Abstract

Gravity Probe-B (GP-B) is the Stanford/NASA experiment being developed to check Einstein's general theory of relativity using orbiting gyroscopes. The gyroscopes, contained in an Earth satellite and placed in polar orbit, are used to detect the extremely small relativistic motions predicted by the theory. Each gyroscope, essentially, consists of a solid sphere of fused quartz (gyro rotor), coated with a very thin uniform layer of superconducting niobium, and electrically suspended in a vacuum(1). So tiny are the motions to be measured, the gyro rotor must be virtually drift free. Newtonian drift is to be less than 10^-11 degrees/hour; any imbalance in the spinning rotor that may overwhelm the relativistic motions has to be eliminated.

© 1994 Optical Society of America