EGRET on the CGRO revealed the GeV gamma ray sky, from 1991 to 2000. The Large Area Telescope (LAT) on the Gamma Large Area Space Telescope (GLAST) is a major NASA mission, designed as the successor to EGRET. Launch is planned for the end of 2007. Compared to EGRET, the LAT will have sensitivity more than 25 times better, angular resolution 3 times better, and a 10-fold improvement in the high energy reach. Instead of the fewer than 300 hundred gamma ray sources discovered by EGRET, Fermi has seen 3033 in the 4-year source catalog, 3FGL, to appear in 2015.
The LAT consists of a silicon tracker (70 m2, for over 800,000 channels), a two ton cesium-iodide calorimeter, and a highly segmented anti-coincidence detector to reject charged cosmic ray backgrounds. Stanford University in California is responsible for the LAT , while the overall GLAST mission is run from the NASA Goddard Space Flight Center (GSFC, near Washington D.C.) .
The IN2P3 has made major contributions to the design and fabrication of the calorimeter, and to the gamma ray energy measurement algorithms. The CENBG team had a leading role in the characterisation of the calorimeter response in various accelerator beams, and using cosmic ray muons . Overall calorimeter responsibility is assigned to the Naval Research Laboratory (NRL, in Washington D.C.), with whom we work closely.
Within France, the CENBG group works closely with the other IN2P3 teams, in Montpellier and at the Ecole Polytechnique in Paris, as well as with the groups assigned to build the gamma ray source catalog during the first year of the mission, at the Service d’Astrophysique of the Commission d’Energie Atomique (SAp/CEA, Saclay, near Paris) and at the Centre d’Etudes Spatiales de Rayonnements (CESR, Toulouse). GLAST is an intensely international mission, and the CENBG group maintains close contacts with collaborators from the Italian Istituto Nazionale di Fisica Nucleare (INFN). The Bordeaux group is known and respected thoughout the collaboration.
14. B. Lott, F. Piron et al: Nucl. Instr. Meth. 560 395-404 (2006)