Suspension torques on a gimballed electrostatically supported gyroscope and requirements on the gyroscope and spacecraft for the relativity gyroscope experiment

The motional and geodetic drift rates of the angular momentum vector of a mechanical electrostatically supported gyroscope to an accuracy of 1 milli-arc-sec/year were measured. These drift rates are predicted by Einstein's General Theory of Relativity to be respectively .044 arc-sec/year and 6.9 arc-sec/year for a gyroscope in a 300 nautical mile circular polar orbit. Four electrostatically supported gyroscopes were mounted in a quartz block which is rigidly attached to a telescope. The quartz block assembly was cooled to 1.7 K by superfluid helium. The entire satellite which contains the gyroscopes will roll about the line of sight to a reference star. Attitude control jets keep the telescope aligned with the line of sight to the star to within 50 milliarc-sec. The peak-to-valley asphericity of the rotors is 0.8 micro inch or better. The orientation of the rotor spin axis was measured by using a SQUID magnetometer to detect changes in the magnetic flux due the London moment of the spinning superconducting rotor. The suspension torques were calculated on an electrostatically supported gyroscope with hexahedral electrodes.