GP-B Post-Flight AnalysisÃ¢Â€Â”Final Report - Gravity Probe B - Stanford ...

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Table 2-2. Weekly summary of IOC accomplishments (Continued)Weekly Summary of IOC AccomplishmentsWeek Activities CompletedWeek 3 All 4 gyroscopes digitally suspended for over 1 weekPracticed Low Temperature Bakeout (Reduces residual He gas pressure)Resulted in 0.001-0.010 Hz science gyroscope spinsWeek 4 Flew position drag-free for 1 st time (gyro 1)ATC system used roll stars to roughly align to guide starBegan series of small maneuvers (dwell scans) to locate guide starWeek 5 Completed magnetic flux reduction: all gyroscopes have very low trapped magnetic flux(desirable situation)A second thruster was turned off due to stuck thruster caused indirectly by the magnetic fluxreductionWeek 6 Sent a low flow of spinup gas (2 sccm for 90 seconds duration) to each gyroscopeEach gyro spun to approximately 0.3 HzMicroHz/Hr spindown rates confirm clean gyroscopesWeek 7 Locked onto IM Pegasi with the science telescopeBegan performing science calibration testsSuccessfully demonstrated the ability to discharge the science gyroscopes to spec (15 mV)Week 8 Verified IM Pegasi by visiting two neighboring starsSuccessfully tested the control effort based drag-free system for 1 orbitWeek 9 Increased the spacecraft roll rate from 0.1 to 0.3 rpm allowing mass trimPerformed updates on gyro biases to improve science performanceWeek 10 Increased the spacecraft roll rate from 0.3 to 0.9 rpm (the maximum for the mission) for liquidhelium bubble wrapApplied 120% of science gyro spinup voltages as a stress/health test: all gyroscopes workedperfectlyCompleted practice of science calibrations of gyroscopesWeek 11 Uploaded new ATC software to provide improved drag-free performance with the turned offthrustersRequired turning off the flight computer and rebootingProcedure was perfectly executedWeek 12 Spun the 4 science gyroscopes to approximately 3 HzFull flow rate of spinup gas for 90 secondsReduced roll rate to 0.5 rpmSelected science roll rate to be 0.52 rpmWeek 13 Successfully demonstrated extended drag-free operationFull Speed Spin of Gyro #4 to 106 HzFull Speed Spin of Gyro #2 to 88 HzWeek 14 ATC Filter TuningCoarse Spin Axis Alignment Gyros #2 and #448 March 2007 Chapter 2 — Overview of the GP-B Experiment & Mission
Table 2-2. Weekly summary of IOC accomplishments (Continued)Weekly Summary of IOC AccomplishmentsWeek Activities CompletedWeek 15 Spinup of gyro 3Spinup of gyro 1Week 16 Coarse Spin Axis Alignment - all gyrosdrag-free and Science Mode TestingWeek 17 Roll up to 0.75 rpmATC AdjustmentsWeek 18 ATC AdjustmentsFine Spin Axis AlignmentWeek 19 Roll up to .77419 rpm ( 77.5 sec period)Fine Spin Axis AlignmentATC AdjustmentsGyros #1, #2, and #3 transition to science modeWeek 20 Spacecraft flying drag-free around gyro #3Gyros #1, #2, and #3 in science mode, collecting dataGyro #4 continuing spin axis alignmentWeek 21 Spacecraft flying drag-free around gyro #3Gyros #1, #2, and #3 in science mode, collecting data.Gyro #4 spin axis slowly moving towards target alignment orientationWeek 22 Spacecraft flying drag-free around gyro #3Gyro #4 completes spin axis alignment and transitions into science modeGyros #1, #2, and #3 continue collecting data in science modeWeek 23 Gyro #3 transitioned out of drag-free mode to analog back-up;Drag-free flight re-established around gyro #1All four gyros in science mode, collecting data.Heat pulse meter test on dewar indicates remaining mission lifetime of 9.9 months, or a totalestimated dewar lifetime of 15.2 months. (The actual dewar lifetime was17.3 months.)2.4.3 Overview of Main IOC TasksFollowing are descriptions of the main tasks accomplished during the IOC phase of the mission.2.4.3.1 Orbit Trim ManeuverThe insertion of the GP-B spacecraft into orbit by the Boeing Delta II launch vehicle was so perfect that no orbittrim was required during IOC. Prior to launch, it was anticipated that orbit trim could have potentially been thelongest running task during the IOC period. Instead, all of the superfluid helium that would have been requiredfor trimming the spacecraft’s orbit was available for IOC contingencies.Gravity Probe B — Post Flight Analysis • Final Report March 2007 49
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Post Flight Analysis — Final Repo
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Signatures & ApprovalsPrepared byPu
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Table of ContentsPreface . . . . .
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6.8 Sources and References . . . .
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11 Telescope Readout Subsystem (TRE
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14 Data Collection, Processing & An
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xiv March 2007 Table of Contents
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Figure 3-4. The GP-B dewar—one of
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Figure 8-5. The Seasons of GP-B . .
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Figure 11-20. Pointing angle differ
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Figure 14-9. In the Anomaly Room, t
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xxiv March 2007
Page 26 and 27: Table 13-3. GP-B payload magnetomet
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Page 30 and 31: 2 March 2007 Chapter 1 — Executiv
Page 32 and 33: facility, it was necessary to recas
Page 34 and 35: spacetime around with them as they
Page 36 and 37: After years of work and the inventi
Page 38 and 39: axis of a gyroscope rotor changes i
Page 40 and 41: Figure 1-8. Clockwise, from top lef
Page 42 and 43: “management experiment.” This w
Page 44 and 45: Attitude-Control Gyroscopes. Two pa
Page 46 and 47: Any significant deviation from “g
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Page 50 and 51: 1.14 The Broader Legacy of GP-BAt l
Page 52 and 53: 24 March 2007 Chapter 2 — Overvie
Page 54 and 55: Figure 2-1. GP-B Historical Time Li
Page 56 and 57: Applied Physics Laboratory, of the
Page 58 and 59: William Fairbank once remarked: “
Page 60 and 61: In Einstein’s view, space and tim
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Page 64 and 65: Figure 2-10. Schematic diagram of t
Page 66 and 67: Figure 2-12. Final assembly of the
Page 68 and 69: Sun Shield. The sun shield is a lon
Page 70 and 71: 2.1.8 The Broader Legacy of GP-BWhe
Page 72 and 73: 2.3 Spacecraft SeparationThe Solar
Page 74 and 75: Flight Anomalies.) Furthermore, a d
Page 78 and 79: 2.4.3.2 Guide Star AcquisitionAbout
Page 80 and 81: A second mass trim operation had be
Page 82 and 83: On Friday, 2 July 2004, the spin ra
Page 84 and 85: Low temperature bakeout was first p
Page 86 and 87: 2.5.1.3 Lockheed Martin Team Phase-
Page 88 and 89: Monthly Highlights of the GP-B Scie
Page 90 and 91: 2.6.1 Overview of the Calibration P
Page 92 and 93: Weekly Highlights of the GP-B Final
Page 94 and 95: 66 March 2007 Chapter 3 — Accompl
Page 96 and 97: It was in this pristine, near-zero
Page 98 and 99: Each quartz rotor is coated with a
Page 100 and 101: Figure 3-3. Functional diagram of a
Page 102 and 103: Based on data from the on-board tel
Page 104 and 105: Ideally, the telescope should have
Page 106 and 107: Figure 3-9. Schematic diagram of st
Page 108 and 109: used. The star trackers are essenti
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Page 112 and 113: Solution: Create a tetrahedral lapp
Page 114 and 115: Constraint 2: The exhaust tube must
Page 116 and 117: Result: The on-orbit gyroscope spin
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Page 120 and 121: Constraint 3: Keep the spacecraft p
Page 122 and 123: Technology Category Specific Implem
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Any significant deviation from “g
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packages, one for each Ping load an
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In addition to these software packa
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Table 4-6. Features & benefits of W
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This software added considerable ef
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It is said that “an experiment is
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Table 4-10. Significant Events/Sour
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Figure 4-5. Pictorial depiction of
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Figure 4-7. Eta-Average Error Assoc
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4.4.4.2 OD Using SLR DataFigure 4-9
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4.4.5 ConclusionsFigure 4-11. Compa
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Overall, the storage issues did not
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Table 4-11. ITF equipment listEQUIP
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124 March 2007 Chapter 5 — Managi
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5.2 Overview of GP-B Anomalies in O
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Figure 5-1. Anomaly Review Team Org
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5.3.3.1 Anomaly Investigation and R
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5.3.5 Anomaly Identification and Re
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5.4.3 Risk Management ApproachThe r
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Table 5-1. Summary of Open GP-B ris
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138 March 2007 Chapter 5 — Managi
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140 March 2007 Chapter 6 — The GP
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3. Payload Integration, Testing and
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Figure 6-1. Clockwise from top left
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MSFC conducted an in-house Phase A
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It is important to note that from t
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6.3.1 Incremental PrototypingThe pe
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alignment, and act as an accelerome
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Figure 6-9. The Lockheed Martin GP-
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Furthermore, a fourth electronic sy
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positive thermal connections betwee
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astrophysics/cosmology. Many of the
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Figure 6-10. MSFC Program Managers/
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As described in Chapter 2, the flig
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6.7 Some Observations on the Manage
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168 March 2007 Chapter 6 — The GP
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170 March 2007 Chapter 7 — Attitu
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7.1.2 Vehicle ATC ModesThere are es
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The output of the pressure transduc
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Figure 7-3. Science Telescope Compo
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Figure 7-5. Pitch and Yaw Pointing
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Figure 7-7. Magnitude of the roll r
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Changing the method by which the gy
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7.3.3 Drag-Free Control SystemFigur
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7.3.3.1 DFS - PerformanceThe GP-B d
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Figure 7-15. Mass flow effects of a
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7.5.2 Successful recovery from mult
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If the vehicle control system were
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accomplish this, the ARPs are mount
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7.5.6.1 South Atlantic AnomalyProto
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Figure 7-23. Effects on telescope p
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200 March 2007 Chapter 7 — Attitu
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202 March 2007 Chapter 8 — Other
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Figure 8-2. Block Diagram of CDH co
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8.1.1.4 WATCH DOG TIMERFigure 8-4.
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of eclipses each day (approximately
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Figure 8-8. GSS1 Temperature Trends
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Figure 8-10. Forward Dewar Vacuum S
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The Gravity Probe B spacecraft has
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Figure 8-13. Forward -X Thruster Te
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gaFigure 8-15. Aft -X Thruster Temp
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Because there are only two SQUID br
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Because the specifications for SRE
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8.3.2 Critical Mission RequirementT
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Figure 8-19 is a plot of the power
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Battery Performance Summary:Figure
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Figure 8-23. Solar Array Temperatur
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8.3.10 ConclusionThe electrical pow
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8.4.1 TDRSS OperationsFigure 8-28.
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Figure 8-30. Xpndr-A STDN (green),
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Figure 8-32. Plot of TDRS AGC vs Te
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The FSW also met its subsystem leve
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Appendix E, Flight Software Applica
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Table 8-4. SCRs Addressed in On-orb
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The software and macro changes resu
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Figure 8-38 below is an excerpt fro
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Figure 8-40. A-side CCCA Single Bit
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Figure 8-43. A-side CCCA Single Bit
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When single MBEs did not result in
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256 March 2007 Chapter 9 — Gyro S
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9.1 GSS Hardware DescriptionFigure
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significantly reduces and thus pres
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9.1.11 Clock synchronizationThe aft
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Figure 9-8. Block diagram of the LQ
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direction (transverse to the space
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9.2.2.2 Spin-up SuspensionDuring sp
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Figure 9-16. Predicted and measured
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Figure 9-18. The GSS passes rotor c
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Figure 9-20. Representative drag-fr
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Table 9-1. GSS Science Mission Mode
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Table 9-3. GSW application source l
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The Design and Testing of the Gravi
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282 March 2007 Chapter 10 — SQUID
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ate uncertainty). Although we have
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All of the GP-B electronics have be
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10.3 Pre-Launch Ground-Based TestsW
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Figure 10-6. AC Magnetic Shielding
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Figure 10-8. Temperature Error of S
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Figure 10-10. Quiescent SQUID Noise
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Analog control loops on the electro
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The science support applications ru
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Table 10-7. SSW application source
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308 March 2007 Chapter 11 — Teles
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Figure 11-1. Block diagram of TRE a
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Additionally, the warm electronics
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Figure 11-3. CLL switch states duri
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Table 11-3. Dates and UTC times whe
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Figure 11-7. Low Gamma Angle Data S
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s N+w i= sign+w i++−+−w i−w i
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expression, which otherwise on a po
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Figure 11-14. Y axis, B side RMS po
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Figure 11-17. X axis, B side curren
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Figure 11-20. Pointing angle differ
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Figure 11-24. Scaled summed current
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Figure 11-26 through Figure 11-29 s
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334 March 2007 Chapter 12 — Cryog
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12.2 Temperature / pressure control
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control the space vehicle without t
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Figure 12-3. Helium flow rate predi
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helium at 1.8 K. It does not appear
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Figure 12-6. Flow meter and ATC flo
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were generally within a day or so o
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shields) and subsequent instability
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350 March 2007 Chapter 12 — Cryog
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352 March 2007 Chapter 13 — Other
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Figure 13-2. ECU-operated heaters i
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13.1.3.1 Vatterfly Valve Operations
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13.1.3.7 Payload MagnetometersThe E
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Figure 13-11. ECU performance durin
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As we entered the second month of o
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During the last month of IOC, prepa
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Figure 13-19. ECU heater activity d
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Table 13-1. Proton monitor channel
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Figure 13-21. Proton Monitor data i
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In November, 2004 there was a large
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Figure 13-28 shows a correlation th
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13.3.1 About the MagnetometersFigur
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13.3.2 Other Applications for Paylo
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Figure 13-35. GPS Antennae Field of
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Figure 13-37. Master Antenna Switch
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Figure 13-39. Time difference betwe
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13.4.6 On-Orbit ResultsThe GPS comp
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and velocity values erroneously cal
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E. G. Lightsey, C. E. Cohen, B. W.
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Figure 13-45. A Bottom View of the
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Figure 13-48. The GMA configuration
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Table 13-10. Summary for Helium Gas
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398 March 2007 Chapter 14 — Data
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a relatively slow data rate, so we
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Figure 14-4. NASA ground stations a
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electronic components to recover fr
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By a process of elimination, the GP
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A special room in the GP-B Mission
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Starting on 3 December 1725, Bradle
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seemed that aberration of starlight
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14.1.6 Telescope Dither—Correlati
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14.1.6.3 The Telescope Dither Patte
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amplifications. Thus, in addition t
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14.2.2 Independent Data Analysis Te
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monthly time scales. Though only sh
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424 March 2007 Chapter 15 — Preli
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Figure 15-2. A diagram of the GP-B
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15.4 The Two Surprises and Their Im
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Near Zeroes.) The exception that we
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Figure 15-8. A slide from the GP-B
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Figure 15-9. A poster on the effect
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electrostatic patches, located at o
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Last summer (2006), Mac Keiser devi
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440 March 2007 Chapter 15 — Preli
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442 March 2007 Chapter 16 — Lesso
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16.1.1.3 Flight science downlink da
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Description of the GP-B experience:
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Lessons:1. Perform all tests with a
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Figure 16-1. Six interacting transl
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16.1.3.2 Training and certification
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Below is an edited summary of six a
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460 March 2007 Chapter 16 — Lesso
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462 March 2007 Appendix A — Gravi
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Apogee altitude659.1 km (409.6 mile
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466 March 2007 Chapter B — Spacec
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Gravity Probe B — Post Flight Ana
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470 March 2007 Appendix C — Weekl
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16 April 2004—Vehicle is Prepared
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The electrical power system is full
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4 JUNE 2004—MISSION UPDATE: DAY 4
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SQUIDs to detect their rotation spe
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17 JULY 2004—MISSION UPDATE: DAY
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indicate that we have reduced the t
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C.4 Science Mission Phase: 8/27/04
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• GP-B also has an independent da
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free suspension parameters to de-tu
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We have received inquiries about a
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One of the effects of geomagnetic s
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egan transmitting, one-by-one, stat
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28 JANUARY 2005—GRAVITY PROBE B M
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magnetic pole. This event triggered
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8 APRIL 2005—GRAVITY PROBE B MISS
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On Tuesday afternoon (19-April), GP
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Norway or through the NASA space ne
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Dewar Temperature: 1.82 kelvin, hol
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visitors on a tour of the GP-B faci
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test, we are planning on running fi
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contractor at the Goddard Space Fli
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On Wednesday, we visited the star H
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Gyro Suspension System (GSS): All 4
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The helium in the dewar has now sur
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the all the spacecraft status data.
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522 March 2007 Appendix D — Summa
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Figure D-2 below shows the distribu
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DateSeveritySubtypeTitle Descriptio
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DateSeverity24 26-Apr-04 Obs F Nois
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DateSeverity40 11-May-04 Obs T Dwel
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DateSeverity68 16-Jun-04 Medium Dec
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DateSeverity84 13-Jul-04 Obs F Slig
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DateSeverity116 26-Sep-04 Obs F SG3
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DateSeverity132 20-Dec-04 Obs F Unc
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DateSeverity149 5-Mar-05 Obs T Few
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DateSeverity169 04-Jun-05 Obs F MBE
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DateSeverity191 04-Oct-05 Obs A GSS
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550 March 2007 Appendix E — Fligh
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ReqIDLevel 1CSCDMP DataMgmtProcessi
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ReqIDLevel 1CSCLevel2 CSC Level 3 C
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ReqIDLevel 1CSCSRM Solid StateRecor
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ReqIDLevel 1CSCSRP SafemodeResponse
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ReqIDLevel 1CSCGUP GSS Processing g
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570 March 2007 Appendix F — Acron
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AcronymDefinitionAcronymDefinitionB
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AcronymDefinitionAcronymDefinitionD
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AcronymDefinitionAcronymDefinitionF
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AcronymDefinitionIRUInertial Refere
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AcronymDefinitionAcronymDefinitionM
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AcronymPMPMAPMCPMEPMETPMSPMSUPNPoPO
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AcronymSCMOSCMTSCNSCPASCPMSCRSCSASC
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AcronymDefinitionAcronymDefinitionT
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588 March 2007 Appendix F — Acron
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