Ground-based survey facilities: New opportunities for astrometry

Three types of facilities offer new opportunities for high accuracy astrometry. In the planning stages are extremely large telescopes (aperture > 20 meters) with adaptive optics, which will enable relative astrometry of faint sources with an accuracy of similar to 0.1 milliarcsec. Existing 4m class telescopes are already being used for large scale surveys with well understood errors and publicly available databases. Several dedicated survey telescopes are tinder construction, and the design of the most ambitious survey telescope-the Large Synoptic Survey Telescope-is advancing. Some of the outstanding questions that must be addressed in order to realize the full potential of the LSST and other survey facilities for astrometry are described briefly.