An Improved Instrument for Investigating Planetary Regolith Microstructure

Source: NTRS

ABSTRACT The Opposition Effect (OE) is the non-linear increase in the intensity of light scattered from a surface as phase angle approaches 0 deg. It is seen in laboratory experiments and in remote sensing observations of planetary surfaces. Understanding the OE is a requirement for fitting photometric models which produce meaningful results about regolith texture. Previously we have reported measurements from the JPL long arm goniometer and we have shown that this instrument enables us to distinguish between two distinct processes which create the opposition surges, Shadow Hiding (SHOE) and Coherent Backscattering (CBOE). SHOE arises because, as phase angle approaches zero, shadows cast by regolith grains on other grains become invisible to the observer. CBOE results from constructive interference between rays traveling the same path but in opposite directions. Additional information is included in the original extended abstract.

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    ABSTRACT: This book is aimed at students and researchers who wish to use reflectance and emittance as quantitative tools to measure the properties of surfaces and materials. It is intended primarily for use in the interpretation of remote observations of the surfaces of the Earth and other planets, and it will also be useful to chemists, physicists, geologists, engineers and others who deal with particulate media. Topics include propagation and absorption of light in continuous media, reflection by smooth surfaces, scattering by spheres and irregular particles, reflectances and emissivities of particulate media, reflectance and emittance spectroscopy, and the polarization of light scattered by particulate media. Many examples of applications are given.