Application of space-VLBI to satellite dynamics

The new VLBI observing technique-space-VLBI-has several aspects which will have implications in the field of geodynamics and satellite dynamics. We point out the particular characteristics of space-VLBI which distinguish it from the ground based VLBI, and from other space geodetic techniques. Three areas are reviewed: the kinematic, the dynamic and the measurements characteristics of space-VLBI. For satellite dynamics the application of space-VLBI delay and delay rate as satellite tracking data is particularly interesting. It has been demonstrated by simulations that this new type of tracking data can significantly contribute to the accuracy of orbit determination. We give a summary of the mathematical model concerning orbit and geodynamical parameter estimations. It implies applications for tying reference frames directly and to give orientation for geodynamic satellites in an extraterrestrial inertial frame. The accuracy requirements of orbit determination for these applications are very stringent - submeter level is needed while the satellites have unfavourable physical shapes in this respect. This poses a challenge for precise modelling and tracking. Simulation studies carried out by different groups are reviewed. Preliminary results indicate, that the submeter level may be achieved if special tracking techniques are applied.