月亮辐照度是可见近红外波段一种稳定的辐射参考基准,对月观测已成为星载遥感仪器辐射定标和验证的一种新方法。风云三号03星(FY-3C)中分辨率光谱成像仪(Moderate Resolution Spectral Imager,MERSI)增加了对月观测功能,改进了太阳反射波段的在轨辐射定标。本文收集分析了MERSI在轨工作以来的全部11组对月观测数据,利用通道间辐照度比值方法移除月相角,日-月-星相对距离等因素对月亮辐照度观测值的影响,开展了可见光近红外波段的辐射定标工作,实现了MERSI太阳反射通道的辐射定标系数动态跟踪和评估。通过线性回归及统计发现,通道8辐射响应的年衰减率达到了14.55%,通道9达到了8.42%,通道1、6、10、11、16和19的年衰减率为1.15%-4.72%,其余通道未检测到衰减。研究结果可以用于订正MERSI数据的辐射定标系统性偏差,提高MERSI全寿命期的辐射定标精度。

The lunar irradiance reflected from the sun is a benchmark for radiance calibration in the visible and near-infrared spectra. Lunar calibration has become a new method to calibrate and validate satellite-based instruments. The Moderate Resolution Spectral Imager(MERSI) on FY-3C adds a function to monitor the lunar disk to improve the on-orbit calibration of solar reflective bands(SRB) for the MERSI. In this study, 11 groups of the dataset have been collected to record the lunar measurements since the launch of the FY-3C. With the ratio between the target channel and the referred channel, the effects of the lunar phase angle and the relative distance of the solar-lunar satellite have been removed from the measured lunar irradiance. The SRB of the MERSI in the visible and near-infrared spectra have been calibrated from the lunar measurements. The long-term trend of the SRB of the MERSI has been analyzed. The annual attenuation rate has increased to 14.55% and 8.42% for bands 8 and 9, respectively. The annual attenuation rate is between 1.15% and 4.72% for bands 1, 6, 10, 11, 16, and 19. No attenuation is observed for the rest of the bands. The aforementioned results can be used to correct the systemic bias of the radiance calibration of the MERSI. The accuracy of the radiance calibration of the MERSI can be improved on basis of the lifetime of the instrument.