Sun synchronous orbits are widely and most successfully employed for Earth observation, as the lighting conditions during each passage of a satellite over a given area are constant in time. Orbital plane precession is caused by the Earth oblateness, but only some specific values of semi-major axis and inclination allow having an orbital plane precession synchronous to the apparent motion of the Sun. The main purpose of this article is to prove the existence of a brand new category of Sun synchronous orbits, achievable by combining the Earth oblateness effect with the solar radiation pressure. Up to now, solar sailing has been successfully employed to modify the spacecraft attitude, as proved by the numerous related patents. In the present paper, given the orbital inclination, the small thrust produced by the solar sail allows raising the typical semi-major axis for Sun-synchronicity, thus increasing the number of available Sun- Synchronous orbits. This paper also provides a detailed dissertation about the attitude control strategy required to achieve Sun-synchronicity with Cosmos 1-like solar sails.
Keywords: Sun-synchronous orbits, solar sail, attitude control, Equatorial Plane, Earth gravitational constant, perturbation, Lagrange planetary equations, Solar radiation pressure, solar sail acceleration, Sail configuration
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