扫描镜热辐射校正对FY-4A星AGRI定标精度的提升研究

Study on the improvement of scan mirror thermal radiation correction on the calibration accuracy of FY-4A AGRI

多通道扫描成像辐射计(Advanced Geostationary Radiation Imager,AGRI)是风云四号A星的主要有效载荷之一。为了满足AGRI长波红外遥感数据高精度定量化应用的要求,构建了扫描镜热辐射随机械转角变化的函数模型,提出了一种可用于星上黑体和地球场景观测遥感数据的校正算法。基于FY-4A星AGRI的在轨数据,分析了模型参数对扫描镜温度的依赖性,研究评估了校正算法对长波红外定标精度的改善效果。在扫描镜温度场平稳时间段内,扫描镜热辐射校正后,B11(8.0~9.0μm)、B12(10.3~11.3μm)、B13(11.5~12.5μm)波段的定标偏差分别可以得到-2.81 K~+1.06 K、-0.60 K~+0.19 K、-0.68 K~+0.24 K的显著改善。与IASI交叉定标检验结果表明,改善后的在轨定标亮度温度偏差优于0.5 K@290 K。

The Advanced Geostationary Radiation Imager(AGRI)is one of the main payloads of Fengyun-4A(FY-4A).In order to satisfy requirements of high-accuracy quantitative application of AGRI long-wave infrared(LWIR)remote sensing data,a function model of scan mirror thermal radiation changing with mechanical rotation angle is constructed,and a correction algorithm for remote sensing data of on-board blackbody and earth scene observation is presented.Based on the on-orbit data of FY-4A AGRI,the dependence of the model parameters on the scan mirror temperature is analyzed,and the improvement effect of the correction algorithm on the calibration accuracy of LWIR is studied and evaluated.After thermal radiation correction of scan mirror in the stationary period of mirror temperature field,the calibration deviation of B11(8.0~9.0μm),B12(10.3~11.3μm),B13(11.5~12.5μm)can be improved significantly by-2.81 K~+1.06 K,-0.60 K~+0.19 K,-0.68 K~+0.24 K respectively.The result of inter-calibration validation with IASI shows that the improved on-orbit calibration brightness temperature bias is better than 0.5 K@290 K.