The Opposition Effect and Negative Polarization of Structural Analogs for Planetary Regoliths

摘要: To better understand the negative polarization and brightness opposition effects observed on airless celestial bodies, we carried out simultaneous photometric polarimetric measurements of laboratory samples that simulate structure planetary regoliths. Computer modeling shadow-hiding coherent backscatter in regolith-like media are also presented. The investigations were with a photometer/polarimeter at phase angles covering 0.2°–4° wavelengths 0.63 0.45 μm. We studied characterize variety microscopic structures albedos. A particle-size dependence branch for powdered dielectric surfaces was found. Colored such as powder Fe2O3 exhibit very prominent wavelength phenomena. Metallic powders usually wide independent size particles. For fine powders, both phenomena become more when compressed. Our computer based ray tracing particulate shows affects only combination enhancement. Modeling reveals scattering orders higher than second contribute to even dark surfaces. model qualitatively reproduces varying sample-compression laboratory. experimental studies mutually confirm degree highly reflective depends not angle but surface tilt. Even exactly zero tilted can be nonzero. tilt normal plane gives parallel shift large values |P|. perpendicular same direction positive polarization. At angle, body irregular shape nonzero integral observations.