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

Increased SBE rates were observed during the periods of high solar activity that resulted from solar flares andcoronal mass ejections. The best example of this occurred on Jan. 20, 2005 when a powerful X7 solar flareerupted into what was considered the strongest radiation storm since October 1989. Figure 8-42 shows protonflux data measured by the GOES11 satellite during the 3-day period from January 19 to January 22, 2005. Thestrength of this particular solar flare was due to the large number of high energy (>100 MeV) particles detected,represented by the green line in Figure 8-42. High-energy proton flux increased to a level four orders ofmagnitude greater than normal. Onboard SBE data over the same time span (January 19 to January 22) isdisplayed in Figure 8-43. At the peak of the solar event, the FSW detected and corrected over 60 SBEs in aperiod of 5 hours, a rate 40 times greater than standard levels.Successful error detection and correction was an important function of the GPB flight software, functionallyinsulating sensitive GPB electronics from the harmful space radiation environment. The FSW memory scrubroutine adequately protected the spacecraft from any hazardous conditions that could result from corruptedmemory caused by single bit errors.Figure 8-42. Proton Flux measured by GOES11 satellite during January 20, 2005 solar flareGravity Probe B — Post Flight Analysis • Final Report March 2007 251