  Astrometric issues for solar system studies are discussed. An overview gives
references and cover all aspects of the solar system where astrometry is
important: orbits of planets, moons, asteroids and NEOs, masses of asteroids,
occultations of asteroids and KBOs, and families of asteroids and KBOs. The
roles of astrometry from the ground, from Gaia and from a Gaia successor are
discussed, but not small-field astrometry from space. It appears from work with
CCD cameras at the 1.55 m astrometric reflector in Flagstaff that an accuracy
of 1 mas is the best possible from the ground during one night observing when
using ordinary telescopes, i.e. without wave-front correctors, and for field
sizes larger than 2 arcmin. It has been seen that the same accuracies can be
reached with the much larger 4-m class telescope on Hawaii although it is not
specifically designed for astrometry. The accuracy of 1 mas from the ground
refers mainly to non-moving point sources, but it is expected that 1 mas can be
reached from the ground for solar system bodies from many nights of
observations when phase effects are taken into account.
