천리안 해양관측위성의 궤도상시험에 서 측정된 분광복사휘도 특성 연구

Abstract

After the successful launch of GOCI(Geostationary Ocean Color Imager), on-board sensor of COMS(Communication, Ocean and Meteorological Satellite), the new era has begun with the worlds first ocean color observation sensor in geostationary orbit, GOCI . In-orbit Test Campaign of GOCI has been also successfully performed by Korea Ocean Satellite Center(KOSC), the main operation center of GOCI in KORDI(Korea Ocean Research & Development Institute). One of the main mission of KOSC is to receive, process and distribute GOCI data with ±5% absolute radiometric accuracy.GOCI implements Solar Diffuser(SD) and Diffuser Aging Monitoring Device(DAMD) as a second solar diffuser for in-orbit solar calibration[1]. These are the main reference optical components to maintain the radiometric accuracy of GOCI during in-orbit operation scheduled for 7.7 years. SD and DAMD of GOCI are QVD(Quasi-Volumic Diffuser) type solar diffusers[2] made of fused silica which are very well-known for the low solar UV sensitivity[3]. SD and DAMD of GOCI are made of same material with same fabrication processes in TNO Co. LTD, Netherlands. Technically, the only difference between SD and DAMD is the size[2]. Diameter of SD and DAMD of GOCI are 140mm and 70mm, respectively.Using the 3rd order polynomial equation with linear gain(G) and 3rd order non-linear gain(b), radiance restitution of GOCI has been successfully performed with new gain matrix(G and b) calculated by the in-orbit solar calibration data. The GOCI linear gain value is about 0.49 for Band 1(412nm) and non-linear gain value is about -1.38E-9 for Band 1(412nm) from the pre-launch GOCI ground test results, and there is no significant variation between the results of ground test and in-orbit test. We present the GOCI radiance restitution results with the variation of gain values of GOCI 3rd order radiometric model, and the preliminary results of GOCI radiometric performance assessments such as SNR, MTF, etc.