Dark Energy Spectroscopic Instrument

Dark Energy Spectroscopic Instrument
Lawrence Berkeley National Lab/KPNO/NOIRLab/NSF/AURA · CC BY 4.0 · source
Name	Dark Energy Spectroscopic Instrument
Acronym	DESI
Location	Kitt Peak National Observatory
Country	United States
Established	2019
Telescope type	Multi-object spectrograph
Aperture	4-meter Mayall Telescope
Operator	Lawrence Berkeley National Laboratory

Dark Energy Spectroscopic Instrument The Dark Energy Spectroscopic Instrument is a ground-based astronomical facility built to map the large-scale structure of the Universe by measuring spectra of tens of millions of galaxies and quasars. The instrument uses robotic fiber positioners on the 4-meter Mayall Telescope at Kitt Peak to obtain redshifts with high multiplexing, enabling cosmological analyses that constrain dark energy, neutrino masses, and models of inflation. Major institutions and observatories across the United States and abroad collaborated to design, build, and operate the instrument.

Overview

DESI was installed on the Mayall Telescope at Kitt Peak National Observatory to conduct a wide-area spectroscopic survey targeting galaxies and quasars across cosmic time. The project was funded by agencies including the U.S. Department of Energy and the National Science Foundation and managed by national laboratories and universities such as Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, Fermi National Accelerator Laboratory, University of Washington, University of Chicago, and Pennsylvania State University. The program builds on prior surveys and facilities including Sloan Digital Sky Survey, Baryon Oscillation Spectroscopic Survey, 2dF Galaxy Redshift Survey, WiggleZ, and instrumentation heritage from projects like DECam and Hubble Space Telescope spectroscopic efforts.

Design and Instrumentation

The instrument couples a prime-focus corrector with an array of 5,000 robotic fiber positioners that feed ten spectrographs, each containing blue, red, and near-infrared arms. Its optical design ties to the heritage of wide-field correctors used at Kitt Peak National Observatory and shares engineering practices with projects at Lawrence Livermore National Laboratory and Brookhaven National Laboratory. The spectrographs employ volume phase holographic gratings and cryogenic CCD detectors provided by vendors and collaborators with expertise from LBNL Radiation Detection groups and teams affiliated with SLAC National Accelerator Laboratory. The fiber positioning system integrates control electronics and software architectures developed in conjunction with groups from University of California, Berkeley, Ohio State University, University of Michigan, and University of Portsmouth.

Survey Strategy and Operations

Survey planning was developed with input from cosmologists and survey scientists at institutions like Princeton University, Harvard University, MIT, Yale University, University of Pennsylvania, and University of Cambridge. The observing strategy includes a Bright Galaxy Survey, a Main Survey of luminous red galaxies and emission-line galaxies, and a quasar sample extending to high redshift. Nightly operations coordinate scheduling, calibration, and fiber assignment via pipelines maintained by teams at National Optical Astronomy Observatory, Space Telescope Science Institute, Carnegie Mellon University, and University of Wisconsin–Madison. Operations also integrate environmental monitoring from facilities such as Kitt Peak National Observatory weather stations and adaptive scheduling tools developed alongside software groups from University of California, Santa Cruz and University of Arizona.

Data Processing and Products

Raw spectral data are processed through calibration, extraction, redshift measurement, and catalog generation software created by collaborations including Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, Fermilab, University of Portsmouth, and University of Utah. Data releases provide spectra, redshift catalogs, targeting catalogs, and value-added products archived with data centers such as NOAO Science Archive and mirrored by institutional repositories at Lawrence Berkeley National Laboratory and Fermilab. Pipeline components draw on algorithms from teams associated with University of Toronto, University of Oxford, Max Planck Institute for Astronomy, Leiden University, and INAF groups, using machine-learning methods developed at Carnegie Mellon University and statistical tools from Imperial College London and University of Chicago.

Science Goals and Key Results

Primary scientific objectives include measuring baryon acoustic oscillations and redshift-space distortions to constrain the expansion history and growth of structure, thereby testing models of dark energy, modified gravity, and neutrino mass. The survey enables ancillary science in galaxy evolution, quasars, intergalactic medium studies, and Galactic archaeology, with contributions from research groups at Caltech, Stanford University, Columbia University, University of California, Berkeley, University of California, Santa Barbara, University of Illinois Urbana–Champaign, University of Texas at Austin, University of Toronto, University of British Columbia, and McGill University. Early results have refined measurements of the distance scale and growth rate, informed constraints on the sum of neutrino masses alongside inputs from Planck (spacecraft), and provided target catalogs for follow-up by facilities such as James Webb Space Telescope, Atacama Large Millimeter Array, Subaru Telescope, Keck Observatory, and Very Large Telescope.

Collaboration and Project History

The collaboration comprises hundreds of scientists and engineers from universities and national laboratories across North America, Europe, and Asia, including participating institutions like DESY, CNRS, Max Planck Society, ETH Zurich, University of Tokyo, Peking University, University of Sydney, Australian National University, and University of Cape Town. Project milestones include proposal selection by DOE and NSF panels, commissioning on the Mayall Telescope, first light observations, and staged public data releases coordinated by governance structures modeled after large survey collaborations such as Sloan Digital Sky Survey and LSST (Vera C. Rubin Observatory). The collaboration maintains working groups for science, software, instrumentation, and outreach, with leadership drawn from Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, Fermilab, University of Washington, and partner universities.

Category:Astronomical instruments Category:Spectrographs