to achieve excellent performances. Specifically, we focus on the Coronagraphic Suppression Verification activity. We were able to produce firm detections at 3.35µm of the white dwarf companion HD 114174 B which is at a separation of ' 0.500and a contrast of ' 10 magnitudes (104 fainter than the K∼5.3 host star). We compare these first on-sky images with our latest, most informed and realistic end-to-end simulations through the same pipeline. Additionally we provide information on how we succeeded with the target acquisition with all five NIRCam focal plane masks and their four corresponding wedged Lyot stops.

The NIRSpec instrument on the James Webb Space Telescope (JWST) brings the first multi-object spectrograph (MOS) into space, enabled by a programmable Micro Shutter Array (MSA) of ∼250,000 individual apertures. During the 6-month Commissioning period, the MSA performed admirably, completing ∼800 reconfigurations with an average success rate of ∼96% for commanding shutters open in science-like patterns. We show that 82.5% of the unvignetted shutter population is usable for science, with electrical short masking now the primary cause of inoperable apertures. In response, we propose a plan to recheck existing shorts during nominal operations, which is expected to reduce the number of affected shutters. We also present a full assessment of the Failed Open and Failed Closed shutter populations, which both show a marginal increase in line with predictions from ground testing. We suggest an amendment to the Failed Closed shutter flagging scheme to improve flexibility for MSA configuration planning. Overall, the NIRSpec MSA performed very well during Commissioning, and the MOS mode was declared ready for science operations on schedule.

The Near-Infrared Spectrograph (NIRSpec) on board of the James Webb Space Telescope will be the first multiobject spectrograph in space offering ∼250,000 configurable micro-shutters, apart from being equipped with an integral field unit and fixed slits. At its heart, the NIRSpec grating wheel assembly is a cryogenic mechanism equipped with six dispersion gratings, a prism, and a mirror. The finite angular positioning repeatability of the wheel causes small but measurable displacements of the light beam on the focal plane, precluding a static solution to predict the light-path. To address that, two magneto-resistive position sensors are used to measure the tip and tilt displacement of the selected GWA element each time the wheel is rotated. The calibration of these sensors is a crucial component of the model-based approach used for NIRSpec for calibration, spectral extraction, and target placement in the micro-shutters. In this paper, we present the results of the evolution of the GWA sensors performance and calibration from ground to space environments.

The Near InfraRed Spectrograph (NIRSpec) on the James Webb Space Telescope (JWST) includes a novel micro shutter array (MSA) to perform multi object spectroscopy. While the MSA is mainly targeting galaxies across a larger field, it can also be used for studying star formation in crowded fields. Crowded star formation regions typically feature strong nebular emission, both in emission lines and continuum. In this work, nebular emission is referred to as nebular contamination. Nebular contamination can obscure the light from the stars, making it more challenging to obtain high quality spectra. The amount of the nebular contamination mainly depends on the brightness distribution of the observed ‘scene’. Here we focus on 30 Doradus in the Large Magellanic Cloud, which is part of the NIRSpec GTO program. Using spectrophotometry of 30 Doradus from the Hubble Space Telescope (HST) and the Very Large Telescope (VLT)/SINFONI, we have created a 3D model of the nebular emission of 30 Doradus. Feeding the NIRSpec Instrument Performance Simulator (IPS) with this model allows us to quantify the impact of nebular emission on target stellar spectra as a function of various parameters, such as configuration of the MSA, angle on the sky, filter band, etc. The results from these simulations show that the subtraction of nebular contamination from the emission lines of pre-main sequence stars produces a typical error of 0.8%, with a 1σ spread of 13%. The results from our simulations will eventually be compared to data obtained in space, and will be important to optimize future NIRSpec observations of massive star forming regions. The results will also be useful to apply the best calibration strategy and to quantify calibration uncertainties due to nebular contamination.

Commissioning the Webb telescope to realize the observatory’s full capability necessitated the development of robust wavefront sensing and control processes. These processes rely on techniques that were adapted or newly innovated for the mission, and further adaptation of these techniques may be expected for future segmented telescopes. Over the course of mission development, these techniques were refined to form a baseline wavefront commissioning plan that assumes several conditions and performance requirements are met. Herein we present efforts carried out to define and develop contingency concepts of operation for Webb telescope commissioning, and the mission-level approach to managing the response to deviations from the baseline plan in the event of significant off-nominal or anomaly scenarios encountered by the wavefront team. An overview of selected contingencies is presented along with more detailed example model cases and instances of interest encountered in flight.

The 18 hexagonal mirrors and the Secondary Mirror of the James Webb Space Telescope (JWST) are precisely aligned in space after deployment using the Influence Function Matrix (IFM). The IFM is calculated from the optical model and predicts how each of the 132 alignment modes impact the telescope wavefront error. This paper will discuss the results from using the IFM in commissioning, including alignment convergence results and analysis comparing the IFM predictions to flight performance.

Segmented-mirror telescopes such as JWST and Keck provide a particular challenge when first pointed to the sky: to access a suitably isolated star with which to align the mirror segments, one must first determine the sky location to which the telescope is pointed. Prior to stacking, the primary mirror segments each produce a separate image of the sky; the expected result is a confusing image in which the star field is convolved with the randomly pointed segments so that each star appears multiple times. To establish the initial sky pointing of JWST, we have developed a pair of novel and complementary approaches for identifying the field. The first approach uses image pairs in which a single primary mirror segment is tilted from its initial pointing by a small amount. This motion of the segment produces a corresponding motion of the stellar images from that segment, allowing us to resolve the ambiguity between the array of stellar images and the array of segment images. The second performs a pattern match within a single image to identify the repeating pattern of the segment array (i.e., the star pattern in the field of view) which can then be matched against an astrometric catalog. Both algorithms produce a resulting array of star positions from which the astrometry.net engine can identify the sky location. We describe the application of these algorithms to both simulated JWST NIRCam images and actual images acquired with MOSFIRE on Keck I, explain how we employed these approaches during the initial stage of JWST primary mirror commissioning, and speculate on future applications for mirrors with more segments.

Launched December 25th 2021 to its final destination at the Sun-Earth Lagrange Point 2, JWST will revolutionize the way the universe is seen back to the early universe beginnings. During the six month commissioning phase of the mission, there were various activities performed which aligned the segmented telescope from eighteen unique Point Spread Functions (PSFs) to a single PSF. One of these steps is to globally align the Secondary Mirror (SM) Assembly (SMA) to the 18 Primary Mirror Segment Assemblies (PMSA) in the primary mirror. This alignment process happens in two phases, and they are named Global Alignment 1 (GA1) and Global Alignment 2 (GA2). A successful completion of GA1 entails coarsely aligning the SM and each PMSA to achieve an RMS Wavefront Error (WFE) less than 200nm. This is accomplished by generating PMSA wavefront maps which are used to determine a correction in the SM using Phase Retrieval and Decomposition. One of the requirements is that the Fine Guidance Sensor (FGS) can guide on a segment during the exposures, minimizing the impacts of motion blur on the images. This paper details a contingency method on how global alignment can be achieved using the observatories star trackers for guiding. The star trackers line of sight (LOS) stability and pointing stability performance are intended for coarse guiding whereas FGS provides fine guiding. It is expected that motion blur will increase should the observatory use coarse guiding during the GA1 exposures. Within the paper, we detail the maximum motion thresholds needed to achieve the desired placement of the SM, as well as exposure methods which can be used to handle motions that exceed the thresholds.