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

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4.4.5 ConclusionsFigure 4-11. Comparison of GPS and SLR Cross-Track Errors.Detailed pre-launch planning for any launch day plus a precise launch on a Delta II 7920-10 allowed the GravityProbe-B satellite to attain an orbit that satisfied all mission control requirements even though the IOC periodwas considerably extended.Accurate and abundant GPS measurements used in the commercial Microcosm orbit determination programhave allowed the GP-B ephemeris to be constructed to within all accuracy requirements throughout themission.4.5 Computer HardwareThe stability of the ground hardware played a vital role during all operational phases of the Gravity Probe Bmission. The Stanford Mission Operations Center (MOC) computer network is a state of the art system used forground commanding and real time telemetry. The Science network is used primarily for science analysis. Bothnetworks are UNIX based and proved to be remarkably robust during all phases of the mission. Figure 4-12shows a block diagram of the hardware network118 March 2007 Chapter 4 — GP-B On Orbit
4.5.1 ReliabilityFigure 4-12. GP-B Computer Network.The computer hardware performed near flawlessly during the Gravity Probe B mission. The moc-server had anuptime of 290 days before a breaker was accidentally tripped during a routine cleanup causing a reboot.During the IOC phase of the mission, two hardware malfunctions occurred, both involving hard drives. ThePOD E5 client disk failed, as did the Science server boot disk. Both disks were replaced within 45 minutes, andno data were lost.During the science phase of the mission, several computer power supplies failed, but were replaced within 2hours (MOC specifications require 24 hour turn around time). The SUN blade computers, the main class ofcomputer on both the MOC and Science Networks, performed exceptionally well.No problems were reported during the calibration phase of the mission.Despite repeated attempts, neither network was ever compromised by hackers. Logs routinely showed hackerattempts on our clients connected to the open IONET. However, our firewall did an excellent job keepinghackers off our science net – not a single entry was recorded.4.5.2 Disk Storage IssuesDisk storage proved a particular problem during the Gravity Probe B mission, with space requirementsconsistently underestimated.The extension of the IOC phase did cause several problems for the hardware group, although more from amanagement standpoint than from equipment concerns. In particular, prior to launch, the decision was madeto lock down all hardware modifications, even though disk usage was close to maximum. Considering a 44 dayIOC, the decision to increase disk storage after IOC seemed reasonable. Unfortunately, increased storage needsdue to an extended IOC caused disk usage to max out several times. User disk storage space was increasedshortly after the end of IOC, and has been sufficient.The GP-B database was similarly stressed, as storage requirements increased and necessary databasemaintenance postponed. Fortunately the database was fully checked out several weeks prior to launch, andefficiently managed during IOC. Prelaunch predictions underestimated the amount of data to be stored,requiring the acquisition of significantly more data base storage space.Gravity Probe B — Post Flight Analysis • Final Report March 2007 119
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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
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Table 13-3. GP-B payload magnetomet
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xxviiiMarch 2007
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2 March 2007 Chapter 1 — Executiv
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facility, it was necessary to recas
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spacetime around with them as they
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After years of work and the inventi
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axis of a gyroscope rotor changes i
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Figure 1-8. Clockwise, from top lef
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“management experiment.” This w
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Attitude-Control Gyroscopes. Two pa
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Any significant deviation from “g
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established, ranging from Level 1 (
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1.14 The Broader Legacy of GP-BAt l
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24 March 2007 Chapter 2 — Overvie
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Figure 2-1. GP-B Historical Time Li
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Applied Physics Laboratory, of the
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William Fairbank once remarked: “
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In Einstein’s view, space and tim
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y a mere 1.1 inches. You can see th
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Figure 2-10. Schematic diagram of t
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Figure 2-12. Final assembly of the
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Sun Shield. The sun shield is a lon
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2.1.8 The Broader Legacy of GP-BWhe
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2.3 Spacecraft SeparationThe Solar
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Flight Anomalies.) Furthermore, a d
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Table 2-2. Weekly summary of IOC ac
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2.4.3.2 Guide Star AcquisitionAbout
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A second mass trim operation had be
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On Friday, 2 July 2004, the spin ra
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Low temperature bakeout was first p
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2.5.1.3 Lockheed Martin Team Phase-
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Monthly Highlights of the GP-B Scie
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2.6.1 Overview of the Calibration P
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Weekly Highlights of the GP-B Final
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66 March 2007 Chapter 3 — Accompl
Page 96 and 97: It was in this pristine, near-zero
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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
Page 110 and 111: Result: By using the porous plug, w
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
Page 118 and 119: spacecraft's subsystems for the dur
Page 120 and 121: Constraint 3: Keep the spacecraft p
Page 122 and 123: Technology Category Specific Implem
Page 124 and 125: 96 March 2007 Chapter 4 — GP-B On
Page 126 and 127: Any significant deviation from “g
Page 128 and 129: packages, one for each Ping load an
Page 130 and 131: In addition to these software packa
Page 132 and 133: Table 4-6. Features & benefits of W
Page 134 and 135: This software added considerable ef
Page 136 and 137: It is said that “an experiment is
Page 138 and 139: Table 4-10. Significant Events/Sour
Page 140 and 141: Figure 4-5. Pictorial depiction of
Page 142 and 143: Figure 4-7. Eta-Average Error Assoc
Page 144 and 145: 4.4.4.2 OD Using SLR DataFigure 4-9
Page 148 and 149: Overall, the storage issues did not
Page 150 and 151: Table 4-11. ITF equipment listEQUIP
Page 152 and 153: 124 March 2007 Chapter 5 — Managi
Page 154 and 155: 5.2 Overview of GP-B Anomalies in O
Page 156 and 157: Figure 5-1. Anomaly Review Team Org
Page 158 and 159: 5.3.3.1 Anomaly Investigation and R
Page 160 and 161: 5.3.5 Anomaly Identification and Re
Page 162 and 163: 5.4.3 Risk Management ApproachThe r
Page 164 and 165: Table 5-1. Summary of Open GP-B ris
Page 166 and 167: 138 March 2007 Chapter 5 — Managi
Page 168 and 169: 140 March 2007 Chapter 6 — The GP
Page 170 and 171: 3. Payload Integration, Testing and
Page 172 and 173: Figure 6-1. Clockwise from top left
Page 174 and 175: MSFC conducted an in-house Phase A
Page 176 and 177: It is important to note that from t
Page 178 and 179: 6.3.1 Incremental PrototypingThe pe
Page 180 and 181: alignment, and act as an accelerome
Page 182 and 183: Figure 6-9. The Lockheed Martin GP-
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Page 192 and 193: As described in Chapter 2, the flig
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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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