GLAST: the gamma ray large area space telescope

The Large Area Telescope (LAT) has been integrated and is currently under test to be ready for launch by NASA in 2008, as the main instrument on the Gamma-ray Large-Area Space Telescope (GLAST) mission. It will survey the sky in the energy range from 20 MeV to 300 GeV. The detector subsystem of the LAT will provide much better angular and energy resolution, effective area and field of view for gamma rays with respect to previous instruments. We present the LAT integration status, tests data taking and its scientific objectives together with the description of science tools preparation.