基于响应率修正的傅里叶变换光谱仪非线性校正算法研究

Research on nonlinear correction algorithm of Fourier transform spectrometer based on responsivity correction

傅里叶变换高光谱仪器在定量化遥感领域展现出极大的优势,非线性校正是保证在轨辐射定标精度不可缺少的过程。针对搭载于风云四号静止轨道干涉式红外探测仪(FY-4/GIIRS)运行轨道受日晒分布不均匀、仪器环境温度日变化剧烈的特点,推导出一种基于仪器光谱响应率修正的非线性校正算法,通过测量一组标准参考辐射源光谱量化值和光谱响应率,拟合得到光谱响应率一次项修正系数。在仪器环境温度变化后,利用一次项修正系数、黑体观测光谱值和黑体观测光谱响应率重新计算光谱响应率常数项修正系数,就可以得到任意仪器环境温度下的仪器非线性校正系数。经仪器发射前地面热真空(TVAC)定标试验数据验证,该算法简单有效,在各试验环境温度工况下,对180~320 K观测范围内的辐射定标精度均有明显的提高。

Fourier transform spectrometer shows great advantages in the field of quantitative remote sensing.Nonlinear correction is an important part to ensure the accuracy of on-orbit radiometric calibration.The FY-4/GIIRS located in the stationary orbit has the characteristics of uneven sunlight exposure and severe daily changes in the background temperature of the instrument.A nonlinear correction algorithm based on instrument spectral responsivity correction is derived.By measuring a set of standard reference radiation source spectral quantification values and spectral responsivity,fitting the correction coefficient of the primary term of spectral responsivity.After the ambient temperature of the instrument changes,the correction coefficient of the response rate constant term can be recalculated using the correction coefficient of the first-order term,the spectral value and the spectral responsivity of the black body observation,and the nonlinear correction coefficient of the instrument under any instrument background temperature can be obtained.Verified by the ground thermal vacuum(TVAC) calibration tests data before the launch of the instrument,the algorithm is simple and effective.In each ambient temperature test,the radiometric calibration accuracy in the observation range of 180-320 K has been improved significantly.