Glossary

Terms

Laplace plane

Definition

The Laplace plane (as used in our satellite orbital elements tables) is defined as the plane in which the satellite’s nodal precession is contained (on average). An equivalent definition is the plane normal to the satellite’s orbital precession pole.

The typical application for the Laplace plane is in describing the orbits of giant-planet satellites which are close enough to the planet to be perturbed primarily by the sun, planet, and the planet’s gravitational harmonics. In such cases, the Laplace plane is constrained to be between the planet’s orbital plane and its equatorial plane. However, in the case of the “outer” Jovian satellites (such as Pasiphae), the perturbations by Saturn and even the Galilean satellites dominate those due to Jupiter’s gravitational harmonics. The result of those “external” perturbations (which are not normally considered in typical descriptions of the Laplace plane) is a Laplace plane which is beyond the confines of Jupiter’s equatorial and orbital planes.