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

11.3.4 Daily Data ExampleIt is unusual to look at data for time periods of greater than a few days duration; a 12 or 24 hour time spanfrequently shows many useful and interesting characteristics. Typical data for the TRE includes a look at howwell the temperature control system is working, whether the detector high levels need adjusting, and a look atthe ATC slopes to verify that the guide star is still in the field of view. These plots usually are done for all of theA-side and all of the B-side channels available. Usually the more boring the better, but shown here are two plotsmade from two distinctly different seasons that show how the sun location and the orbit affect the TRE (with theshutter open continuously). Both plots contain the same four signals, with a similar scaling range. The limits aredifferent to accommodate the seasonal difference. The first plot, Figure 11-6, is from 20 August 04 when thegamma angle was near its maximum value. The uncontrolled warm electronics box temperature is at a fewdegrees Celsius and the platform heater is supplying additional heat to the detector platforms during most of theguide star invalid period. During the guide star invalid period, the box warms, due to amplifier saturation, andthen during guide star valid, it cools again. A noticeable slope exists in the detector high level waveform. TheTRE gains were set at gain code 11 for both plots.Figure 11-6. High Gamma Angle Data SampleThe second plot, Figure 11-7, is from 12 February 05 when the gamma angle was near its minimum. The heatervoltage shows only small blips at the beginning and end of guide star invalid, the box temperature is near 15 °Cwith much smaller excursions, and the detector high levels show much less sloping.Gravity Probe B — Post Flight Analysis • Final Report March 2007 317