MG11 
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Polhode Motion of GP-B Gyros and SQUID Readout Scale Factor Variation due to Trapped Flux

Magnetic fluxons on the gyro’s surface affect GP-B London moment readout. They are frozen in the surface, so their flux through the SQUID magnetometer pick-up loop, and thus the readout scale factor, varies in time with the polhode period of the rotor motion. Surprisingly, the polhode period itself was found slowly changing on-orbit, which is explained by an extremely small kinetic energy dissipation. The adiabatic theory of the dissipative free motion of GP-B gyros taking into account the moment of inertia asymmetry and the spin down torque is given, with its application to the GP-B data analysis.