Solar Two Gamma-Ray Observatory: a high-sensitivity telescope for intermediate high-energy gamma-ray astronomy

The Solar Two Gamma-Ray Observatory is a ground-based instrument designed to detect 20-300 GeV gamma rays by sampling the Cherenkov light generated as gamma rays and cosmic rays interact with the atmosphere. The observatory utilizes the solar two pilot power plant in Barstow, California which has the largest heliostat mirror area in the world. It has over 2,000 heliostats each with about 41 m2 mirror are. the total active are is over 75,000 m2. Thus, Solar Two Observatory has the potential to be the most sensitive ground-based gamma-ray detector between 20-300 GeV. The secondary mirror system, each capable of viewing 32 heliostats has been designed. The secondary mirror systems also include the photomultiplier tube camera, electronics, and heliostat field. The first secondary camera system is now being manufactured and tested.