多角度偏振遥感器带外偏振响应校正方法研究

The out-of-band response caused by the spectral specular and diffuse leaks arising from the filters in the directional polarization remote sensors is a key factor effecting the polarization calibration accuracy. The phenomena have been observed and the principles have been studied elementally，but the masterful theoretic model and the correction method are still absent. To improve the accuracy of the directional polarization calibration, the proposal is devoted to conducting the correction method research on the out-of-band response by experiment and theoretic model. First, from the basic rules of out-of-band response in the directional polarization remote sensors, presenting a new correction method to solve out-of-band polarized response of all channels in the directional polarization remote sensors. Second, establishing polarized calibration model with out-of-band polarized response correction of the directional polarization remote sensors by multispectral remote sensor out-of-band response correction model and the Levenberg-Marquardt iterative algorithm development. The directional polarization remote sensors are developing rapidly, it is likely to be applied operationally in the near future. The proposal is promising to provide the theoretic basis and essential data and support the development, calibration and quantitative applications for the polarized remote sensors.

多角度偏振遥感器中滤光片的直射和漫射带外泄露会引起带外偏振响应，这是影响偏振定标精度的重要因素。在前期研究中观测到了直射带外偏振响应和漫射带外偏振响应的现象及相关规律,目前尚无完备的理论模型诠释和相应的校正方法。从提高多角度偏振遥感器偏振定标精度的角度出发，课题从实验和建模两方面开展带外偏振响应的校正方法研究。（1）本项目从多角度偏振遥感器的带外偏振响应规律入手，提出了一种实现所有通道的带外偏振响应校正方法；（2）通过多光谱遥感器的带外校正模型及Levenberg-Marquardt迭代算法，建立具有带外偏振响应校正的偏振定标模型，有效保障多角度偏振遥感器偏振定标精度。我国多角度偏振遥感器正处于快速发展的阶段，在不久的将来极有可能实现业务化运行，本课题可为其工程研制、定标和定量化应用提供原始设计理论依据和基础数据支持。

本项目旨在研究多角度偏振遥感器带外泄露的空间分布和偏振特性规律，构建带外偏振响应的数学模型，研究带外偏振响应校正方法，，期望实现优于0.5%的偏振定标精度。具体完成情况如下：基于前期实验研究数据和后期的理论分析推导分析，带外偏振响应是带外响应度、目标偏振态和检偏器的消光比的函数，详见结题报告。根据构建的数学模型，分析了主要参数对偏振定标精度的影响：即带内响应非一致性和带外响应引起的不确定度均低于0.4%是满足偏振定标精度优于0.5%的前提条件。以大气校正仪为应用示范，开展了滤光片的检测与筛选方法，确保这两项参数满足偏振定标要求。.通过开展带外偏振响应校正的实验研究，证明了带外偏振响应数学模型构建的有效性。以大气气溶胶多角度偏振探测仪（DPC）初样应用示范，设计了多光谱遥感器带外响应的测量、校正和精度验证方法，并开展了实验验证。结果表明，带外响应校正前后的带内权重辐亮度与参考值的差异由8.8%降低到2.9%。开展了以GF 5号DPC正样为应用示范，开展带外偏振响应校正规范化流程和验证实验研究，通过可调偏振度光源VPOLS和大口径积分球辐射源IS2500-1000进行了偏振定标精度的验证。VPOLS验证结果表明，DPC中心0°视场、15°视场、30°视场和45°视场在偏振度10%~40%等5种状态下的偏振测量精度均优于0.5%。IS2500-1000验证结果为：中心视场80%区域和边缘视场20%区域的偏振定标精度分别为0.2%~0.5%和0.5%~0.8%。初步预计为空间杂光的影响所致，其机理有待进一步研究。.空间多角度多光谱多偏振的遥感技术是近年来国内外迅速发展的一项对地观测技术。例如欧洲气象卫星组织、国内安徽光机所和气象卫星中心等航天载荷单位，正在研发下一代航天多角度多光谱多偏振载荷3MI，光谱偏振测量通道拓展至近红外波段。本项目研究成果有望在下一代航天偏振载荷的研制、定标和定量化应用得到应用。