Status of the COMPASS experiment at CERN

The COMPASS experiment, in its initial phase, uses longitudinally polarised mu beams in the 100-200 GeV energy range, and polarised solid targets; its main focus is the measurement of Delta G/G, a key element in the nucleon-spin problem plus a wide range of semi- inclusive measurements in both longitudinally and transverse mu nucleon deep inelastic scattering to measure the flavor-dependent spin distributions of the quarks. In 2001, the apparatus was featured by all types of detectors of the initial setup; after a setting up period, all novel detectors could be operated at nominal conditions and be used in the off-line reconstruction. In this paper, the status of the 2001 data taking is reviewed and the plans for the 2002 are outlined. (4 refs).