In-orbit radiometric performance variations of geostationary ocean color imager

Geostationary Ocean Color Imager (GOCI), a payload of the Communication, Ocean and Meteorology Satellite (COMS), is the world's first ocean color observation satellite in geostationary orbit. It was launched at Kourou Space Center in French Guiana in June 2010. The detector array in GOCI is custom CMOS Image sensor about 2 Mega-pixels, featuring rectangular pixel size to compensate for the Earth oblique projection. This satellite is being operated on geostationary orbit about 36,500km far from the earth; hence it can be more influenced by sun activities than the other on low Earth orbit. Especially, the detector is sensitive of heat and it may give rise to increasing the defective pixels. In this paper, radiometric performance variations have been analyzed through the time series analysis, using the offset parameters and detector temperature estimated in GOCI radiometric model. It is essential to monitor the overall sensitivity of GOCI sensor, and it will helpful to the radiometric calibration. In the result, we notified there was no great variation in time series of offset parameters after operating the GOCI in July 2010, but we monitored an anomaly by an operational event. One of them related to thermal electron showed slightly increasing trend and the diurnal variation by the sun energy. Although sun interferences are occurred sometimes, any significant anomaly isn't found. With these results of characterization, we find that GOCI has been carrying out stably in the aspect of radiometric performance, and expect that it will be kept during the mission life.