1. The angular motion of the orbital line of nodes in fixed space; positive to the east, negative to the west. The precession rate for a sun-synchronous orbit is −0. 986° per day, or about 360° per year. The net effect is that the satellite's orbital plane rotates slowly around the earth at the same rate and direction that the earth rotates around the sun, hence, sun-synchronous. 2. The period of time needed for a positional shift in the location of astronomical bodies.