传感器每个波段的中心波长和半高全宽(Full Width at Half Maximum, FWHM)随成像环境变化会发生较大的系统性漂移。这种漂移最终会影响发射率和温度的反演精度, 尤其是在大气吸收波段附近的发射率反演精度。选择水汽在11.73 μm处的吸收通道作为参考波段, 提出了适用于热红外高光谱数据的光谱定标技术流程。模拟实验表明: 光谱分辨率为50 nm, 中心波长偏移在-50~50 nm、FWHM变化在-25~25 nm时, 大气水汽含量对光谱定标误差的影响最大。同时, 对误差分布曲面进行拟合得到描述误差分布模型, 用于误差的估计。当大气水汽含量足够大时, 光谱中心波长偏移估算误差可达到1 nm以内。最后, 将所提方法应用于机载热红外高光谱数据光谱定标。结果显示, 热红外高光谱成像仪中心波长偏移为28.4 nm, FWHM变化为-18.5 nm。

Compared with a given laboratory calibration, systematic shifts on the center wavelength and the Full Width at Half Maximum (FWHM) of each band of a hyperspectral sensor, will emerge as the imagery environment changes. The center wavelength shift and the FWHM variation have influence on the inversion precision of the emissivity and temperature, especially near the atmospheric absorption bands. A technical process of spectral calibration for thermal infrared hyperspectral data was proposed, which was verified through a simulation experiment with the water vapor absorption band at 11.73 μm selected as the reference band. The experiment shows when the spectral resolution is 50 nm, the center wavelength shift ranges from -50 nm to 50 nm and the FWHM variation ranges from -25 nm to 25 nm, atmospheric water vapor content has the most influence on the error of the estimated wavelength shift and the FWHM variation. Meanwhile, the error distribution were also fitted using different surface functions, and the error distribution models used to estimate the errors were obtained. When the atmospheric water vapor content was high enough, the estimation error of the spectral center wavelength shift was able to reach within 1 nm. Finally, the proposed approach was applied to spectral calibration of the airborne thermal infrared hyperspectral data obtained by a push-broom hyperspectral thermal-infrared imager. The results show that the center wavelength shift of the thermal infrared hyperspectral imager is 28.4 nm and the FWHM variation of the imager is -18.5 nm.