No abstract

No abstract

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.

No abstract