红外高光谱大气探测仪（FY-3E/HIRAS-II）在轨数据非线性校正方法

风云三号E星（FY-3E）搭载的高光谱大气探测仪（HIRAS-II）能够实现大气的垂直探测，具有高光谱、高灵敏度、高精度的特点。仪器在轨之后由于仪器衰减和环境变化的原因产生非线性响应，影响在轨定标精度。针对非线性响应的问题，提出了一种基于带内光谱的非线性校正方法。首先基于带外低频光谱的非线性特征求解非线性校正系数，将此系数作为初值输入到辐射定标模型中，以星上测量的黑体带内光谱与理想光谱的偏差为目标函数，通过迭代优化非线性校正系数。通过辐射定标实验得出，校正后的黑体亮温偏差明显低于未校正和基于带外光谱的校正方法。将HIRAS-II的观测数据与IASI进行交叉比对并计算平均亮温偏差和偏差绝对值，经过带内校正法非线性校正后的亮温平均偏差为-0.13K，优于带外校正方法。

Nonlinear response correction method for on-orbit data of FY-3E hyperspectral infrared atmospheric sounder II

The Infrared Hyperspectral Atmospheric Sounder II （HIRAS-II） mounted on Funyun-3E satellite （FY-3E） can realize vertical atmospheric detection， featuring hyper spectral， high sensitivity and high precision. When the satellite has been on-orbit， nonlinear response would occur due to instrument attenuation and environmental change， which affects the accuracy of on-orbit calibration. For nonlinear response problems， a nonlinear correction method based on in-band spectrum is proposed. Firstly， the nonlinear correction coefficient was solved based on the nonlinear characteristics of the out-of-band in low-frequency spectra， and the coefficient was input into the radiological calibration model as the initial value. The deviation between the black-body spectrum measured on board and the ideal spectrum was taken as the objective function， and the nonlinear correction coefficient was optimized by iterative calculation. Radiation calibration experiments have shown that the brightness temperature deviation of black body is reduced compared to uncorrected result and the out-of-band correction method using the proposed method.Based on the simultaneous nadir overpass method， After matching the observed data of HIRAS-II with IASI and calculating the mean brightness temperature deviation and the absolute value of the deviation， the mean brightness temperature deviation after nonlinear correction by the in-band correction method is -0.13 K， which is better than the out-of-band correction method.