arXiv subjects

Diane Chapuis

Publications and source records attributed to Diane Chapuis.

4 recordsLinked to original sources

arXiv2026

MOSAIC at ELT: Design and First Prototyping of Novel Robotic Optical-Relay Positioners

The Extremely Large Telescope (ELT) is, to date, the most ambitious ground-based telescope under construction. MOSAIC is a multi-objects spectrograph (MOS) that aims to make full use of the largest telescope in the world. At its heart, about 300 robotic positioners will pick-off skylight from the focal surface of the ELT to feed it to its Near Infrared (NIR) and visible (VIS) spectrographs. The gigantic scale of the ELT presents three main challenges for MOSAIC positioners: (1) the light beams on the focal surface cannot be focused in a single fiber, similarly to other MOS instruments, involving a design with relay mirrors patrolling the field of view, and reimaging the sub-field on 2 fixed fiber bundles located 600 mm behind the ELT focal plane (2) The positioner needs to adapt to the local telecentricity, which means it has to point at the ELT pupil center located 37.868 m away from the focal plane (3) The Atmospheric Dispersion Corrector (ADC) needed to cover the whole focal surface of the ELT is impossible to build to this scale; hence each positioner needs its own ADC. EPFL is responsible for designing and supervising the mass manufacturing of the positioners. This paper aims to present its initial design and prototypes.

astro-ph.IM↗

arXiv2026

Focal Plate Prototyping for Modular Focal Planes of Stage-5 Instruments For Ground-Based Telescopes

As current Stage-4 multi-object instruments such as SDSS-V, DESI, MOONS or 4MOST are providing astrophysicists data to study the objects of the Universe, effort is arising to build the next generation of Stage-5 multi-object focal planes; aiming for 20'000 fibers-class instruments. The focal plate structure is a central element of the future focal plane assemblies. It maintains the fiber positioners, the Guide, Focus and Alignment cameras (GFAs) and wave-front sensors together on the focal surface of the telescope. In addition to being optimized for stiffness and mass, the plate needs to meet tight tolerances in tilt, typically pm 0.05 degres, and focus, typically, pm 30 um, to match the telescope's curved focal surface. The presented focal plate prototype shows that 5-axes machining is promising to meet the desired tolerances.

astro-ph.IM↗

arXiv2026

Motorized Mount for the 3-DoF Folding Mirror 2 of the VLT's BlueMUSE Instrument

BlueMUSE is a blue-optimized, medium spectral resolution, panoramic integral field spectrograph under development for the Very Large Telescope (VLT). The project is now fully entering design phase. With an optimized transmission down to 350 nm, spectral resolution of R~3500 on average across the wavelength range, and a large FoV (1 arcmin2), BlueMUSE will open up a new range of galactic and extragalactic science cases facilitated by its specific capabilities. To meet the stability demands required for BlueMUSE, motorized mounts for precise and repeatable positioning of key optics are developed. This paper explores candidate mechanical designs for BlueMUSE's Folding Mirror 2 (FM2), a high-precision mirror mount with three degrees-of-freedom: tip, tilt rotations, and vertical translation. The study includes a comparative performance analysis through theoretical simulations, details the mechanical, software and electronics architecture of the chosen design, as well as the dedicated optical setup design to characterize repeatability, precision, and thermal stability. The resulting performance of the chosen FM2 mount is then evaluated against the specified requirements for BlueMUSE.

astro-ph.IM↗

arXiv2024

The Blue Multi Unit Spectroscopic Explorer (BlueMUSE) on the VLT: science drivers and overview of instrument design

BlueMUSE is a blue-optimised, medium spectral resolution, panoramic integral field spectrograph under development for the Very Large Telescope (VLT). With an optimised transmission down to 350 nm, spectral resolution of R$\sim$3500 on average across the wavelength range, and a large FoV (1 arcmin$^2$), BlueMUSE will open up a new range of galactic and extragalactic science cases facilitated by its specific capabilities. The BlueMUSE consortium includes 9 institutes located in 7 countries and is led by the Centre de Recherche Astrophysique de Lyon (CRAL). The BlueMUSE project development is currently in Phase A, with an expected first light at the VLT in 2031. We introduce here the Top Level Requirements (TLRs) derived from the main science cases, and then present an overview of the BlueMUSE system and its subsystems fulfilling these TLRs. We specifically emphasize the tradeoffs that are made and the key distinctions compared to the MUSE instrument, upon which the system architecture is built.

astro-ph.IM↗