Radiometric calibration experiment of the field campaign equipment for GOCI data validation

Abstract

After launching Geostationary Ocean Color Imager (GOCI) on June 2010, in-situ measurementcampaigns for data calibration and validation were performed many times around Koreanpeninsula. For each field campaign, Korea Ocean Satellite Center (KOSC) has characterizedoptical performance of measurement instruments such as Analytical Spectral Devices (ASD) andTriOS with NIST calibrated light source and reference spectrometer. We, in the paper, introducethe optical laboratory built in KOSC and the relative calibration method for in-situ measurementinstrument. The laboratory is equipped with a 20 inches integrating sphere (USS-2000S,LabSphere) in 98% uniformity, a reference spectrometer (MCPD9800, Photal) covering from360nm to 1100nm with 1.6nm spectral resolution, and an optical table (3600 ´ 1500 ´ 800 mm3)having a flatness of ± 0.1 mm. In the laboratory, the radiometric experiments have controlled in theconstant temperature and humidity condition, and the reference spectrometer and in-situmeasurement instrument have checked the same light source in the same distance. In the results,we figured out a slight difference among in-situ measurement instruments in blue band range, andalso confirmed the changed optical characteristics according to the measurement time andenvironment as well. These results show that the continuous calibrations are needed to maintainthe measurement accuracy and GOCI der (KOSC) has characterizedoptical performance of measurement instruments such as Analytical Spectral Devices (ASD) andTriOS with NIST calibrated light source and reference spectrometer. We, in the paper, introducethe optical laboratory built in KOSC and the relative calibration method for in-situ measurementinstrument. The laboratory is equipped with a 20 inches integrating sphere (USS-2000S,LabSphere) in 98% uniformity, a reference spectrometer (MCPD9800, Photal) covering from360nm to 1100nm with 1.6nm spectral resolution, and an optical table (3600 ´ 1500 ´ 800 mm3)having a flatness of ± 0.1 mm. In the laboratory, the radiometric experiments have controlled in theconstant temperature and humidity condition, and the reference spectrometer and in-situmeasurement instrument have checked the same light source in the same distance. In the results,we figured out a slight difference among in-situ measurement instruments in blue band range, andalso confirmed the changed optical characteristics according to the measurement time andenvironment as well. These results show that the continuous calibrations are needed to maintainthe measurement accuracy and GOCI d