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 f orces. Drifts are examined for both forces transmitted through the gyr oscope suspension and torques due to the gravity gradient acting direc tly on the spherical rotor. The orbit averaged gravity gradients torqu es are derived considering a nonspherical Earth (J(2) oblateness only) and a slightly eccentric orbit. The effects of the Sun and Moon on th e gyroscopes are also discussed. The resulting drift rates for various guide star candidates is presented.