MINOR PLANETS EPHEMERIDES IMPROVEMENT - FROM JOINT ANALYSIS OF HIPPARCOS AND GROUND-BASED OBSERVATIONS

Two methods are considered for the improvement of the ephemerides of t he asteroids observed by the Hipparcos satellite. They utilize differe nt combinations of ground-based and space-based data. In particular, w e develop a method based on an analysis of the variance matrix in the least-squares solution of Hipparcos observations taken alone. Applicat ion and comparison of the results for (2) Pallas and (324) Bamberga ar e given. It is shown that one of the methods is less sensitive to the weighting of the equations of condition. This procedure can be applied to the improvement of the ephemerides of asteroids when the observati onal data consist of subsets of very different accuracies.