The COMPASS experiment at CERN: present and future

COMPASS is a new fixed target experiment presently in operation at CERN. It consists of a modern two-stage magnetic spectrometer, with particle identification and calorimetry in both stages, which has started collecting physics data in 2002, and will run at the CERN SPS at least until 2010. First results obtained with a 160 GeV muon beam on a polarized deuteron target are presented for several physics channels under investigation: in the longitudinal target cofiguration, a very precise measurement of the structure function g, and the first precise measurement of Delta G/G, the gluon polarization in a polarized nucleon; in the transverse target mode, the first ever measurements of single spin asymmetries of the deuteron in DIS processes. An outline is also given of the physics programme of COMPASS with hadron beams, as well as the plans of the Collaboration for the near future. Topical to this workshop, are possible extensions of the presently approved COMPASS programme after 2010. A brief account is given of the present speculations of the Collaboration on this matter, which foresee both an increase of luminosity of the CERN SPS muon beam and a strengthening of the spectrometer.