GLAST, a Gamma-Ray Large Area Space Telescope

The GLAST LAT instrument has been designed for high precision gamma-ray detection in space. It will contain more than 80 m2 of single-sided AC-coupled silicon detectors. The design of the instrument will be described, and the predicted performance will be traced back to the scientific goals of the GLAST mission. The application in space will require stringent requirements for the silicon detectors, and the R&D work needed to put the instrument into space by 2005 will be described.