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

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Figure 7-7. Magnitude of the roll rate component of pitch yaw pointing performanceFigure 7-8, again shows the correlation between pointing performance and the angle between the telescope axisand the sun vector. The notch filter was implemented in December 2004, and the roll component of thepointing error was only slightly affected by the sun’s position following that date.180 March 2007 Chapter 7 — Attitude & Translation Control Subsystem Analysis
Figure 7-8. Correlation of pointing roll rate component with telescope/sun angle7.3.1.4 SAA BehaviorThe configuration of the ATC has been slightly adjusted to allow for continued pointing toward the Guide Starduring periods of South Atlantic Anomaly (SAA). This was done at the request of the Science Team, and whileexcessive noise to the telescope detectors is noticed during these periods, much of the noise is filtered out byATC filters and limits. The remaining noise which does slightly effect high-precision pointing during SAA isfound to be a manageable risk as compared to the large benefit of greater mission duration in GSV (anadditional 70 minutes, approximately., per day of GSV). Further improvement of the pointing accuracy throughthe SAA has been achieved by setting the TRE gains and clamp settings to avert the effects of a compilation errorin the exception handling of the ATC slopes. This is discussed in more detail in a section below.7.3.1.5 Guide Star Capture TimesFigure 7-9 and Figure 7-10 below show yaw errors immediately at the beginning of a GSV period, taken fromtwo different dates (07 July 2004 and 27 Aug. 2004, respectively). First, one may note that the overall “capture”duration, the time required to damp out gyro hold errors accumulated during the previous GSI period, has beensubstantially reduced from approximately 13 minutes (07 July 2004) to about 3 minutes. This has beenaccomplished through the judicious selection of ATC controller gains and limits, and by removing the 7th orderpolynomial fit for ATC slope in favor of a truncated linear fit. The immediate benefit of this reduced captureduration (10 minutes shorter, approximately) is an additional 10 minutes of science data during a typical 55minute GSV period. This represents nearly a 20% gain in usable science data per GSV period.In addition to the gain and limit changes that have been made, we have also expanded the definition of thelinear range of the telescope to more heavily weight the proportional term even outside the linear range. Part ofthe reason the guide star captures were so long, was the rate capture mode was actually driving the telescopeaway from the guide star before the integrator caught up to the error in the rate gyros due to the motion of theARP.Gravity Probe B — Post Flight Analysis • Final Report March 2007 181
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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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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
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
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Page 182 and 183: Figure 6-9. The Lockheed Martin GP-
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Page 190 and 191: Figure 6-10. MSFC Program Managers/
Page 192 and 193: As described in Chapter 2, the flig
Page 194 and 195: 6.7 Some Observations on the Manage
Page 196 and 197: 168 March 2007 Chapter 6 — The GP
Page 198 and 199: 170 March 2007 Chapter 7 — Attitu
Page 200 and 201: 7.1.2 Vehicle ATC ModesThere are es
Page 202 and 203: The output of the pressure transduc
Page 204 and 205: Figure 7-3. Science Telescope Compo
Page 206 and 207: Figure 7-5. Pitch and Yaw Pointing
Page 210 and 211: Changing the method by which the gy
Page 212 and 213: 7.3.3 Drag-Free Control SystemFigur
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
Page 222 and 223: accomplish this, the ARPs are mount
Page 224 and 225: 7.5.6.1 South Atlantic AnomalyProto
Page 226 and 227: Figure 7-23. Effects on telescope p
Page 228 and 229: 200 March 2007 Chapter 7 — Attitu
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.
Page 236 and 237: of eclipses each day (approximately
Page 238 and 239: Figure 8-8. GSS1 Temperature Trends
Page 240 and 241: Figure 8-10. Forward Dewar Vacuum S
Page 242 and 243: The Gravity Probe B spacecraft has
Page 244 and 245: Figure 8-13. Forward -X Thruster Te
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Page 248 and 249: Because there are only two SQUID br
Page 250 and 251: Because the specifications for SRE
Page 252 and 253: 8.3.2 Critical Mission RequirementT
Page 254 and 255: Figure 8-19 is a plot of the power
Page 256 and 257: 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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