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

13.2.3 History of PerformanceThe PM operated nominally from the beginning of the mission until Nov. 16, 2004 when we began receivingcorrupt telemetry data. After a couple of days, telemetry went back to normal. On December 14, 2004 the PMtelemetry data became corrupt again. No good data was available for the following two weeks. In early January,2005, the PM came back online, but stopped sending data shortly before the major peak of solar activity on Jan.20, 2005. After that, the data from the PM appeared invalid and there was a period when no data was received.On April 25, we discovered that if we apply a different parsing method to the incoming telemetry data, we seemuch more good data coming from the PM. Using this new parsing method, we went back and saw that the PMappeared to operate nominally starting on March 17, 2005.13.2.4 Data CollectedFigure 13-20, shown below, illustrates data collected on all horizontal channels over a one-month period,August 1 – September 1, 2004. The figure also shows the AP8min SAA model, ATC SAA model, and SLAC SAAmodel for GLAST contours [1]. Features of interest are active areas over the SAA, the poles and a band betweenthe south-east SAA boundary and the South pole.Figure 13-20. Typical Month of Proton Monitor DataFigure 13-21 shows proton monitor data versus time. Levels of increased activity over the SAA are clearly visibleas sharp spikes. Passes over the SAA are marked by red asterisks.Gravity Probe B — Post Flight Analysis • Final Report March 2007 369