Channel ratio normalized calibration of the solar reflectance bands from FY-3D/MERSI lunar observations

In order to further improve the accuracy of the lunar radiation correction, a normalized calibration method with a reference channel ratio is proposed in this paper. This approach effectively eliminates the influences of the lunar phase angle, the sun–moon–satellite distance and other related factors on the lunar irradiance, thereby calibrating the observed irradiances of all channels to the same level. The normalized calibration coefficient of a target channel is derived by comparing its lunar irradiance with that of a stable reference channel, thereby transforming absolute calibration into a relative inter-channel framework. Using lunar observation data from the FY-3D/MERSI, the annual decay rates of the normalized calibration coefficients and their associated uncertainties are systematically evaluated. The results show that the estimated decay trends are consistent with those derived from the ROLO model, while exhibiting lower uncertainty in most channels. This study demonstrates that the proposed method provides a reliable and practical alternative for on-orbit radiometric calibration, offering both theoretical support and operational guidance for satellite radiometric stability monitoring.