GNSS Research Center, Wuhan University, Wuhan 430079, China.
School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China.
Sensors (Basel). 2019 Oct 8;19(19):4347. doi: 10.3390/s19194347.
Utilizing global positioning system (GPS) to determine the precise kinematic orbits for the twin satellites of the Gravity Recovery and Climate Experiment (GRACE) plays a very important role in the earth's gravitational and other scientific fields. However, the orbit quality is highly depended on the geometry of observed GPS satellites. In this study, we propose a kinematic orbit determination method for improving the GRACE orbit quality especially when the geometry of observed GPS satellites is weak, where an appropriate random walk clock constraint between adjacent epochs is recommended according to the stability of on-board GPS receiver clocks. GRACE data over one month were adopted in the experimental validation. Results show that the proposed method could improve the root mean square (RMS) by 20-40% in radial component and 5-20% in along and cross components. For those epochs with position dilution of precision (PDOP) larger than 4, the orbits were improved by 50-70% in radial component and 17-50% in along and cross components. Meanwhile, the Allan deviation of clock estimates in the proposed method was much closer to the reported Allan deviation of GRACE on-board oscillator. All the results confirmed the improvement of the proposed method.
利用全球定位系统（GPS）来确定地球重力恢复和气候实验（GRACE）双星的精确运动轨道，在地球引力和其他科学领域发挥着非常重要的作用。然而，轨道质量高度依赖于观测 GPS 卫星的几何结构。在这项研究中，我们提出了一种运动轨道确定方法，用于改善 GRACE 轨道质量，特别是当观测 GPS 卫星的几何结构较弱时，根据星载 GPS 接收机时钟的稳定性，在相邻历元之间推荐适当的随机游走钟约束。实验验证采用了一个月的 GRACE 数据。结果表明，该方法可以将径向分量的均方根（RMS）提高 20-40%，沿迹和垂迹分量提高 5-20%。对于位置精度衰减因子（PDOP）大于 4 的历元，径向分量的轨道精度提高了 50-70%，沿迹和垂迹分量提高了 17-50%。同时，所提出方法中钟估计的 Allan 偏差更接近 GRACE 星载振荡器报告的 Allan 偏差。所有结果都证实了该方法的改进。
