低轨卫星星载GNSS反射事件模拟分析

基于低轨（low earth orbit，LEO）卫星星载GNSS反射事件的数学判据，分别用BDS、GPS、Galileo、GLONASS和4系统耦合GNSS星座模拟信号源，仿真分析了LEO卫星轨道高度、轨道倾角、下视天线视场角等参量对反射事件数量和时空分布的影响；进而研究了用上述4大GNSS系统进行GNSS反射信号遥感技术（GNSS reflectometry，GNSS-R）探测对接收机通道数量的需求。统计结果表明:LEO卫星轨道越高，天线视场越大，反射事件越多，镜面反射点分布越稠密；轨道倾角越小，反射事件镜面点越趋于赤道地区分布；GNSS-R接收机所需通道数随LEO卫星轨道高度和下视天线视场范围增大而增加；而LEO卫星轨道倾角变化对通道数需求影响不明显。研究结果对GNSS-R低轨卫星系统设计具有一定的理论参考价值。

Simulation Study of Spaceborne GNSS-R Events

The effects of LEO (low earth orbit) satellite orbit altitude, inclination and look-down antenna field of view on the number and distribution of specular reflection points in GNSS-R events were analyzed, based on GNSS-R mathematical criterion. Using the BDS, GPS, Galileo, and GLONASS data, we combined these 4-system constellations. The number of channels of GNSS-R receiver required was estimated. The results show that the number of GNSS-R events increase with the increase in the LEO orbit altitude and look-down antenna field of view. With a decrease of LEO satellite orbit inclination, the specular reflection points tend to distribute in the equatorial region. Meanwhile, the requested number of GNSS-R receiver channels increase with the increase of LEO orbit altitude and look-down antenna field of view, but might be affected slightly by the variation of LEO orbit inclination. The study provides a theoretical reference for future GNSS-R mission design.