iibsfract-If off-nadir satellite sensing of vegetative surfaces is con\idered, understanding the angular distribution of the radiance exiting the atmosphere in all upward directions is of interest. Of particular interest is the discovery of those surface reflectance features that map be invariant to atmospheric perturbations. When mono-directional radiation is incident on a vegetative scene, a characteristic angular reflectance signature called the canopy hot-spot, or Heiligenschein, is produced in the retro-direction. M'e use an analytic model BRDF to describe such a typical angular reflectance peak in the retro-direction. l h e remotely sensed angular signature is modified by atmospheric extinction of the direct and reflected solar radiation, atmospheric backscattering, and the diffuse sky irradiance incident on the surface. We explicitly demonstrate, however, by radiative transfer calculations through model atmospheres that at least one parameter that characterides the backscattering peak, namely its angular half width, is invariant to atmospheric perturbations.
The narrow intensity peak in the reverse solar direction , also called the canopy hot spot or Heiligenschein, is studied using a artificial canopy. Polar Fourier analysis is proposed to classify asymmetric peaks for various canopy architectures.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.