附加先验轨道约束的LEO几何法实时精密定轨验证分析

低轨卫星的实时精密定轨能够极大拓展其完成复杂科学任务的能力，例如实时环境监测、机动控制和卫星自主导航等.本文根据几何法实时精密定轨模型，提出了附加LEO先验轨道约束从而改善实时定轨的精度、收敛速度和稳定性的构想.分别采用广播星历、超快速星历预报部分和实时精密星历，设计了6种实时定轨方案，并利用Swarm-A，B，C星7天的观测数据进行方案验证与分析.结果表明，使用广播星历、IGU和IGC星历的方案精度递增，附加先验轨道约束能够进一步提升精度.使用IGC星历并附加标准差为1m的先验轨道约束后，在径向、切向和法向的定轨精度分别达到6.12cm，5.55cm和4.98cm.此外，附加先验轨道约束能够显著提升收敛速度，使用IGC星历平均收敛时间约为31min，附加标准差为1m的先验轨道约束后收敛仅需约4min. 

Demonstration and Analysis of LEO Real-time Kinematic Precise Orbit Determination with Priori Orbit Constraint ormalsize

Real-Time Precise Orbit Determination (RTPOD) of Low-Earth-Orbit (LEO) satellites can greatly expand their ability to perform complex scientific missions, such as real-time environment monitoring, maneuver control and satellite autonomous navigation. In this paper, the model of real-time kinematic precise orbit determination is introduced. We present a conception that the LEO Priori Orbit Constraint (POC) is used in the process of RTPOD for the sake of improving the accuracy, convergence speed and stability. The broadcast ephemeris, predicted part of ultra-rapid ephemeris and real-time precise ephemeris are adopted respectively to propose 6 different RTPOD solutions, which are then demonstrated and analyzed using the observations from Swarm A/B/C satellites during 7 days. The results show that the accuracy is improved in turn by using broadcast ephemeris, IGU and IGC ephemeris. Moreover, adding POC can further enhance the result while using the same ephemeris. The IGC+POC solution using the priori orbit with a 1m standard deviation reaches an accuracy of 6.12cm, 5.55cm and 4.98cm in the radial, along and cross component, respectively, which is comparable to the post-processing kinematic POD. Analyses based on different priori orbits indicate that the ideal priori orbit should appear less noise and long-term systematic biases, and short-term systematic biases show little influence on constraint results. Furthermore, adding POC can remarkably speed up the convergence. The convergence of IGC solution needs about 31min on average, whereas the average convergence time after adding POC with a 1m standard deviation is about only 4min, which is beneficial to the fast re-convergence after the occurrences of cycle slip, loss of lock and communication link interruption, and is of great significance in practical application scenarios.