双行根数编目体系轨道误差研究

Study on Orbit Error of TLE Catalogue System

大量空间目标的真实轨道无法精确知道,目前只能通过跟踪观测的数据进行定轨来得到估计轨道,而估计的轨道就会有误差.双行根数(TLE)是广泛使用的一种特殊编目轨道根数,其配套的轨道模型为Simplified General Perturbations 4(SGP4)/Simplified Deep-space Perturbations 4(SDP4)模型.编目轨道的精度主要依赖于相应的观测模型和动力学模型,这些模型一般都不会非常准确,往往会有误差,有些误差可能直接导致编目定轨结果在局部为有偏估计.通过理论研究和仿真模拟,分析了动力学模型中地球非球形引力位田谐摄动项对编目轨道精度的影响,发现TLE编目轨道中存在随时间周期变化的系统差,该系统误差甚至可以达到千米量级.几何构型较好的测站分布在一定程度上可以削弱编目定轨中产生的系统误差,由于力学模型的限制,无法彻底消除.

The real orbits of a large number of space objects cannot be accurately known, and the orbits can only be estimated by tracking the observed data, so the estimated orbits will have errors. Two-line element （TLE） is a kind of special catalogue of orbit elements, and the Simplified General Perturbations 4 （SGP4）/Simplified Deep-space Perturbations 4 （SDP4） model is used to propagate it. The precision of catalogue orbit mainly depends on corresponding observation model and dynamic model. These models are generally not very accurate, and there will be errors. Some errors may directly lead to the estimated orbit being biased. In this paper, a theoretical analysis and numerical simulation are performed to analyze the effect of dynamic model error on the precision of catalogue orbit. The results indicate that there is systematic error changing periodically with time in TLE catalogue system, and the maximum magnitude can be km level. The distribution of the observing stations with a better geometrical configuration can weaken the system error in the catalogue orbit, but it cannot be completely eliminated due to the limitation of dynamic model.