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Proceedings Paper

An approach to retrieve BRDF from satellite and airborne measurements of surface-reflected radiance based on decoupling of atmospheric radiative transfer and surface reflection
Author(s): Alexander Radkevich
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Paper Abstract

Bi-directional Reflection Distribution Function (BRDF) defines anisotropy of the surface reflection. It is required to specify the boundary condition for radiative transfer (RT) modeling. Measurements of reflected radiance by satellite- and air-borne sensors provide information about anisotropy of surface reflection. Atmospheric correction needs to be performed to derive BRDF from the reflected radiance. Common approach for BRDF retrievals consists of the use of kernel-based BRDF and RT modeling that needs to be done anew at every step of the iterative process. The kernels’ weights are obtained by minimization of the difference between measured and modeled radiance. This study develops a new method of retrieving kernel-based BRDF that requires RT calculations to be done only once. The method employs the exact analytical expression of radiance at any atmospheric level through the solutions to two auxiliary atmosphere-only RT problems and the surface-reflected radiance at the surface level. The latter is related to BRDF and solutions to the auxiliary RT problems by a Fredholm integral equation of the second kind. The approach requires to perform RT calculations one time before the iterations. It can use observations taken at different atmospheric conditions assuming that surface conditions remain unchanged during the time span of observations. The algorithm accurately catches zero weights of the kernels that may be a concern if the number of kernels is greater than 3 in current mainstream approaches. The study presents numerical tests of the BRDF retrieval algorithm for various surface and atmospheric conditions.

Paper Details

Date Published: 9 October 2019
PDF: 16 pages
Proc. SPIE 11152, Remote Sensing of Clouds and the Atmosphere XXIV, 111520D (9 October 2019); doi: 10.1117/12.2530662
Show Author Affiliations
Alexander Radkevich, Science Systems and Applications, Inc. (United States)

Published in SPIE Proceedings Vol. 11152:
Remote Sensing of Clouds and the Atmosphere XXIV
Adolfo Comerón; Evgueni I. Kassianov; Klaus Schäfer; Richard H. Picard; Konradin Weber; Upendra N. Singh, Editor(s)

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