TG-2多角度偏振成像仪遥感影像地理定位与误差订正

搭载多个遥感应用载荷的天宫二号空间实验室(TG-2)于2016年9月发射,其中多角度偏振成像仪共设置12个观测通道(565~910 nm),是国内首个应用于空间探测的多角度偏振仪器。该仪器的数据质量对气溶胶和云的光学、微物理特性参数的精确反演至关重要,而高精度的影像地理定位是观测数据得以定量应用的基础。根据多角度偏振成像仪光学几何设计参数和航天器的姿态信息,基于参数法建立了影像观测像元与地面空间位置之间的关系模型。首先分析地球自转和航天器姿态偏差对像移造成的影响,进行相应的偏流角和安装矩阵初步订正,接着采用海岸线拐点法探测初步订正结果在沿轨和交轨方向的误差,并使用焦点纠正法直接在焦平面坐标系中补偿了两个方向上的地理定位误差。最终的定位误差评估表明,沿轨和交轨方向的平均误差保持在一个像元以内。

TG-2 Multi-angle Polarization Imager Remote Sensing Image Geolocation and Error Correction

The Tiangong-2 Space Laboratory(TG-2), equipped with multiple remote sensing application payloads, was launched in September 2016. The multi-angle polarization imager has 12 observation channels (565nm to 910 nm), which is the first multi-angle polarization instrument used in space exploration in China. The data quality of the instrument is crucial for the precise inversion of the optical and microphysical characteristic parameters of aerosol and cloud, and accurate image geolocation is the basis for the quantitative application of observational data. This paper is based on the multi-angle polarization design parameters of optical geometry, spacecraft attitude information, and the relation model between the image observation pixel and the ground space location is established by using parametric approaches. Firstly, the impact of both the earth's rotation and spacecraft attitude deviation on image motion is analyzed, and the preliminary correction of the corresponding drift angle and the mounting matrix is carried out, Then, the coastline inflection point method is used to detect the error of the initial correction result in the direction along-track and cross-track, and the focus correction method is used to directly compensate the geolocation error in two directions in the focal plane coordinate system. The final geolocation errors assessment shows that the mean error in both along and cross-track directions is within one pixel.