Field retermination of APOGEE spectrograph MTP fiber connectors

Abstract

We discuss the field retermination of high-fiber count MTP fiber connectors used with the APOGEE spectrograph at Apache Point Observatory (APO) in 2021. We address lessons-learned, wear-analysis of removed MTPs, and throughput of the fiber train with the newly terminated fibers in SDSS-V. For the past decade the spectrograph at APO, as part of multiple incarnations of the Sloan Digital Sky Survey (SDSS), has relied upon rapid changes of ten MTP connectors, each containing 30 terminated fibers, and all contained within a custom gang connector system. These rapid changes enable the iterative plugging of the gang connector into multiple cartridges with different plug plates to observe various survey fields throughout the night. While robotic Focal Plane Systems have been developed for SDSS-V to replace plug plates, which will minimize the fiber connector cycles, we nonetheless reterminated the most heavily used MTP connectors. The connector cycles had far exceeded manufacturer lifetimes and the overall system throughput was degrading.