Talk detail

Participant	Conklin, John
Institution	Stanford University - 452 Lomita Mall, room 225 - Stanford - CA - USA

Session	SG4	Accepted	Yes	Order	5	Time
Talk	Oral abstract	Title	Gravity Probe B Data Analysis II: Parameter estimation, systematics and results
Co-authors	The GP-B Collaboration
Abstract	The Gravity Probe B experiment, sponsored by NASA and launched on 20 April 2004, has estimated the geodetic and frame-dragging effects consistent with General Relativity with accuracies of 0.28% and 19% respectively. The GP-B spacecraft measured the non-Newtonian drift rates of four ultra-precise cryogenic gyroscopes placed in a circular polar low Earth orbit. The data analysis was complicated by two unexpected phenomena, a) a continually damping gyroscope polhode affecting the calibration of the gyro readout and b) two larger than expected Newtonian torques acting on the gyroscopes, comparable in magnitude to the relativistic effects. The five-year data analysis effort involved first determining the root cause for these classical effects, then developing mathematical models for them, and finally building an optimal estimator to determine them simultaneously with the relativistic drift rates. This paper describes the estimation methods, the evaluation systematic effects, the final results, and several verifying cross-checks.