Precise orbit determination of a geosynchronous satellite by Delta-VLBI method

An experiment was carried out to track a geosynchronous satellite by Delta-VLBI method for 17 hours in the 4 GHz frequency band. A real time VLBI system with the baseline of 46 km was used, in which the observed data at the substation were transmitted to the main station via a microwave data link. Seven quasars were observed as reference sources. The geometrical delay was estimated within 0.3 nsec in the case of the satellite observations and within 10-140 nsec in the case of the quasars. The final accuracy of the Delta-VLBI observables was approximately 2 nsec (60 cm). The satellite orbit was determined to the accuracy of 100 m using the Delta-VLBI observables in addition to range and angle data which were obtained by a conventional radio tracking method. It was proved that Delta-VLBI with appropriate baselines is a prospective method of precise tracking of a geosynchronous satellite for highly accurate orbit determination.