Evaluation and analysis of on-orbit performance of GF-5B GMI

This study proposes an on-orbit radiative spectral performance evaluation method for the Greenhouse Gas Monitoring Instrument (GMI) payload. Firstly, based on the SCIATRAN (Scientific Computing of Atmospheric Radiative Transfer and Applications) radiative transfer model, a forward simulation of high-resolution reference spectra was conducted by considering surface reflectance and atmospheric composition parameters, providing a benchmark for performance evaluation. Next, four core evaluation metrics were proposed: relative radiometric accuracy (k), absolute radiometric accuracy (RMSE), spectral offset (Δλ), and spectral shape matching accuracy (SSM), which comprehensively quantify the differences in radiance intensity and spectral shape between the payload-observed spectra and the reference spectra. Using this method, a detailed analysis of the on-orbit performance of the GMI payload onboard the GaoFen-5B satellite was conducted in this study. The research results indicate that there are certain issues with the on-orbit performance of the GF-5B GMI: the O2 channel exhibits relatively stable performance but with spectral shape distortion; the CO2-1 channel shows more significant spectral distortion, accompanied by some degree of deviation; while the spectral offset in the CO2-2 channel is even more pronounced, and over time, the spectral shape has undergone significant changes, indicating severe performance degradation.