High accuracy on-ground attitude reconstitution for the ESA astrometry mission HIPPARCOS.

The ESA space-astrometry mission Hipparcos will provide a uniform and high-precision stellar catalogue of the whole sky. The data processing requires that the star coordinates in-the telescope focal plane be transformed into a common inertial reference frame. To correctly perform this transformation, the satellite three-axes attitude must be reconstituted within a specified accuracy (rms error of less than 0.1 arcsec on each angle) for the mission lifetime, by processing the data of the on-board attitude sensors: star mapper and gyros. In this paper, after an overview of the Hipparcos mission, the attitude reconstitution is formulated as a Gauss-Markov estimation problem and solved by processing only star mapper data. The Gauss-Markov procedure takes advantage from a guaranteed error linear model describing the attitude evolution over the desired time interval.