The Robotic Multi-Object Focal Plane System of the Dark Energy Spectroscopic Instrument (DESI)

TL;DR

The paper describes the design, construction, and validation of a complex robotic fiber positioning system for DESI, enabling large-scale spectroscopic surveys to map the universe's expansion.

Contribution

It presents the first comprehensive account of the DESI focal plane system, including innovative robotic fiber positioners and integration processes for large-scale astronomical instruments.

Findings

Successful deployment of 5,020 robotic positioners with micron-level precision.

System enables rapid reconfiguration within 2 minutes for large-scale galaxy surveys.

On-sky validation confirms system meets all key performance requirements.

Abstract

A system of 5,020 robotic fiber positioners was installed in 2019 on the Mayall Telescope, at Kitt Peak National Observatory. The robots automatically re-target their optical fibers every 10 - 20 minutes, each to a precision of several microns, with a reconfiguration time less than 2 minutes. Over the next five years, they will enable the newly-constructed Dark Energy Spectroscopic Instrument (DESI) to measure the spectra of 35 million galaxies and quasars. DESI will produce the largest 3D map of the universe to date and measure the expansion history of the cosmos. In addition to the 5,020 robotic positioners and optical fibers, DESI's Focal Plane System includes 6 guide cameras, 4 wavefront cameras, 123 fiducial point sources, and a metrology camera mounted at the primary mirror. The system also includes associated structural, thermal, and electrical systems. In all, it contains over 675,000 individual parts. We discuss the design, construction, quality control, and integration of all these components. We include a summary of the key requirements, the review and acceptance process, on-sky validations of requirements, and lessons learned for future multi-object, fiber-fed spectrographs.