Si Xiaolong, Li Xiuju, Chen Hongyao, Bao Shiwei, Xu Heyu, Zhang Liming, Huang Wenxin
Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, China.
Key Laboratory of Optical Calibration and Characterization, Hefei Institute of Physical Science, Chinese Academy of Sciences, Hefei 230031, China.
Sensors (Basel). 2022 Feb 25;22(5):1832. doi: 10.3390/s22051832.
A partial aperture onboard calibration method can solve the onboard calibration problems of some large aperture remote sensors, which is of great significance for the development trend of increasingly large apertures in optical remote sensors. In this paper, the solar diffuser reflectance degradation monitor (SDRDM) in the onboard calibration assembly (CA) of the FengYun-4 (FY-4) advanced geostationary radiance imager (AGRI) was used as the reference radiometer. It was designed for measuring the partial aperture factor (PAF) for the AGRI onboard calibration. First, the linear response count variation relationship between the two was established under the same radiance source input. Then, according to the known bidirectional reflection distribution function (BRDF) of the solar diffuser () in the CA, the relative reflectance ratio coefficient between the AGRI observation direction and the SDRDM observation direction was calculated. On this basis, the response count value of the AGRI and the SDRDM was used to realize the high-precision measurement of the PAF of the AGRI B1~B3 bands by simulating the AGRI onboard calibration measurement under the illumination of a solar simulator in the laboratory. According to the determination process of the relevant parameters of the PAF, the measurement uncertainty of the PAF was analyzed; this uncertainty was greater than 2.04% and provided an important reference for the evaluation of the onboard absolute radiometric calibration uncertainty after launch.
一种局部孔径在轨校准方法能够解决某些大孔径遥感器的在轨校准问题，这对于光学遥感器孔径日益增大的发展趋势具有重要意义。本文将风云四号（FY-4）先进静止轨道辐射成像仪（AGRI）在轨校准组件（CA）中的太阳漫射器反射率退化监测仪（SDRDM）用作参考辐射计，其设计目的是测量AGRI在轨校准的局部孔径因子（PAF）。首先，在相同辐射源输入下建立两者之间的线性响应计数变化关系。然后，根据CA中太阳漫射器已知的双向反射分布函数（BRDF），计算AGRI观测方向与SDRDM观测方向之间的相对反射率比系数。在此基础上，利用AGRI和SDRDM的响应计数值，通过在实验室太阳模拟器光照下模拟AGRI在轨校准测量，实现了对AGRI B1~B3波段PAF的高精度测量。根据PAF相关参数的确定过程，分析了PAF的测量不确定度；该不确定度大于2.04%，为发射后在轨绝对辐射校准不确定度的评估提供了重要参考。
