EXPERIMENTAL-TECHNIQUES FOR GYROSCOPE PERFORMANCE ENHANCEMENT FOR THEGRAVITY PROBE-B RELATIVITY MISSION

The Gravity Probe B relativity mission experiment is designed to measu re the frame dragging and geodetic relativistic precessions in a 650 k m polar orbit. We describe some of the advanced experimental technique s used to achieve the required gyroscope accuracy of between 0.05 and 0.3 marcsec yr(-1). The subjects discussed are: (i) the development of high-precision gyroscopes with drift rates of less than 0.02 marcsec yr(-1), (ii) a low-temperature bake-out procedure resulting in a heliu m pressure of less than 3 x 10(-12) Pa at 2.5 K, (iii) a read-out syst em using DC SQUID magnetometers with a noise figure of 5 x 10(-29) J H z(-1) at 5 mHz and (iv) AC and DC magnetic shielding techniques which produce an AC attenuation factor in excess of 10(13) and a residual DC field of less than 10(-7) G.