Radiometric Characteristics of KOMPSAT-3 Multispectral Images Using the Spectra of Well-Known Surface Tarps

A vicarious calibration with reference to characterized surface tarps was conducted to determine the first radiometric characteristics of KOMPSAT-3. The 6S radiative transfer model was also used by inputting various initial parameters, such as the spectral response function of KOMPSAT-3, and atmospheric and geometric conditions. Moderate-Resolution Imaging Spectroradiometer atmospheric products, such as aerosol optical depth, precipitable water, and total ozone, were used as input parameters to interpret solar radiation reflection, scattering, and absorption effects. In the first field campaign, the radiometric coefficients from each of the spectral bands were estimated by calculating the predicted radiance at sensor level and the digital number (DN) of KOMPSAT-3 based on a linear least squares fit over a range of target reflectance levels. The second field campaign measurements were also used to upgrade the KOMPSAT-3 DNs to radiance coefficients. The root-mean-square error differences between simulated radiance and measured radiance during the second field campaign for 'sensor-To-itself' calibration were 2.072 W/m²sr (blue), 6.80 W/m²sr (green), 7.512 W/m²sr (NIR), and 5.712 W/m²sr (red), respectively. This highlights that radiometric calibration with tarps is a reliable method. Furthermore, the gain ratio between the first and the second one was < 5%, indicating reasonable radiometric calibration results. Additionally, cross-validation of KOMPSAT-3 with radiometrically well-calibrated Landsat-8 was performed over bright desert. Although the difference between the vicarious calibration with surface tarps and cross-validation with Landsat-8 was significant, reasonable results were obtained under close geometrical conditions, despite inherent vicarious calibration error.