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Quantification of porosity and surface roughness in laboratory measurements of the bidirectional reflectance of asteroid surface analogues
Earth, Planets and Space volume 57, pages71–76(2005)
We studied the effects of the surface roughness and porosity of a sample layer on its light-scattering properties in laboratory experiments using fly ash, iron, graphite, and olivine powders. Three types of surface structure were prepared: compacted, knocked, and fluffy surfaces. The surface roughness is represented by the mean slope angle of small facets on the surface. We found a positive correlation between the surface roughness and the porosity of the layer. The bidirectional reflectance of the surface at the wavelength of a He-Ne laser (633 nm) was measured to illustrate the influence of surface structure on scattering properties, with the incidence angle fixed at 0°, while varying the phase angle from 2 to 80°. The reflectance of a relatively rough surface was lower than that of a relatively smooth one for all of the materials measured. The reflectance measured at 30° in phase angle decreased by between ∼25 and ∼60%. This effect may explain the discrepancy between the absolute reflectance in previous laboratory results and the observed results for C class asteroids (Kamei and Nakamura, 2002; Nakamura et al., 2002).
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Sakai, T., Nakamura, A.M. Quantification of porosity and surface roughness in laboratory measurements of the bidirectional reflectance of asteroid surface analogues. Earth Planet Sp 57, 71–76 (2005) doi:10.1186/BF03351807