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

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Figure 6-10. MSFC Program Managers/supporters of GP-B since 1995. Clockwise from top left: Rudolph Decher,Richard Potter, Joyce Neighbors, Rein Ise, Steve Richards, Rex Geveden, Tony Lyons, and Arthur Stephenson.In addition to the NASA/MSFC managers/leaders above, four other persons pictured below in Figure 6-11played important roles in the success of GP-B. They include NASA Resident Manager, Edward Ingraham,Integration Manager, Todd May, Chief Engineer/Lead Systems Engineer, Buddy Randolph, and ChiefEngineer/Subsystem Manager, Stephan Davis.Figure 6-11. MSFC resident and engineering managers. Left to right: Edward Ingraham, Todd May,Buddy Randolph, and Stephan Davis.Among many at NASA Headquarters who helped make GP-B happen, in addition to Nancy Roman and JeffreyRosendhal, were Dixon Ashworth, George Albright, Colleen Hartman, Samuel Keller, Anne Kinney, FrankMartin, Frank McDonald, Ernest Ott, and Charles Pellerin. The current GP-B program executive at NASAHeadquarters is Alan Smale.162 March 2007 Chapter 6 — The GP-B Management Experiment
6.5 Final Integrated Testing, Launch & Science Mission(2002-2005)In November 2002, Gaylord Green became Program Manager. During 2001-2002, Green, who had considerableprior spacecraft operations experience—including working with Parkinson on the development anddeployment of the U.S. Air Force’s Global Positioning Satellite System—had been responsible for organizing theground support operations for GP-B at the Vandenberg Air Force Base launch site on the southern Californiacoast. At the time he assumed the job of Program Manager, the spacecraft was being prepared at LockheedMartin for a thermal vacuum test—a ground simulation of the conditions that the spacecraft would encounterin orbit.6.5.1 The Thermal Vacuum TestBefore the thermal vacuum test began, the LM mechanical team inadvertently left some unshielded wires restingagainst the spacecraft. Then, on the next shift, when the electronics team powered up the spacecraft for theelectronics test, four fuses blew, preventing heater strips from being powered. Thus, during the thermal vacuumtest at the cold temperatures of space, the associated heaters were not turned on and certain parts of thespacecraft were too cold. Also, a vent on the dewar's guard tank leaked into the thermal vacuum chamber,degrading the vacuum.With the launch date now set for December 2003, and what appeared to be yet another possible problem withthe spacecraft, NASA Headquarters convened yet another program review to determine whether to proceedtowards launch or cancel the program. Both the NASA Independent Review Team and the GP-B ScienceAdvisory Committee recommended that GP-B continue with launch preparations. To ensure minimal risk,NASA decided to repeat the thermal vacuum test following a spin balance test early in 2003. The second thermalvacuum test was performed in May 2003 without issue. Shortly thereafter, in July 2003, the spacecraft wasloaded aboard a special truck and driven to the launch complex at Vandenberg Air Force Base.Back at Stanford, throughout the latter part of 2002 and most of 2003, the GP-B Mission Operations Center andthe mission operations team worked very hard, preparing for launch. Under Green's management, a total ofseven procedural simulations were held to rehearse the GP-B mission operations team both for launch and foran unusually sophisticated initialization and orbit checkout period. Rehearsals for dealing with a number ofpotential anomalies that could occur on orbit were included in these simulations.6.5.2 Six-Month Launch Postponement for ECU RepairIn early November 2003, as part of a final spacecraft acceptance review, a grounding problem was discovered ina voltage converter on the Experiment Control Unit (ECU). The ECU was essential for gyro spinup and dewarmonitoring, but not for collecting experimental data. Stanford's recommendation was to turn off the ECUduring the actual science experiment, but LM recommended repairing it. NASA Headquarters then had to makea difficult go/no-go decision. This was the ultimate risk management decision, and not wanting to possiblyjeopardize the experimental results, NASA Headquarters reluctantly decided to postpone the launch for 5-6months so that the ECU could be returned to LM for correction of the voltage converter problem.6.5.3 Successful Launch and Flight MissionModifications to the ECU were completed in March 2004, and the ECU was then shipped back to Vandenbergand reinstalled on the spacecraft frame. A new launch date was set for mid April, and a pre-launch pressconference was held at NASA Headquarters at the beginning of April. The GP-B team, which at that timeincluded people from LM and NASA and totaled close to 200 people was primed and ready when GP-B finallylaunched on April 20, 2004. It was a flawless launch.Gravity Probe B — Post Flight Analysis • Final Report March 2007 163
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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
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It was in this pristine, near-zero
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Each quartz rotor is coated with a
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Figure 3-3. Functional diagram of a
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Based on data from the on-board tel
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Ideally, the telescope should have
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Figure 3-9. Schematic diagram of st
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used. The star trackers are essenti
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Result: By using the porous plug, w
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Solution: Create a tetrahedral lapp
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Constraint 2: The exhaust tube must
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Result: The on-orbit gyroscope spin
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spacecraft's subsystems for the dur
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Constraint 3: Keep the spacecraft p
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Technology Category Specific Implem
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96 March 2007 Chapter 4 — GP-B On
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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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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 146 and 147: 4.4.5 ConclusionsFigure 4-11. Compa
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
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Page 162 and 163: 5.4.3 Risk Management ApproachThe r
Page 164 and 165: Table 5-1. Summary of Open GP-B ris
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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
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Page 182 and 183: Figure 6-9. The Lockheed Martin GP-
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Page 198 and 199: 170 March 2007 Chapter 7 — Attitu
Page 200 and 201: 7.1.2 Vehicle ATC ModesThere are es
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Page 204 and 205: Figure 7-3. Science Telescope Compo
Page 206 and 207: Figure 7-5. Pitch and Yaw Pointing
Page 208 and 209: Figure 7-7. Magnitude of the roll r
Page 210 and 211: Changing the method by which the gy
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Page 214 and 215: 7.3.3.1 DFS - PerformanceThe GP-B d
Page 216 and 217: Figure 7-15. Mass flow effects of a
Page 218 and 219: 7.5.2 Successful recovery from mult
Page 220 and 221: If the vehicle control system were
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Page 224 and 225: 7.5.6.1 South Atlantic AnomalyProto
Page 226 and 227: Figure 7-23. Effects on telescope p
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Page 230 and 231: 202 March 2007 Chapter 8 — Other
Page 232 and 233: Figure 8-2. Block Diagram of CDH co
Page 234 and 235: 8.1.1.4 WATCH DOG TIMERFigure 8-4.
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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
Page 602 and 603:
AcronymDefinitionAcronymDefinitionD
Page 604 and 605:
AcronymDefinitionAcronymDefinitionF
Page 606 and 607:
AcronymDefinitionIRUInertial Refere
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AcronymDefinitionAcronymDefinitionM
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AcronymPMPMAPMCPMEPMETPMSPMSUPNPoPO
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AcronymSCMOSCMTSCNSCPASCPMSCRSCSASC
Page 614 and 615:
AcronymDefinitionAcronymDefinitionT
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588 March 2007 Appendix F — Acron
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