基于月球反射的遥感仪器在轨定标方法

Methods of On-orbit Calibration of Satellite Radiometer Reflective Solar Bands Using the Moon

月球在太阳反射波段的光度特性稳定,使其成为光学遥感仪器在轨定标的理想参考源。论述了月球定标的主要数据处理流程,包括月球圆盘积分辐照度或平均辐亮度的计算、过采样修正、距离修正、月相修正和月球天平动效应修正等,后三项统称为几何修正。对月相修正和天平动效应修正提出了两种处理方法,包括基于观测数据回归分析拟合修正的方法和基于月球光度模型的方法。给出了遥感仪器响应率趋势分析的方法和定标系数修正的形式。

The quantitative applications of satellite remote sensing,especially the application of detecting trends in environmental parameters,place stringent requirements on the stability of instruments and consistency among different platforms.The stability of lunar photometry in solar reflective bands makes it ideal calibration reference for on-orbit calibration of satellite radiometers.The principle of lunar calibration is straightforward.Irradiance or radiance of the moon received by the instrument will not change if the relative geometry of the Sun,the Moon and the instrument remains unchanged.So the series of the Moon measurements can monitor the change of the instrument＇s responsivity.The same relative geometry is unattainable due to the orbits of the Earth and the Sun and the operation of the satellite.The series of the Moon measurements should be corrected and normalized to the same geometry in order to determine the trend of the instrument＇s responsivity.The main procedures of data processing are discussed,including lunar disk-integrated irradiance calculation or mean radiance calculation,over-sampling correction,distance correction,lunar phase correction and lunar liberation effect correction.The latter three items are also called geometric effects correction.Key methods of lunar phase correction and lunar liberation effect correction are analyzed,including method of multiple regression and data fitting for raw data and method based on lunar photometric models.The method of quantifying the trend of responsivity for satellite radiometer and the form of correction for calibration coefficients are proposed.