对静止轨道卫星成像的SAL载星轨道

星载合成孔径激光雷达对卫星成像面临相对运动复杂、目标搜索困难、成像时机难把握等问题。以对静止轨道卫星成像为例,初步设计了一种适于对同步轨道卫星成像的载星轨道。推导了载星与目标间相对运动关系式;绘制并分析了两星相对运动曲线;分析了两星距离最近期间距离、径向速度、加速度变化规律。提出了基于径向速度门限的成像时机判定方法,研究了成像期间光束指向偏移和成像时机判决速度门限。研究结果表明:轨道高度低于目标星轨道,并与之有一定偏角的载星轨道适于对目标进行成像;两星相距最近的时间附近是较佳成像时机,可降低相位误差补偿难度,提高系统工作效率;在对目标进行搜索跟踪和判决成像时机时,系统需根据两星轨道特性进行动态调整。

Orbit of spaceborne SAL for geostationary satellites imaging

Satellite-to-satellite imaging by synthetic aperture lidar(SAL) is facing many problems,such as complex relative movement,target acquisition,imaging time,etc.In order to study the orbit of spaceborne SAL,taking the geostationary satellites imaging as an example,an orbit for geosynchronous satellites imaging was preliminary designed.The formula of relative motion between the SAL and the target was deduced,and the relative motion curve of two stars was drawn and analyzed.The changes of the distance,radial velocity,acceleration between the two stars were analyzed during the closest period.A solution of judging the imaging time based on threshold of radial velocity was proposed and the imaging beam pointing offset and the velocity threshold were discussed.The results of the study show that an orbit whose altitude is lower than the target orbit,and with a certain inclination to the goals orbit is fitting for imaging;the ideal imaging opportunity is when the two stars are nearest,it can reduce the difficulty of phase error compensation and improve the system efficiency;in searching and tracking the target and decide imaging time,the system′s relevant parameter must be preset dynamically based on the characteristics of the two stars orbit.