Vicarious calibration of ASTER backward-looking telescope - art. no. 629611

The Remote Sensing Group at the University of Arizona has successfully used various vicarious calibration methods for the absolute radiometric calibration of over 13 separate sensors since 2000 including nearly 40 sets of ground-based data collected at large uniform test sites imaged by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). The results from this work have been used to examine the VNIR and SWIR bands showing differences that exceed 10% in some bands. The current work extends the reflectance-based approach to the backward-looking telescope of the VNIR system of ASTER that is used for development of digital elevation models. The off-nadir band, Band 3B is identical to the NIR band of ASTER Band 3 except with a view of 23.5 degrees relative to the nadir-looking telescope. The study of Band 3B is done relative to Band 3 using the playa sites in California and Nevada as well as reflectance-based calibration approaches. The calibration of the nadir and off-nadir views agreed to better than 0.7% for five dates spanning 2000-2002 in the summer months at Ivanpah Playa. Other dates and sites showed differences much larger than can be explained by radiative transfer modeling and atmospheric effects pointing to a possible surface directional effect.