Call for Proposals for DECam Science Verification

Science Verification of the Dark Energy Camera on the Blanco 4m Telescope

DEADLINE: April 15, 2012, at 11:59pm Mountain Standard Time

The wide-field optical imager, Dark Energy Camera (DECam), is expected to achieve first light in August 2012, and be commissioned during the August/September timeframe. Immediately after the engineering commissioning, which involves testing all of the components of the DECam system, we anticipate launching into a phase of Science Verification observations, which will be driven by a combination of staff and community proposals to fully test DECam as a scientifically productive system (including the camera hardware, control software, and data reduction and archiving systems).  More information about the capabilities and technical specifications of DECam, including the exposure time calculator, is available on the instrument webpage at 
          http://www.ctio.noao.edu/noao/content/dark-energy-camera-decam

With this call for proposals (CfP), we are announcing the opportunity for community involvement in the DECam SV process.  Proposals are due April 15, 2012.  This SV process is complementary and parallel to shared risk proposals submitted through the normal 2012B CfP.

What is "Science Verification"?

"Science verification" (SV) is observing time set aside for scientifically motivated proposals that thoroughly test the scientific operations of the instrument, while also producing imaging data products with high immediate and archival science value.  As part of commissioning, intensive science driven usage serves to identify and pursue subtle performance issues that may not be apparent during engineering quick-look checks, may be intermittent, or may arise only in special circumstances not explored in engineering tests (high airmass, very crowded fields). SV projects will also be used to optimize operating protocols and finalize automated data reduction pipelines. The total set of SV projects must characterize performance in all the scientifically interesting operating modes of the DECam system.  Finally, the observations should highlight DECam capabilities to the broadest possible community.
 
Our approach is to define and carry out a program of SV observations, using approximately 10 to 15 nights of 4-m time in two or three blocks, likely scheduled in September through November 2012.  These observations will be scientifically motivated investigations intended to produce new and interesting results, with some follow-on utility for data mining. The scale of the observing efforts may range from single PI runs with very specific objectives, to mini-surveys with multiple, perhaps exploratory, ends.  Note that one night with DECam can produce as much data as ten nights with Mosaic, so even one or two night runs may produce datasets of mini-survey scale.
 
Two parallel SV programs will be run to provide for broad coverage of the capabilities of the DECam system for the community.  The SV program for the Dark Energy Survey (DES) will test the specific survey capabilities in DES survey mode and ensure that the camera meets DES specifications.  The Community SV programs will test a broad range of observing capabilities in order to ensure that the camera meets community requirements and is producing data products that can serve the wide range of observational uses that are required for an NOAO facility instrument.
 
These data sets (both community SV and DES SV) will have no proprietary period. They will flow from pipeline reduction directly to a publicly accessible archive.  SV observations will be made as "shared risk", and observations may not be made as scheduled depending on instrument commissioning and performance.
 
 
Capabilities to be tested
 
We will test the broadest range of DECam capabilities allowed by time constraints with SV observations.  The following list includes many of the fundamental aspects of the system we plan to test with some combination of commissioning and SV observations.  The results of commissioning tests will be made available rapidly to the successful SV teams to allow for tuning the SV observations.  Proposers are encouraged to address how their observations will test these capabilities. We also encourage proposers to suggest additional instrument system tests that we should consider!
  • Image quality across complete field of view in all available filters (grizY, and possibly u)
  • PSF stability across the field of view as function of time, hour angle, etc.
  • Scattered light and ghosting vs position and brightness of sources (including sources off the focal plane, including the Moon)
  • Saturation (bright targets), impacts on lines/columns and cross-talk
  • Astrometry, and astrometric stability over time, hour angle, etc.
  • Precision photometry, repeatability as well as standardization
  • Precision flat-fielding, including dome flats vs twilight flats
  • Timing resolution (stability on multiple quick succession reads)
  • Short time exposures
  • Guider performance: in crowded fields, over long periods, with faint stars, and sensitivity to seeing, background illumination, and other conditions
  • Non-sidereal tracking
  • Varied observing protocols, including individual objects scattered across the sky, dithered exposures, "mapping" mode with various overlaps, etc.
  • End to end test of quick look/system health software
  • End to end test of DECam Community Pipeline
Note that DES SV observations will extensively test DES survey mode, in which the sky is mapped by taking images in a grid of roughly field-width offsets in all available filters.  While some community observations in this mode may be useful in testing the mode for use by community users, extensive use of this mode for community SV is not considered necessary.

 
Criteria for evaluation of SV Proposals
 
A panel of commissioning team scientists will review all of the SV proposals, and choose a selection based on both scientific impact and the ability to develop an overall SV plan that tests the broadest range of capabilities possible.  In addition to testing the capabilities listed above, evaluation criteria will include:
  • Tests of additional capabilities not listed above
  • Clear plan to analyze the data shortly after the observations, to provide rapid feedback regarding the performance of the DECam system
  • Previous experience involving reduction and analysis of large imaging datasets, including special capabilities (e.g., photometric, astrometric, or other specialized software)
  • Possibility of reducing data with alternative methods/pipelines, thereby providing external verification of the community pipeline reductions
  • Archival value of dataset for further data mining
  • The broader impacts of the proposed research, for example, in education and public awareness of science (e.g., public outreach images)
Complementarity to the DES survey observations will also be considered in the proposal evaluation.  

Additional information about DES survey observations can be found at http://www.darkenergysurvey.org/ , under the link to "Survey", and at these links:

"Update on Blanco 4-m Availability: 2012A Shutdown and DECam Commissioning and Science Verification in 2012B" - see p. 18 of NOAO Newsletter March 2012
"The Dark Energy Survey (DES) & Camera (DECam)" - slides from talk by Tom Diehl at January 2012 AAS meeting.
NOAO Newsletter March 2011, page 17
NOAO Newsletter March 2010, page 10
NOAO Newsletter September 2010, page 11
"Status of the dark energy survey camera (DECam) project" - Flaugher et al. 2010, SPIE Vol. 7735.

How to submit an SV Proposal
 
Individuals or groups wishing to participate in the science verification of DECam should submit proposals by sending email to decamsv@ctio.noao.edu before the proposal deadline of 15 April 2012. Details about the instrument capabilities are available at:
          http://www.ctio.noao.edu/noao/content/dark-energy-camera-decam
 
Proposals should be text-based, formatted with the following sections:
  1. PI and Co-I names and institutions (Last name, first name, email, & institution, one per line)
  2. Scientific Project Description (no more than 1 printed page)
  3. Technical description of observations, addressing how observations will be taken, including filters, exposure times, etc.  (no more than 2 printed pages)
  4. Description of how proposed observations test the DECam system capabilities (no more than 1 printed page)
  5. Description of plans for reduction and analysis of dataset, including description of previous experience and/or specialized software or existing pipelines.
SV proposals will be evaluated in the June/July timeframe as commissioning plans are finalized and successful proposers will be notified no later than 31 July 2012.  Upon notification, successful proposal teams will be expected to participate (via email) in the planning and coordination of SV observations in the September through November timeframe.  On-site participation in DECam observations will be optional, but successful teams may be invited depending on the success of commissioning and the stability of the SV observing schedule.