Research On Core Algorithm Of GNSS Earth Station Observation Simulation System

The construction of satellite navigation system is a long-term systemic project. To reduce the debugging cycle of ground operation control system and space satellite system, and carry on the simulation test and the technical confirmation to the satellite navigation system quantitatively, it is imperative to build an earth station observation simulation system. The paper performed a systemic research on modeling, simulation and verification of GNSS earth station observation.Firstly, the satellite orbit model, signal space propagation error model and clock error model were introduced, based on the pseudo-random code ranging principle and laser ranging principle, and a chart of modular organization for simulation system was presented.Secondly, the paper studied the observation simulation algorithm respectively, aiming at the commonness and individuality of four kinds of observation which are monitor receiver observation, satellite-ground time synchronization observation, ground-ground time synchronization observation and laser ranging observation.In order to verify the earth station observations, a self-closing test method was presented. Five types of processing algorithm were used, such as Pseudo-range positioning, orbit determination, satellite-to-ground pseudo-range two-way time synchronization, satellite two-way time synchronization and laser time synchronization. These algorithms were used to processing the simulated data, and obtained meter-level precision of positioning, decimeter-level precision of orbit determination and nanosecond-level precision of time synchronization.Finally, two-way time synchronization was researched. The influence of the error sources to the time synchronization was analyzed. A method of observation differential correction was presented, by analyzing the influence of satellite-to-ground range variation on two-way time synchronization. It was demonstrated by a numerical simulation performed later that a precision of nanosecond could be reached by this method.The research work in the paper can satisfy the test demand of the master control station for the new generation satellite navigation system, and it has certain engineering application value.