GLAST: The Gamma-ray Large Area Space Telescope

Initiated by the spectacular successes of the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory, the Gamma ray Large Area Space Telescope (GLAST) collaboration has been developing a next generation, high-energy gamma ray experiment. The goal of the GLAST mission is to image photons with sufficient angular resolution for unique, point source identification in the energy range of 10 MeV to greater than 100 GeV with good energy resolution and with a large field of view. Operating as a pair-conversion telescope, GLAST will use silicon microstrip detectors interspersed with thin layers of high-Z material to form an upper, tracker section which will be followed by a 10 radiation length deep, segmented calorimeter. The large area required to achieve the desired sensitivity and the development of ultralow-power electronics has led to a baseline configuration employing over 87 m2 of silicon microstrip detectors with approximately 1.3×106 channels. The GLAST instrument will operate with the tracker and the calorimeter acquiring data asynchronously and semi-independently, thus self-triggering on events as they occur.