Vicarious calibration of CCD camera on CBERS02B using Gongger test site

on September 19 2007, CBERS02B, the third land resource satellite jointly developed by China and Brazil was successfully launched with three payloads on it, one of which is CCD camera. Calibration of CCD is a precursor for its quantitative application because there wasn’t onboard calibrator for CCD. Then a comprehensive vicarious calibration and validation experiment of CCD was performed at Gongger test site located in Inner Mongolia , in the middle of October 2007. Gongger test site is a quite flat uniform grassland with an area of 4×5km , which is devious of grass in October. a area of 400 400m at the site was chosen for CCD calibration. Reflectance-based calibration method was used for absolute calibration of CCD in this calibration experiment. The ground reflectance of the test site was measured in the reflectance-based method during CBERS02B overpass. Atmospheric conditions, including solar extinction measurements and sounding and meteorologic observations were also measured at the same time. The data were analyzed to determine inputs to radiative transfer codes. It can be assumed that the measured surface reflectance was representative of the whole CCD pixel due to the site uniform characteristics. BRF needed not to be corrected due to on-nadir. By calculating relative reflectance with reference panel and surface measurement data and interpolating BRF of reference panel according to solar zenith angle at the view time, the surface absolute reflectance T( ) could be obtained as ) ( ) ( ( ) ( s v v T s T , where s( ) was spectral BRF of reference panel corresponding to solar zenith angle at the view time; vs( ) and vT( ) were respectively counts for reference panel and the target under the same view condition. By intergrating surface spectral reflectance data with CCD relative spectral response the equivalent spectral reflectances i for band i were calculated as