The DESI Experiment Part II: Instrument Design

TL;DR

The DESI instrument is a sophisticated, high-throughput spectrograph designed for a large-scale dark energy survey, capable of capturing thousands of spectra simultaneously over a broad wavelength range, enabling detailed cosmological measurements.

Contribution

This paper details the design and capabilities of the DESI instrument, including its fiber-fed spectrograph system and integration with the Mayall telescope for a major cosmological survey.

Findings

Instrument can take up to 5,000 spectra simultaneously.

Wavelength coverage from 360 nm to 980 nm.

Designed for a 14,000 deg² survey over five years.

Abstract

DESI (Dark Energy Spectropic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. The DESI instrument is a robotically-actuated, fiber-fed spectrograph capable of taking up to 5,000 simultaneous spectra over a wavelength range from 360 nm to 980 nm. The fibers feed ten three-arm spectrographs with resolution $R= \lambda/\Delta\lambda$ between 2000 and 5500, depending on wavelength. The DESI instrument will be used to conduct a five-year survey designed to cover 14,000 deg$^2$. This powerful instrument will be installed at prime focus on the 4-m Mayall telescope in Kitt Peak, Arizona, along with a new optical corrector, which will provide a three-degree diameter field of view. The DESI collaboration will also deliver a spectroscopic pipeline and data management system to reduce and archive all data for eventual public use.