Design and Construction of an Optical Polarimeter for the Study of Ice-like Analogs using Near Zero Phase Angle Measurements

Previous studies for analog samples measuring polarized backscatter near zero phase angles have suggested strong presence of multiple scattering effects. Radar data for Mercury, Moon and other Icy Galilean satellites exhibit high circular polarization ratios with decreasing phase angle that indicates the possible presence of icy deposits in the polar craters. An examination of powder samples with known composition and grain sizes was undertaken to try and further understand the interaction of polarized light with closely packed particulate medium. The goal of this research was to construct and test a long arm Goniometric optical instrument capable of measuring polarization ratios in the range from 0-5 degree phase angle for understanding and differentiating the scattering effects that occur near zero phase angle. Measuring signal intensity and circular polarization ratios with the Goniometric polarimeter for various analog samples will provide an understanding for the characteristics of embedded scatterers within the icy regoliths.