Sensor Calibration of the Ocean Color Imager


Ocean Color Imager (OCI) aboard the ROCSAT-1 satellite is a multispectral imaging spectrometer for observing pigment distribution in lowlatitude oceans. Sensor calibration contributes to characterization of its radiometric response and to the development of a processing segment for recovering the at-sensor radiance data. The major characteristics of OCI are presented. A mathematical model is developed to approximate the radiometric response of OCI and the corresponding parameters are initially identified by pre-flight calibration and adapted in-flight by a method of cross-platform calibration. The procedure of the pre-flight calibration is described and the results are shown. The cross-platform in-flight calibration compares the radiance data with those measured by the vicarious orbital sensor over the cross points so that performance degradation or parameter change in OCI will not bias the sensor calibration. The difficulties in spectral matching, spatial resolution, sun-sensor geometry, radiometric compatibility, and data set registration have been considered. An algorithm of the parameter adaptation and data conversion has been developed and implemented.

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