Combination of space geodesy techniques for monitoring the kinematics of the Earth

In the framework of activities of the International Earth Rotation and Reference Systems Service (IERS) Combination Research Centres (CRC), the french Groupe de Recherche en Geodesie Spatiale (GRGS) studies the benefit of combining four geodetic techniques (SLR, VLBI, GPS and DORIS) at the measurement level in order to obtain a global and consistent solution for Earth Orientation Parameters (EOPs): polar motion xp and yp, universal time UT and celestial pole offsets in longitude and obliquity d and d with a six-hour sampling, as well as weekly station positions. A one-year test period (the year 2002) has been chosen to prove the power of such a combination moreover worked out in a homogeneous global terrestrial reference frame. All techniques were processed with the same computational framework (GINS/DYNAMO) so with the same a priori models and a priori values for parameters. The optimal relative weights between each geodetic technique were obtained with an optimal variance component estimation method. The aim of this paper is to describe the processing and the precision level of each individual technique for EOPs, to show how we handled with the combination of techniques and to discuss some results.