FY-3 visible infrared scanning radiometer (FY-3/VIRR) has provided Earth-observation data in orbit for more than 10 years since the launch of FY-3A in 2008. These data are important for atmospheric, surface, and environmental product inversion, weather, and climate change research. In this study, the calibration bias characteristics of FY-3/VIRR thermal infrared channel were analyzed, and the main sources of error were preliminarily identified in combination with the operational calibration model in day-night difference and seasonal variation of the operational calibration bias. In addition, the on-board calibration model and the on-board blackbody radiation model were optimized to construct the fine re-calibration model of the thermal infrared channel. In the linear calibration model plus nonlinear correction adopted by the FY-3/VIRR infrared channel, the quadratic term is related to the calibrated blackbody radiation. When the satellite is in orbit, the temperature change of the blackbody causes change in the quadratic term coefficient. As a result, the shape of the quadratic response of the infrared channel is changed. When the blackbody temperature changes, the quadratic term coefficient is changed, thereby introducing calibration deviation. In addition, the blackbody radiation on the infrared channel is calculated using the equivalent brightness temperature coefficient of the blackbody obtained from the pre-launch test. In fact, the radiation in the blackbody observation path is reflected in a set of polynomial fitting coefficients. This fitting process is based on the pre-launch vacuum test, and the on-orbit application results in calibration deviation. The FY-3/VIRR re-calibration model of thermal infrared channel directly uses quadratic calibration equation for on-board calibration model and considers the influence of instrument environmental radiation. The blackbody radiation model on the planet is reconstructed by considering the blackbody temperature as the proxy ambient temperature given that traditional instruments lack temperature measurement points on the planet. Based on the matching samples of Simultaneous Nadir Observation (SNO) recommended by GSICS, The parameters of the refined re-calibration model were determined using the internationally recognized high-precision Infrared Atmospheric Sounding Interferometer (IASI) as the reference instrument. The results show that the refined re-calibration model has a significant correction effect on the systematic deviation, diurnal difference, and seasonal variation of the operational calibration model, and the monthly mean deviation is within ±0.3K after re-calibration using the refined re-calibration model. In 2018, for example, the difference between day and night in winter decreased from approximately 0.4 K of the service calibration to less than 0.1 K.

Visible and Infra-Red Radiometer (VIRR);infrared calibration;on-board calibration;refinement calibration model;re-calibration;onboard blackbody radiance model