Schema Illustrating the Effects of the non-spherical Nature of the Earth on a Low-Altitude Near Polar Orbit.

This schema is viewed in a plane crossing the poles and perpendicular to the orbital plane. The flattening of the Earth at the poles is emphasized for a clearer representation.

S Satellite Satellite velocity Gravitational acceleration Satellite angular momentum, with respect to O Moment of the gravity force, with respect to O

This schema illustrates the precession of the satellite's angular momentum caused by the moment of the forces.