CLASSICAL TORQUE ERRORS IN GRAVITY PROBE B EXPERIMENT

Classical torques are the first to come into one's mind when thinking about sources of systematic errors in Gravity Probe B (GP-B) Relativity Science Mission, which is why they have been most thoroughly investigated. In this paper we give a brief survey of these studies and their results. First, the classification of all known non-relativistic torques that is used in the GP-B Error Tree is given, and the Error Tree spreadsheet is described. Second, the theory of electrostatic support dependent torques is outlined, including the universal expression for the housing-fixed components of the torques, the definition of the fifteen torque coefficients and their relation to the rotor shape. Examples of the final formulas for the drift rates of several particular support dependent and support independent torques are presented. Finally, contributions of different groups of torques to the total expected experimental error are compared, and the top contributing torques are discussed.