Study On The Orbit Determination Of COMPASS Navigation Satellites

Because of the importance of GNSS to the civil and military applications, a number of countries or regions in the world have developed or having been developing their satellite navigation systems. The satellite’s precision orbit determination (POD) is a key technique to the construction of the satellite navigation system. Concerning this issue, the paper pays attention on three problem:the POD of combining different altitude satellites, the POD and orbit prediction of GEO,/and the method to create the ephemeris autonomously for the navigation system based on crosslink. The main work and contribution are listed as follows:(1) The basic theory and method of POD for the satellite navigation system were introduced, and the advantage of various parameter estimation method was analyzed. A smooth function method was used to solve the discontinue problem of the right function of the dynamical equation in numerical integration, the validation of this method was verified using Keplerian orbit.(2) The dynamical model for POD of GEO/IGSO/MEO was constructed, and the measurement correction model was introduced. The method for constructing double difference operator was described in detail, and a non-difference algorithm which can eliminates the local parameter was presented.(3) A multi-satellite POD software was developed, which uses pseudo-ranges as observations. For this software, a double-difference method and a non-difference method was used to determinate orbits, with GPS or simulation data from regional stations as their measurements. It is shown that the accuracy of orbit determination for combining different altitude satellites is better than 10 meters.(4) The covariance expression of the ambiguity parameter was derived in the case where the carrier phase and pseudo-range data was used to determinate the orbit. Based on this expression, the effect of satellite’s altitude on the accuracy of ambiguity resolution was analyzed, and the factor limiting the precise estimation of the ambiguity parameter was point out. The carrier phase data of GPS and simulated data from regional stations were used to verify the accuracy of the orbit determination of navigation satellites.(5) The piecewise constant acceleration model, The pulse acceleration model, and impulse motor acceleration model was used to model the thrust force during the GEO maneuver, and the observations from TWTFT were used to validated these models.(6) The extended Kalman filter algorithm was used to determinate GEO orbit, and the algorithm was validated by observation data. It is shown that the accuracy of orbit is smoother during the maneuver stage with Kalman filter algorithm by proper constraint of the dynamical stochastic noise.(7) Based on the thruster force and satellite attitude observations of GEO, a thrust force model was constructed, and this model was validated by TWTFT observations. It is shown that the model can be used to predict the orbit during the orbit maneuver.(8) The advantages of different cross-link techniques were compared, the main error that affects the accuracy of crosslink was analyzed and correction model was presented. The polynomial model was used to solve the asynchronous problem in the two-way crosslink observations.(9) The time synchronization method based on the crosslink observations was presented. The algorithm involving one-step Kalman filter, the two-step Kalman filter and integrated Kalman filter was used to synchronize times between satellites. It is shown that the accuracy of synchronization depends on the accuracy of observation.(10) The theory and data flow chart of distribution process algorithm for autonav was presented. The algorithm includes one-step filter, two-step filter and SRIF were used to determinate the orbit in autonav mode, and the advantages of different methods were compared.(11) The unobservable rotation of the navigation constellation was studied based on the crosslink observations, the long term prediction accuracy of the orbit orientation of navigation satellites was analyzed, and the algorithm for getting rid of the unobservable rotation of constellation by constraining orientation of prediction orbit was derived and the detail process steps were given.(12)The autonomous orbit determination software for the distribution-processing mode with crosslink measurements was developed. The GPS precision ephemeris was used to simulate the crosslink observations and validate the accuracy of autonav. It is shown that, the accuracy of autonomous orbit determination is better than 3m during 60 days.