arXiv subjects

Markus Thurneysen

Publications and source records attributed to Markus Thurneysen.

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↗

arXiv2024

Investigations on assembly and coverage for modular focal planes of multiplexed telescopes

Multiplexed surveys have the ambition to grow larger for the next generation of focal plane instruments. Future projects such as Spec-S5, MUST, and WST have an ever-growing need for multi-object spectroscopy (13,000 - 20,000 simultaneous objects) which demands further investigations of novel focal plane instrumentation. In this paper, we present a rigorous study of focal plane coverage optimization and assembly of triangular modules of alpha-beta fiber positioners with a 6.2 mm pitch. The main focus here is to examine different module arrangements namely, framed, semi-frameless, and fullyframeless assemblies. Framed and semi-frameless describe here the usage of a manufactured focal plate to hold the modules together and provide the correct focus and tilt to the fibers. Work on automatically generating such focal plates for project adaptability and ease of manufacturing will also be presented. On the other hand, the frameless approach proposes a connection method freed from the need of a focal plate. The following paper will also present their capabilities to meet the requirements for focal plane assembly such as focus, tilt and coverage.

astro-ph.IM↗

arXiv2022

25,000 optical fiber positioning robots for next-generation cosmology

Massively parallel multi-object spectrographs are on the leading edge of cosmology instrumentation. The highly successful Dark Energy Spectroscopic Instrument (DESI) which begun survey operations in May 2021, for example, has 5,000 robotically-actuated multimode fibers, which deliver light from thousands of individual galaxies and quasars simultaneously to an array of high-resolution spectrographs off-telescope. The redshifts are individually measured, thus providing 3D maps of the Universe in unprecedented detail, and enabling precise measurement of dark energy expansion and other key cosmological parameters. Here we present new work in the design and prototyping of the next generation of fiber-positioning robots. At 6.2 mm center-to-center pitch, with 1-2 um positioning precision, and in a scalable form factor, these devices will enable the next generation of cosmology instruments, scaling up to instruments with 10,000 to 25,000 fiber robots.

astro-ph.IM↗