Dark Energy Spectroscopic Instrument (DESI):

The Dark Energy Spectroscopic Instrument (DESI) will measure the effect of dark energy on the expansion of the universe.  It will obtain optical spectra for tens of millions of galaxies and quasars, constructing a 3-dimensional map spanning the nearby universe to 10 billion light years.

DESI will be conducted on the Mayall 4-meter telescope at Kitt Peak National Observatory starting in 2018.  DESI is supported by the Department of Energy Office of Science to perform this Stage IV dark energy measurement using baryon acoustic oscillations and other techniques that rely on spectroscopic measurements.