Precise satellite-ground baseline determination

In order to calibrate the measurement error (range error, velocity error and angle error) of spaceflight telemetry, tracking and commanding (TT&C) systems, double-difference GPS system between the calibration satellite and the ground station is established and precise satellite-ground baseline solution is used as the comparative reference of the TT&C measurement. An extended Kalman filter (EKF) modeling the satellite-ground relative dynamics has been developed and a fixed-interval smoother is adopted to smooth the baseline solution of EKF forward and backward filters. Meanwhile, double-difference GPS carrier phase ambiguity is fixed by a cascading integer resolution method. To test and validate the precise baseline determination algorithm, a hardware-in-the-loop simulation platform is constructed with independently developed spaceborne dual-frequency GPS receivers and a SPIRENT GPS signal generator. The simulation results show that with the fixed-interval smoother, the baseline accuracy (rms, single axis) of better than 10cm is achieved. The precise baseline solution can be used to calibrate the TT&C measurement error.