基于非均匀同区域线性CCD成像的卫星姿态调整与非线性定标方法

Satellite attitude adjustment and nonlinear relative radiometric calibration method based on linear CCD imaging the same region of non-uniform scene

提出了对非均匀场景同一区域成像的卫星姿态调整及基于直方图匹配的线阵CCD非线性相对辐射定标方法。当在轨卫星需要执行相对辐射定标任务时,首先计算初始偏流角并调整卫星偏航角进入在轨定标成像模式;然后在定标成像过程中控制卫星偏航角,使得线阵CCD阵列的所有像元能够依次对同一区域成像;最后基于直方图匹配方法建立高精度非线性相对辐射定标模型。仿真实验给出了不同姿态对应的定标成像情况下的偏航角调整大小与调整周期,并分析了引起偏流角误差的因素及其对偏流角的不确定性。该方法既不需要地面均匀定标场等,也不需要统计分析大量在轨图像数据;且每一轨都可以执行定标任务,避免了卫星不同轨数据之间的不稳定性所带来的定标源自身不可靠问题。

The satellite attitude calculation method for linear CCD imaging the same region of non-uniform scene was presented, and a nonlinear relative radiometric calibration method based on histogram matching was put forward. Firstly, when it was needed to perform relative radiometric calibration task,the initial drift angle was calculated, according to which the yaw angle could be adjusted to ensure on-orbit satellite performing the calibration imaging mode. Secondly, in calibration imaging process the yaw angle was controlled to ensure all CCD detectors imaging the same region. Finally, after obtaining the same region image with CCD camera, histogram matching method was used to establish high-precision nonlinear relative radiometric calibration model. The simulation results show the magnitude and time interval of yaw angle adjustment with various attitudes, such as nadir imaging, roll attitude, pitch attitude,roll and pitch attitude, etc, and also analyze the error factors and the uncertainty of drift angle. This method needs neither the ground uniform scaling field, nor lots of on-orbit images for statistical analysis.More importantly, each track satellite images can meet the calibration condition, which avoids the unreliable problem of calibration source itself caused by the unstable of images between different tracks.