Study Of Precise Orbit Determination For GNSS Enhanced By LEO Satellite And Inter-Satellite Ranging

With the usage of inter-satellite link technology,the success of on board GNSS technology and continuous increase of important demand,a new method is provided for navigation satellite orbit determination based on the multi-souce observation.The precise orbit determination for GNSS Enhanced by inter-satellite link and LEO satellite data is of great significance in lowering the reliance of precision orbit determination of navigation satellites on ground stations and strengthening the system performance.With the application background of the precision orbit determination of China's Beidou global navigation satellite system in progress,the theories and methods of comprehensive utilization of ground observation data,LEO satellite data and inter-satellite link data for precision orbit determination of navigation satellites are studied in this paper.The main innovative points are as follows:1.The concept of joint orbit determination using space-based monitoring station(LEO)and Beidou satellite relying on inter-satellite link enhancement is put forward in this dissertation,which enriches the fusion orbit determination technological using multi-source observation,and the orbit determination technological innovation combining ground-based,space-based and inter-satellite link data can be achieved.A new approach to increase the orbit determination precision of navigation satellites is proposed,especially to improve precision orbit determination under the setting conditions of a certain regional monitor station;2.The principle of inter-satellite link two-way ranging system and the methods for inter-satellite distance acquisition,correction and processing in detail are inferred and the epoch planning method for observed inter-satellite link data in Ka band is given;the correlation between inter-satellite ranging observations after preprocessing and L-band observations and LEO satellite observations and navigation satellite priori orbit parameters after pretreatment is established.3.The mathematic model for combined orbit determination of navigation satellites based on LEO satellite enhancement and the kinetic model for LEO navigation and satellites suitable for combined orbit determination as well as the data processing flow are proposed.The orbit determination experiments of navigation satellite show that: if the data of a LEO satellite is added to the certain region station observation,the improvement in orbit determination precision of a navigation satellite is respectively around 11%~63%,25%~64% and 25%~65% in the radial,transverse and normal directions,and the more prominent improvement effect in the transverse and normal directions is shown by contrast with the radial direction;The first attempt of Beidou satellite orbit determination based on space-borne data enhancement is made.The results indicate that the orbit determination precision of LEO satellite in the transverse direction of GEO satellite is approximately doubled,while the orbit determination precision in the transverse direction of IGSO and MEO satellites is unobvious.4.The processing method combining Beidou inter-satellite data and ground data and the parameter estimation scheme are presented.By utilizing the measured inter-satellite link data of Beidou experimental satellite,the combined orbit determination experiment is conducted for verification,which analyzes the correctness of deviation parameter estimation method in the inter-satellite measurement system and the contribution rate of inter-satellite link data to the enhancement on orbit determination of the regional ground station of Beidou Satellite.The experiment results show that the time delay parameters of experimental satellite equipment estimated in different time are in stable short-term changes at an average value of about 0.036 m.The radial precision of orbit determination of the regional satellite station is around 1.0m by the utilization of laser inspection tests.Through the enhancement on inter-satellite link data,the radial precision of Beidou satellite orbit determination could be improved by an order of magnitude,and its precision was about 0.2m.The precision of some satellites is even better than 0.1m.5.The optimization design model for LEP satellite constellation based on space monitor station is proposed and the numerical grid mode based on the flying area of a navigation satellite is built as well as the rationality of such model by the satellite evolution analysis is verified.With the model as the quantitative index,the basic constellation configuration,orbit types,orbit altitude,number of satellites and other aspects are analyzed,and then the constellation parameter options of space-based LEO satellite is given which was applicable for navigation satellite monitoring.The analysis shows that the Walker constellation,consisting of sun-synchronous orbit satellite at a height of 500 km to 750 km,is suitable as space based monitor station and at least six low earth orbit satellites can satisfy full arc coverage of the navigation constellation.6.A systemic analysis and demonstration is made on the precision of orbit determination combining data from ground monitor station,LEO satellite and inter-satellite link.Through simulated analysis,the impact of the number of LEO satellites and orbit distribution on the precision of combined orbit determination is explored and the efficiency of LEO satellite and inter-satellite link data on combined orbit determination are compared.The results indicate that the orbits of 6 LEO satellites uniformly and rationally distributed could meet the demand of the combined orbit determination precision of a navigation satellite.By contrast with the orbit determination precision of a regional navigation satellite,the URE precision is improved from 0.155 m to 0.044 m,with the increase rate of up to 72%.7.Aiming at the differences between various data involved in orbit determination and the feature of system errors contained in inter-satellite data,the weighting method based on Helmert variance component estimation is proposed.Aiming at the limitations of the constraint of rigorous variance component estimation method on the number of parameters during the process of orbit determination,the data processing method for combined orbit determination parameter classification is presented.Compared to the conventional weighting strategy based on the observation precision,the precision of orbit determination by Helmert variance component estimation method could be increased from 0.075 m to 0.058 m,and the overall precision is increased by around 21%,and the precision in the radial,transverse and normal directions is respectively increased by around 31.8%,14.6% and 20.4%.