Abstract:In Beidou satellite real-time precise orbit determination, the filtering method has a long convergence time when using the initial orbit parameter obtained from broadcast ephemeris. To solve this problem, an enhanced method is proposed in this paper: the initial orbit parameter is derived by orbit fitting using the predicted part of ultra-rapid ephemeris and a constraint is introduced to the orbit parameter during a certain period after filtering starts. To validate our method, 7 days’ real tracking data collected from 51 globally distributed MGEX stations are used to determine BDS satellites’ real-time precise orbit based on square root information filtering(SRIF). A 3-day solution obtained in a batch estimation is used as “truth” to evaluate the precision of the real-time orbit. Results show that, an average value of 15 hours is needed before the BDS satellites’ orbit comes to a steady state with high accuracy, while a rather stable result is obtained and no obvious convergence is found during this period when the new method is used. In addition, the RMS of GEO satellites’ orbit is better than 2.5 m, 20 cm and 30 cm in along-track, cross-track and radial respectively in 7 days; meanwhile, values better than 30 cm, 15 cm and 10 cm can be achieved for IGSO and MEO satellites respectively.