Characterizing robotic positioners under the influence of changing gravity vectors for future spectroscopic surveys
Abstract
Future (Stage V) spectroscopic surveys intend to accurately map billions of galaxies. To accomplish this goal, these surveys will employ highly multiplexed focal planes composed of robotic fiber positioners to accurately place individual optical fibers on targets of interest. The ambitious science objectives place stringent requirements on the mechanical performance of these positioners. Experience from previous surveys has shown that testing positioners under conditions closely resembling those on the telescope is of utmost importance during the prototyping and quality assurance phases of construction. We present an automated telescope simulator test stand that characterizes the performance of these positioners at different orientations, reproducing the changing gravity vectors encountered during telescope operations. The test stand aims to verify position stability down to 1 um, focus stability down to 5 um, as well as tilt variations lower than 0.4 deg. We discuss the design of our setup, along with early characterization of image quality due to turbulence and the compensation of the enclosure deformation via calibration using fixed spots. Finally, we present initial results of positioning stability tests using a prototype module built by Orbray Co., Ltd. This test setup fulfills an important need for integrated testing of advanced focal plane prototypes under conditions similar to on-telescope conditions.
Versions
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BibTeX
@misc{wuthrich2026characterizing,
title = {{Characterizing robotic positioners under the influence of changing gravity vectors for future spectroscopic surveys}},
author = {Johannes Wüthrich and Guandi Zhao and Banan Yamani and Léonard Lebrun and Sean MacBride and Andrin Fazan and Felipe Andrade-Oliveira and Marcelle Soares-Santos},
howpublished = {arXiv},
year = {2026},
month = jun,
doi = {10.48550/arxiv.2606.26821},
eprint = {2606.26821},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.26821},
}
RIS
TY - UNPB
TI - Characterizing robotic positioners under the influence of changing gravity vectors for future spectroscopic surveys
AU - Johannes Wüthrich
AU - Guandi Zhao
AU - Banan Yamani
AU - Léonard Lebrun
AU - Sean MacBride
AU - Andrin Fazan
AU - Felipe Andrade-Oliveira
AU - Marcelle Soares-Santos
PY - 2026
DA - 2026/06/25
PB - arXiv
DO - 10.48550/arxiv.2606.26821
UR - https://arxiv.org/abs/2606.26821
AB - Future (Stage V) spectroscopic surveys intend to accurately map billions of galaxies. To accomplish this goal, these surveys will employ highly multiplexed focal planes composed of robotic fiber positioners to accurately place individual optical fibers on targets of interest. The ambitious science objectives place stringent requirements on the mechanical performance of these positioners. Experience from previous surveys has shown that testing positioners under conditions closely resembling those on the telescope is of utmost importance during the prototyping and quality assurance phases of construction. We present an automated telescope simulator test stand that characterizes the performance of these positioners at different orientations, reproducing the changing gravity vectors encountered during telescope operations. The test stand aims to verify position stability down to 1 um, focus stability down to 5 um, as well as tilt variations lower than 0.4 deg. We discuss the design of our setup, along with early characterization of image quality due to turbulence and the compensation of the enclosure deformation via calibration using fixed spots. Finally, we present initial results of positioning stability tests using a prototype module built by Orbray Co., Ltd. This test setup fulfills an important need for integrated testing of advanced focal plane prototypes under conditions similar to on-telescope conditions.
ER -