An orbit in which gravitational influences are used to induce a precession in a satellite's orbital plane.

The distance from crest to crest, or trough to trough, of an electromagnetic or other wave. Wavelengths are related to frequency: The longer the wavelength, the lower the frequency.

The force acting on a body in a gravitational field, equal to the product of its mass and the acceleration of the body produced by the field.

A state experienced in a ballistic trajectory (i.e. in orbit or free fall) when, because the gravitational attraction is opposed by equal and opposite inertial forces, a body experiences no mechanical stress.