DESI

DESI
Name	DESI
Caption	The Mayall Telescope with DESI instrument
Location	Kitt Peak National Observatory, Arizona, United States
Established	2019 (commissioning)
Telescope	Nicholas U. Mayall 4-meter Telescope
Operator	Lawrence Berkeley National Laboratory
Purpose	Spectroscopic cosmology survey

DESI is a wide-field spectroscopic instrument and survey project designed to map the large-scale structure of the visible universe by measuring redshifts for millions of galaxies and quasars. The collaboration involves multiple national laboratories, universities, and observatories and builds on prior programs in observational cosmology to constrain models of dark energy, dark matter, and the expansion history of the universe. DESI operates on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory and integrates technologies and scientific goals developed in the contexts of experiments and missions such as SDSS, BOSS, eBOSS, LSST, Euclid (spacecraft), and WFIRST.

Overview

The DESI project was led by teams from Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, Fermi National Accelerator Laboratory, SLAC National Accelerator Laboratory, and participating institutions across the United States, Europe, and Asia, including University of California, Berkeley, University of Chicago, University of Michigan, University of Cambridge, Oxford University, Carnegie Mellon University, University of Tokyo, Peking University, and Max Planck Society. The instrument and survey design drew on heritage from programs at Cerro Tololo Inter-American Observatory, Palomar Observatory, Arecibo Observatory, Keck Observatory, and Subaru Telescope. DESI coordinated with initiatives such as Dark Energy Survey, Planck (spacecraft), Hubble Space Telescope, Chandra X-ray Observatory, GALEX, WISE, and Spitzer Space Telescope for target selection, calibration, and ancillary science.

Scientific Goals

DESI's primary cosmological objectives include precise measurements of the expansion history via baryon acoustic oscillations (BAO) and redshift-space distortions (RSD), improving constraints on dark energy models and testing predictions from Lambda-CDM and alternatives such as modified gravity frameworks explored by theorists at institutions like CERN, Perimeter Institute, Institute for Advanced Study, and Kavli Institute for Cosmological Physics. DESI aims to produce large-scale maps to refine measurements of the Hubble parameter alongside results from SH0ES, H0LiCOW, Planck Collaboration, and measurements from Type Ia supernova programs including teams at Carnegie Observatories and Harvard-Smithsonian Center for Astrophysics. The survey also targets neutrino mass constraints complementary to laboratory experiments such as IceCube Neutrino Observatory, Super-Kamiokande, DUNE, and KATRIN, and provides samples for galaxy evolution studies related to work at Sloan Digital Sky Survey, COSMOS (survey), CANDELS, DEEP2, and VIPERS.

Instrumentation and Design

DESI is mounted on the Nicholas U. Mayall 4-meter Telescope and incorporates a prime-focus corrector, a robotic fiber positioner system, and ten spectrographs. The design team included engineers from Lawrence Berkeley National Laboratory, SLAC National Accelerator Laboratory, Brookhaven National Laboratory, and industry partners such as Thales Group and Winlight Optics. The focal plane hosts 5,000 fiber positioners coordinated by control systems developed with software concepts from LSST Data Management and algorithms influenced by work at NASA Ames Research Center and National Optical-Infrared Astronomy Research Laboratory. The spectrographs split light into blue, red, and near-infrared channels, leveraging detector technologies developed by Teledyne, Hamamatsu, and teams at Columbia University, Caltech, and MIT. Calibration systems were informed by practices at Gemini Observatory, Very Large Telescope, Keck Observatory, and Subaru Telescope.

Survey Strategy and Operations

The DESI Bright Galaxy Survey and Dark Time surveys target emission-line galaxies (ELGs), luminous red galaxies (LRGs), and quasars (QSOs) selected using imaging from DECam, Pan-STARRS1, WISE, and GALEX. The survey footprint spans thousands of square degrees including fields overlapping with SDSS Legacy Survey, Stripe 82, COSMOS (survey), HETDEX, and southern fields used by DES. Observing operations at Kitt Peak National Observatory coordinated scheduling, weather monitoring, and maintenance with teams experienced from Palomar Transient Factory, Zwicky Transient Facility, and Dark Energy Camera operations. The project schedule and cadence were planned in consultation with initiatives such as Time-Domain Astronomy programs at LIGO Scientific Collaboration follow-up teams and multi-wavelength consortia including ALMA, VLA, and Chandra X-ray Observatory partners to enable transient and multi-messenger science follow-up.

Data Processing and Products

Data reduction and spectroscopic redshift determination pipelines were developed drawing on legacy software from SDSS, BOSS, and eBOSS and computational resources from NERSC, Lawrence Berkeley National Laboratory, Argonne National Laboratory, and Fermi National Accelerator Laboratory. The DESI collaboration produces data releases including raw frames, calibrated spectra, redshift catalogs, and value-added catalogs for stellar, galactic, and extragalactic science that interface with archives such as NASA/IPAC Infrared Science Archive, Vizier, Mikulski Archive for Space Telescopes, and virtual observatory standards advocated by International Astronomical Union. Quality assurance and validation activities referenced methodologies from Planck Collaboration, Gaia (spacecraft), HST Archives, and statistical frameworks developed at Institute for Advanced Study, Princeton University, and Stanford University.

Results and Publications

DESI has enabled measurements of BAO and RSD across redshift ranges complementary to results from BOSS, eBOSS, and 2dF Galaxy Redshift Survey, contributing to cosmological parameter estimation alongside constraints from Planck (spacecraft), SH0ES, and supernova compilations such as Union2 and Pantheon. Early science papers involved collaborations with groups at University of Portsmouth, UC Santa Cruz, University of Toronto, University of Pennsylvania, and were submitted to journals including The Astrophysical Journal, Monthly Notices of the Royal Astronomical Society, and Physical Review D. DESI data have supported studies of galaxy clustering, quasar physics, and Milky Way structure in synergy with surveys like Gaia (spacecraft), LAMOST, RAVE, and APOGEE. Outreach and education efforts mirrored programs at European Southern Observatory, Space Telescope Science Institute, and national observatories, while ongoing analyses continue to refine measurements relevant to theoretical programs at CERN, Perimeter Institute, and Kavli Institute for the Physics and Mathematics of the Universe.

Category:Astronomical surveys