First performances of COMPASS RICH-1 Albrecht, E Albrecht E Baum, Günter Baum Günter Bellunato, T Bellunato T Birsa, R Birsa R Bradamante, F Bradamante F Bressan, A Bressan A Chapiro, A Chapiro A Cicuttin, A Cicuttin A Colavita, A Colavita A Costa, S Costa S Crespo, M Crespo M Cristaudo, P Cristaudo P Dalla Torre, S Dalla Torre S D'Ambrosio, C D'Ambrosio C Diaz, V Diaz V Pinto, SD Pinto SD Duic, V Duic V Fauland, P Fauland P Fabro, M Fabro M Finger, M Finger M Fratnik, F Fratnik F Giorgi, M Giorgi M Gobbo, B Gobbo B Lamanna, M Lamanna M Martin, A Martin A Pagano, P Pagano P Piedigrossi, D Piedigrossi D Schiavon, P Schiavon P Tessarotto, F Tessarotto F COMPASS RICH-1, designed in 1996 for hadron identification at high momenta in the COMPASS large angle spectrometer, is based on the use of MWPCs with large size CsI photon detectors. This choice, dictated by technical and economical considerations, has imposed VUV requirements for mirror reflectance and radiator transparency. The detector is now fully operative and its preliminary performances are presented. (C) 2003 Elsevier B.V. All rights reserved. 518 1-2 586-589 586-589 Elsevier Science BV 2004