The Backup Program of the Dark Energy Spectroscopic Instrument’s Milky Way Survey

Abstract The Milky Way Backup Program (MWBP), a survey currently underway with the Dark Energy Spectroscopic Instrument (DESI) on the Nicholas U. Mayall 4 m Telescope, works at the margins of the DESI Main surveys to obtain spectra of millions of additional stars from the Gaia catalog. Efficiently utilizing times between ∼12° and 18° twilight and poor weather conditions, the MWBP extends the range of stellar sources studied to both brighter magnitudes and lower Galactic latitude and declination than the stars studied in DESI’s Main Milky Way Survey. While the MWBP prioritizes candidate giant stars selected from the Gaia catalog (using color and parallax criteria), it also includes an unbiased sample of bright stars (i.e., 11.2 ≲ G < 16 mag) as well as fainter sources (to G ≲ 19 mag). As of 2025 March 1, the survey had obtained spectra of ∼7 million stars, approximately 1.2 million of which are included in the DESI Data Release 1. The DESI spectra cover the wavelength range from 3600 to 9800 Å at a resolution λ /Δ λ varying from 2000 to 5000. The full survey, when completed, will cover an area of more than 21,000 deg 2 and include approximately 10 million Gaia sources, roughly equal to the number of stellar spectra obtained through the DESI Main Survey, while only utilizing ≈9% of all DESI observing time. This paper provides an overview of the MWBP, describing the target selection, observing strategy, and an introduction to the resulting data.

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Publication Details

Journal
The Astronomical Journal
Published
2026-05-13
DOI
https://doi.org/10.3847/1538-3881/ae5dd0
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
0.00

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article

The Backup Program of the Dark Energy Spectroscopic Instrument’s Milky Way Survey

D. Kirkby, Will J. Percival, Mika Lambert, Paul Martini et al.
The Astronomical Journal
Astronomy and Astrophysical Research
article

The Backup Program of the Dark Energy Spectroscopic Instrument’s Milky Way Survey

D. Kirkby, Will J. Percival, Mika Lambert, Paul Martini, Anand Raichoor, Michael S. Schubnell, Ting S. Li, J. Jimenez, N. Palanque‐Delabrouille, S. Nadathur, Gregory Tarlé, Andreu Font-Ribera, Boris Gaensicke, John Della Costa, Laurent Le Guillou, Alexander H. Riley, D. Bianchi, Ignasi Pérez-Ràfols, Axel de la Macorra, S. Bailey, Martin Landriau, M. E. Levi, Marc Manera, J. Aguilar, J. Guy, Eusebio Sanchez, Satya Gontcho A Gontcho, ChangHoon Hahn, Namitha Kizhuprakkat, ENRIQUE GAZTAÑAGA, Edward F. Schlafly, Daniel J. Eisenstein, Andrei Cuceu, R. H. Wechsler, Arjun T. Dey, Jeffrey H. Silber, Joan Najita, J. E. Forero-Romero, Steven P. Ahlen, Andrew P. Cooper, Aaron Meisner, Sergey E. Koposov, Guillaume F. Thomas, Biprateep Dey, R. Kehoe, John Moustakas, Monica Valluri, Wenting Wang, Shuo Li, Hao Zou, Luís F.O. Silva, Rong Zhou, C. Lamman, T. Claybaugh, Graziano Rossi, P. Doel, G Gutierrez, F. Prada, B. A. Weaver, R. Miquel, T. Kisner, Klaus Honscheid, C. Allende Prieto, Marc Manera, M Ishak, Stéphanie Juneau, Adam D. Myers, Francisco Prada, Donal Brooks, K. Fanning, D. Sprayberry
article en

Abstract

Abstract The Milky Way Backup Program (MWBP), a survey currently underway with the Dark Energy Spectroscopic Instrument (DESI) on the Nicholas U. Mayall 4 m Telescope, works at the margins of the DESI Main surveys to obtain spectra of millions of additional stars from the Gaia catalog. Efficiently utilizing times between ∼12° and 18° twilight and poor weather conditions, the MWBP extends the range of stellar sources studied to both brighter magnitudes and lower Galactic latitude and declination than the stars studied in DESI’s Main Milky Way Survey. While the MWBP prioritizes candidate giant stars selected from the Gaia catalog (using color and parallax criteria), it also includes an unbiased sample of bright stars (i.e., 11.2 ≲ G < 16 mag) as well as fainter sources (to G ≲ 19 mag). As of 2025 March 1, the survey had obtained spectra of ∼7 million stars, approximately 1.2 million of which are included in the DESI Data Release 1. The DESI spectra cover the wavelength range from 3600 to 9800 Å at a resolution λ /Δ λ varying from 2000 to 5000. The full survey, when completed, will cover an area of more than 21,000 deg 2 and include approximately 10 million Gaia sources, roughly equal to the number of stellar spectra obtained through the DESI Main Survey, while only utilizing ≈9% of all DESI observing time. This paper provides an overview of the MWBP, describing the target selection, observing strategy, and an introduction to the resulting data.

The Astronomical JournalVol. 171(6)
Institució Catalana de Recerca i Estudis Avançats (ES), Universitat Autònoma de Barcelona (ES), University of Wyoming (US), Space Telescope Science Institute (US), Fermi National Accelerator Laboratory (US), Institute of Space Sciences (ES), University of Arizona (US), Lawrence Berkeley National Laboratory (US), University of Waterloo (CA), Universidad de La Laguna (ES), The University of Texas at Dallas (US), University of Pittsburgh (US), Southern Methodist University (US), Shanghai Jiao Tong University (CN), Perimeter Institute (CA), University of Toronto (CA), University of Milan (IT), Durham University (GB), Chinese Academy of Sciences (CN), University of Cambridge (GB), National Tsing Hua University (TW), San Diego State University (US), Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR), University of Michigan (US), SLAC National Accelerator Laboratory (US), Brera Astronomical Observatory (IT), University of California System (US), Sejong University (KR), University of Warwick (GB), Sorbonne Université (FR), Institut d'Estudis Espacials de Catalunya (ES), Institute of Particle Physics (CA), Laboratoire de Physique Nucléaire et de Hautes Énergies (FR), Wyoming Department of Education (US), Center for Astrophysics Harvard & Smithsonian (US), National Observatory (BR), CEA Paris-Saclay (FR), Instituto de Astrofísica de Canarias (ES), Barcelona Institute of Science and Technology (ES), Institute of Space Science - INFLPR Subsidiary (RO), Universidad de Los Andes (BO), Instituto de Astrofísica de Andalucía (ES), Institut de Recherche sur les Lois Fondamentales de l'Univers (FR), Laboratoire Médiations (FR), University College London (GB), The Ohio State University (US), University of Portsmouth (GB), Universidad Nacional Autónoma de México (MX), Siena College (US), Universitat Politècnica de Catalunya (ES), Stanford University (US), University of Edinburgh (GB)
National Science Foundation, U.S. Department of Energy, Office of Science, Division of Astronomical Sciences
Openalex Percentile: Top 98%
Astronomy and Astrophysical Research
DOIOpen Access PDFOpenAlex
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