UC Davis physicists are helping turn the world's largest solar-power farm into the most powerful ground-based gamma-ray observatory. Gamma rays offer clues to many mysteries about the universe, such as the birth of galaxies. Scientists detect gamma rays on Earth by collecting Cherenkov light, which travels at wavelengths in the visible spectrum but is too faint to be seen by human eyes. At ground level, Cherenkov light is typically spread out over a circle the size of a football stadium and lasts for a few billionths of a second. Solar farms, which are essentially large groups of very big mirrors, are particularly well suited for this task. The Solar Two farm under conversion, in the Mojave Desert at Barstow, Calif., has an array of 1,800 mirrors, each with an area of more than 400 square feet. At least 128 mirrors will be instrumented for the observatory by the end of 2001, surpassing the previous largest observatory, at the Sandia National Laboratory in New Mexico. Last week, at the American Astronomical Society annual meeting, researchers from the UC campuses at Davis and Riverside presented promising results of calibration tests of the telescope. "The $200 million infrastructure at Solar Two has been converted into a unique scientific resource," said UC Davis physics professor Mani Tripathi. "The cost would have been prohibitive to build such a detector from scratch." Tripathi and UC Davis senior engineer Britt Holbrook helped build the electronics for the camera at Solar Two and are now upgrading it with a state-of-the-art trigger system. They are also working with researchers at Lawrence Livermore National Laboratory to develop a new camera. Their collaborators on the overall project are UC Riverside astrophysicists Tumay Tumer, Gora Mohanty, Jeff Zweerink, Harry Tom and Umar Mohideen. The W.M. Keck Foundation supported the conversion effort with a grant of $1 million. Tripathi's work on the camera is supported by a $60,000 grant from the University of California. Color photos and graphics are online at .