In-orbit cross-calibration of HY-1A satellite sensor COCTS

The Chinese Ocean Color and Temperature Scanner (COCTS) is the main sensor launched in May of 2002 on the Chinese first ocean color satellite named HY-1A. In this paper, first, the properties of HY-1A and COCTS are introduced briefly. Second, the theory and methodology of cross-calibration for COCTS ocean color bands by using the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data are discussed in detail. Third, with the quasi-synchronized SeaWiFS data, we simulate the COCTS radiances at the top of atmosphere (TOA), and then obtain the calibration coeffi- cients for COCTS ocean color bands. The results show that the cross-calibration TOA radiances are consistent with the in situ vicarious calibration TOA radiances at the COCTS ocean color bands. Finally, we compare the COCTS-re- trieved water leaving radiances with SeaWiFS-retrieved ones and the results show that the cross-calibration method could provide reasonable accuracy for ocean color measurement.