Research On The Zero-difference Dynamic Orbit Determination Method For LEO Satellites Using Space-borne GPS

Because of their special orbital height,Low Earth Orbit(LEO)satellites are very suitable to be platforms on which many scientific applications and tests can be completed.This means that LEO satellites have important strategic significance and scientific value.The precise orbit determination(POD)of low orbit satellites is the prerequisite and basis for the successful completion of scientific tasks.Because of its mature technology and unparalleled advantages,Space-borne GPS has become the main measure of precise orbit determination.This paper focuses on the zero-difference dynamic orbit determination of low-orbit satellites based on space-borne GPS,involving software implementation and cases of orbit computation,then draws some conclusions.The main works and contributions are as the following:(1)The observation and observation equations of space-borne GPS are introduced.The non-ionospheric combination observation model of the spaceborne dual-frequency receiver is given.The observation errors and correction methods are also expounded so that we can make preparations for next research of POD from the perspective of observation model.(2)This paper expounds the principle of POD for LEO satellite dynamics from the aspects of dynamics information and satellite motion state information.The mathematical process of orbit solving is given.In view of the problem that the clock bias parameters are too many in the least square batch processing method,the derivation process and implementation method of the clock bias parameters reduction algorithm are given.(3)Study the effects of Lagrange and Chebyshev interpolation accuracy of IGS precision ephemeris.Experiments show that the use of 13-order Lagrange interpolation or Chebyshev interpolation can achieve the position of GPS satellite at the accuracy of what LEO satellites POD need.And the interpolation performance of linear interpolation and spline interpolation for different interval IGS precise clock bias is analyzed.Experiments show that in the same case,the linear interpolation method is more accurate than the spline interpolation method,and in order to obtain the required time GPS satellite clock error,30-second interval precise clock bias can be used to interpolate.(4)Participate in programming,debugging,refining and testing a suit of POD software based on zero-difference dynamic method.This paper describes the functional structure of the software and the POD process.The software is used as a platform to calculate the orbit of the domestic micro-nano satellite APOD and the internationally renowned gravity satellite GRACE for several days,and the accuracy of the orbit determination is verified.The results show that the accuracy of the pseudo range and phase observations of APOD satellites is about 2m and 2.5cm respectively,which is in accordance with the satellite research project,the accuracy level based on the orbit overlap test is better than decimeter level;The accuracy of the GRACE-A satellite pseudo range and phase observations is about 0.9m and 1.2cm respectively,the accuracy level based on the orbit overlap test is about 7cm,compared with the PSO standard orbit,the three-dimensional position accuracy is about 12cm.