Huang Wen-xin, Zhang Li-ming, Si Xiao-long, Cao Xing-jia, Lj Jun-lin, Wang Wei, Zhu Xue-mei
Guang Pu Xue Yu Guang Pu Fen Xi. 2017 Mar;37(3):952-7.
As one of the most important ways of improving the calibration accuracy at present, the calibration method based on a solar diffuser(SD) is an independent calibration way with advantages of high accuracy, high frequency and high efficiency . The principles, methods and implementation process of on-orbit calibration based on the SD is described in this thesis. The radiance reference for calibration in space is found and the physical model of the on-orbit reflectance calibration is provided. The main factor which affects the calibration uncertainty is the determination of the SD bidirectional reflectance distribution function (BRDF) value by analyzing the physical models of on-orbit calibration. Thus, the timing selection of the on-orbit calibration is introduced and the BRDF in the range of angles variety within the calibration timing is tested in the lab. During the on-orbit calibration time, the high accuracy on-orbit calibration in the remote sensors’ whole life is achieved by the accurate radiance input which is ensured by monitoring and correcting the SD BRDF value from its fabrication to its life end. Finally, the on-orbit calibration uncertainty is estimated based on the measurement levels of the parameters in the physical model. And the uncertainties of on-orbit reflectance calibration and method of radiance calibration are better than 2.03% and 2.04% by type B standard uncertainty evaluation method.
作为目前提高定标精度的最重要方法之一，基于太阳漫射器（SD）的定标方法是一种独立定标方式，具有高精度、高频率和高效率的优点。本文描述了基于SD的在轨定标原理、方法及实现过程。找到了空间定标中的辐射度基准，并给出了在轨反射率定标的物理模型。通过分析在轨定标物理模型，确定影响定标不确定度的主要因素是SD双向反射分布函数（BRDF）值的确定。为此，介绍了在轨定标的时机选择，并在实验室对定标时机内角度变化范围内的BRDF进行了测试。在轨定标期间，通过从SD制造到其寿命结束全程监测和校正其BRDF值，确保准确的辐射度输入，从而在遥感器的整个寿命期内实现高精度在轨定标。最后，基于物理模型中各参数的测量水平对在轨定标不确定度进行了估计。采用B类标准不确定度评定方法，在轨反射率定标和辐射度定标方法的不确定度分别优于2.03%和2.04%。
