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Advances in astronomy led to the demand for measuring the spectra of multiple night sky objects simultaneously. Some of these Multi-Object Spectrographs use robotic systems that position optical fibers in the focal plane of the observing telescope. These systems rely on precise fiber placement in order to collect the light spectra of faint stars and galaxies. Here, we present how to design, control, and operate micro SCARA-like robots to position optical fibers to micrometer precision. As an illustrative example, we show the design and performance results of the SDSS-V fiber positioner, which has been build for the Apache Point Observatory and the Las Campanas Observatory with 500 units for each telescope.

International audience; In next generation space instrumentation for Earth and Universe Observation, new instrument concepts include often non planar gratings. Their realization is complex and costly. We propose a new technology for designing and realizing convex blazed gratings for high throughput spectrographs. For this purpose, our requirements are driven by a Digital-Micromirror-Device-based (DMD) MOS instrument to be mounted on the Telescopio Nazionale Galileo (TNG) and called BATMAN. The two-arm instrument is providing in parallel imaging and spectroscopic capabilities. The objects/field selector is a 2048 x 1080 micromirrors DMD, placed at the focal plane of the telescope; it is used as a programmable multi-slit mask at the entrance of the spectrograph. The compact Offner-type spectrograph design contains a low density convex grating to disperse light. For optimization of the spectrograph efficiency, this convex grating must be blazed. A blazed reflective grating has been designed with a period of 3300 nm and a blaze angle of 5.04°, and fabricated into convex substrates with 225 mm radius of curvature and a footprint diameter of 63.5 mm. The blaze is optimized for the center wavelength of 580 nm within the spectral range of 400 – 800 nm. Such gratings have been fabricated and coated with a silver-based layer, with a final 7° blaze angle over the whole surface. Efficiency close to 90% on the 1st diffraction order at 700nm has been obtained, measured on BATMAN spectroscopic arm. Detailed mapping of the blazed grating showed a very good period uniformity with up to 0.5% deviation. Grating depth and blaze angle have higher deviation, up to 7%. An optimized device with the exact required blaze angle would reach the same efficiency and be centered on the mid of 400-800nm wavelength band: its realization is on-going. The grating brings a significant contribution in the total amount of straylight at instrument level. Their straylight level remains a critical issue, and its reduction by specific and controlled implementation of improvements in manufacturing process is a challenge to tackle. Preliminary straylight measurement has been done and shows a lowest straylight level below 10-2 sr-1 between the diffraction orders. This new type of non-planar reflective gratings will be the key component for future high throughput spectrographs in space missions.

International audience; The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment that will measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 square degrees will be measured during the life of the experiment. We describe the installation of the major elements of the instrument at the Mayall 4m telescope, completed in late 2019. The previous prime focus corrector, spider vanes, and upper rings were removed from the Mayall’s Serrurier truss and replaced with the newlyconstructed DESI ring, vanes, cage, hexapod, and optical corrector. The new corrector was optically aligned with the primary mirror using a laser tracker system. The DESI focal plane system was integrated to the corrector, with each of its ten 500-fiber-positioner petal segments installed using custom installation hardware and the laser tracker. Ten DESI spectrographs with 30 cryostats were installed in a newly assembled clean room in the Large Coude Room. The ten cables carrying 5000 optical fibers from the positioners in the focal plane were routed down the telescope through cable wraps at the declination and hour angle axes, and their integral slitheads were integrated with the ten spectrographs. The fiber view camera assembly was installed to the Mayall’s primary mirror cell. Servers for the instrument control system replaced existing computer equipment. The fully integrated instrument has been commissioned and is ready to start its operations phase.

The recently commissioned Dark Energy Spectroscopic Instrument (DESI) will measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 sqdeg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope delivers light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with LPNHE (CNRS, IN2P3, Sorbonne Universit\'e and Universit\'e de Paris) and the WINLIGHT Systems company based in Pertuis (France), were in charge of integrating and validating the performance requirements of the ten full spectrographs, equipped with their cryostats, shutters and other mechanisms. We present a summary of our activity which allowed an efficient validation of the systems in a short-time schedule. We detail the main results. We emphasize the benefits of our approach and also its limitations., Comment: 20 pages, 16 figures, in 2020 SPIE Astronomical Telescopes + Instrumentation conference proceedings

The Multi Object Optical and Near-infrared Spectrograph (MOONS) instrument is the next generation multi-object spectrograph for the VLT. This powerful instrument will combine for the first time: the large collecting power of the VLT with a high multipexing capability offered by 1000 optical fibres moved with individual robotic positioners and a novel, very fast spectrograph able to provide both low- and high-resolution spectroscopy simultaneously across the wavelength range 0.64μm - 1.8μm. Such a facility will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic, Extragalactic and Cosmological studies. Th final assembly, integration and verification phase of the instrument is now about to start performance testing.

Maunakea Spectroscopic Explorer (MSE) is the only dedicated, >10 m class, multi-object facility under development on the best site in the Northern Hemisphere. MSE is designed to simultaneously obtain 4,332 spectra in three resolution modes in the optical and NIR. The design attributes of a wide field of view, a high multiplex capability, and the use of optical fibers to transport the light from the prime focus to two suites of spectrographs, mandate an efficient and precise science calibration process to account for the throughput and imaging variations between the astronomical targets at the detectors. To achieve MSE's science goals, the calibration process must enable accurate sky subtraction, wavelength correction, and spectrophotometry. In this paper, we continue our discussion on the science calibration requirements and procedures, and provide an update to the adopted calibration strategy, including likely operational features and hardware. This paper particularly focuses on two new aspects of MSE analysis, ghost behavior of the wide field corrector and the possible impact of satellite constellations on MSE observations., Observatory Operations: Strategies, Processes, and Systems VIII, December 14-18, 2020, Online Only, United States, Series: Proceedings of SPIE

The Maunakea Spectroscopic Explorer (MSE) project will transform the CFHT 3.6m optical telescope to an 11.25 m multi- object spectroscopic facility with an ability to simultaneously detect thousands of objects with three spectral resolution modes, low resolution of R ~ 3,000, moderate resolution of R ~ 5,000, and high resolution of R 20,000 ~ 40,000, respectively. The multi-object high resolution (HR) spectrographs can derive simultaneously around one thousand high- resolution spectra of Blue, Green, and Red channels, respectively. Based on the discussion of the science cases in 2019, the design team suggested that the optimal design of HR spectrograph should balance between the new scientific requirements and technical feasibility. Here, the HR design team shows the trade-off study's progress and introduces a new preliminary design., Ground-based and Airborne Instrumentation for Astronomy VIII, December 14-18, 2020, Online Only, United States, Series: Proceedings of SPIE

Maunakea Spectroscopic Explorer (MSE) is a dedicated multi-object spectroscopic facility that is a major upgrade to the Canada-France-Hawaii-Telescope (CFHT) on Maunakea, Hawaii, with a larger aperture and an expanded international partnership. MSE has completed its Conceptual Design Phase (CoDP) and is preparing for the upcoming Preliminary Design Phase., Advances in Optical Astronomical Instrumentation 2019, ANZCOP 2019, December 8-12, 2019, Melbourne, Australia, Series: Proceedings of SPIE

How does one study the evolution of the Milky Way, or the expansion of the Universe, or explore the mysteries of Dark energy? To investigate these complex topics, astronomers require data, and a great deal of it, in the form of the spectra of stars, galaxies, and quasars. In recent years remarkable efforts have been made to develop telescopes and instruments that can measure more light spectra in parallel than ever before. One solution for building these instruments, called Multi-Object Spectrographs, requires the use of several hundreds of small precise automated robots in the telescope's focal plane. Each robot can position an optical fiber with micrometer precision along the focal surface in order to capture and transmit the light of a celestial object to a spectrograph, which then measures the spectrum with great precision. In the future, new instruments will be able to measure over 10000 celestial objects simultaneously, which would consequently require the implementation of as many optical fiber positioners. To assure the development and successful operation of the instrument, every single fiber positioner requires design and validation testing. Tools for such quality assurance have yet to be developed. This thesis proposes solutions to verify, calibrate, control, and operate optical fiber positioners with two actuated rotation axes, serially linked. A metrology system is presented which is capable of accurately measuring position and alignment of the optical fiber, and a detailed model describing the correct behavior of the positioner is introduced. Based on the model, an automated measurement procedure enables calibration and validation of the positioners. The introduced measurement procedure identifies not only flaws in performance, but also various error sources, which help to detect possible design and manufacturing problems. Finally, a method is proposed on how to operate these positioners in the focal plane. Taken together, the results of this thesis can inform the present and future manufacturer of Multi-Object Spectrographs.

The Maunakea Spectroscopic Explorer (MSE) is a next-generation observatory, designed to provide highly multiplexed, multi-object spectroscopy over a wide field of view. The observatory will consist of (1) a telescope with an 11.25 m aperture, (2) a 1.5 square-degree science field of view, (3) fibre optic positioning and transmission systems, and (4) a suite of low (R=3000), moderate (R=6000) and high resolution (R=40,000) spectrographs. The Fibre Transmission System (FiTS) consists of 4332 optical fibres, designed to transmit the light from the telescope prime focus to the dedicated spectrographs. The ambitious science goals of MSE require the Fibre Transmission System to deliver performance well beyond the current state of the art for multi-fibre systems, e.g., the sensitivity to observe magnitude 24 objects (@ SNR=2) over a very broad wavelength range (0.37 – 1.8 μm) while achieving relative spectrophotometric accuracy of < 3% and radial velocity precision of 20 km/s (@ SNR=5). This paper details the design of the FiTS fibre system. It places FiTS into context with existing and planned spectroscopic facilities, such as Subaru/PFS, KPNO/DESI, ESO/4MOST and Gemini/GRACES. The results and lessons learned from GRACES are particularly applicable, since FiTS and GRACES share many team members, including industrial partner FiberTech Optica (Kitchener, ON). The FiTS system consists of 57 identical fibre cables. These cables have been designed to be modular, facilitating efficient construction and automated acceptance testing. Each cable consists of 76 fibres, including 57 fibres feeding light to the low and moderate resolution spectrographs and 19 fibres feeding the high-resolution spectrographs. Thus, the MSE/FiTS consists of 4332 fibres in total. Novel construction techniques utilizing continuous high-NA (f/2) fibres, pioneered by FiberTech Optica, are outlined and test results showing < 5% focal ratio degradation (FRD) in V-band are presented. The effect on FRD from varying the input f/# is also shown. Where test data is unavailable, system error budgets have been created to assess design choices on options such as fibre material, anti-reflection coatings, and fibre-optic connectors., Ground-based and Airborne Instrumentation for Astronomy VII, June 10-15, 2018, Austin, TX, USA, Series: Proceedings of SPIE; no. 10702

International audience; Assembly, Integration, Test and Validation (AIT/V) phases for AO instruments, in laboratory as in the telescope, represent numerous technical challenges. The Laboratoire d’Astrophysique de Marseille (LAM) is in charge of the AIT/V preparation and planning for the MOSAIC (ELT-MOS) instrument, from identification of needs, challenges, risks, to defining the optimal AIT strategy for this highly modular and serialized instrument. In this paper, we present the status of this study and describe several AIT/V scenarios as well as a planning for AIT phases in Europe and in Chile. We also show our capabilities, experience and expertise to lead the instrument MOSAIC AIT/V activities.

International audience; The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 deg² will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with LPNHE (CNRS, Universities Pierre et Marie Curie and Paris-Diderot) and the WINLIGHT Systems company based in Pertuis (France), are in charge of integrating and validating the performance requirements of the full spectrographs. This includes the cryostats, shutters and other mechanisms. The first spectrograph of the series of ten has been fully tested and the performance requirements verified for the following items: focus, image quality, straylight, stability, detector properties and throughput. We present the experimental setup, the test procedures and the results.

The instrumentation group of the Herzberg Institute of Astrophysics was commissioned by the Gemini Observatory to develop a new focal plane assembly for the Gemini Multi-Object Spectrograph with an array of three deep-depletion Hamamatsu CCDs. The main objective of the upgrade is to improve the sensitivity of the instrument in the red and nearinfrared wavelengths, with the additional benefits of reduced fringing, faster readout, and better performance in the "nod and shuffle" mode. We describe what we learned about these relatively new CCDs, including several problems encountered during testing, and report on the performance of the system. © 2012 SPIE., High Energy, Optical, and Infrared Detectors for Astronomy V, 1 July 2012 through 4 July 2012, Amsterdam, Series: Proceedings of SPIE

We report on the design, on-sky performance, and status of the FLAMINGOS-2 instrument - the fully-cryogenic facility near-infrared imager and multi-object spectrograph for the Gemini 8-meter telescopes. FLAMINGOS-2 has a refractive all-spherical optical system providing 0.18-arcsecond pixels and a 6.2-arcminute circular field-of-view on a 2048x2048-pixel HAWAII-2 0.9-2.4 μm detector array. A slit/decker wheel mechanism allows the selection of up to 9 multi-object laser-machined plates or 3 long slits for spectroscopy over a 6x2-arcminute field of view, and selectable grisms provide resolutions from ∼1300 to ∼3000 over the entire spectrograph bandpass. FLAMINGOS-2 is also compatible with the Gemini Multi-Conjugate Adaptive Optics system, providing multi-object spectroscopic capabilities over a 3x1-arcminute field with high spatial resolution (0.09-arcsec/pixel). We review the designs of optical, mechanical, electronics, software, and On-Instrument WaveFront Sensor subsystems. We also present the on-sky performance measured during acceptance testing in 2009, as well as current status of the project and future plans., Ground-Based and Airborne Instrumentation for Astronomy IV, July 1-6, 2012, Amsterdam, Netherlands, Series: Proceedings of SPIE

Multi-object spectroscopy is a powerful tool for space and ground-based telescopes for the study of the formation of galaxies. This technique requires a programmable slit mask for astronomical object selection. We are developing MEMS-based programmable reflective slit masks for multi-object spectroscopy that consist of micromirror arrays on which each micromirror of size 100 x 200 mu m(2) is electrostatically tilted providing a precise angle. The main requirements for these arrays are cryogenic environment capabilities, precise and uniform tilt angle over the whole device, uniformity of the mirror voltage-tilt hysteresis and a low mirror deformation. A first generation of MEMS-based programmable reflective slit masks composed of 5 x 5 micromirrors was tested in cryogenic conditions at 92 K. Then, first prototypes of large arrays were microfabricated and characterized, but the reliability of these arrays had to be improved. To increase the reliability of these devices, a third generation of micromirror arrays composed of 64 x 32 micromirrors is under development. This generation was especially designed for individual actuation of each mirror, applying a line-column algorithm based on the voltage-tilt hysteresis of the actuator. The fabrication process was optimized and is now based on multiple wafer level bonding steps. Microfabricated devices have micromirror with a peak-to-valley deformation less than 3 nm. The mirrors can be tilted at 20 degrees by an actuation voltage lower than 100 V. First experiments showed that our micromirrors are well suited for the line-column addressing of each micromirror.

We are developing MEMS-based programmable reflective slit masks for future generation infrared multi-object spectroscopy (MOS) for space and ground-based telescopes. These devices are composed of monocrystalline silicon micromirrors of size 200 x 100 um(2) which can be tilted by electrostatic actuation yielding a tilt-angle of 20 degrees. An electromechanical clamping mechanism has been demonstrated providing uniform tilt-angle within one arc minute precision over the whole array (5 x 5 micromirrors). Slit masks of different sizes have been produced; the largest one measures 25 x 22 mm(2) and is composed of 20'000 micromirrors. Thanks to the architecture and the fabrication process of these slit masks; the micromirror peak-to-valley deformation (PTV) is uniform over the device and was measured being below 10 nm for uncoated micromirror. A slit mask of size 5 x 5 micromirrors was successfully tested in cryogenic conditions at 92 K; the micromirrors were actuated before, during and after the cryogenic experiment. To achieve for the large arrays a better fabrication yield and a higher reliability, the architecture, the process flow, the assembly and the electronics are being optimized. Optical characterizations as well as experiments of the large devices are underway.

2007-12-07; The near-infrared multi-object spectrograph NIRSpec is one of the three science instruments onboard the future James Webb Space Telescope. It is developed by EADS/Astrium for the European Space Agency (ESA). NIRSpec will cover the 0.6 to 5.0 µm wavelength range and will be able to obtain simultaneous spectra of more than 100 objects in a 9 square arcminute field of view, thanks to an array of micro-shutters.An accurate modeling of the instrument has been performed to obtain realistic estimates of NIRSpec expected performances and to check that the science goals could be achieved. Such a model has also been used to define and validate the operation and calibration scenarios and,on the long run, to develop and test the data reduction software. This model is based on an end-to-end (from the sky to the detectors) Fourier-optics model of the instrument taking into account both geometrical aberrations and diffraction. In this manuscript, we discuss both the hypothesis and the limitations of such a Fourier Optics model. Our study is then focused on NIRSpec image quality, distortion and overall efficiency.In the last sections, we describe the algorithms designed and implemented to compute realistic fake exposures. These exposures are currently used to test NIRSpec exposures data processing software.; Le futur télescope spatial JWST (James Webb Space Telescope) sera lancé en 2013. Conçu pour observer dans l'infrarouge de 0.6 à 27 µm, ce télescope sera équipé, entre autres instruments, du spectrographe multi-objets NIRSpec (Near Infrared Spectrograph). Dans cette thèse, nous modélisons et analysons les performances optiques de cet instrument développé par EADS/Astrium pour l'Agence Spatiale Européenne (ESA).Notre étude se concentre sur la qualité d'image, la distorsion et l'efficacité totale de NIRSpec.Ces calculs de performances reposent sur un code d'optique de Fourier développé durant cette thèse. Dans ce manuscrit, nous discutons les hypothèses et les limites de notre approche et nous présentons les résultats obtenus par l'étude de la distorsion et des effets de la diffraction. Ces résultats ont été utilisés pour vérifier des points clefs de la conception de NIRSpec. La complexité de NIRSpec nous a également amenés à développer un simulateur complet de l'optique et des détecteurs. Nous décrivons les algorithmes mis au point pour ces simulations ainsi que les éléments importants de leur implémentation (optimisation des temps de calculs). Les poses ainsi crées sont actuellement utilisées pour tester les futurs logiciels de traitement des données NIRSpec.

Next-generation infra-red astronomical instrumentation for space and ground-based telescopes requires MOEMS-based programmable slit masks for multi-object spectroscopy (MOS) which has to work in cryogenic environment. A first prototype of micromirror arrays (MMA) of 5 x 5 single-crystal silicon micromirrors was successfully designed, fabricated and tested. 100 x 200 mu m(2) micromirrors can be tilted by electrostatic actuation yielding 20 degrees mechanical tilt-angle. The MMA were successfully actuated before, during and after cryogenic cooling, below 100 K. A MMA is composed of two different chips fabricated on silicon on insulator (SOI) wafers: the mirror chip and the electrode chip. The array was obtained by assembling these two chips. For the assembly step of large array (100 x 200 micromirrors) we needed high precision alignment as well as the suppression of manual handling. Therefore we developed a technique of assembly for such devices and we designed and fabricated a dedicated XYZ tip/tilt stage. This stage allows aligning the electrodes towards the micromirrors with a micrometer precision. Large MMA of 100 x 200 micromirrors, measuring 22 mm x 25 mm, for large field of view were microfabricated and assembled using the above setup. No additional deformations were observed due to the assembly step. The peak to valley (PTV) deformation of the micromirrors was found to be 14 nm PTV. The first actuation tests were carried out.

Multi-object spectroscopy (MOS) is a powerful tool for space and ground-based telescopes for studying the formation of galaxies. This technique requires a programmable slit mask for astronomical object selection. A first sample of MEMS-based programmable reflective slit masks with elements of size 200x100 mu m(2) has been successfully tested in cryogenic conditions at 92 K. Devices of larger size were microfabricated, the largest chip measures 25x22 mm(2) and is composed of 200x100 electrostatic actuated micromirrors. These devices are composed of two chips: the electrode chip and the mirror chip, which are processed separately and assembled consecutively. The mirror chip is bonded on top of the electrode chip and microfabricated pillars on the electrode chip provide the necessary spacing between the two parts. A process flow utilizing refilling techniques based on borophosphosilicate glass (BPSG) deposition and reflow was developed. Programmable reflective slit masks based on this fabrication process were microfabricated and characterized. These devices exhibit a micromirror deformation of 11 nm peak-to-valley and an actuation voltage of 145 V for a tilt angle of 9 degrees. Preparation of samples for MOS experiments are underway.