— What is dark energy? It's one of the key questions facing physicists today, because observations indicate that two-thirds of the universe's mass-energy content consists of that mysterious repulsive force. It's now come to light (heh, heh) that NASA is providing support for three potential space missions designed to delve into the nature of dark energy: SNAP, DESTINY and ADEPT.
The three proposals are all candidates for the Joint Dark Energy Mission, sponsored by NASA as well as the Department of Energy. Plans call for one of the proposals to be selected for launch in the 2011-2013 time frame. Here's a brief rundown on the three missions:
- ADEPT: The Advanced Dark Energy Physics Telescope would survey 100 million galaxies, creating a three-dimensional map showing the effect of dark energy on the universe's expansion rate during different epochs. Johns Hopkins University astrophysicist Charles L. Bennett, a veteran of the Wilkinson Microwave Anisotropy Probe's mission to measure the afterglow of the Big Bang, is the principal investigator.
- DESTINY: The 65-inch (1.65-meter) Dark Energy Space Telescope would observe more than 3,000 supernovae over its two-year primary mission to measure the expansion rate, followed by a sky survey at near-infrared wavelengths to measure how the large-scale distribution of matter in the universe has evolved since the Big Bang. Tod Lauer, an astronomer at the National Optical Astronomy Observatory, is the principal investigator.
- SNAP: The SuperNova/Acceleration Probe would measure thousands of distant supernovae and map hundreds to thousands of square degrees of the sky for weak gravitational lensing - providing two methods to check for dark energy's effect. Berkeley Lab's Saul Perlmutter, who was among the first to detect dark energy as the head of the Supernova Cosmology Project, is SNAP's principal investigator.