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5 October 2007 Retrieval of surface BRDF for reflectance-based calibration
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The University of Arizona has recently deployed a set of automated, downlooking radiometers to retrieve surface reflectance of the Railroad Valley test site in Nevada. Results from these radiometers have been combined with atmospheric data from the same site to provide a reflectance-based, vicarious calibration of multiple sensors. The accuracy of the calibrations is similar to those obtained from on-site personnel. Past work has emphasized near-nadir views by the satellite sensors under study to match more closely the view geometry of the automated radiometers to minimize the effect of bi-directional effects in the surface reflectance. Extension to off-nadir views requires an accurate understanding of the surface BRDF. Surface bi-directional reflectance effects have always played a key role in the accuracy of the vicarious calibration of imaging sensors. Such effects are especially important for the large, off-nadir views of sensors such as AVHRR and MODIS. The current work presents a method for retrieving the BRDF using the nadir-viewing data from the automated radiometers throughout the day. The concept of reciprocity is used to derive the reflectance as a function of view angle based on the measurements as a function of solar zenith angle. Comparisons of the results from this approach are compared to MODIS-derived BRDF data as well as ground-based measurements.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
K. Thome, J. Czapla-Myers, and J. McCorkel "Retrieval of surface BRDF for reflectance-based calibration", Proc. SPIE 6677, Earth Observing Systems XII, 66770T (5 October 2007);

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