Asteroid lightcurves simulated by the rotation of a three-axes ellipsoid model

A triaxial-ellipsoid model is used to simulate the smooth and nearly symmetric light curves that are usually characteristic of asteroids which exhibit large brightness variations. The mathematical model is developed and applied to two problems involving an asteroid moving with its rotational axis either perpendicular to or lying within the plane containing the sun and earth. The numerical results obtained are compared with Dunlap's (1971) simulations of asteroid brightness variations, and it is argued that typical asteroid phase coefficients cannot be interpreted unambiguously. The results are shown to favor the Hapke-Irvine relation for describing the scattering properties of a dark asteroid surface.