Autonomous optical satellite navigation at sighting the stars and unknown planetary landmarks

An algorithm is defined for the autonomous navigation of satellites in orbit around a planet by sightings of distinctive landmarks on the planetary surface and known stars at calculated elevations above the horizon. The spacecraft would need a clock, two optical units and an on-board computer. Landmarks are optically defined during overflights and the coordinate system of the satellite above the landmark relative to a library of known star positions above the horizon is computed. The algorithm simulates the spacecraft motion relative to the landmarks and yields the orbital elements and perturbing forces. Error calculations are also carried out, based on the established coordinates of the recorded landmarks. The application of the algorithm is illustrated in terms of a satellite in a circular 300 km earth orbit.