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National Space Science Data Center Header  Gyroscope Drift Rate
Experiment  NSSDC ID: 2004-014A-01 Mission Name: Gravity Probe B
Principal Investigator: Dr. C. W. Everitt   The primary
objective was to measure two relativistic effects on nearly
perfect gyroscopes. Einstein's General Theory of Relativity
precisely predicts both of these effects; the spacecraft
measurements are an experimental test of the General Theory of
Relativity.  The two measured relativistic effects are the
geodetic effect, which is due to the gravitational interaction
of the spinning gyroscope and its orbital angular momentum about
the earth, and the motional or frame-dragging effect which is
due to the gravitational interaction between the spinning
gyroscope and the angular momentum of the earth. The geodetic
effect is predicted to cause a drift rate of 6.6 arc seconds per
year in the plane of the orbit for a gyroscope in a ~640 km
circular orbit, and the motional effect is predi