Astrometry of minor planets with Hipparcos.

Abstract

After the processing of 30 months of the observations carried out by Hipparcos it is possible to provide a reliable idea of the astrometric results to be obtained on the 48 minor planets included in the observing programme. Hipparcos observations are one-dimensional measurements of the separation of objects along a precessing scanning circle, these scanning circles are averaged over approximately 0.3 day yielding a reference great circle. The main output will consist of about 100 astrometric abscissae on a reference great circle for each minor planet with an individual accuracy of about 0.02arcsec. We discuss in this paper the reduction procedure and assess the systematic errors due to the shape and scattering properties of the asteroids. The use of the results to improve the orbital parameters of the minor planets as well as the link of the kinematical and dynamical frames is briefly touched upon in the last section.