分类： 地球科学 >> 地球科学其他学科 提交时间： 2018-01-07
摘要： The BeiDou navigation satellite system (BDS) developed by China, and provided official service for Asia-pacific region freely since 2012. With development of BDS, BDS-based time transfer has become an important research direction in BDS’s application fields. At present, the main method of BDS-based time transfer is BDS Common View (BDS CV), which can reach nanoseconds magnitude. Hence, we investigate the performance time transfer based on BDS precise point positioning (PPP) toward UTC/TAI compute. In this contribution, we focus on UTC/TAI comparison based on BDS PPP by using developed quad-constellation GNSS software, which called National Time System Center’s (NTSC) Bernese. And a long-term data analysis is presented. The experiments include two parts: (1) The reliability of the software and multi-GNSS products; (2) The performance of the BDS PPP toward International UTC/TAI comparison. The experimental results reveal that the accuracy of NTSC’s Bernese GPS PPP can reach about 0.1 ns relative to BIPM TAI PPP solutions. Compared with BIPM TAI PPP solutions, the accuracy of GPS PPP solutions can achieve about 0.2 ns by using multi-GNSS precise products, such as GBM, COM. For BDS PPP solutions, the solutions of GPS PPP are regarded as reference values. It is demonstrated that the accuracy of time transfer based on BDS PPP can reach better 1 ns toward UTC/TAI comparison for the statistics of 30 days-arc solutions, while 0.1 ns magnitude can be achieved for the statistics of daily solutions due to the influence of the day boundary discontinuity. Moreover, four different processing strategies of BDS PPP which include tropospheric delay fixed, tropospheric delay and coordinates fixed, coordinates fixed, and BDS-only are tested. Results show that the comparable accuracy can be achieved for four processing strategies. Hence, one can conclude that the time transfer based on BDS-only PPP show a good performance toward UTC/TAI computation.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2017-12-02
摘要： GPS Precise Point Position (PPP) has become one of the main methods for time transfer in International Atomic Time (TAI) computation. The reliability and precision of TAI would be further increased with adding the new GNSS systems like Galileo and BeiDou. The Galileo initial service is officially launched on December 15, 2016, by the European Commission. This contribution investigates the possible performance of PPP time transfer with the Galileo constellation in the initial service phase toward UTC/TAI computation. We choose 7 stations with excellent external clocks to do Galileo PPP time transfer experiments. Daily RINEX files of 138 days, with a 30s sampling interval, were collected from December 15, 2016 until May 1, 2017. We designed seven solutions with different options on the parameter selection, products utilization and the frequency selection. For most links and solutions, the STD of time transfer differences between Galileo PPP and GPS PPP ranged from 0.2ns to 0.5ns. The time transfer performance was increased by fixing coordinates and/or troposphere delays to values obtained from GPS PPP. The results reveal that the stability of PPP time transfer with Galileo initial service could reach the level of sub-nanoseconds. The Galileo PPP technique will play a more important role in remote time transfer fields such as UTC/TAI computation.
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