Micro-scale modeling of contaminant effects on surface optical properties

The optical properties of a surface may change significantly in response to contaminants from the environment and/or human activity. We utilize a first principles, physics-based radiometric ray tracing software package to evaluate the spectral polarimetric bi-directional reflectance distribution function (BRDF) of the virgin and contaminated surfaces. In the absence of contaminants, we find the simulated reflectance properties of randomly rough Gaussian surfaces to be well represented by micro-facet based polarimetric BRDF models. However the addition of contaminants introduces phenomenology that falls outside the basic assumptions of the microfacet BRDF models. We will present results of BRDF simulations of painted surfaces with liquid and solid contaminants.