Ams : a Particle Observatory in Space

The AMS spectrometer will be implemented on the International Space Station at the end of 2003 (or beginning of 2004). The instrument will be made of a superconducting magnet which inner volume will be mapped with a tracker consisting of 8 planes of silicon microstrips surrounded by several sub-detectors: a time-of-flight (TOF), a ring imaging Cherenkov (RICH), an electromagnetic calorimeter (ECAL), a transition radiation detector (TRD) and, possibly, a synchrotron radiation detector (SRD). The expected performances will be reviewed together with the physics goals : high statistics study of cosmic rays in a wide range of energies, search for primordial antimatter, search for non-baryonic dark matter and, to some extent, gamma-ray astrophysics. A simplified version of the spectrometer has already been flown during a precursor flight (june 2-12, 1998) on the Space Shuttle Discovery. The technical success together with the first physics results and their interpretation will be briefly reviewed.