On the method of determining onboard ephemeris data L1OC and L3OC GLONASS aimed at testing positioning algorithms in the GNSS receiver

The paper considers a method of determining GLONASS ephemeris data in the L1OC and L3OC digital form aimed at testing the algorithms of accurate navigation determinations in consumer navigation equipment. The task of determining long-term motion model parameters of a navigation spacecraft is set as nonlinear problem of designing a matching model. This task is unstable and according to the analysis is categorized as incorrect. The application of a traditional least squares method to determine the long-term motion model parameters of a navigation spacecraft does not allow to obtain equally accurate solutions of condition equations system when initial conditions and/ or iterations amount have been changed. In this respect, Tikhonov’s regularization method has been carried out. It is based on the application of additional prior information. The obtained results have been tested by the comparison of estimated navigation spacecraft position according to the adjusted (speed and acceleration) ephemeris data, long-term motion model parameters and SP3 final reference ephemeris published on the SVOEVP website. The long-term motion model parameters of GLONASS navigation spacecraft that were defined by regularizing algorithms, have allowed to calculate the position of navigation spacecraft orbital grouping in terms of four-hours fitting intervals within 0,2 m tolerance (maximum deviations according to module of estimated navigation spacecraft position from SVOEVP SP3 reference ephemeris).