arXiv subjects

Stefane Caseiro

Publications and source records attributed to Stefane Caseiro.

4 recordsLinked to original sources

arXiv2026

Testing of a 15-Positioner Module Based on the MPS Design for Stage-5 Telescopes

Assessing the performance metrics of theta-phi micro-robotic positioners is a key step toward understanding their operational behavior and ensuring that they meet the specifications of Stage-5 astronomical facilities, including the Chinese MUST, the American Spec-S5, and the European WST. A detailed examination of these metrics enables a clear evaluation of the system's current capabilities while also revealing aspects that require further refinement, which in turn guides improvements in design and manufacturing. In this work, carried out in collaboration with Micro Precision Systems (MPS) in Switzerland, we present the results of positioning performance and angular tilt characterization conducted on a 6.2-mm-pitch robotic positioner module developed for high-density fiber placement in next-generation spectroscopic instruments. The prototype unit evaluated in this study was produced by MPS. The measured metrics, including positioning repeatability, datum repeatability, backlash, non-linearity, and angular tilt, are compared directly with the nominal performance targets defined for Stage-5 telescope systems.

astro-ph.IM↗

arXiv2026

Thermal Characterization of a 6-Positioner, 6.2-mm-Pitch Module for Stage-5 Telescopes

Ensuring thermal stability of robotic fiber positioners is essential for reliable operation in the real environments of Stage-5 telescopes, where temperature variations can influence mechanical behavior and impact fiber-target accuracy. We present the results of thermal qualification tests conducted on 6.2-mm-pitch robotic positioner modules developed for high-density fiber positioning in next-generation astronomical systems. The positioners were characterized at discrete temperatures spanning negative 20 deg C to positive 30 deg C, representative of expected operational conditions. At each temperature point, key performance metrics, positioning repeatability, hard-stop repeatability, backlash, and non-linearity, were measured and compared to nominal performance. Across the full temperature range, the positioners maintained stable behavior with no measurable degradation in any metric and no evidence of mechanical or electrical damage. These results confirm that the 6.2-mm-pitch architecture provides the necessary thermal resilience for deployment in Stage-5 telescope instrumentation.

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arXiv2025

Prototyping of 6.2-mm-Pitch Fiber Positioner Modules for Stage-V Telescope Instrumentation

Small-pitch populated focal planes are essential enabling technologies for the next generation of highly multiplexed astronomical instruments. As modern astrophysics relies on massive spectroscopic surveys to study dark energy, dark matter, and galactic assembly, the ability to observe thousands of targets simultaneously has become paramount. To achieve these ambitious scientific goals, optical fibers must be packed into the telescope's focal plane with unprecedented density and accuracy. This work reports on comprehensive prototyping activities for novel 6.2 mm-pitch alpha-beta (theta-phi) fiber positioner modules. Achieving reliable operation at this extremely miniaturized scale presents formidable mechanical and control-system challenges. We provide a detailed comparative analysis of two primary architectural approaches: trillium-based mechanisms and independently actuated robotic designs. A rigorous quantitative assessment was conducted for both prototype models. Critical metrics such as XY positioning repeatability, non-linearity, and gear backlash were evaluated, as these directly dictate the targeting accuracy of the fiber on the sky. Furthermore, we analyzed fiber tilt angles, a crucial factor given its severe implications for Focal Ratio Degradation and the subsequent loss of optical throughput to the spectrographs. Our analysis contextualizes these mechanical constraints with their direct implications for overall instrument performance and survey efficiency. Initial results are highly encouraging, indicating that these miniaturized positioners can successfully overcome spatial limitations while maintaining stringent tolerances. These promising metrics demonstrate that 6.2 mm-pitch modules are highly suitable for the next generation telescopes and the massive multi-object spectroscopic facilities.

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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.

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