A robotic Focal Plane System (FPS) for the Sloan Digital Sky Survey V

Abstract

The Sloan Digital Sky Survey V (SDSS-V) is an all-sky spectroscopic survey of <6 million objects, designed to decode the history of the Milky Way, reveal the inner workings of stars, investigate the origin of solar systems, and track the growth of supermassive black holes across the Universe. This paper describes the design and construction of two robotic Focal Plane System (FPS) units that will replace the traditional SDSS fiber plug-plate systems at the Sloan and du Pont telescopes for SDSS-V. Each FPS deploys 500 zonal fiber positioners that allow us to reconfigure the fibers onto a new target field within 2-3 minutes of acquisition. Each positioner carries three fibers: two science fibers that feed the BOSS and APOGEE spectrographs and a third back-illuminated metrology fiber is used in conjunction with a telescopemounted Fiber Viewing Camera (FVC) to measure the absolute positions of the fiber heads. The 300 APOGEE fibers are distributed among the 500 positioners to maximize common field coverage. A set of fiber-illuminated fiducials distributed in and around the positioner array establish a fixed reference frame for the FVC system. Finally, six CCD cameras mounted around the periphery of the focal plane provide acquisition, guiding, and focus monitoring functions. The FPS is a key enabling technology of the SDSS-V Milky Way and Black Hole Mapper surveys.