A twin-channel difference model for cross-calibration of thermal infrared band
A twin-channel difference model for cross-calibration of thermal infrared band
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DOI：
10.1007/s11431-012-4819-4
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发表时间：
2012-04
期刊：
影响因子：
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通讯作者：
Jiaguo Li;Xingfa Gu;Tao Yu;Xiaoying Li;Hailiang Gao;Li Liu;Hui Xu
中科院分区：
文献类型：
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作者：
Jiaguo Li;Xingfa Gu;Tao Yu;Xiaoying Li;Hailiang Gao;Li Liu;Hui Xu
为了克服传统辐射模拟定标方法不能真实获取图像获取时大气条件的局限性，在对水目标热红外辐射传输方程进行推导和变换的基础上，提出了一种双通道差分模型（DM），以提高定标精度。地面、大气和大气层顶（TOA）辐射能量分解分析表明，未定标通道的表观TOA辐射是两个参考通道的差分组合。DM避免了大气温度和密度的影响。唯一的影响来自水蒸气（WV）含量。通过对TIGR数据库中742条中纬度大气廓线（列WV含量：0-5× 103 atm cm）的拟合误差分析，发现DM对WV含量不敏感。当参考通道和未定标通道的观测天顶角（VZAs）小于30°时，最大误差小于0.2K。当VZA在30° ~ 40°范围内时，误差为0.3K;当VZA在40° ~ 50 °范围内时，误差为0.6K。由于VZA大于50°时不确定度增加，因此VZA的最佳范围为30° ~ 50 °。青海湖野外替代定标结果表明，以MODIS波段31和32为参考通道，对IRS波段08进行DM交叉定标，其定标精度与替代定标相当。因此，DM是一种可靠的替代工具，用于高精度和高频率的传感器在轨校准和验证。
Based on the conduction and transformation of the thermal infrared radiative transfer equation of water target, a twin-channel difference model (DM) was proposed to improve the calibration precision by conquering the limitation that the atmospheric condition when image is acquiring cannot be truly obtained in the traditional radiometric simulation calibration method. The analysis of surface, atmosphere and top-of-atmosphere (TOA) radiative energy decomposition demonstrated that the apparent TOA radiance of the uncalibrated channel is the differential combination of two reference channels. The DM avoids impacts from atmospheric temperature and density. The only impact is from water vapor (WV) content. Based on the fitting error analysis of 742 mid-latitude atmospheric profiles (column WV content: 0–5×103atm cm) selected from TIGR database, the DM is insensitive to WV content. The maximum error is less than 0.2 K when the view zenith angels (VZAs) of reference channels and uncalibrated channel are less than 30°. The error becomes 0.3 K when VZAs range from 30° to 40° and 0.6 K when VZAs are in 40°–50°. Because the uncertainty increases when VZAs are larger than 50°, the best range of VZAs is 30°–50°. The vicarious calibration results at Lake Qinghai field indicated that the calibration precision of the DM cross-calibration by using MODIS bands 31 and 32 as reference channels to calibrate IRS band 08 is similar to that of vicarious calibration. Therefore, the DM is a reliable alternative tool for sensor on-orbit calibration and validation with high precision and frequency.