APPLICATIONS OF SUPERCONDUCTIVITY TO SPACE-BASED GRAVITATIONAL EXPERIMENTS

Techniques based on superconductivity are crucial in providing the mea ns of achieving the high accuracy and low noise required by experiment al tests of gravitational theories. We discuss applications of superco nductivity to two space-based experiments: the Gravity Probe B Relativ ity Mission (GP-B), and the Satellite Test of the Equivalence Principl e (STEP). Superconducting shields attenuate the dc magnetic field to l ess than 10(-11) T and provide an ac shielding factor in excess of 10( 12). The readout of the GP-B gyroscopes is based on the London magneti c dipole generated by a rotating superconductor and detected with stat e-of-the-art dc SQUIDs, which are also used in STEP.