姿态对地指向不断变化成像时的偏流角分析

 针对敏捷卫星在三轴姿态机动过程中同时进行推扫成像的偏流角问题，基于线阵TDICCD推扫成像原理，分析了动态成像过程中的偏流原理，通过速度矢量法推导出动态成像方式下的偏流角数学解析表达式。数值仿真分析表明：当相机推扫速度方向与星下点速度方向的夹角η为0°（沿航迹方向推扫成像）或180°（沿航迹反方向推扫成像），偏流是由地球自转产生的，数值较小；当夹角为0°＜η＜180°时，偏流是地球自转和轨道运动共同产生的，偏流角数值较大；当夹角η=90°（垂直于航迹方向推扫成像）时，偏流角随地理纬度的增大而增大。基于以上结论，采用姿态偏航控制对偏流角进行调整，可以实现在三轴姿态机动过程中开启光学有效载荷进行推扫成像的动态成像技术。

Drift Angle Analysis for Agile Satellite Imaging When Its Attitude Points to the Earth Changing Continuously

 Drift angle exists in dynamic imaging for an agile satellite in three axis attitude maneuvering, e.g. the direction of image acquisition is not parallel with the satellite platform motion. Based on TDICCD imaging principle, drift angle in dynamic imaging procedure is analyzed.  The analytical mathematic expression of drift angle in dynamic imaging is derived from velocity vector method. Numerical simulation results show that when the angle between the camera snap speed and ground speed is 0° or 180°, the drift angle generated by the rotation of the earth is small in value; when the angle is   0°＜η＜180° , the drift angle produced by the earth’s rotation and orbital motion is large in value. Besides, with high maneuverable satellites, when the camera snap speed is perpendicular to the natural platform motion, the drift angle increases with the increasing geographical latitude. The yaw controlling method is effective to minimize the drift angle in the dynamic imaging technology.