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通过对水体目标热红外辐射传输方程进行推导和变换,建立热红外双通道交叉定标差分模型,克服辐射传输模拟法定标过程中不能真实反映成像时大气条件的不足,提高定标精度.地表、大气和表观能量解析表明,待定通道表观亮温是参考通道表观亮温的差分组合,差分模型避开了成像时大气分层温度和密度状态的影响,唯一需要考虑的是水汽吸收的影响.通过对742条中纬度TIGR大气廓线数据(柱水汽含量范围0～5×103atmcm)的拟合误差分析表明,当参考通道和待定通道观测天顶角在30?以内时,差分模型对水汽含量大小并不敏感,最大误差在0.2K以内,40?以内时最大误差在0.3K,50?以内时最大误差在0.6K,当超过50?时误差不确定性增加,因此差分模型最佳观测角度在30?以内而不要超过50?.青海湖场地替代定标结果作为真值的精度验证表明,以MODISB31,32作为参考通道对IRSB08通道进行的差分模型交叉定标精度与场地替代定标精度一致,差分模型可以作为在轨传感器一种高精度和高频率的替代定标和真实性检验的手段.
Through the derivation and transformation of the thermal infrared radiation transfer equation of the water body, a thermal infrared two-channel cross-calibration differential model is established to overcome the shortcomings of the atmospheric conditions that can not be truly reflected during the calibration of the radiation transmission simulation method and improve the calibration accuracy. Atmospheric and apparent energy analysis shows that the apparent bright temperature of the to-be-determined channel is the differential combination of the apparent bright temperature of the reference channel. The difference model avoids the influence of the atmospheric stratification temperature and the density state during imaging. The only consideration is the water vapor absorption The error of 742 mid-latitude TIGR atmospheric profile data (column water vapor content range of 0 ~ 5 × 103atmcm) fitting error analysis shows that when the reference channel and the channel to be determined when the zenith angle within 30 ?, the differential model pair Water vapor content is not sensitive to the size of the maximum error within 0.2K, the maximum error within 40? When 0.3K, 50? Within the maximum error of 0.6K, when more than 50? Error uncertainty increases, so the best differential model The observation angle is less than 30 ° but not more than 50 °. The accuracy of the alternative calibration result of Qinghai Lake site as a true value indicates that the difference of IRSB08 channel with MODISB31 and 32 as the reference channel The accuracy of sub-model cross-calibration is consistent with that of site replacement calibration. The differential model can be used as an alternative calibration and trueness test for on-orbit sensors with high accuracy and high frequency.