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J. Li, M. F. A'Hearn, L. McFadden (U. Maryland)
The integrated phase law of an irregularly shaped body is often determined as much by its shape as by the scattering properties of its surface. Ellipsoidal shapes and the real shape model for Eros were used as examples to compare completely convex shapes with a real shape that has concavity in some places and to determine how the shape affects the fitting of parameters in Hapke's theory. Theoretical brightnesses were calculated as a function of solar phase angle and rotational phase, assuming the Hapke parameters for Eros determined from the NEAR mission. The Hapke parameters were then calculated with a standard spherical model by fitting to the calculated brightnesses. We show that the resultant parameters can differ significantly from the "correct" answer if the shape is not explicitly taken into account.
Provided that full, rotational light-curves are available, fitting the mid-points with a spherical model can lead to a good approximation of the true values if the shape is totally convex. However, for complex shapes, the phase curve of the spherical model deviates significantly from the mid-points of the rotational light curves at phase angles larger than 60 degrees.
The author(s) of this abstract have provided an email address for comments about the abstract: jyli@astro.umd.edu
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.