Abstract:

Navigation signal equipment group delay is assimilated into satellite clock corrections broadcasted in the navigation message. Considering the necessity to keep consistent with GNSS user algorithms for positioning and timing, it’s pointed out that the satellite clock offsets solved with inter-satellite ranging observations should also include the group delay of navigation payload onboard GNSS satellites. It was found that equipment delays of crosslink devices appear in observation equation in the form of combination with the group delay of navigation payloads: the sum of receiving equipment delay and the group delay forms combined receiving delay, while transmitting equipment delay subtracting the group delay forms combined transmitting delay. We made many efforts to discuss the method for dealing with the problem of equipment delay and two approaches were proposed: one is to estimate the combined transmitting and receiving delay parameters for each satellite, another is to estimate the delay bias (the sum of combined transmitting delay and combined receiving delay) parameters for each pair of directed linked satellites. Software for simulation and data processing has been developed and the feasibility of the proposed method and data processing strategy were validated by simulation analysis. The result indicates that. by implementation of both the two proposed approach, the accuracy of orbit and clock result would be significantly improved and the effect is nearly the same as if the combined delays have been exactly corrected.

Key words: Inter-satellite pseudorange, Equipment delay, Combined Equipment delay, Orbit determination, Clock solution