Radiative Transfer Model for Contaminated Rough Surfaces
Final technical rept. Jan-Sep 2012
ARMY EDGEWOOD CHEMICAL BIOLOGICAL CENTER APG MD
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We studied the radiative transfer and reflectance of potassium chlorate and ammonium nitrate contaminated surfaces in mid-wavelength and long-wavelength infrared for detection. Our framework is a combination of theoretical-based radiative transfer conservation of energy, an empirical approximation for reflectance of rough surfaces, and empirical modifications of the target absorption coefficients to account for effects of deposition morphology. Our model is formulated such that two-way attenuation by absorption through the target material is the primary source for spectral features to appear in the observed radiance. We obtained excellent or good results for lab measurements of potassium chlorate on most aluminum surfaces however, ammonium nitrate on painted aluminum was more complicated due to spectral correlation between compound and surface. Most of the signal energy came from the specular direction, hence, the ability of the model to explain off-specular reflection is of lower importance. Good specificity was demonstrated against lab data low probability to misidentify potassium chlorate as ammonium nitrate and vice versa. We also observed moderate success on field data.
- Physical Chemistry