Developing Engineering Model Cobra fiber positioners for the Subaru Telescope Prime Focus Spectrometer

TL;DR

This paper details the development, design validation, and testing of an engineering model for Cobra fiber positioners, crucial for the Subaru Telescope's Prime Focus Spectrograph, aiming to enable precise fiber positioning for astronomical observations.

Contribution

It introduces the design, assembly, and validation process of the EM Cobra fiber positioner, supporting large-scale production for the Subaru Telescope's spectrograph.

Findings

Validated design and performance of EM Cobra positioners

Reduced manufacturing costs through optimized assembly techniques

Confirmed reliability for large-scale deployment

Abstract

The Cobra fiber positioner is being developed by the California Institute of Technology (CIT) and the Jet Propulsion Laboratory (JPL) for the Prime Focus Spectrograph (PFS) instrument that will be installed at the Subaru Telescope on Mauna Kea, Hawaii. PFS is a fiber fed multi-object spectrometer that uses an array of Cobra fiber positioners to rapidly reconfigure 2394 optical fibers at the prime focus of the Subaru Telescope that are capable of positioning a fiber to within 5um of a specified target location. A single Cobra fiber positioner measures 7.7mm in diameter and is 115mm tall. The Cobra fiber positioner uses two piezo-electric rotary motors to move a fiber optic anywhere in a 9.5mm diameter patrol area. In preparation for full-scale production of 2550 Cobra positioners an Engineering Model (EM) version was developed, built and tested to validate the design, reduce manufacturing costs, and improve system reliability. The EM leveraged the previously developed prototype versions of the Cobra fiber positioner. The requirements, design, assembly techniques, development testing, design qualification and performance evaluation of EM Cobra fiber positioners are described here. Also discussed is the use of the EM build and test campaign to validate the plans for full-scale production of 2550 Cobra fiber positioners scheduled to begin in late-2014.