Long-term attitude drift of spinning spacecraft under solar radiation torques

Solar radiation pressure effects have been exploited by satellites for about four decades. Concepts have been developed for using solar radiation forces and torques in practical applications, for instance, for orbit stationkeeping and attitude stabilization of geostationary communications satellites. The forces and torques induced by solar radiation pressure can substantially alter the orbital and attitude behavior of spacecraft, especially in long-duration missions. The present work analyzes the long-term effect of the solar radiation torques on the evolution of the spin-axis attitude pointing of any type of spacecraft (e.g., Earth-orbiting spacecraft, deep space probes, and solar sails). Analytic models are presented that can be applied to a spacecraft of an arbitrary geometrical shape. Compact results are established that predict the annual drift of the spacecraft spin axis under solar radiation torques. The models presented will be useful for the design of spacecraft attitude control systems as well as for space mission planning, including hibernation concepts.