Over its 5-year observing lifetime, DESI will measure the spectra of more than 30 million galaxies and quasars covering 14,000 square degrees. The DESI instrument will provide unprecedented multi-object spectroscopy incorporating a novel design.
DESI’s new corrector optics provides a 3-degree-diameter field of view that feeds a focal plate containing 5,000 robotic positioners. The positioners can be reconfigured within 3 minutes to measure the spectra of a new set of galaxies. Optical fibers mounted to the positioners extend 50 meters down the telescope to feed 10 broad-band spectrographs, each containing three detectors. The spectrographs cover a spectral range of 360 nanometers (nm) to 980 nm with a resolution of 2,000 to 5,000, enabling DESI to probe redshifts up to 1.7 for emission line galaxies and 3.5 for the lyman-α spectra from quasars.
All commands and data transfers are run by the Instrument Control System, while the data acquisition system ensures accurate targeting and fast analysis of large amounts of data.
The instrument has been mounted on the 4-meter Mayall Telescope in 2018. The construction and integration of the instrument is the result of collaborations between several institutions.