2004年3月1日更新


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日時　： ２００４年３月２日
　　　　 １５：００-１６：３０
場所　：自然科学３号館６階セミナー室 (６０９号室)

Physical characterization of asteroid regoliths using photometric and
polarimetric observations

Karri Muinonen
Observatory, University of Helsinki

Abstract
A review is offered on recent theoretical advances in the interpretation
of photometric and polarimetric observations of asteroids. Photometric
lightcurves contain information about an asteroid's spin vector and shape,
as well as the scattering characteristics of its regolith.  Photometric
phase effects, such as the opposition effect, the overall phase function,
and the so-called amplitude-phase relationship, provide insight into local
physical characteristics of the surface, e.g., surface roughness and
porosity, and single-particle geometrical and optical properties.
Polarimetric phase effects, the negative degree of linear polarization in
particular, unveil single-particle properties beyond those derivable from
photometry. We review the primary physical mechanisms for the opposition
effect and the negative linear polarization. The coherent backscattering
mechanism has been established to contribute to the observed opposition
effects and negative linear polarizations. The traditional shadowing
mechanism explanation of the opposition effect has been studied via
extensive computer simulations.