Ellipsoids and lightcurves

The determination of the light curve (LC) of a geometrically scattering ellipsoid is considered in relation to the problem of investigating the physical properties of asteroids. A simple concise formula is derived for the area of a projection of an ellipsoid, and this expression is used to obtain a general formula for the projected, visible, illuminated area of a triaxial ellipsoid for arbitrary sun-earth-asteroid geometry. It is found that the LC of an ellipsoid has special properties that can be exploited to test the hypothesis that a given optical or radar LC could be due to a geometrically scattering ellipsoid.