arXiv subjects

Jonathan Wei

Publications and source records attributed to Jonathan Wei.

7 recordsLinked to original sources

arXiv2026

WST, the wide-field spectroscopic telescope: progress on the design of the instruments

WST, the Wide-field Spectroscopic Telescope is a proposed new facility that will provide a transformational gain in spectroscopic survey capability over existing facilities. The WST is a 12 metre class telescope equipped with instrumentation to provide simultaneous observations in both multiple-object spectroscopy and integral field spectroscopy modes. This paper will describe the status of the instruments being designed for the WST, the fibre positioner module, the low and high-resolution multiple object spectrographs, the integral field spectrograph, disperser technology, sustainable detector and cryostat technology, and the calibration system. An overview of the overall layout of the instruments within the WST facility will be provided.

astro-ph.IM↗

arXiv2026

Performance Testing of a Trillium-based 21-Positioner Module for Stage-5 Telescopes

Evaluating the performance metrics of theta-phi robotic positioners is crucial to gather insights into the system's behavior and ensure their reliability during operation in Stage-5 telescopes such as the Chinese MUST, the American Spec-S5 and the European WST. With a careful analysis of these metrics, a comprehensive characterization of the system's strengths is obtained, alongside a clear identification of aspects requiring improvement. Thus, providing potential avenues for streamlining and optimizing its design and functionality. In this paper we present the results of the positioning performance and angular tilt tests conducted on 6.2-mm pitch robotic positioner modules developed for high-density fiber positioning in next-generation astronomical systems. The fiber positioners from the tested prototype adopt a mechanical design based on the Trillium open design from the Lawrence Berkeley National Laboratory (LBNL) and were produced by the Japanese company Orbray. The evaluated performance metrics of positioning repeatability, datum repeatability, backlash, non-linearity, and angular tilt were measured and compared to the desired performance for Stage-5 telescopes. The positioners exhibited a generally acceptable performance, although noticeable anomalies affecting several metrics were identified and will require mitigation in subsequent prototypes. Nevertheless, the results indicate promising performance suitable for Stage-5 telescope instrumentation, provided that these issues are successfully resolved.

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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.

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arXiv2026

Advancing Control Electronics for Next-Generation Astronomical Fiber Robotic Positioners

Next-generation spectroscopic surveys require compact, high-density fiber robotic positioner systems achieving 5um precision, placing strict constraints on the size and the power budget of the control electronics. We present a compact control electronics architecture that drives 21 theta phi SCARA positioners (42 BLDC motors) on a single board, representing a significant increase in complexity compared to the electronics used in ongoing surveys such as SDSS V and DESI, where each positioner relies on dedicated hardware. The design integrates power distribution, CAN communication, and a synchronization line for simultaneous motion in high-density environments. Sensorless Field Oriented Control with collision detection and mechanical and magnetic hard-stop calibration enables accurate positioning without Hall sensors or encoders, reducing system cost and complexity. We describe the system architecture and performance validation, demonstrating that the module meets precision requirements while reducing the space required for control electronics and improving energy efficiency for future survey instruments.

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arXiv2026

WST Multi-Object Spectrograph Fiber Positioners:Development of a 32,000-Unit Precision Robotic System

The Wide-field Spectroscopic Telescope Multi-Object Spectrograph requires an unprecedented fiber positioning system comprising 30'000 low-resolution and 2'000 high-resolution positioners across a 3.1 deg squared field of view. Each robotic positioner must achieve 5um RMS positioning accuracy in a densely packed focal plane, representing a more than sixfold scale increase over current instruments like 4MOST and DESI. To mitigate risks associated with industrial-scale production of 32'000 precision mechanisms, WST is pursuing a multi-concept development strategy. Four distinct positioner architectures are being prototyped and tested by an international collaboration (EPFL, AIP, UKATC, AAO) using 6.2 mm pitch triangular modules of 63 units each or a new inline modular concept. Performance metrics including positioning accuracy, repeatability, reconfiguration speed, collision avoidance, and manufacturability are being systematically evaluated. Down-selection to one or two concepts is planned for 2026-2027 during the HORIZON Europe-funded conceptual study phase. Current prototype testing demonstrates feasibility of meeting specifications, supporting WST's path toward first light in the early 2040s as ESO's next major spectroscopic facility.

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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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