Dark Energy Camera (DECam)

DECam is the new high-performance, wide-field CCD imager for the prime focus of the Blanco 4-m telescope
at CTIO.   The DECam imager contains 62 CCDs for science with 519 megapixels, and at the Blanco telescope's
prime focus, will image 3 square degrees (2.2 degree wide field) at 0.27 arcsecond/pixel resolution.

CALL FOR PROPOSALS for DECam Science Verification observing programs

The camera was built as part of the Dark Energy Survey (DES) Project by the DES Collaboration,
which is a Fermilab-led  international collaboration of over 120 scientists from 15 institutions and consortia
in the USA, UK, Spain, Brazil and Germany.   DECam is a facility instrument, available for all users (tentatively)
starting in late 2012. The DES Collaboration, in exchange for the instrument and a community pipeline will receive
525 nights over 5 years to carry out the Dark Energy Survey.   The project is funded by the DOE and NSF,
the funding agencies of the UK, Spain, Brazil, and Germany, and contributions from the Collaboration institutions.

Characteristics of DECam

• 3 square degree field (2.2 degree wide field of view), 519 megapixel imager, 0.27 arcsec/pixel
• New Prime Focus cage and 5-element optical corrector
• 62 2Kx4K LBNL red-sensitive CCDs,  (QE 60% at 0.4 mu, 90% at 0.9 mu).  Full frame read time is 17 seconds, with a read-noise of 7 e-/pixel.
• g,r,i,z,Y filters.  A "SDSS u" filter is on order from Asahi Spectra (Japan).  Expected Delivery date as of March 20 is August 31 2012. Filter transmission curve data (best available as of March 2012, please read notes.txt file for caveats).
• A hexapod will provide active control of focus and alignment.
• A "Community Pipeline" operated by NOAO will provide raw and processed (single and stacked frames, astrometric and rough photometric solutions).
• Data will be served from NOAO Science Archive.
• Preliminary Exposure Time Calculator (Excel spreadsheet, courtesy of Darren DePoy). This ETC includes the as-built optics tranmissions, filter transmissions and CCD quantum efficiencies, as a function of wavelength.  It should give reasonable estimates for stellar photometry with DECam, but it gives optimistic results for extended objects such as galaxies.  Efforts are underway to provide reliable extended-object photometry in the DECam ETC. 

DECam was delivered to the CTIO Blanco 4-m telescope in late 2011, and the installation is
proceeding during a shutdown of the Blanco which commenced 20 February 2012.
Commissioning will take place during mid-2012 (late in the 2012A observing season).

Dark Energy Survey

• Next-generation imaging sky survey ("Super Sloan") aimed at understanding the acceleration of the universe.
• 525 nights 2012-2017 to cover 5000 sq-degrees of the South Galactic Cap in five filters (grizY).
• Survey area overlaps with the South Pole Telescope and the VHS Vista Survey.
• Measures the dark energy equation of state parameter with four complementary techniques: galaxy cluster counts, weak lensing, angular power spectrum, type Ia supernovae
• Raw DES data will be public after 12 months through the NOAO Science Archive. As the DES progresses, and we work toward a smooth and efficient operation model of the main survey and its concomitant Data Management, single processed frames will also become available (resources permitting). A stable release of the NOAO Community Pipeline should also allow for the availability of single processed DECam images after 12 months.
• High level data products (catalogs, etc) available approximately 12 months after mid-survey, and again after the end of the survey
• Will enable a great deal of other science for the community, as did SDSS.
• See Dark Energy Survey website:  http://www.darkenergysurvey.org
• See the short presentation by DES Director Josh Frieman from the January 2011 AAS Meeting and a recent presentation by Tom Diehl from the January 2012 AAS meeting

The construction of the DES Project was organized into three sub-projects -  The construction of DECam (lead institution
is Fermilab), the DES Data Management System (lead institution is U. Illinois) and CTIO Facilities
Improvement Project (CFIP, lead institution is CTIO). The CFIP improvements included a new Telescope
Control System (TCS) for the Blanco 4-m telescope, a repaired & improved Blanco primary mirror support
system, and a new cleanroon in the Blanco dome to accomodate DECam and NEWFIRM (see update).

A radiometric all-sky infrared camera (RASICAM) has been built to monitor night sky conditions
to support DECam observations (i.e. detect and quantify the optical depth of clouds, and determine photometricity)

CTIO Contacts

• DECam Instrument Scientist:  Alistair Walker
• Science support:   David James, Andrea Kunder, Tim Abbott