Radiometric cross-calibration of polar orbital sensors using Geostationary Ocean Color imager (Goci)

The possibility of radiometric cross-calibration between a Geostationary Ocean Color Image (GOCI) and polarorbital sensors is discussed. A sensor on a geostationary satellite is useful for the cross-calibration with sensors mounted on polar orbit satellites due to frequent data acquisition. The GOCI has a limitation on precisely measuring the reflectance of land objects because spectral setting of the GOCI is originally designed for ocean monitoring, and therefore GOCI images must be carefully calibrated first with a help of in-situ data to be used as a standard image. Preliminary results from the comparison between the GOCI and MODIS AQUA are presented. Test sites were selected from a snow cover in Baekdu-san (or Mt. Baekdu), a playa and a sand dune in the Inner Mongolia, and snow cover or water (seasonal) in the Hankka Lake. The results showed the GOCI data is good for cross-calibration as defined by spectral differences less than 7% under various conditions (four bands and four different surface conditions) compared with a simulated GOCI radiance from MODIS AQUA land bands. Correlation coefficient R2 was over 0.93 in most cases. Scale effect due to surface inhomogeneity and different spatial resolutions between different sensors will be further examined in the near future. The geostationary sensor can be utilized for radiometric cross-calibration of SENTINEL-2.