MOEMS deformable mirror testing in cryo for future optical instrumentation

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 <20nm rms. A specific mount including electronic and opto-mechanical interfaces has been designed for fitting in the test chamber. Segment deformation, mirror shaping, open-loop operation are tested at room and cryo temperature and results are compared. The device could be operated successfully at 160K. An additional, mainly focus-like, 500 nm deformation is measured at 160K; we were able to recover the best flat in cryo by correcting the focus and local tip-tilts on some segments. Tests on DM with different mirror thicknesses (25{\mu}m and 50{\mu}m) and different coatings (silver and gold) are currently under way.Comment: 11 pages, 12 Figure

Operation of a MOEMS Deformable Mirror in Cryo: Challenges and Results

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 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. 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

Manufacturing and integration of the IRDIS dual imaging camera and spectrograph for SPHERE

International audienceSPHERE is a planet hunting instrument for the VLT 8m telescope in Chile whose prime objective is the discovery and characterization of young Jupiter-sized planets outside of the solar system. It is a complex instrument, consisting of an extreme Adaptive Optics System (SAXO), various coronagraphs, an infrared differential imaging camera (IRDIS), an infrared integral field spectrograph (IFS) and a visible differential polarimeter (ZIMPOL). The performance of the IRDIS camera is directly related to various wavefront error budgets of the instrument, in particular the differential aberrations occurring after separation of the two image beams. We report on the ongoing integration and testing activities in terms of optical, mechanical, and cryo-vacuum instrument parts. In particular, we show results of component level tests of the optics and indicate expected overall performance in comparison with design-level budgets. We also describe the plans for instrumental performance and science testing of the instrument, foreseen to be conducted during coming months

Prime Focus Spectrograph (PFS) for the Subaru telescope: ongoing integration and future plans

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Prime Focus Spectrograph (PFS): a next-generation facility instrument of the Subaru telescope has started coming

PFS (Prime Focus Spectrograph) is a next generation facility instruments on the Subaru telescope. 2394 reconfigurable fibers will be distributed in the 1.3 degree field of view, and the spectrograph has 3 arms (blue, red, and near-infrared) to simultaneously observe spectra from 380nm to 1260nm in one exposure. In 2018, Metrology Camera System was delivered to the observatory and successfully tested on the telescope. Now in Nov 2019 the first spectrograph module with visible cameras is being shipped to Hawaii. The other subsystems are actively being developed to start on-sky engineering observation in 2020, and science operation in 2022. In this contribution, an overview of the current status and future perspectives will be presented

Prime Focus Spectrograph (PFS) for the Subaru Telescope: its start of the last development phase

International audiencePFS (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