光学像消旋系统在FY-3 MERSI图像定位中的应用

45°旋转扫描反射镜模式是一种最常见的光机扫描模式。但45°镜的旋转反射会产生像旋转, 对于线列探测器并扫成像系统时会产生轴外视场无法配准。在遥感图像地理定位计算中, 如果只考虑45°旋转扫描反射镜的反射成像, 也同样会造成地理定位结果在轴外的大误差。在遥感图像地理定位处理中, 计算了K镜反射特性矩阵, 通过光学矢量反射和旋转计算, 在图像地理定位结果中消除了轴外误差。在分析了45°旋转扫描反射镜产生像旋转原因基础上, 给出了在遥感图像地理定位中45°旋转扫描反射镜和K镜光学像消旋系统的处理方法。将该方法用于FY-3 MERSI 10元并扫探测器的遥感图像地理定位处理, 在图像定位结果中减小了误差, 地理定位结果平滑连续。并讨论了45°旋转扫描反射镜和K镜光学像消旋系统对遥感图像地理定位可能造成的其他误差。该方法同样适合于其他45°旋转扫描反射镜和K镜像消旋系统以及多元并扫遥感仪器的图像地理定位。

Offsetting Image Rotation System in FY-3 MERSI's Geolocation

45°rotating scan mirror is one of the most popular scanning modes in optics and fine mechanics, but out-of-axis misalignment will be brought about for the multi-detector combined scanning system because image rotation is caused by 45°rotating scan mirror. In order to obtain high resolution, multi-detector or linear sensor techniques are often adopted by current remote sensing instruments. For example, Chinese Ocean Color and Temperature Scanner (COCTS) on HY-1 satellite is a four-detector combined scanning scheme, 10 detectors and 40 detectors for sampling are adopted by the Medium Resolution Spectral Imager (MERSI) on FY-3 satellite. In order to eliminate this misalignment of image rotation, K mirror is applied in COCTS and MERSI to offset image rotation from 45°rotating scan mirror. A larger out-of-axis error in geolocation of remote sensing image will also be produced if the rotation and reflection of 45°rotating scan mirror is considered only but not the K mirror.An algorithmic model in the remote sensing image's geolocation is introduced. In the model, K mirror's reflection matrix is deduced and the error in remote sensing image's geolocation has been eliminated by vector reflection and rotation. First, the cause of image rotation from 45°rotating scan mirror is analyzed, then the processing method of "45°mirror & K mirror" offsetting image rotation system in the geolocation, including building the coordinate system and calculating the reflection matrix of 45°rotating scan mirror and K mirror, is presented. This model has been applied in FY-3 MERSI's geolocation. The categories of land and water have been searched from global Land Water Mask database according to longitude and latitude. It is proved by the geolocation results that this method can offset the error of image rotation. Finally, the error resources which are produced from "45°mirror & K mirror" offsetting image rotation system in geolocation are discussed.This model is also fit for the geolocation of other remote sensors that use 45°mirror and K mirror and multiple detectors.