The space-based high-precision time transfer method based on navigation constellation inter-satellite link

With the development of space technology with increasing number of spacecraft and its expanding orbit, a uniform and high performance timing method is urgently required to guarantee the efficient cooperation among spacecrafts. Inter-satellite link (ISL) of navigation constellation is widely used for precise orbit determination and time synchronization. Because the coverage of ISL extends to medium Earth orbits (MEO) and high Earth orbits (HEO) users, it can be used as an ideal space-based high-precision time transfer method. Highly depending on ephemeris parameters, current ISL based time synchronization method is inappliable to spacecraft with low-precision and incomplete space position information. A new dynamic delay correction method is proposed on the basis of dual-way ranging. Assume the Doppler or pseudo-range can be measured by the ISL terminal in users, the method can achieve high-precision time synchronization with middle-precision position information which is easily calculated and realized. Theoretic analysis shows that the timing accuracy is prior to 0.1 ns. Finally, experiments on time synchronization between BeiDou satellite and ground station which is used to simulate a spacecraft are conducted. The test results verify the validity of the method.