Galileo三频非组合精密定轨模型及精度评估

不断丰富的多频信号为GNSS精密数据处理带来了新的机遇与挑战。本文首先推导了适用于多频非组合（UC）观测值的GNSS卫星精密定轨模型，并给出了多频UC模糊度的双差约束策略。在此基础上，本文基于全球分布的150个MGEX测站的观测数据，对UC模型和无电离层组合（IF）模型分别使用E1/E5a、E1/E5b和E1/E5a/E5b观测值进行了Galileo卫星精密定轨。采用与外部精密产品对比、轨道边界不连续性比较和卫星激光测距（SLR）检核等方法评估了不同策略的定轨精度。结果表明：双频情况下，本文提出的UC模型与目前常用的IF模型定轨精度基本一致，两者定轨结果的1DRMS差异在1 mm以内，钟差STD差异在0.01 ns以内，SLR残差差异在2 mm以内。使用E1/E5a/E5b观测值后，UC模型和IF模型的浮点解精度相较于使用E1/E5b观测值的结果有1~2 mm的改善。

Galileo triple-frequency uncombined precise orbit determination: model and quality assessment

Multi-frequency signals have brought new opportunities and challenges to global navigation satellite system (GNSS) precise data processing. In this contribution, the uncombined (UC) observation model suitable for multi-frequency precise orbit determination (POD) was derived, and the double-differenced constraining strategy for multi-frequency UC ambiguity was given. Afterwards, Galileo POD was carried out by using the observation data of 150 multi-GNSS experiment (MGEX) stations. Different solutions using E1/E5a double-frequency, E1/E5b double-frequency and E1/E1a/E5b triple-frequency observations based on UC model and the traditional ionosphere free (IF) model respectively are applied to generate Galileo orbits.The comparison with external precise orbit products, orbit boundary discontinuities comparison and satellite laser ranging (SLR) validation were used to evaluate the orbit accuracy of different solutions. The results showed that the UC model and IF model having comparable orbit accuracy for double-frequency solutions.The differences of orbit accuracy between UC and IF model are within 1 mm, and the differences of the estimated satellite clock and SLR residuals are within 0.01 ns and 2 mm, respectively. When triple-frequency observations (E1/E5a/E5b) were used, the accuracy of float UC and float IF solutions can be improved by 1~2 mm compared to that using E1/E5b observations.