A Multi-layer Radiative Transfer Model for the Analysis of Planetary Surface Hyperspectral Images at Visible and near Infrared Wavelengths
S. Douté (L.G.G.E, Grenoble, France), B. Schmitt (L.G.G.E., Grenoble, France)
The study of terrestrial and more generally planetary surfaces by high resolution spectrophotometry and hyperspectral imaging in the UV, visible and infrared ranges of the solar spectrum is experiencing dramatic development.
Beyond a visual or automated identification of characteristic spectral features, giving the chemical nature of the pure components present (minerals, water ice, etc...), modeling of reflectance spectra seems to be the only efficient way to extract broad and weak spectral signatures, to obtain the proportions of intimately mixed elements, and to determine the phase or the texture of the present materials and their physical conditions (mainly temperature) for the uppermost centimeters or meters of a surface. Stratigraphic variation of the previous chemical or physical parameters may be derived as well.
Following, but improving and extending the simple approaches adopted by Hapke , and Ahmad and Deering , we have derived a practical, and effective radiative transfer algorithm for the calculation of bidirectional reflectance by a plane parallel, absorbing, scattering and slightly stratified medium. Each layer can present two different kinds of texture : granular (frost, snow, sand, ...) or compact with inclusions (e.g. bubbly ice). The nature of the simplified method we use is well suited for an efficient integration of the resulting radiative transfer algorithm into a modeling system dedicated to the qualitative and quantitative analysis of high resolution hyper-spectral images.
Ahmad, S. P., and D. W. Deering, J. Geophys. Res., 97, pp. 18,867-18,886, 1992.
Hapke, B., Theory of reflectance and emittance spectroscopy, Cambridge University Press , Cambridge, 1993.