The Dark Energy Survey (DES) is a next generation optical survey aimed at understanding the accelerating expansion of the universe using four complementary methods: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. To perform the 5000 sq-degree wide field and 30 sq-degree supernova surveys, the DES Collaboration built the Dark Energy Camera (DECam), a 3 square-degree, 570-Megapixel CCD camera that was installed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO). DES started its first observing season on August 31, 2013 and observed for 105 nights through mid-February 2014. This paper describes DES “Year 1” (Y1), the strategy and goals for the first year's data, provides an outline of the operations procedures, lists the efficiency of survey operations and the causes of lost observing time, provides details about the quality of the first year's data, and hints at the “Year 2” plan and outlook.
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 Survey Camera (DECam) will be comprised of a mosaic of 74 charge-coupled devices (CCDs). The
Dark Energy Survey (DES) science goals set stringent technical requirements for the CCDs. The CCDs are provided by
LBNL with valuable cold probe data at 233 K, providing an indication of which CCDs are more likely to pass. After
comprehensive testing at 173 K, about half of these qualify as science grade. Testing this large number of CCDs to
determine which best meet the DES requirements is a very time-consuming task. We have developed a multistage
testing program to automatically collect and analyze CCD test data. The test results are reviewed to select those CCDs
that best meet the technical specifications for charge transfer efficiency, linearity, full well capacity, quantum efficiency,
noise, dark current, cross talk, diffusion, and cosmetics.
Large mosaic multiCCD camera is the key instrument for modern digital sky survey. DECam is an extremely
red sensitive 520 Megapixel camera designed for the incoming Dark Energy Survey (DES). It is consist of sixty
two 4k2k and twelve 2k2k 250-micron thick fully-depleted CCDs, with a focal plane of 44 cm in diameter and
a eld of view of 2.2 square degree. It will be attached to the Blanco 4-meter telescope at CTIO. The DES will
cover 5000 square-degrees of the southern galactic cap in 5 color bands (g, r, i, z, Y) in 5 years starting from
To achieve the science goal of constraining the Dark Energy evolution, stringent requirements are laid down
for the design of DECam. Among them, the
atness of the focal plane needs to be controlled within a 60-micron
envelope in order to achieve the specied PSF variation limit. It is very challenging to measure the
the focal plane to such precision when it is placed in a high vacuum dewar at 173 K. We developed two image
based techniques to measure the
atness of the focal plane. By imaging a regular grid of dots on the focal plane,
the CCD oset along the optical axis is converted to the variation the grid spacings at dierent positions on the
focal plane. After extracting the patterns and comparing the change in spacings, we can measure the
to high precision. In method 1, the regular dots are kept in high sub micron precision and cover the whole focal
plane. In method 2, no high precision for the grid is required. Instead, we use a precise XY stage moves the
pattern across the whole focal plane and comparing the variations of the spacing when it is imaged by dierent
CCDs. Simulation and real measurements show that the two methods work very well for our purpose, and are
in good agreement with the direct optical measurements.
The Dark Energy Camera is a new prime-focus instrument to be delivered to the Blanco 4-meter telescope at the Cerro
Tololo Inter-American Observatory (CTIO) in 2011. Construction is in-progress at this time at Fermilab. In order to
verify that the camera meets technical specifications for the Dark Energy Survey and to reduce the time required to
commission the instrument while it is on the telescope, we are constructing a "Telescope Simulator" and performing full
system testing prior to shipping to CTIO. This presentation will describe the Telescope Simulator and how we use it to
verify some of the technical specifications.
The Dark Energy Camera is an wide field imager currently
under construction for the Dark Energy Survey.
This instrument will use fully depleted 250 μm thick
CCD detectors selected for their higher quantum efficiency
in the near infrared with respect to thinner devices.
The detectors were developed by LBNL using
high resistivity Si substrate. The full set of scientific
detectors needed for DECam has now been fabricated,
packaged and tested. We present here the results of
the testing and characterization for these devices and
compare these results with the technical requirements
for the Dark Energy Survey.
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.