Assessing the quality of the radiometric and spectral calibration of casi data and retrieval of surface reflectance factors

The spectral and radiometric data quality of the Compact Airborne Spectrogr aphic Imager (casi) was assessed using atmospheric modeling and fitting the band center location of the oxygen absorption feature centered around 0.76 2 mu m. Atmospheric modeling was used to assess the quality of the radiomet ric calibration. A software program that locates the position of the oxygen absorption feature and performs atmospheric modeling was used to assess th e spectral calibration of the scanner. These methods were adequate to revea l problems with the radiometric and spectral calibration and spectral align ment, The analyses required image data with a continuous spectrum and were performed on spectral mode data. Based on one calibration target, two different methods for retrieving surfa ce reflectance factors were applied to the spectral and spatial mode data, respectively. Atmospheric modeling and normalization to the calibration tar get were used on the spectral image data because water vapor correction on a pixel-by-pixel basis was possible. Water vapor correction on a pixel-by-p ixel basis was not possible on the spatial data, and surface reflectance re trieval was accomplished using modeled path radiance and field spectra from the calibration target.