Vicarious radiometric calibration of EO-1 sensors by reference to high-reflectance ground targets

The Remote Sensing Group at the University of Arizona has been using ground targets for the in-flight vicarious calibration of airborne and satellite sensors since the early 1980s. Targets such as Railroad Valley Playa in north central Nevada and White Sands Missile Range in New Mexico have proven to be useful for this work. This paper presents the results from multiple vicarious calibration experiments at a variety of sites for two of the Earth Observing 1 (EO-1) optical sensors. The Advanced Land Imager (ALI) and Hyperion sensors operate in the visible and shortwave infrared portions of the spectrum. The ground sample distance of about 30 m works well for vicarious calibration and allows an easy comparison to legacy sensors such as the Enhanced Thematic Mapper Plus (ETM+) which has the same 30-m ground sample distance. The approach used in this work is to measure the surface reflectance and atmospheric properties during the sensor image acquisition. These data are used as input to a radiative transfer code which computes the top of atmosphere spectral radiance. This predicted radiance is compared to the radiance from the image of the site. Results show that the preflight calibrations of ALI and Hyperion are probably not consistent with in-flight performance of the instruments. New calibration coefficients adopted in December 2001 improve the comparison to the vicarious predictions.