Vicarious Calibration of ASTER via the Reflectance-Based Approach

The reflectance-based vicarious calibration approach has been applied to the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) that is on the Terra platform. The results from three separate groups operating at the same sites at the same time are presented. The three groups show good agreement between each other, with differences between the groups being smaller than 4% in all bands ranging from 0.6 to 2.2 mu m and with larger differences being seen at shorter wavelengths and beyond 2.2 mu m. Comparisons between the groups and to the ASTER sensor are best at 1.66 mu m (band 4), with differences between each group being less than 0.5% and all of the groups agreeing with ASTER to better than 5%. Differences in the visible and near infrared (VNIR) are larger, particularly prior to August 2002 when an update to the calibration processing was performed. These differences exceed 10% in some bands. In addition, the vicarious results appear to show a different trend than the onboard calibration for the VNIR indicating a possible problem with the onboard calibrator for bands 1-3.