=-1.5truecm truecm 1truecm 0pt
Copenhagen University Observatory
Østervoldgade 3, 1350 Copenhagen K, Denmark
We discuss the possible photometric detection of microlensing events in GAIA observations and the subsequent analysis of the astrometric effect during such events. It seems that measurement of distances, proper motions and masses of MACHOs might be possible. We also discuss the photometric detection of a MACHO passing the face of a star which could be used to determine the proper motion of the MACHO. The discussion concludes that such detections will be rare, but they seem frequent enough to warrant further consideration in connection with GAIA.
Keywords: space astrometry; MACHO; microlensing; ROEMER; GAIA; photometry.
 A contribution to Future Possibilities for Astrometry in Space, a workshop at RGO, Cambridge, England, 19-21 June 1995