Overview of the Instrumentation for the Dark Energy Spectroscopic Instrument
Authors: DESI Collaboration  , Abareshi B. , Aguilar J. , Ahlen S. , Alam Shadab , Alexander David M. , Alfarsy R. , Allen L. , Allende Prieto C. , Alves O. , Ameel J. , Armengaud E. , Asorey J. , Aviles Alejandro , Bailey S. , Balaguera-Antolínez A. , Ballester O. , Baltay C. , Bault A. , Beltran S. F. , Benavides B. , BenZvi S. , Berti A. , Besuner R. , Beutler Florian , Bianchi D. , Blake C. , Blanc P. , Blum R. , Bolton A. , Bose S. , Bramall D. , Brieden S. , Brodzeller A. , Brooks D. , Brownewell C. , Buckley-Geer E. , Cahn R. N. , Cai Z. , Canning R. , Capasso R. , Carnero Rosell A. , Carton P. , Casas R. , Castander F. J. , Cervantes-Cota J. L. , Chabanier S. , Chaussidon E. , Chuang C. , Circosta C. , Cole S. , Cooper A. P. , da Costa L. , Cousinou M.-C. , Cuceu A. , Davis T. M. , Dawson K. , de la Cruz-Noriega R. , de la Macorra A. , de Mattia A. , Della Costa J. , Demmer P. , Derwent M. , Dey A. , Dey B. , Dhungana G. , Ding Z. , Dobson C. , Doel P. , Donald-McCann J. , Donaldson J. , Douglass K. , Duan Y. , Dunlop P. , Edelstein J. , Eftekharzadeh S. , Eisenstein D. J. , Enriquez-Vargas M. , Escoffier S. , Evatt M. , Fagrelius P. , Fan X. , Fanning K. , Fawcett V. A. , Ferraro S. , Ereza J. , Flaugher B. , Font-Ribera A. , Forero-Romero J. E. , Frenk C. S. , Fromenteau S. , Gänsicke B. T. , Garcia-Quintero C. , Garrison L. , Gaztañaga E. , Gerardi F. , Gil-Marín H. , Gontcho A Gontcho S. , Gonzalez-Morales Alma X. , Gonzalez-de-Rivera G. , Gonzalez-Perez V. , Gordon C. , Graur O. , Green D. , Grove C. , Gruen D. , Gutierrez G. , Guy J. , Hahn C. , Harris S. , Herrera D. , Herrera-Alcantar Hiram K. , Honscheid K. , Howlett C. , Huterer D. , Iršič V. , Ishak M. , Jelinsky P. , Jiang L. , Jimenez J. , Jing Y. P. , Joyce R. , Jullo E. , Juneau S. , Karaçaylı N. G. , Karamanis M. , Karcher A. , Karim T. , Kehoe R. , Kent S. , Kirkby D. , Kisner T. , Kitaura F. , Koposov S. E. , Kovács A. , Kremin A. , Krolewski Alex , L’Huillier B. , Lahav O. , Lambert A. , Lamman C. , Lan Ting-Wen , Landriau M. , Lane S. , Lang D. , Lange J. U. , Lasker J. , Le Guillou L. , Leauthaud A. , Le Van Suu A. , Levi Michael E. , Li T. S. , Magneville C. , Manera M. , Manser Christopher J. , Marshall B. , Martini Paul , McCollam W. , McDonald P. , Meisner Aaron M. , Mena-Fernández J. , Meneses-Rizo J. , Mezcua M. , Miller T. , Miquel R. , Montero-Camacho P. , Moon J. , Moustakas J. , Mueller E. , Muñoz-Gutiérrez Andrea , Myers Adam D. , Nadathur S. , Najita J. , Napolitano L. , Neilsen E. , Newman Jeffrey A. , Nie J. D. , Ning Y. , Niz G. , Norberg P. , Noriega Hernán E. , O’Brien T. , Obuljen A. , Palanque-Delabrouille N. , Palmese A. , Zhiwei P. , Pappalardo D. , PENG X. , Percival W. J. , Perruchot S. , Pogge R. , Poppett C. , Porredon A. , Prada F. , Prochaska J. , Pucha R. , Pérez-Fernández A. , Pérez-Ràfols I. , Rabinowitz D. , Raichoor A. , Ramirez-Solano S. , Ramírez-Pérez César , Ravoux C. , Reil K. , Rezaie M. , Rocher A. , Rockosi C. , Roe N. A. , Roodman A. , Ross A. J. , Rossi G. , Ruggeri R. , Ruhlmann-Kleider V. , Sabiu C. G. , Gaines S. , Said K. , Saintonge A. , Salas Catonga Javier , Samushia L. , Sanchez E. , Saulder C. , Schaan E. , Schlafly E. , Schlegel D. , Schmoll J. , Scholte D. , Schubnell M. , Secroun A. , Seo H. , Serrano S. , Sharples Ray M. , Sholl Michael J. , Silber Joseph Harry , Silva D. R. , Sirk M. , Siudek M. , Smith A. , Sprayberry D. , Staten R. , Stupak B. , Tan T. , Tarlé Gregory , Tie Suk Sien , Tojeiro R. , Ureña-López L. A. , Valdes F. , Valenzuela O. , Valluri M. , Vargas-Magaña M. , Verde L. , Walther M. , Wang B. , Wang M. S. , Weaver B. A. , Weaverdyck C. , Wechsler R. , Wilson Michael J. , Yang J. , Yu Y. , Yuan S. , Yèche Christophe , Zhang H. , Zhang K. , Zhao Cheng , Zhou Rongpu , Zhou Zhimin , Zou H. , Zou J. , Zou S. , Zu Y. 
Published: October 2022

Abstract
The Dark Energy Spectroscopic Instrument (DESI) embarked on an ambitious 5 yr survey in 2021 May to explore the nature of dark energy with spectroscopic measurements of 40 million galaxies and quasars. DESI will determine precise redshifts and employ the baryon acoustic oscillation method to measure distances from the nearby universe to beyond redshift z > 3.5, and employ redshift space distortions to measure the growth of structure and probe potential modifications to general relativity. We describe the significant instrumentation we developed to conduct the DESI survey. This includes: a wide-field, 3.°2 diameter prime-focus corrector; a focal plane system with 5020 fiber positioners on the 0.812 m diameter, aspheric focal surface; 10 continuous, high-efficiency fiber cable bundles that connect the focal plane to the spectrographs; and 10 identical spectrographs. Each spectrograph employs a pair of dichroics to split the light into three channels that together record the light from 360–980 nm with a spectral resolution that ranges from 2000–5000. We describe the science requirements, their connection to the technical requirements, the management of the project, and interfaces between subsystems. DESI was installed at the 4 m Mayall Telescope at Kitt Peak National Observatory and has achieved all of its performance goals. Some performance highlights include an rms positioner accuracy of better than 0.″1 and a median signal-to-noise ratio of 7 of the [O ii] doublet at 8 × 10−17 erg s−1 cm−2 in 1000 s for galaxies at z = 1.4–1.6. We conclude with additional highlights from the on-sky validation and commissioning, key successes, and lessons learned.