GP-B Post-Flight Analysis—Final Report - Gravity Probe B - Stanford ...

The niobium coatings on the rotors were sputtered on in a series of 64 stages, turning the rotor to a new positionfor each new coating. This process created a very uniform niobium coating on each rotor. However, it turns outthat the final, 64th layer effectively created two large patches on the rotors, defined by its edge. In other words,the edge of the final coating essentially divides the rotor into two halves, each of which is, in fact, a largeelectrostatic patch at opposite poles of the rotor—the very situation that we had tested for pre-launch and haddetermined was “not going to be an issue.”Knowing that this unprecedented experiment would likely uncover some surprises, we purposely collectedcopious spacecraft and instrument status data in addition to the scientific data and we thoroughly tested andcalibrated the science instrument throughout the flight mission. This meticulous planning has paid off in manyways. For example, it has enabled our science team to develop a methodology for precisely modeling the polhodemotion and trapped magnetic flux on each gyro. Most important, in the final months of the data analysis, ourscientists will be able to use this modeled data to separate and remove the misalignment torques caused by thesepatch effects, thereby significantly improving the accuracy of the final results.15.5 Next Steps—Moving Towards a Final ResultOur GP-B data analysis team comprises 34 people, including Principal Investigator, Francis Everitt. ProgramManager, William Bencze, manages the team, and Chief Scientist, Mac Keiser, is ultimately responsible for thedata analysis and results. The remainder of the team includes 22 scientists (physicists, mathematicians,engineers, and computer scientists), plus 9 physics and engineering graduate students. The entire data analysisteam, except for Francis Everitt, is pictured in Figure 15-12 below.Figure 15-12. A slide from the GP-B plenary talk that Francis Everitt will deliver at the APS meeting on April 14,2007. This slide shows the GP-B data analysis team, except for Principal Investigator, Francis Everitt.A copy of this talk will be available on our APS Web site: http://einstein.stanford.edu/content/aps_posters#talks.Gravity Probe B — Post Flight Analysis • Final Report March 2007 437