Results of the CENSAR synchronization and orbit perturbation measurement experiments

The paper describes experiments with a TDMA synchronization system and the use of measurements in orbital perturbation studies. The Centralized Synchronization and Ranging (CENSAR) system measures effective delays through three satellite links and broadcasts relevant information to the network. User stations recover timing and control data to enable them to calculate their own delays to the satellite. Measurements have a precision of 1 ns and system timing errors are bounded by +10 ns. The measurements of link delays and knowledge of the locations of earth stations make possible solutions for satellite locations and the evaluation of the sensitivity of the solution to errors from various sources. The paper contains results of the sensitivity analysis, describes compensation for the major errors and demonstrates the close agreement between predicted and CENSAR-derived satellite position. Also included are data encompassing a stationkeeping exercise, showing the observability of some orbit perturbations.