Research On Bds Real-time Precise Orbit Determination And Technology Of Enhanced By LEOs

Since 27 December 2012,the Beidou regional navigation system has provided the regional services over the Asia-Pacific region with 14 BeiDou satellites,including 5 Geostationary Orbit(GEO)satellites,6 Inclined Geosynchronous Orbit(IGSO)satellites and 3 Medium Earth Orbit(MEO)satellites.By 2020,there will be 35 BeiDou satellites in outer space,including 5 GEO satellites,3 IGSO satellites and 27 MEO satellites,and the BeiDou global satellite navigation system will be completed.Satellite orbit is the spatial reference of the navigation system and an important index to measure the service capability of the system.With the developing of BDS,the demand to provide the real-time service is more urgent.The high-precision real-time orbit is the foundation and key to meet the real-time PNT service.The globally distributed ground tracking stations play vital roles in satellite orbit determination,limited by political factors and national land area,fully controlled BDS ground monitoring stations are all located in China and difficult to achieve global establishment in a short period of time.Therefore,it is of great significance to study BDS satellite real-time orbit determination using regional ground monitoring network in China to provide real-time PNT services at this stage and and in the future.However,it is not possible for IGSO and MEO satellites to form continuous coverage tracking through regional ground stations,limiting the precision of IGSO and MEO satellite orbits.At the same time,the geometrical configuration of GEO satellites and ground monitoring stations remains essentially unchanged,resulting in poor precision of GEO orbit determination.Therefore,how to improve BDS orbital accuracy,especially the real-time orbital product accuracy is the urgent problem for BDS.Based on this,the dissertation focuses on the real-time orbit determination of satellites,the main research contents and the results are as follows:(1)Aiming at the calculation problem of high-precision real-time orbit calculation of BDS satellites,the key two technologies of parameter elimination and recovery and double difference ambiguity fixed are studied.Then the long arc sliding window real-time orbit determination method is proposed.Also the specific processes and strategies are optimized.The results of real-time precise orbit determination of satellites using global ground monitoring stations are as follows: the real-time orbital precision of GEO,IGSO and MEO satellites was 2.3 m,25 cm and 15 cm,.The precision of the real-time orbits of GPS,GLONASS and GALILEO satellites obtained in the same way was 5 cm,12 cm and 12 cm respectively.In addition,the precision of real-time orbital products of 4 BeiDou-3 experimental satellites was firstly revealed,using observations from eight iGMAS stations.(2)Aiming at the problem that the number of BDS ground control stations is small and the stations are all distributed in China,using the long arc sliding window real-time orbit determination method,the influence of 5 factors on the precision of BDS regional real-time orbit determination is analyzed.Specifically,the 5 factors include the including the ambiguity fixed of different types of satellites,the number of regional ground monitoring stations,the length of the observation data arc,the selection of solar pressure perturbation model and multi-system combination orbit determination.Then,the optimal strategy of orbit determination under regional stations distribution is put forward.The experimental results show that: selecting 27 uniformly distributed ground area monitoring stations in China,using 72 h arc length of the BDS/GPS multi-system observation data,adopting ECOM 5 parameters model of the solar pressure perturbation,can achieve a better orbital accuracy.The precision of GEO,IGSO and MEO satellites orbit was about 113.7 cm,11.5 cm and 9.2 cm,respectively.If the above strategy was used for BDS single system orbit determination,approximate equivalent orbital accuracy can be achieved.GEO,IGSO and MEO satellites orbital accuracy was about 109.7 cm,19.1 cm and 14.4 cm,respectively.(3)In order to solve the problem that orbital accuracy of BDS satellites is limited by regional ground monitoring stations,the technology of combining LEO satellites with ground monitoring stations to enhance the precision of BDS orbit determination is put forward.The technical characteristics and the orbit determination principle are systematically analyzed.The mathematical model of the joint processing of the ground monitoring stations and the LEO satellite spaceborne observation data is studied.And the specific data processing flow and strategy are designed.The numerical experiments show that the real-time orbital precision of GPS satellites was increased from 28.6 cm to 22.4 cm,19.1 cm and 13.8 cm after adding 1,2 and 3 LEO satellites,with increasing rates of 21.7%,33.1% and 51.7%,respectively.At the same time,Combining with the observation data of FY3 C satellite and regional ground monitoring stations to enhance the precision of BDS satellites orbit determination is analyzed.The experimental results show that the real-time orbital precision of BDS GEO,IGSO and MEO satellites was increased from 774.7 cm,108.5 cm and 203.9 cm to 110.4 cm,91.1 cm and 106.6 cm,with increasing rates of 85.7%,16.0% and 47.7%,respectively.The research results show that the technology of using LEO satellites to enhance BDS satellites orbit determination can effectively improve the real-time orbital accuracy of BDS satellites.(4)Aiming at the problem of improvement of the low precision of BDS GEO satellite orbit determination,the technology of combining LEO satellites with ground monitoring stations to enhance the precision of BDS orbit determination is designed.The experimental,using FY3 C satellites and 29 ground monitoring stations distributed around the world,is analyzed,it was concluded that the technology can improve the real-time orbit accuracy of GEO satellites from 225.3 cm to 115.3 cm,Specially,the improving effect of along component was the most obvious and the cross direction was the least.The research results show that LEO satellites can improve the geometric configuration of GEO satellites and ground monitoring stations,and then improve the accuracy of GEO satellites orbit determination.(5)In order to improve the service performance of BDS and to reduce the risk of inter-satellite links,a space-based enhancement system is designed.This system is expected to enhance BDS orbit determination and time synchronization using LEO satellites space-based monitoring stations and ground monitoring stations.The initial composition of the system is researched and proposed.The key elements involved in the system,such as the LEO satellite resources,the GNSS spaceborne receiver resources and data transmission are demonstrated.The optimal selection of related elements is analyzed.Also the system workflow is discussed and designed.The experimental results show that,according to the different delay of LEO satellite data with 0h,2 h and 12 h,the real-time orbital accuracy of GEO satellites was all about 150 cm,IGSO were 78.2 cm,79.4 cm and 87.6 cm,MEO were 91.3 cm,98.3 cm and 123.7 cm respectively.The research results have an important supporting role in the enhancement of BDS and the backup of inter-satellite links.