  In this paper we describe the Dark Energy Camera (DECam), which will be the
primary instrument used in the Dark Energy Survey. DECam will be a 3 sq. deg.
mosaic camera mounted at the prime focus of the Blanco 4m telescope at the
Cerro-Tololo International Observatory (CTIO). It consists of a large mosaic
CCD focal plane, a five element optical corrector, five filters (g,r,i,z,Y), a
modern data acquisition and control system and the associated infrastructure
for operation in the prime focus cage. The focal plane includes of 62 2K x 4K
CCD modules (0.27"/pixel) arranged in a hexagon inscribed within the roughly
2.2 degree diameter field of view and 12 smaller 2K x 2K CCDs for guiding,
focus and alignment. The CCDs will be 250 micron thick fully-depleted CCDs that
have been developed at the Lawrence Berkeley National Laboratory (LBNL).
Production of the CCDs and fabrication of the optics, mechanical structure,
mechanisms, and control system for DECam are underway; delivery of the
instrument to CTIO is scheduled for 2010.
