Vicarious Calibrations of GOES Imager Visible Channels

Due to the lack of on-board calibration systems, vicarious calibration is the only way to provide accurate radiometric data for the GOES Imager visible channel. Even with the onboard calibration devices for future GEO satellite instruments such as GOES-R Advanced Baseline Imager (ABI), vicarious calibration will continue to play an important role to verify the results of the onboard system and reduce its calibration risk as well. At NOAA/NESDIS, a variety of vicarious calibration methods have been developed to monitor and evaluate the instrument performance for the solar reflective channels. These methods include the satellite observations of stable earth targets (e.g. deep convective clouds and desert) and extra-terrestrial targets (e.g. the Moon and stars), and the inter-calibrations with well-calibrated instruments onboard low-earth-orbit satellites. The GOES star data, due to their stable point sources, predictable orbits, and abundant observations, have been used over the long term for the degradation trending of the GOES Imager visible channel. In this study, we will explore the application of the star observations, combined with the other vicarious calibration results, to improve the radiometric calibration accuracy of the GOES Imager visible channel. Results will be presented in the coming meeting.