Long-term calibration monitoring of medium resolution spectral imager (MERSI) solar bands onboard FY-3

Abstract

Medium Resolution Spectral Imager (MERSI) is a keystone instrument onboard Fengyun-3 (FY-3), the second generation of polar-orbiting meteorological satellites in China. This paper summarizes the knowledge of MERSI instrument in terms of sensor design, calibration algorithm, and long term calibration monitoring. The calibration monitoring of its reflective solar bands (RSBs) is conducted using China Radiometric Calibration Sites (CRCS) vicarious calibration (VC), global multi-site calibration tracking, visible onboard calibrator (VOC) monitoring and deep convective cloud (DCC) monitoring. All these methods provide results with good consistency . It is found that there is significant degradation over 10% in the shorter RSB bands (<500 nm), with the largest in band 8 (412 nm) of approximately 35% during the past four years. The performance in the red and near-infrared (600 to 900 nm) is relatively stable. The overall uncertainty of the MERSI top-of-the-atmosphere (TOA) reflectance is less than 5% verified through several methods.