Studies on Algorithm of High-Accuracy Intersatellite Clock Offset Measurement

Intersatellite clock offset measurement is one of the key techniques to implement intersatellite time synchronization. Two-way time transfer is one of the methods with the high-accuracy applied to clock offset measurement. Since satellite moves at high speeds, the propagation delay of two-way time transfer signals between moving satellites is not equal. Therefore, the clock offset obtained with this method does not equal the actual clock offset. On the basis of two-way satellite time transfer algorithm, a situation of two-way time transfer between moving satellites is considered. The impact of the motions of satellite on the propagation delay of two-way time transfer signals in this situation is discussed. The characteristics of the propagation delay of two-way time transfer signals between moving satellites varying with the intersatellite range are analyzed, and the rule of the intersatellite clock offset varying with the intersatellite range obtained with this algorithm is deduced. This paper presents a new dynamic two-way intersatellite clock offset measurement algorithm (DTWICOMA) with which high-accuracy intersatellite clock offset is measured through the combination of intersatellite pseudo-range polynomial fitting and clock-offset polynomial fitting. Simulation data of satellites showed that with the algorithm the intersatellite clock offset error can be controlled within 5ns. As a result the DTWICOMA can be used for high-accuracy intersatellite clock offset measurement between moving satellites.