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. 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 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.