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
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.
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
, M. Crocce, P. Fosalba, E. Gaztañaga