From a Berkeley Lab press release, April 30, 2015:
For the past several years, scientists at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory have been planning the construction of and developing technologies for a very special instrument that will create the most extensive three-dimensional map of the universe to date. Called DESI for Dark Energy Spectroscopic Instrument, this project will trace the growth history of the Universe rather like the way you might track a child’s height with pencil marks climbing up a doorframe. But DESI will start from the present and work back into the past.
DESI will make a full 3D map pinpointing galaxies’ locations across the Universe. The map, unprecedented in its size and scope, will allow scientists to test theories of dark energy, the mysterious force that appears to cause the accelerating expansion and stretching of the Universe first discovered in observations of supernovae by groups led by Saul Perlmutter at Berkeley Lab and by Brian Schmidt, now at Australian National University, and Adam Riess, now at Johns Hopkins University.
Read interviews with Michael Levi and David Schlegel, two key physicists who have been involved in DESI from the beginning, here.