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International audience; PFS (Prime Focus Spectrograph), a next generation facility instrument on the Subaru telescope, is now being tested on the telescope. The instrument is equipped with very wide (1.3 degrees in diameter) field of view on the Subaru's prime focus, high multiplexity by 2394 reconfigurable fibers, and wide waveband spectrograph that covers from 380nm to 1260nm simultaneously in one exposure. Currently engineering observations are ongoing with Prime Focus Instrument (PFI), Metrology Camera System (MCS), the first spectrpgraph module (SM1) with visible cameras and the first fiber cable providing optical link between PFI and SM1. Among the rest of the hardware, the second fiber cable has been already installed on the telescope and in the dome building since April 2022, and the two others were also delivered in June 2022. The integration and test of next SMs including near-infrared cameras are ongoing for timely deliveries. The progress in the software development is also worth noting. The instrument control software delivered with the subsystems is being well integrated with its system-level layer, the telescope system, observation planning software and associated databases. The data reduction pipelines are also rapidly progressing especially since sky spectra started being taken in early 2021 using Subaru Nigh Sky Spectrograph (SuNSS), and more recently using PFI during the engineering observations. In parallel to these instrumentation activities, the PFS science team in the collaboration is timely formulating a plan of large-sky survey observation to be proposed and conducted as a Subaru Strategic Program (SSP) from 2024. In this article, we report these recent progresses, ongoing developments and future perspectives of the PFS instrumentation.

PFS (Prime Focus Spectrograph), a next generation facility instrument on the Subaru telescope, is a very wide- field, massively multiplexed, and optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed in the 1.3 degree-diameter field of view. The spectrograph system has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously deliver spectra from 380nm to 1260nm in one exposure. The instrumentation has been conducted by the international collaboration managed by the project office hosted by Kavli IPMU. The team is actively integrating and testing the hardware and software of the subsystems some of which such as Metrology Camera System, the first Spectrograph Module, and the first on-telescope fiber cable have been delivered to the Subaru telescope observatory at the summit of Maunakea since 2018. The development is progressing in order to start on-sky engineering observation in 2021, and science operation in 2023. In parallel, the collaboration is trying to timely develop a plan of large-sky survey observation to be proposed and conducted in the framework of Subaru Strategic Program (SSP). This article gives an overview of the recent progress, current status and future perspectives of the instrumentation and scientific operation.

In future space missions for Universe and Earth Observation, scientific return could be optimized using MOEMS devices. Large micromirror arrays (MMA) are used for designing new generation of instruments. In Universe Observation, multi-object spectrographs (MOS) are powerful tools for space and ground-based telescopes for the study of the formation and evolution of galaxies. This technique requires a programmable slit mask for astronomical object selection; 2D micromirror arrays are perfectly suited for this task. In Earth Observation, removing dynamically the straylight at the entrance of spectrographs could be obtained by using a Smart Slit, composed of a 1D micro-mirror array as a gating device. We are currently engaged in a European development of micro-mirror arrays, called MIRA, exhibiting remarkable performances in terms of surface quality as well as ability to work at cryogenic temperatures. MMA with 100 × 200 μm2 single-crystal silicon micromirrors were successfully designed, fabricated and tested down to 162 K. In order to fill large focal planes (mosaicing of several chips), we are currently developing large micromirror arrays to be integrated with their electronics. 1D and 2D arrays are built on wafer with Through Wafer Vias in order to allow routing of the device on wafer backside, foreseeing integration with dedicated ASICs. The yield of these devices as well as contrast enhancement have been successfully implemented.

MOEMS Deformable Mirrors (DM) are key components for next generation optical instruments implementing innovative adaptive optics systems, both in existing telescopes and in the future ELTs. Characterizing these components well is critical for next generation instruments. This is done by interferometry, including surface quality measurement in static and dynamical modes, at ambient and in vacuum/cryo. We use a compact cryo-vacuum chamber designed for reaching 10–6 mbar and 160 K in front of our custom Michelson interferometer, which is able to measure performance of the DM at actuator/segment level and at the entire mirror level, with a lateral resolution of 2 μm and a sub-nanometer z-resolution. We tested the PTT 111 DM from Iris AO: an array of single crystalline silicon hexagonal mirrors with a pitch of 606 μm, able to move in tip, tilt, and piston (stroke 5–7 μm, tilt +/− 5 mrad). The device could be operated successfully from ambient to 160 K. At room temperature, we developed an improved best flat procedure and obtained a mirror surface deformation, as low as 10 nm RMS. An additional, 500 nm deformation of the entire mirror is measured at 160K; by analyzing at all spatial scales our measurements, we are able to discriminate the different effects at packaging, actuator and mirror segment level. We developed a strategy of weighted addition of the consecutive measurement residual errors to be applied to each actuator; in a single measurement step, we were able to recover the cryo best flat by correcting the focus and local tip-tilts on all segments, reaching a mirror surface deformation as low as 12 nm RMS at 160K. Finally, the goal of these studies is to test DMs in cryo and vacuum conditions as well as to improve their architecture for stable operation in a harsh environment. They are foreseen in a wide variety of applications, from astronomy as presented in this paper, but also in microscopy and in laser beam shaping.

The Prime Focus Spectrograph (PFS) of the Subaru Measurement of Images and Redshifts (SuMIRe) project for Subaru telescope includes four identical spectrograph modules fed by 600 fibers each. This paper presents the integration, alignment and test procedures for the first spectrograph module composed by an optical entrance unit that creates a collimated beam and distributes the light to three channels, two visible and one near infrared. In particular, we present the performance of the single Red channel module. Firstly, we report on the measured optical performance: optical quality and ghost analysis. We also report on the thermal performance of the visible camera cryostat. Finally, we describe the software used to control and monitor the instrument.

International audience; ESA EUCLID mission will be launched in 2020 to understand the nature of the dark energy responsible of the accelerated expansion of the Universe and to map the geometry of the dark matter. The map will investigate the distanceredshift relationship and the evolution of cosmic structures thanks to two instruments: the NISP and the VIS. The NISP (Near Infrared Spectro-Photometer) is operating in the near-IR spectral range (0.9-2μm) with two observing modes: the photometric mode for the acquisition of images with broad band filters, and the spectroscopic mode for the acquisition of slitless dispersed images on the detectors. The spectroscopic mode uses four low resolution grisms to cover two spectral ranges: three "red" grisms for 1250-1850nm range, with three different orientations, and one "blue" grism for 920- 1300nm range. The NISP grisms are complex optical components combining four main optical functions: a grism function (dispersion without beam deviation of the first diffracted order) done by the grating on the prism hypotenuse, a spectral filter done by a multilayer filter deposited on the first face of the prism to select the spectral bandpass, a focus function done by the curved filter face of the prism (curvature radius of 10m) and a spectral wavefront correction done by the grating which grooves paths are nor parallel, neither straight. The development of these components have been started since 10 years at the Laboratoire d’Astrophysique de Marseille (LAM) and was linked to the project phases: prototypes have been developed to demonstrate the feasibility, then engineering and qualification models to validate the optical and mechanical performance of the component, finally the flight models have been manufactured and tested and will be installed on NISP instrument. In this paper, we present the optical performance of the four EUCLID NISP grisms flight models characterized at LAM: wavefront error, spectral transmission and grating groove profiles. The test devices and the methods developed for the characterization of these specific optical components are described. The analysis of the test results have shown that the grisms flight models for NISP are within specifications with an efficiency better than 70% on the spectral bandpass and a wavefront error on surfaces better than 30nm RMS. The components have withstood vibration qualification level up to 11.6g RMS in random test and vacuum cryogenics test down to 130K with measurement of optical quality in transmission. The EUCLID grisms flight models have been delivered to NISP project in November 2017 after the test campaign done at LAM that has demonstrated the compliance to the specifications.

PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~ 1.6-2.7Å. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project recently started undertaking the commissioning process of a subsystem at the Subaru Telescope side, with the integration and test processes of the other subsystems ongoing in parallel. We are aiming to start engineering night-sky operations in 2019, and observations for scientific use in 2021. This article gives an overview of the instrument, current project status and future paths forward.

Large field of view surveys with a high density of objects such as high-z galaxies or stars benefit of multi-object spectroscopy (MOS) technique. This technique is the best approach to eliminate the problem of spectral confusion, to optimize the quality and the SNR of the spectra, to reach fainter limiting fluxes and to maximize the scientific return. Next generation MOS for space like the Near Infrared Multi-Object Spectrograph (NIRSpec) for the James Webb Space Telescope (JWST) require a programmable multi-slit mask. The European EUCLID mission has also considered a MOS instrument in its early study phase. Conventional masks or complex fiber-optics-based mechanisms are not attractive for space. The programmable multi-slit mask requires remote control of the multi-slit configuration in real time. A promising possible solution is the use of MOEMS devices such as micromirror arrays (MMA) [1,2,3] or micro-shutter arrays (MSA) [4]. MMAs are designed for generating reflecting slits, while MSAs generate transmissive slits. MSA has been selected to be the multi-slit device for NIRSpec and is under development at NASA's Goddard Space Flight Center. In Europe, an effort is currently under way to develop single-crystalline silicon micromirror arrays for future generation infrared multi-object spectroscopy [5]. By placing the programmable slit mask in the focal plane of the telescope, the light from selected objects is directed toward the spectrograph, while the light from other objects and from the sky background is blocked. Visitech is an engineering company experienced in developing DMD solution for industrial customers. The Laboratoire d’Astrophysique de Marseille (LAM) has, over several years, developed different tools for modeling and characterization of MOEMS-based slit masks, especially during the design studies on JWSTNIRSpec [6,7]. ESA has engaged with Visitech and LAM in a technical assessment of using a Digital Micromirror Devices (DMD) from Texas Instruments for space applications (for example in ESA EUCLID mission). The DMD features 2048 x 1080 mirrors on a 13.68μm mirror pitch (left-hand side of Fig. 1). Typical operational parameters of this device are room temperature, atmospheric pressure and mirrors switching thousands of times in a second, while for MOS applications in space, the device should work in vacuum, at low temperature, and each MOS exposure would last for typically 1500s with micromirrors held in a static state (either ON or OFF) during that duration. A specific thermal / vacuum test chamber has been developed for test conditions down to -40°C at 10-5 mbar vacuum. Imaging capability for resolving each micro-mirror has also been developed for determining any single mirror failure. Dedicated electronics and software allows us to hold any pattern on the DMD for duration of up to 1500s. We present the summary of this ESA study, the electronic test vehicle as well as the cold temperature test set-up we have developed. Then, results of tests in vacuum at low temperature, including low temperature stress test, low temperature nominal test, thermal cycling, and life test are presented. Results after radiation (TID and proton), and vibration and shock are also shown.

An Iris AO MOEMS deformable mirror has been successfully operated and tested at 160K. Surface deformation at room temperature and in cryo has been measured and DM architecture contributions analyzed.

International audience; Micro‐opto‐electro‐mechanical systems (MOEMS) Deformable Mirrors (DM) are key components for next generation optical instruments implementing innovative adaptive optics systems, both in existing telescopes and in the future ELTs. Characterizing these components well is critical for next generation instruments. This is done by interferometry, including surface quality measurement in static and dynamical modes, at ambient and in vacuum/cryo. We use a compact cryo‐vacuum chamber designed for reaching 10‐6 mbar and 160 K in front of our custom Michelson interferometer, which is able to measure performance of the DM at actuator/segment level and at the entire mirror level, with a lateral resolution of 2 mu m and a sub‐nanometer z‐resolution. We tested the PTT 111 DM from Iris AO: an array of single crystalline silicon hexagonal mirrors with a pitch of 606 mu m, able to move in tip, tilt, and piston (stroke 5‐7 mu m, tilt +/‐ 5 mrad). The device could be operated successfully from ambient to 160 K. An additional, mainly focus‐like, 500 nm deformation of the entire mirror is measured at 160 K; we were able to recover the best flat in cryo by correcting the focus and local tip‐tilts on all segments, reaching 12 nm rms. Finally, the goal of these studies is to test DMs in cryo and vacuum conditions as well as to improve their architecture for stable operation in harsh environments.

MOEMS Deformable Mirrors (DM) are key components for next generation instruments with innovative adaptive optics systems, in existing telescopes and in the future ELTs. These DMs must perform at room temperature as well as in cryogenic and vacuum environment. Ideally, the MOEMS-DMs must be designed to operate in such environment. We present some major rules for designing / operating DMs in cryo and vacuum. We chose to use interferometry for the full characterization of these devices, including surface quality measurement in static and dynamical modes, at ambient and in vacuum/cryo. Thanks to our previous set-up developments, we placed a compact cryo-vacuum chamber designed for reaching 10-6 mbar and 160K, in front of our custom Michelson interferometer, able to measure performances of the DM at actuator/segment level as well as whole mirror level, with a lateral resolution of 2{\mu}m and a sub-nanometric z-resolution. Using this interferometric bench, we tested the Iris AO PTT111 DM: this unique and robust design uses an array of single crystalline silicon hexagonal mirrors with a pitch of 606{\mu}m, able to move in tip, tilt and piston with strokes from 5 to 7{\mu}m, and tilt angle in the range of +/-5mrad. They exhibit typically an open-loop flat surface figure as good as, Comment: 11 pages, 12 Figures

Next-generation infrared multi-object spectrographs (MOS) for ground-based and space telescopes could be based on MOEMS programmable slit masks. This astronomical technique is used extensively to investigate the formation and evolution of galaxies. ESA has engaged a study for a technical assessment of using a DMD from Texas Instruments for space applications. The DMD features 2048 × 1080 mirrors on a 13.68μm pitch, where each mirror can be independently switched between an ON (+12°) position and an OFF (-12°) position. For MOS applications in space, the device should work in vacuum, at low temperature, and each MOS exposure would last for typically 1500s with micromirrors held in a static state (either ON or OFF). A specific thermal/vacuum test chamber has been developed for test conditions down to -40°C at 10 -5 mbar vacuum. Imaging capability for resolving each micromirror has also been developed for determining degradation in any single mirror. Our first tests reveal that the DMD remains fully operational at -40°C and in vacuum. A 1038 hours life test in space conditions, Total Ionizing Dose radiation, thermal cycling and vibrations/shocks have also been successfully completed. These results do not reveal any concerns regarding the ability of the DMD to meet environmental space requirements. Detailed analysis of micromirror throughputs has also been studied for a whole set of tests, and shows a rather low variation and no impact of the space environment. We have also developed a bench for MOS demonstration using MOEMS devices. DMD chip has been successfully tested revealing good contrast values as well as good functionality for applying any mask pattern, demonstrating its full ability for space instrumentation, especially in multi-object spectroscopy applications.

Next-generation infrared astronomical instrumentation for ground-based and space telescopes requires MOEMS-based programmable slit masks for multi-object spectroscopy. We made a full space evaluation of Texas Instruments DMD chips, including tests at cold temperature and in vacuum, life tests, radiations, and vibrations and shocks. These results do not reveal any show-stopper concerning its ability to meet environmental space requirements. In parallel, a 100×200µm2 micro-mirror array was successfully designed for cryogenic temperature, fabricated and tested at 92K. Large micromirror arrays of 20'000 micromirrors have also been fabricated. These tests demonstrate the full ability of this type of components for space instrumentation.

Next-generation infrared astronomical instrumentation for ground-based and space telescopes could be based on MOEMS programmable slit masks for multi-object spectroscopy (MOS). This astronomical technique is used extensively to investigate the formation and evolution of galaxies. We are engaged in an ESA study for a technical assessment of using a DMD from Texas Instruments for space applications (for example in ESA EUCLID mission). The DMD features 2048×1080 mirrors on a 13.68μm pitch, where each mirror can be independently switched between an ON (+12°) position and an OFF (-12°) position. For MOS applications in space, the device should work in vacuum, at low temperature, and each MOS exposure would last for typically 1500s with micromirrors held in a static state (either ON or OFF). A specific thermal/vacuum test chamber has been developed for test conditions down to -40°C at 10 -5 mbar vacuum. Imaging capability for resolving each micromirror has also been developed for determining degradation in any single mirror. Our first tests reveal that the DMD remains fully operational at -40°C and in vacuum. A 1038 hours life test in space conditions, Total Ionizing Dose radiation, thermal cycling and vibrations/shocks have also been successfully completed. These results do not reveal any concerns regarding the ability of the DMD to meet environmental space requirements. We have also developed a bench for MOS demonstration using MOEMS devices. DMD chip has been successfully tested revealing good contrast values as well as good functionality for applying any mask pattern, demonstrating its full ability for space instrumentation, especially in multi-object spectroscopy applications.

Next generation of infra-red astronomical instrumentation for space telescopes as well as ground-based extremely large telescopes requires MOEMS devices with remote control capab ility and cryogenic operation, including programmable multi-slit masks for mu lti-object spectroscopy (MOS). For the complete testing of these devices, we have developed in parallel and coupled a high-resolu tion Twyman-Green interferometer and a cryogenic-chamber for full surface and operation characterization. The interferometer exhibits a nanometer accuracy by using phase-shifting technique and low-coherence source. The cryogenic-chamber has a pressure as low as 10e-6 mbar and is able to cool down to 60K. Specific interfaces minimizing stresses for vacuum and cryo have been set. Within the framework of the European program on Smart Focal Planes, micro-mirrors have been sel ected for generating MOEMS-based slit masks. A first 5x5 micro-mirror array (MMA) with 100x200µm 2 mirrors was successfully fabricated using a combination of bulk and surface silicon micromachining. They show a mechanical tilting angle of 20° at a driving voltage below 100V, with excellent surface quality and uniform tilt-angle. The mirrors could be successfully actuated before, during and after cryogenic cooling. The surface quality of the gold coated micro-mirrors at room temperature and below 100K, when they are actuated, shows a slight increase of the deformation from 35nm peak-to-valley to 50nm peak-to-v alley, due to CTE mismatch between silicon and gold layer. This small deformation is still well within the requiremen t for MOS application. Keywords : micro-mirror array, mu lti-object spectrograph, MOEMS.