The Dark Energy Survey Collaboration has completed construction of the Dark Energy Camera (DECam), a 3 square
degree, 570 Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be
used to perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the
remainder of the time, and after the survey, DECam will be available as a community instrument. All components of
DECam have been shipped to Chile and post-shipping checkout finished in Jan. 2012. Installation is in progress. A
summary of lessons learned and an update of the performance of DECam and the status of the DECam installation and
commissioning will be presented.
The Dark Energy Camera and its cooling system has been shipped to Cerro Tololo Inter-American Observatory in Chile
for installation onto the Blanco 4m telescope. Along with the camera, the cooling system has been installed in the Coudé
room at the Blanco Telescope. Final installation of the cooling system and operations on the telescope is planned for the
middle of 2012. Initial commissioning experiences and cooling system performance is described.
The Dark Energy Camera (DECam) is the new wide field prime-focus imager for the Blanco 4m telescope at CTIO. This
instrument is a 3 sq. deg. camera with a 45 cm diameter focal plane consisting of 62 2k × 4k CCDs and 12 2k × 2k CCDs
and was developed for the Dark Energy Survey that will start operations at CTIO in 2011. The DECam CCD array is
inside the imager vessel. The focal plate is cooled using a closed loop liquid nitrogen system. As part of the development
of the mechanical and cooling design, a full scale prototype imager vessel has been constructed and is now being used
for Multi-CCD readout tests. The cryogenic cooling system and thermal controls are described along with cooling
results from the prototype camera. The cooling system layout on the Blanco telescope in Chile is described.
The Dark Energy Survey Collaboration is building the Dark Energy Camera (DECam), a 3 square degree, 520
Megapixel CCD camera which will be mounted on the Blanco 4-meter telescope at CTIO. DECam will be used to
perform the 5000 sq. deg. Dark Energy Survey with 30% of the telescope time over a 5 year period. During the
remainder of the time, and after the survey, DECam will be available as a community instrument. Construction of
DECam is well underway. Integration and testing of the major system components has already begun at Fermilab and
the collaborating institutions.
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). DECam includes a large mosaic CCD focal plane, a five element optical corrector,
five filters (g,r,i,z,Y), and the associated infrastructure for operation in the prime focus cage. The focal plane consists 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. 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.
DECam, camera for the Dark Energy Survey (DES), is undergoing general design and component testing.
For an overview see DePoy, et al in these proceedings. For a description of the imager, see Cease, et al in
these proceedings. The CCD instrument will be mounted at the prime focus of the CTIO Blanco 4m
telescope. The instrument temperature will be 173K with a heat load of 113W. In similar applications,
cooling CCD instruments at the prime focus has been accomplished by three general methods. Liquid
nitrogen reservoirs have been constructed to operate in any orientation, pulse tube cryocoolers have been used
when tilt angles are limited and Joule-Thompson or Stirling cryocoolers have been used with smaller heat
loads. Gifford-MacMahon cooling has been used at the Cassegrain but not at the prime focus. For DES, the
combined requirements of high heat load, temperature stability, low vibration, operation in any orientation,
liquid nitrogen cost and limited space available led to the design of a pumped, closed loop, circulating
nitrogen system. At zenith the instrument will be twelve meters above the pump/cryocooler station. This
cooling system expected to have a 10,000 hour maintenance interval. This paper will describe the
engineering basis including the thermal model, unbalanced forces, cooldown time, the single and two-phase
The Dark Energy Survey is planning to use a 3 sq. deg. camera that houses a ~ 0.5m diameter focal plane of 62 2k×4k
CCDs. The camera vessel including the optical window cell, focal plate, focal plate mounts, cooling system and thermal
controls is described. As part of the development of the mechanical and cooling design, a full scale prototype camera
vessel has been constructed and is now being used for multi-CCD readout tests. Results from this prototype camera are