GF-5卫星多角度偏振成像仪(DPC)同一波段三个偏振通道(0°、60°及120°)必须进行响应非一致性校正,才能达到偏振探测的精度要求。将范围为-50°~50°的DPC宽视场划分为15×15个分视场,使用高精度的二维转动平台调整各分视场的位置以对准积分球参考光源进行成像。设计基于时间稳定性的分视场图像数据的拼接算法,得到全视场的拼接图像,并应用对数增强方法检测拼接图像中坏像元的位置与数量。采用拼接图像计算DPC同一波段三偏振通道的相对透过率、低频相对透过率及高频相对透过率,为DPC偏振通道响应非一致性校正提供了校正系数。结果表明,DPC偏振通道的响应非一致性测量不确定度优于0.67%。所提方法为校正DPC偏振通道间的响应非一致性、提高偏振信息的解析精度提供了高精度的手段。

Only calibrating the response non-uniformity among three polarization channels of 0°, 60°, and 120° in the same waveband of a GF-5 satellite directional polarization camera (DPC) can make the accuracy requirement of polarization detection met. The wide field-of-view with DPC range of -50°--50° is divided into 15×15 sectional field-of-view and a high-accuracy two-dimensional turntable is used to adjust the position of each sectional field-of-view for aiming the integrating sphere reference light for imaging. The mosaic algorithm of the sectional field-of-view image data based on time stability is designed to obtain the mosaic images of the entire field-of-view. Furthermore, the logarithm enhancement method is used to detect the location and number of bad pixels in the mosaic images. The mosaic images are used to calculate the relative transmittance, low frequency relative transmittance, and high frequency relative transmittance of three polarization channels in the same waveband of DPC, and a calibration factor is provided for the calibration of DPC polarization channel response non-uniformity. The results show that the measurement uncertainty of DPC polarization channel response non-uniformity is superior to 0.67%. The proposed method provides a high-precision tool for calibrating the response non-uniformity among DPC polarization channels and for improving the analytical accuracy of polarization information.