THE INFLUENCE OF PHYSICAL VARIABLES ON SPECTRAL SIGNATURES OF NATURAL TARGETS.
Final rept. 1 May 67-31 Dec 69,
LITTLE (ARTHUR D) INC CAMBRIDGE MASS
Pagination or Media Count:
Application of remote spectroscopic techniques to target discrimination is hindered by the lack of an adequate theory of reflection and emission from complex natural surfaces. The reflection and emission signals from such surfaces depend in a complicated way on such physical variables as particle size, packing, and surface roughness. This report describes an experimental and theoretical investigation of the effect of these physical variables on the spectra of natural surfaces. Because of the complicated nature of the problem, the investigation led to the development of a detailed computer model of the spectral reflectance of particulate media. The experimental program has involved measurement of the infrared spectra of mineral powders using Fourier spectroscopy. These spectra, together with other available data, have been used to guide the development of the theory of reflectance. The theoretical treatment was based on a random interface model in which the measurable reflectance is considered to be made up of both surface and volume terms. The fundamental parameters were taken to be the refractive index, absorption coefficient, volume fraction, and particle size of the various components of a mixture of minerals. Comparisons of the computed theoretical spectra and the experimental spectra given. These comparisons show that the fundamental compositional and physical information can, to a large extent, be extracted from remote spectral measurements. That is, the observed spectral shapes and many of the variations with particle size are well accounted for by the theory. Most of the discrepancies that remain appear to be capable of rectification by certain modifications of the theory. Author
- Infrared Detection and Detectors
- Atomic and Molecular Physics and Spectroscopy