Calculation of the new series of the Earth orientation parameters in the HIPPARCOS reference frame.

Abstract

The succesful lauchch of the HIPPARCOS astrometric satellite by the ESA in August 1989 enables the past observations, obtained by optical astrometry all over the world since the beginning of the century, to be re-reduced in order to get the Earth orientation parameters in a homogeneous and unique celestial reference frame. Completely new algorithms, based on the information obtained from individual star observations rather than the traditional star group results, are proposed. In addition to the three fundamental Earth orientation parameters (coordinates of the instantaneous pole of rotation x, y and the integrated speed of the Earth's rotation UT1-UTC), the nutation angles (defining the position of the rotational axis in space) and some other relevent parameters will be obtained in a single global adjustment.