Improving GOCI-II In-Orbit Radiometric Calibration for the Stability of Ocean Color Data

In ocean color remote sensing, the importance of developing and validating atmospheric correction and ocean bio-optical algorithms has been emphasized. However, if uncertainty remains in the fundamental procedure of converting the sensor signal to the top of the atmosphere (TOA) radiance, the errors will affects the overall reliability of the ocean satellite products.The purpose of this study is to monitor the gain parameters of two on-board GOCI-II calibration using Solar Diffuser (SD) and Diffuser Aging Monitoring Device (DAMD) and to improve the accuracy of ocean color sensors for radiometric calibration (RC) quality at the TOA level. Our results show that the SD gains parameter tends to decrease with seasonal periodicity in all bands, confirming sensor degradation and solar azimuth angle over time. In addition to the current RC model using only SD gain in the relationship between the sensor-observed digital counts and TOA radiance, we develop an azimuth angle correction model and a sensor degradation correction model. Verification will be performed by calculating the TOA radiation applied with an improved RC model around the Korean Peninsula. It will contribute to providing more stable GOCI-II ocean color products for short-term and long-term analysis.