Laboratory photometry of regolith analogues: Effect of porosity

New Laboratory phase curves are presented, to examine the effect of porosity on reflectance as a function of phase angle for grain size having dimension about half, twice and those larger than the illuminating wavelength. The experimental setup used for generating reflectance data is a goniometric device developed at the Department of Physics, Assam University, Silchar, India. Some of the well-documented samples having different sizes were chosen; alumina, olivine, basalt, rutile, chromite and iron. The sample surfaces were prepared with different porosities, in order to simulate natural regolith surface as much as possible. The wavelength of observation is 632.8 nm. A model based on the Radiative Transfer Equation is presented here to analyze and model the laboratory data. In the present modelling work, the empirical relation of Hapke, Mie theory and Henyey-Greenstein phase function are used. For particles having dimension about half, twice to the wavelength, Mie theory is used to calculate single scattering albedo. Although the Mie theory is insufficient for describing the scattering properties of particles larger than the wavelength, for such large particle single scattering albedo (SSA) is estimated through method of best fit. It has been found that, the porosity has a distinguishable effect on reflectance. Also the contribution of multiple scattering function for different porosity is examined. Further the results presented in the current work, demonstrates the light scattering properties of a diverse collections of regolith like samples.