Research on Backup Strategy of BeiDou Global Navigation System Constellation

Abstract

BeiDou Global Navigation System (BDS-3) will be fully completed by 2020, and provide global users with high-quality services including positioning, navigation and timing, global short messages communication (GSMC), international search and rescue(SAR) etc. Compared with the regional navigation system, the global navigation system serves a wider area and more users, and the consequences are more serious in the event of a service outage. It is necessary to study the backup strategy of the space segment as early as possible in the early stage of system operation. Firstly, the paper analyses the effects of three kinds of satellite in different positions on the system performance, then analyses the probability distribution of multiple satellites failure, and then puts forward the satellite backup strategy. From the perspectives of improving GSMC coverage and increasing the available time of SAR, combined with the remaining life and configuration of the satellites in orbit, the orbit positions of redundancy satellites are suggested. The analysis results show that if one or two satellites are backed up in three MEO orbital planes, the robustness of the system will be improved effectively, and the availability of the system will be guaranteed even if any satellite fails. Furthermore, if four satellites equipped with SAR and GSMC load are backed up in proper phase on the first and third orbit planes, the availability of GSMC service will reach 100% in the global scope, and the availability of SAR service will be significantly improved.