Further tracking experiments with OTS using the MITREX modem

Precision ranging tests with the 'Microwave Time and Ranging Experiment' modem MITREX and the ESA telecommunications satellite OTS are described. The tests were based upon a very-short-baseline interferometer consisting of two small earth-station antennas and two modems. The test objectives were to: (1) demonstrate the precision of the modem for measuring the range difference between neighbouring satellites. This is of interest in connection with orbit determination for geosynchronous clusters and rendezvous; (2) simulate a rendezvous configuration, using two antennas in place of satellites, and laser ranging between the antennas; (3) demonstrate the very-short-baseline interferometer for the angular tracking of geosynchronous satellites. The results demonstrate that precision ranging from the ground can meet the immediate requirements of cluster control and rendezvous for synchronous satellites. The use of the short-baseline interferometer from one ground station, equipped with small receive-only antennas, is also an interesting tracking option for geosynchronous missions.