The DESI project

Andreu Font-Ribera

In 2015, IFAE joined the Dark Energy Spectroscopic Instrument (DESI), an international project led by LBNL (USA). Together with groups at ICE (Institut de Ciències de l’Espai), CIEMAT (Centro de Investigaciones Energéticas, Medio Ambientales y Tecnológicas) and Universidad Autónoma de Madrid (UAM), IFAE designed and built the Guiding, Focus and Alignment cameras (GFA), a key hardware component of DESI.

Start of DESI observations in May 2021

After a successful commissioning during 2020 (temporarily interrupted by the pandemic), DESI finished the phase of Survey Validation in May 2021, and started the main survey observations. The instrument, and the GFAs, are performing very well, and after a few months of observations DESI is already the largest spectroscopic survey ever, with more than 10 million galaxy redshifts obtained. During the next 5 years, DESI will build the largest 3D map of the distribution of galaxies in the universe. This will allow us to unravel the mysteries of dark energy, the repulsive force that drives the accelerated expansion of the universe.

Figure 1: The disk of the Andromeda Galaxy (M31), which spans more than 3 degrees, is targeted by a single DESI pointing, represented by the large, pale green, circular overlay. The smaller circles within this overlay represent the regions accessible to each of the 5000 DESI robotic fiber positioners. In this sample, the 5000 spectra that were simultaneously collected by DESI include not only stars within the Andromeda Galaxy, but also distant galaxies and quasars. The example DESI spectrum that overlays this image is of a distant quasar (QSO) 11 billion years old. (Credit: DESI collaboration and DESI Legacy Imaging Surveys)