星基增强系统10参数广播星历拟合分析

Analysis in Fitting SBAS 10-Parameter Broadcast Ephemeris Model

为满足多种卫星轨道的应用需求,在星基增强系统新增的L5信号接口中重新设计了一种10参数星历模型。使用2016年北斗卫星系统地球同步轨道卫星、倾斜地球同步轨道卫星和中地球轨道卫星的精密轨道数据,在内符合精度、拟合成功率以及运算速度等方面,分别评估了10参数星历模型在这些卫星轨道上的拟合效果。试验结果表明,10参数星历模型可以保证10^(-3)cm左右的内符合精度。但地球同步轨道卫星和倾斜地球同步轨道卫星的拟合成功率分别为89.36%和99.17%。尝试去除idot参数以解决拟合失败的问题,结果表明,该处理可以实现100%的拟合成功率,但拟合误差有所上升,且对不同的轨道类型,拟合运算速度有不同程度的提升或下降。

SBAS designed a new 10-parameter ephemeris model, which would be broadcast on the new SBAS signal at L5. The model was a subset of GPS 16-parameter ephemerismodel, which was based on an augmented set of Kepler orbital elements. The purpose of this model was to support the wide range of orbit classes being considered for SBAS, such as MEO and IGSO. Based on a year of Beidou GEO, IGSO and MEO satellite precise orbit data, this paper evaluated the new SBAS ephemeris model in terms of the fitting accuracy and failure rate, as well as the computational effort. To avoid fitting failure, this paper tried a method which was to exclude the IDOT term in the model fitting. The conclusion was that SBAS 10-parameter ephemeris model can achieve a 10^（-3） cm fitting accuracy on average. Excluding the IDOT term was effective to avoid failure in some circumstances during the calculation. Fitting without the IDOT term can avoid fitting failure, but in the cost of decreasing the accuracy to about 10^（-1） cm to 1 cm. Moreover, for different classes of orbit, the computational effort has different degree of increasing or decreasing after excluding the IDOT term.