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

Throughout the mission, all essential elements performed nominally with one possible exception. Morespecifically:• All thermal systems have been and continue to be within tolerances.• The TCS thermal monitor limits were developed early and the used extensively during the pre-flighttesting of GP-B. All essential elements remained inside their limits for the duration of the mission.• The success of the TCS during the mission was due to a qualified, certified and highly motivated TCSteam. Notable contributions were made by Kevin Burns, as well as many others.• The TCS’s success can be directly attributed to extensive thermal modeling, limit development andthermal vacuum testing.• The dedication, ability and willingness of the LMMS TCS team to develop limit updates and thermalmodel additions throughout the mission was exemplary and contributed in no small part to the GP-Bmission success.The thermal system for the GP-B spacecraft has an extremely robust design. GP-B, more than any otherspacecraft, requires this robustness due to the large temperature swings the vehicle experiences during thedifferent seasons. The science mission mandates that GP-B point in a fixed direction at a distant guide starthroughout its mission. It is due to this fixed pointing in local inertial space that the spacecraft experiencesdifferent seasons as the sun appears to “walk” around the vehicle. The seasons of GP-B are illustrated inFigure 8-5 below.Figure 8-5. The Seasons of GP-BThis effect is also shown in the variation of the spacecraft’s gamma angle throughout the year. The gamma angleis defined as the angle to the sun from the bore sight of the telescope. Also adding to the thermal complexities ofthe spacecraft is the fact that GP-B is in a low Earth polar orbit; therefore the vehicle experiences a high numberGravity Probe B — Post Flight Analysis • Final Report March 2007 207