The Gamma-ray Large Area Space Telescope: an astro-particle mission to explore the high energy sky

The Gamma-ray Large Area Space Telescope (GLAST) is a space mission that will study the mostly unexplored, high energy spectrum (10 keV - 300 GeV) of photons coming from active sources or diffused in the Universe. The integration and test of all the subsystems of the telescope is almost completed, as the launch is currently scheduled by NASA for August 2007. We report on the basic design choices, on the status of the assembly and on the first results from ground tests of the Large Area Telescope (the main instrument onboard GLAST), with particular emphasis on the tracker subsystem which, with its 80 m² of active silicon surface, is by far the largest ever built for a space application