Gravity gradient gyroscope drifts in the NASA relativity mission/gravity probe B experiment

This paper examines the torques and resulting drift of the Relativity Mission or Gravity Probe B (GP-B) gyroscopes due to gravity gradient forces. Drifts are examined for both forces transmitted through the gyroscope suspension and torques due to the gravity gradient acting directly on the spherical rotor. The orbit averaged gravity gradients torques are derived Considering a nonspherical Earth (J₂ oblateness only) and a slightly eccentric orbit. The effects of the Sun and Moon on the gyroscopes are also discussed. The resulting drift rates for various guide star candidates is presented.