Research On High-Precision Orbit Determination Algorithm Of Low Orbit Satellite Based On Satellite-Borne GNSS

Many low-orbit satellites for different purposes have been successfully launched by countries all over the world.Low-orbit satellites are characterized by low orbital altitude,so many important scientific research missions choose low-orbit satellites as experimental carriers,such as gravity measurement,atmospheric detection,altitude measurement,etc.The advantages of satellite-borne GNSS are high precision,continuous observation and all-weather,so the technology has become the mainstream means of orbit determination of low-orbit satellites.This paper mainly studies the high precision orbit determination algorithm based on satellite-borne GNSS,including the study of the influence of atmospheric drag on the orbit determination of low orbit satellite and the low orbit satellite orbit determination by integrating the observation data of inter-satellite link.Through the research,the space-borne GNSS orbit determination algorithm has been improved to provide technical reference for some future engineering practice and scientific research project application.The main research contents are as follows:First of all,this paper describes the time coordinate system and space coordinate system involved in orbit determination of space-borne GNSS and their mutual transformation relationship.The observation model and linearization method of GNSS are described.The perturbation model of the low-orbit satellite is analyzed,and then the motion equation of the low-orbit satellite is established.The quality of the observed data was analyzed.Secondly,the maximum non-conservative perturbation force is studied,and the influence of atmospheric drag on orbit determination of low-orbit satellite is mainly studied.A model of atmospheric density suitable for dynamic orbit determination of low-orbit satellites is proposed and verified by simulation experiments.The atmospheric drag perturbation acceleration of low orbit satellite is calculated under different atmospheric density models.The satellite orbit was fitted for 4h and extrapolated for 48 h and 72 h to compare the influence of different atmospheric density models on orbit accuracy.The experimental results show that the orbit fitting and extrapolation results of the three-dimensional atmospheric density model are better than that of the one-dimensional atmospheric density model.Compared with the onedimensional atmospheric density model,the accuracy improvement of the threedimensional atmospheric density model DTM model for orbit extrapolation 48 h and72h is 12.9% and 9.5%,respectively.Finally,study the improvement of orbit determination accuracy by measuring data from inter satellite links.A method for improving GPS orbit determination results using KBR data was proposed.In response to the H-matrix defect rank problem using only KBR observation data,the orbit determination orbit was taken as the observation and the observation weight was determined based on the uncertainty of the orbit determination.A weighted least squares orbit improvement algorithm was constructed.Taking GRACE satellite as an example for simulation,based on the proposed algorithm,KBR data was used to improve the carrier phase orbit determination and pseudo range orbit determination of onboard GPS,and compared with GRACE satellite’s post precision orbit.The results showed that KBR data improved the tangential direction of carrier phase orbit determination by about 5%,and the tangential direction of pseudo range orbit determination by about 11%.