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

13.4.6 On-Orbit ResultsThe GPS components on GP-B have exceeded performance expectation through-out the GP-B mission.In particular, coverage has been significantly better than ground tests predicted. At a roll rate of 0.77 rpm,simulator testing suggests that the coverage rate should be 86% (see Figure 13-41). Nevertheless, the receiver hasenjoyed an average coverage rate of better than 97%.Figure 13-41. Coverage Curves for GPS simulator, rolling rig, and flight data. At GP-B's roll rate, the simulatedcoverage is 86%, while flight rate is better than 95%The receiver also did well whilst changing roll rate, as shown in Figure 13-42, where the roll rate was increasedfrom 0.6 to 0.9 rpm in 8 hours; the receiver maintained a coverage of better than 95%.The GP-B orbit modeling software, Microcosm, uses 30 hours of GPS solutions to compute a best fit orbitmodel. By comparing overlapping 30 hour data sets, accuracy of orbit position and velocity solutions can beestimated. The estimates are consistent with simulated orbit modeling done prior to launch and shown inTable 13-7 and Table 13-8, and suggest that on-orbit positions are known to better than 10 meters, andvelocities are known to better than 2 cm/s.386 March 2007 Chapter 13 — Other Payload Subsystems Analyses