Study On The On-orbit Estimation Of Antenna Phase Center Correction Model And Precision Orbit Determination Of The BeiDou Satellites

Precise,stable and reliable orbit products are the prerequisites for achieving high-precision positioning services for navigation satellites.The Bei Dou navigation satellite system contains three types of satellites,GEO,IGSO and MEO,and its precise orbit determination(POD)is more complicated.The precision orbit determination of navigation satellites mainly uses reduced dynamic orbit determination methods,and the errors involved mainly include geometric observation errors and dynamic model errors.The satellite antenna phase center correction(PCC)error is the main geometric error source at the satellite end.It is the deviation between the center of the mass(satellite's precision orbit)and the phase center of the transmitted signal.It will not only cause centimeters to the precision of the orbit overlap.The influence of the accuracy of the level will also have a centimeter-level accuracy impact on the estimation of the precision point positioning(PPP),such as the up-direction and the zenith tropospheric delay.The satellite dynamics model is mainly described by the solar pressure model.The true pressure act on the satellite is related to the satellite geometry,the optical properties and attitude.The solar radiation pressure is more complicated,and it is difficult to correct with the model as the satellite position changes continuously.At present,the solar pressure is mainly used model parameters for absorption.If there is an error in the solar pressure model,or the perturbation of the solar radiation cannot be well expressed,the influence on the absolute accuracy(SLR inspection)of precision orbit determination can be up to 20 cm.Therefore,it is very important for the satellite high-precision orbit determination to study the satellite antenna phase center correction model and the solar radiation pressure model.At present,the z-offset parameters of the phase center correction model of BDS-2 IGSO satellite antenna have relatively poor consistency between the orbit estimation results.The high accuracy on-orbit antenna phase center correction model of BDS-3 satellite is missing.The high-precision solar radiation pressure model of the BDS-3 satellite is missing.These problems limit the high-precision orbit determination of the BDS satellite.This paper focuses on the BDS-2/BDS-3 satellite antenna phase center correction(PCC)models and BDS-3 satellite solar radiation pressure(SRP)model.The main research results and innovations are summarized as follows:(1)The theoretical methods of the navigation satellite PCC modeling are systematically studied,including the relationship between the satellite PCC and the receiver PCC,the satellite antenna phase center offset(PCO)function model,and the satellite antenna phase center variation(PCV)function model.The establishment,development and update of GPS,GLONASS,Galileo and BDS satellite PCC models are summarized.In addition,the basic theory of establishing a priori SRP model is systematically studied,which is mainly analyzed from three types of analytical,empirical and semi-analytical semi-empirical models.And then,the advantages and disadvantages of the three types of models are studied and summarized.(2)For the high accurate PCO parameter estimations of the BDS-2 IGSO and MEO satellites,the correlation between PCO and orbit and clock offset parameters is studied and analyzed,and the influencing factors of PCO estimations are obtained.The PCO parameters were estimated and the uncertainty was evaluated using ground measured data.The difference between the PCO estimations of the IGSO and MEO satellites were analyzed,and the reasons for the difference were explored,and then,the defects of the pure empirical SRP model in the PCO estimations were revealed.Finally,the precision of the estimated PCO model is evaluated from the three aspects of orbit overlap,clock offset overlap,and PPP.The results show that the accuracy of the IGSO and MEO satellite orbit and clock offset overlapping have been improved,and the positioning accuracy in the Up-direction has been significantly improved by 24 mm(30%).(3)For the BDS-3 satellite,the SLR residuals of the precise orbit determination using the pure empirical ECOM1 model show a systematic variation with the eps-angle.Based on the size parameters of the CAST and SECM satellites,the precise SRP accelerations were obtained by the POD with the adjustable Box-wing model,and then the parameters of the a priori were estimated by the precise accelerations of the BDS-3 MEO satellites.The experimental results show that the a priori SRP model can significantly improve the accuracy of precision orbit determination,and the systemic variation of the SLR residual with the eps-angle is reduced from 14 cm to 5cm;meanwhile,the a priori SRP model can also improve the clock offset precision.(4)Aiming at the strong correlation between the x-offset and the SRP model parameters,the x-offset sequence has a "V"-shaped system problem.Reasonable constraint of the D0 parameter are imposed to eliminate the systematic variation error of x-offset sequences.The PCC models of BDS-3 MEO satellite of the transition signal combination(B1I/B3I)and new signal combination(B1C/B2a)were established,respectively,and their uncertainties were analyzed.In addition,when evaluating the uncertainty of the satellite PCC model,the influence of the receiver PCC error is usually ignored,thereby causing the problem that the accuracy of the model cannot be objectively evaluated.In this paper,the difference between the z-offset parameters is estimated using different receiver PCC models,which fills the uncertainty of the receiver PCC error on the satellite PCC estimation.(5)In view of the improvement of the accuracy of the joint orbit determination of BDS-2/3 satellite,the transition signal(B1I/B3I)and new signal(B1C/B2a)of BDS-2/3 satellites were evaluated from two aspects of carrier-to-noise ratio,multipath and noise characteristics.The precision of the BDS-3 satellite POD by using the transition signals and new signals is compared and analyzed.The influence of BDS-2/3 orbit determination accuracy by the estimated a priori SRP model and the refined PCC model is comprehensively verified.Finally,the refined BDS-2/3 satellite PCC model is compared with the ground-calibrated PCO model published by Bei Dou official.The PPP results show that the refined PCC model can significantly improve the Up-direction accuracy by 9.5mm(37.2%),compared with the PCO ground-calibrated PCO model.