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

contractor at the Goddard Space Flight Center. Throughout hercareer, Dr. Roman has been a spokesperson and advocate of women inthe sciences.This past week was Dr. Roman's first trip to Stanford since 1979, butshe has been following the progress of Gravity Probe B through ourweekly updates. During her visit, she sat in on several mission statusbriefings, she met with scientists and engineers on the GP-B team, sheattended a student presentation session and had lunch with thestudents and staff, and she toured the GP-B development labs andMission Operations Center. We've included some photos from Dr.Roman's GP-B visit, plus a black and white NASA photo taken early inher career, in this week's highlights on our Web site. You can readmore about Dr. Nancy Roman athttp://solarsystem.nasa.gov/people/profile.cfm?Code=RomanN.REX GEVEDEN APPOINTED ASSOCIATE NASAADMINISTRATORAlso in the news this past week, NASA Administrator Michael Griffinnamed Rex Geveden as the agency's associate administrator. In thiscapacity, Geveden has oversight for all the agency's technical missions'areas and field center operations. He will be responsible forprogrammatic integration between NASA's mission directorates andfield centers. In November 2004, Geveden moved from NASA'sMarshall Space Flight Center (MSFC) in Huntsville, AL to NASAHeadquarters in Washington DC to become NASA Chief Engineer.He has been serving as acting associate administrator since June 2005.26 AUGUST 2005—GRAVITY PROBE B MISSIONUPDATEMission Elapsed Time: 493 days (70 weeks/ 16.2 months)—IOC Phase: 129 days (4.2 months)—Science Phase: 352 days (11.6 months)—Final Calibration Phase: 12 daysCurrent Orbit #: 7,272 as of 1:00PM PSTSpacecraft General Health: GoodRoll Rate: Normal at 0.7742 rpm (77.5 seconds per revolution)Gyro Suspension System (GSS): Drag-free off during calibrationphaseDewar Temperature: 1.82 kelvin, holding steadyGlobal Positioning System (GPS) lock: Greater than 98.0%Attitude & Translation Control (ATC): X-axis attitude error: 127.7marcs rmsY-axis error: 181.5 marcs rmsCommand & Data Handling (CDH): B-side (backup) computer incontrolMulti-bit errors (MBE): 1 (in GSS#2 computer on 8/26)Single-bit errors (SBE): 10 (daily avg.)Gyro #1 Drag-free Status: Backup Drag-free mode (OFF duringcalibration maneuvers)As of Mission Day 493, the Gravity Probe B vehicle and payload are ingood health and all subsystems are performing nominally.The Gravity Probe B mission has continued with the final calibrationphase this week, which it began ten days ago. Last Friday, the spacevehicle was pointed toward HD216635 (the one-degree star) for thethird time in five days and then returned to IM Pegasi for theweekend. On Monday, we maneuvered the space vehicle towards ZetaPegasi (aka Homam or HD 214923/ HR 8634), which is our sevendegreestar.On Wednesday, the space vehicle was returned to the guide star (IMPeg) after spending ~30 hours on Zeta Pegasi. Later this week, we willperform DC mis-centering on Gyros #1, #2 and #4, and GSS torquecalibrations on Gyros #1 and #4 with five hours of nominal sciencebetween the two tests. Three additional visits to the one-degree starhave been added to the schedule starting August 26.The calibrations are scheduled to be complete by next Wednesday(August 31). The projected helium depletion date remains Friday,September 2. With any remaining helium, further calibrations will beperformed at a different spacecraft roll rate (0.5 rpm).POINTING AT A LUCKY STARPrior to moving to NASA Headquarters, Geveden held variousleadership positions at MSFC. He served as deputy director of theMarshall Center from July 2003-November 2004. Prior to that, he wasdeputy director of the MSFC Science Directorate, leading research anddevelopment projects in space science, materials science,biotechnology, earth science and space optics. Geveden was projectmanager for several successful efforts, including the Optical TransientDetector and Lightning Imaging Sensor satellites, which produceddata for the world's first global map of lightning.However, we here at GP-B have a special connection with RexGeveden. From 1995-2003, Geveden was the NASA MSFC ProgramManager overseeing GP-B’s final development and testing, andreadying the spacecraft for launch. Geveden has long been a staunchsupporter of GP-B, and we wish him every success in his new positionat NASA. You can read the NASA press release announcing Geveden’sappointment last week at:http://www.nasa.gov/home/hqnews/2005/aug/HQ_05227_geveden.htmlAs noted in the Mission Director's summary above, we are now in thefinal days of our instrument calibration testing. Last week, we slewedthe on-board telescope (and the spacecraft) away from the guide star,IM Pegasi, to point at a neighboring star about one degree away. The512 March 2007 Appendix C — Weekly Chronicle of the GP-B Mission