Satellite lifetime program

The gravitational forces of the sun, moon, and oblate earth can cause significant changes in the orbit of a near-earth satellite. These orbital perturbations can cause an early failure of the satellite. The solar and linear perturbations vary in their effect, for any given initial orbit, according to the day and hour of injection. In fact, the change of a fraction of an hour in injection time may cause a change in the satellite's lifetime of several months. So for effective planning of a satellite mission, these perturbations must be predicted.