大气后向散射对高重复率卫星激光测距(Satellite Laser Ranging, SLR)的回波接收产生干扰且随测量频率增加愈发严重, 已成为制约SLR工作频率提升的关键因素之一。根据大气散射雷达探测方程, 分析了探测系统接收到的大气后向散射光功率及对回波接收的影响, 以上海天文台现有收发分离的SLR系统为平台, 通过试验验证了分析的合理性; 据此厘清后向散射干扰产生时序, 给出基于激光发射时序控制的后向散射规避方法。通过在高重复率距离门控电路中添加激光点火信号产生模块, 并实时判断后向散射干扰情况以控制点火信号是否延迟输出, 基于FPGA(Field Programmable Gate Array)完成了后向散射自动规避电路, 成功应用在上海天文台高重复率SLR的常规观测中, 实现了对散射的完全规避, 且对Lageos等重点激光卫星的平均点火频率下降率低于2%, 具有很好的推广应用价值。

For satellite laser ranging(SLR) with high repetition rate, the interference of atmospheric backscattering on the echo receiving has been more serious by the increase of measuring rate, and has become one of the key factors which restrict the maximal working frequency of SLR technology. According to the atmospheric scattering radar detection equation, the received optical power of atmospheric backscattering from a certain distance was analyzed. Based on the platform of bi-static SLR system in SHAO, the rationality of theory was verified by interference experiment of atmospheric backscattering. According to the theory, making clear production mechanism of backscattering interference, backscattering avoiding methods on the basis of controlling laser emitting epoch were presented. With a module for outputting laser fire signal integrated into range-gate generating circuit with high repetition rate, and the control of the laser firing delayed by judging the existence of backscattering in real time, the backscatter auto avoiding circuit was finally completed based on FPGA. Now it has been successfully applied in the routine SLR measurement of SHAO, the average fire frequency reduction rate has been lower than 2% for most important satellites such as Lageos, and will has a very good propagation and application value.