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D.C. Boice (SwRI), H. Hasagawa (ASTEC), K. Muroi, R. Tanabe (Tokyo Gakugei U.), J.-I. Watanabe (NAOJ)
A versatile model that represents the three-dimensional shape and surface properties of cometary nuclei and asteroids is presented. The model consistently simulates the aspects of illumination, thermal emission, rotational state, and gas production (when volatiles are present). The geometrical model approximates a triaxial ellipsoid by a large number of triangular patches that can be modified to add surface features, such as craters, mounds, and plains. The physical model allows arbitrary illumination and viewing angles with shadowing and scattering properties that may vary over the surface. By considering the energy balance at each surface patch, temperatures and sublimation rates are found which are integrated to yield total thermal emission and gas production. Applications of the model to comets (19P/Borrelly, 10P/Tempel 2, 1P/Halley, and C/Hale-Bopp) and asteroids (951 Gaspra and 216 Kleopatra) are presented. The model is useful for analyzing observations of comet nuclei and asteroids from spacecraft and Earth-based observations when available.
This work was partially supported by the NSF Planetary Astronomy Program and the NASA NMP Deep Space 1 Mission.