Maximum Pivot Angle for a Small Element of a Concave Spherical Mirror Illuminated from Its Center of Curvature
Zoran Pazameta

Abstract
A concave spherical mirror, composed of a large number of infinitesimally small reflective elements and illuminated by a source located at its center of curvature, is considered. The maximum angle through which an arbitrary element may pivot about a meridian before its reflected ray grazes the periphery of the mirror’s aperture is derived geometrically; this angle is found to be independent of the mirror’s radius of curvature. Corrections are derived for the maximum pivot angle and maximum angular displacement from the principal axis for small but finite-size elements. These results may be applicable to propulsive mirrors (solar sails) in space.

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