2013年世界导航卫星回顾

首先以IGS（international GNSS service）的最终轨道产品为依据，具体介绍并验证了分析中心轨道综合的原理及方法。其次，针对产品一致性改正项，分析了其对综合轨道的影响，结果表明该项改正可以引起2 mm的轨道差异。最后针对试运行中的iGMAS轨道产品，通过对综合轨道质量稳定性和抗差性分析，进一步验证了本文给出的轨道综合方法适用于目前iGMAS分析中心多系统轨道。通过选定外部的参考产品，对iGMAS各个分析中心轨道产品及综合轨道的精度进行了初步分析。

Review of Global Navigation Satellite in 2013

Currently, analysis centers(ACs) of International GNSS continuous monitoring and assessment system (iGMAS) could provide precise GNSS orbit products. To improve the stability and reliability of orbit products for high-precision users, we usually combine the orbit products from ACs. In this paper, we present a robust least square method of combing satellite orbits from different solutions. We first verify this method by combining GPS and GLONASS final orbit products provided by IGS Analysis Centers. Results show that the RMS differences between our combined GPS orbits and those from IGS are about 4 mm, and the RMS differences between our combined GLONASS orbits and those from IGS are about 5 mm. As the orbits of different IGS ACs are calculated in different reference frames, we first transform the orbits of different IGS ACs to the reference frame of IGS combined solution independent exchange format (SINEX) solutions before orbit combination. Results show that this transformation can improve the quality of combined orbits up to 2 mm. We then apply this method to analyze and combine GNSS satellite orbit products provided by ten of iGMAS ACs. For most iGMAS ACs, results show that the precision of GPS final and rapid orbits are better than 2.5 cm, and the precision of GPS ultra-rapid orbits are better than 6 cm and 15 cm for observed part and predicted part, respectively. The precision of iGMAS combined final orbits are 2 cm, 2~3 cm and 6 cm for GPS, GLONASS and Galileo satellites, respectively. The precision of iGMAS combined final orbits are 1.5 m and 20 cm for IGSO and MEO/IGSO of BDS, respectively. The relatively lower precision for combined GEO orbits is due to the different satellite antenna phase center offset (PCO) models adopted by different iGMAS ACs.