GPS掩星切点水平漂移规律的数值研究

NUMERICAL STUDY OF THE HORIZONTAL DRIFT OF THE GPS SIGNAL RAY’S PERIGEE IN OCCULTATION EVENT

在现有GPS星座和大气球对称假设条件下 ,利用射线追踪法对掩星事件进行了数值模拟 ,讨论了大气折射指数垂直分布、LEO卫星轨道倾角和高度对GPS掩星切点水平漂移的影响情况。结果表明 :在太阳活动剧烈的白天和夜间两种典型情况下 ,切点平均水平漂移变化约 2 0km ;对 735km高度的LEO卫星来说 ,轨道倾角在 1 30°附近时 ,切点平均水平漂移最小 ,并随着倾角向 0°或 1 80°变化 ,切点平均水平漂移均增大 ,但在 5 5°附近时随倾角变化稍有波动 ;对倾角为 70°的LEO卫星来说 ,当轨道高度从 40 0km变化到 1 5 0 0km时 ,切点平均水平漂移变化约 1 41km 。

The GPS signal ray's perigee from the top of neutral atmosphere to the ground drifts largely in horizontal direction at an occultation event. The occultation event is simulated using the ray-tracking technique on the situation of the specified atmospheric refractive index model and the GPS constellation. The effect of atmospheric refractive index profile, LEO satellite's height and inclination on the horizontal drift of the perigee is studied. The results indicate that the difference between the average horizontal drift on day and that at night is about 20 km, the minimum of the average horizontal drift appears at some inclination 130°and the average horizontal drift increases from inclination 130°to 0°or 180°for a LEO satellite which is at an altitude of 735 km above ground, and the average horizontal drift decreases from 400 km to 1500 km above ground for a LEO satellite at inclination 70°.