微光凝视成像曝光自适应研究

为实现高分视频卫星微光条件下对目标进行长周期凝视曝光成像,设计了适应凝视跟踪稳像姿态变化的自适应曝光周期算法.建立卫星对地实时凝视跟踪数学模型,搭建矢量映射的速度匹配曝光成像关系,利用蒙特卡洛方法对卫星三轴姿态角和姿态角速度控制准确度在微光成像曝光时间内引起的像移量进行统计计算,分析了一定姿态控制准确度下满足高分卫星微光成像的曝光周期.最后,利用灵巧验证卫星进行微光成像曝光周期自适应稳像姿态的在轨试验.结果表明,卫星姿态控制准确度分别为0.08°与0.0088°/s和0.04°与0.003°/s时,对应的成像曝光时间分别为18ms和55.2ms,通过对微光成像的目标点进行分析,曝光过程中成像目标点的实际偏差像元量小于1个像元,此偏差对成像质量影响较小,成像影像的信噪比高.

Study on Adaptive Exposure Time for Low-light Staring Imaging

In order to realize the long period gaze exposure imaging for low-light application,an exposure period algorithm was designed to match the attitude change of gaze tracking image.Based on the mathematical model of the satellite to ground real-time gaze tracking,the velocity matching exposure imaging relations was set up.Image motion was induced by three-axis attitude angle and control accuracy of attitude angular velocity during the low-light imaging exposure period produces,and it can be calculated by using the method of the Monte Carlo.And exposure period was analyzed to meet the satellite attitude control accuracy in the low-light imaging.Finally,an on-orbit test of adaptive exposure period of low-light imaging algorithm was carried out on the smart verification satellite.Results show that:the corresponding imaging exposure time is18 ms and 55.2 ms respectively when the control accuracy of satellite attitude is 0.08°,0.0088°/s and 0.04°,0.003°/s.The actual deviation pixel of target point in the process exposure at imaging is less than 1 pixel.This bias has little influence on the imaging quality and image signal-to-noise ratio.