Dear Colleague,

NASA and the Department of Energy have constituted a Science Coordination Group (SCG) for the Joint Dark Energy Mission (JDEM).

This group of scientists is aiding the agencies in establishing the preliminary requirements and capabilities of a Reference Mission design for JDEM. The SCG is meeting from October through December 2008. To ensure the widest input of ideas to the SCG, we would welcome your thoughts on topics that include, but are not limited to, the most important aspect of dark energy to be tested, the most promising methods for measuring dark energy, aspects of the mission that might enable other science and mission design (mirror size, plate scale, wavelength coverage, ...). The input can be either a comment in the box below or a .pdf file of a longer document (up to 3 pages) e-mailed to J.D. Myers (john.d.myers@nasa.gov).

The JDEM mission is currently under study for launch in approximately 2015. The high priority for the mission and endorsements are given in the SCG Charter document on the JDEM web site:
http://jdem.gsfc.nasa.gov/

The mission will be a wide-field optical-infrared telescope to determine through precision measurements the nature of the mysterious dark energy that dominates our universe. It will incorporate, at a minimum, the Baryon Acoustic Oscillation (BAO), Supernovae (SNe) and Weak Lensing (WL) techniques. The mission capabilities are under active development by the SCG. The SCG is considering mission parameters approximately in the range as follows:

• wavelength range of at least 0.7 - 1.7 microns
• single telescope with mirror size of ~1.4 meters
• Near-IR (HgCdTe) and possibly visible (CCD) detectors with a total pixel count of 100-150 million pixels
• Plate scale of 0.2 - 0.4 arcseconds; multiple filters and dispersers
• wide-field imaging survey of thousands of square degrees to a limiting depth of ~25th AB magnitude (S/N>15), detecting hundreds of millions of galaxies
• wide-field spectroscopic survey of tens of thousands of square degrees to measure redshifts for at least one hundred million galaxies
• repeated monitoring of fields of several square degree to 24.5th AB magnitude (S/N>100) per visit to yield thousands of SN Ia detections
• mission lifetime of 5 years

Your input would be very much appreciated. Submissions can be made at any time, but no later than December 5, 2008.

Sincerely,
Neil Gehrels (SCG Chair) on behalf of the SCG