A General Treatment of Orbiting Gyroscope Precession

Abstract

We review the derivation of the metric for a spinning body of any shape and composition using linearized general relativity theory, and also obtain the same metric using a transformation argument. The latter derivation makes it clear that the linearized metric contains only the Eddington $α$ and $γ$ parameters, so no new parameter is involved in frame-dragging or Lense-Thirring effects. We then calculate the precession of an orbiting gyroscope in a general weak gravitational field, described by a Newtonian potential (the gravito-electric field) and a vector potential (the gravito-magnetic field). Next we make a multipole analysis of the potentials and the precession equations, giving all of these in terms of the spherical harmonics moments of the density distribution. The analysis is not limited to an axially symmetric source, although the Earth, which is the main application, is very nearly axisymmetric. Finally we analyze the precession in regard to the Gravity Probe B (GP-B) experiment, and find that the effect of the Earth's quadrupole moment (J_2) on the geodetic precession is large enough to be measured by GP-B (a previously known result), but the effect on the Lense-Thirring precession is somewhat beyond the expected GP-B accuracy.