The Dark Energy Spectroscopic Instrument (DESI) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations (BAO) and the growth of structure through redshift-space distortions (RSD) with a wide-area galaxy and quasar redshift survey. For that purpose the project is building a multifiber spectrograph for the Mayall 4-metre telescope at Kitt Peak, with the goal to obtain tens of millions of spectra to map the structure of the universe and study dark energy. 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 = ?/Æ? between 2000 and 5500, depending on wavelength. 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.

The DESI instrument will be used to conduct a five-year survey designed to cover 14,000 deg2. To trace the underlying dark matter distribution, spectroscopic targets will be selected in four classes from imaging data. We will measure luminous red galaxies (LRGs) up to z = 1.0, extending the BOSS LRG survey in both redshift and survey area. To probe the Universe out to even higher redshift, DESI will target bright [O II] emission line galaxies (ELGs) up to z = 1.7. Quasars will be targeted both as direct tracers of the underlying dark matter distribution and, at higher redshifts (2.1 < z < 3.5), for the Ly-alpha forest absorption features in their spectra, which will be used to trace the distribution of neutral hydrogen. When moonlight prevents efficient observations of the faint targets of the baseline survey, DESI will conduct a magnitude-limited Bright Galaxy Survey (BGS) comprising approximately 10 million galaxies with a median z Å 0.2. In total, more than 30 million galaxy and quasar redshifts will be obtained to measure the BAO feature and determine the matter power spectrum, including redshift space distortions
The Kitt Peak National ObservatoryÕs Mayall 4-meter telescope (Image: NOAO/AURA/NSF)
Aim of our participation

The Institute of Space Sciences (IEEC-CSIC) participates in the DESI project as part of the BCN-MAD Regional Participation Group (RPG), composed of ICE, IFAE, CIEMAT and IFT. We represent our RGP in the DESI Institutional Board. Our RPG is responsible for delivering the Guiding, Focus and Alignment units of DESI's focal plane. We are also responsible of delivering the guiding software for the instrument. We lead the Image Validation Working Group and participate in other Working Groups.
GFA unit delivered to LBL. It was mounted and tested in protoDESI in Summer 2016.
Recent developments

In May 2016 we passed the Critical Decision 3 Review. This is step in the reviewing process of the Department of Energy of the US after which the project and budget are approved. In August 2016, we delivered a GFA unit to LBL to be mounted in protoDESI, a small testing instrument for DESI. In September 2016, we participated in the testing campaign of protoDESI when it was mounted at the prime focus of the Mayall 4-m telescope.

Recent Publications
DESI collaboration, 2016, " The DESI Experiment Part I: Science, Targeting, and Survey Design", arXiv/1611.00036

DESI collaboration, 2016, " The DESI Experiment Part II: Instrument Design", arXiv/1611.00037

Honscheid, K., et al, 2016, " The DESI instrument control system", SPIE, 9913 Fragelius, P., et al., 2016, " ProtoDESI: risk reduction experiment for the Dark Energy Spectroscopic Instrument", SPIE, 9908

Senior Institute members involved

F. Castander, M. Crocce, P. Fosalba, E. Gaztañaga
Institute of Space Sciences (IEEC-CSIC)

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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya