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

More documents

Recommendations

Info

Figure 4-7. Eta-Average Error Associated with GP-B Orbit as a function of IOC duration and sciencemission lifetime4.4.4 Orbit Determination CalculationsGP-B operations also require an accurate knowledge of the satellite ephemeris throughout the mission. Themost stringent requirements are for 25 m and 7.5 cm/sec RMS position and velocity accuracy, to permitaccurate relativistic drift scaling and allow the computed aberration signature to be used for science signalcalibration. There also is a looser requirement for regular three-week predictions for scheduling missionoperations.For those purposes, GP-B ephemeris segments have been generated every day using independent batch fits to30-hour data spans centered on Greenwich noon. That allows for 6-hours overlap before and after each segmentfor consistency comparisons.Global positioning system (GPS) measurements have been used as the primary means of orbit determinationwhile Satellite Laser Ranging (SLR) measurements have been used as an independent means since late-July2004. A similar procedure is used on both data sets to generate daily solutions.4.4.4.1 OD Using GPS DataGPS data points are taken once every 10 seconds. Duplicate points and points with impossibly large or smallradius values are removed from the data set before a GPS solution is generated. The result is a data set at around7500-8500 time points in each 30-hour segment (Figure 4-5). The decrease in usable points available after day66 reflects a switch from A-side to B-side GPS receiver.Next, the commercial software package Microcosm was used to fit an ephemeris to the data. The 35 x 35 gravitymodel jgm3 was used for these fits, along with lunar-solar and earth-tide effects, a constant (shadowed)radiation pressure model and a Jacchia 71 atmospheric density model, both with adjustable scale factors.114 March 2007 Chapter 4 — GP-B On Orbit
After some initial experimentation a decision was made to solve for 9 parameters during each fit. Initially thosewere the 6 state variables (position and velocity) plus a drag coefficient and two sinusoidal in-track accelerationsat orbital period to account for mis-modeled drag and eccentricity vector component rates. Because slowlyvarying constant and sinusoidal axial thrusting components persisted throughout the science mission, GP-Borbit determination continued to solve for those 9 parameters after IOC. The unconstrained drag coefficientabsorbed the dominant in-track effects of the slow semi-major axis variations due to the sinusoidal axialthrusting term, and the in-track sinusoidal parameters modeled the eccentricity vector rate errors due to theconstant axial thrusting term.Figure 4-8. Usable GPS Points per Day (2005)Daily residual plots (Figure 4-9) are generated to assess how well the ephemeris fits the data. Standarddeviations for cross-track residuals are typically less than 5 meters, in-track residuals less than 10 meters, andradial residuals around 15 meters. It can be seen from Figure 4-6 that, for this solution, RMS values areprimarily due to data noise – the ephemeris errors are far smaller. The corresponding overlap comparisonsbetween successive daily 30-hr solutions are a better indication of actual orbit errors. Those daily orbitcomparisons typically yield in-track and radial variations of just a few meters, and cross-track variations areoften less than a meter.There are exceptions to this general pattern of operations. On several days (for example, day 66 in Figure 4-5)there were gaps in the GPS data that prevented the use of a normal 30-hour fit span. When such gaps occurred,2 or 3 days of GPS data were used to create an ephemeris segment spanning the gap. Also, on some days whenthe sinusoidal axial thrusting interacted with the orbital motion so as to generate in-track perturbations with anearly daily period, the in-track effects could not be well approximated by fitting a drag coefficient alone. Forthose ephemeris segments, it is possible to reprocess the data with shorter fit spans and fit additional parametersas needed.Gravity Probe B — Post Flight Analysis • Final Report March 2007 115
Page 1 and 2:
Post Flight Analysis — Final Repo
Page 3 and 4:
Signatures & ApprovalsPrepared byPu
Page 5 and 6:
Table of ContentsPreface . . . . .
Page 8 and 9:
6.8 Sources and References . . . .
Page 10 and 11:
11 Telescope Readout Subsystem (TRE
Page 12 and 13:
14 Data Collection, Processing & An
Page 14 and 15:
xiv March 2007 Table of Contents
Page 16 and 17:
Figure 3-4. The GP-B dewar—one of
Page 18 and 19:
Figure 8-5. The Seasons of GP-B . .
Page 20 and 21:
Figure 11-20. Pointing angle differ
Page 22 and 23:
Figure 14-9. In the Anomaly Room, t
Page 24 and 25:
xxiv March 2007
Page 26 and 27:
Table 13-3. GP-B payload magnetomet
Page 28 and 29:
xxviiiMarch 2007
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
Page 48 and 49:
established, ranging from Level 1 (
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
Page 62 and 63:
y a mere 1.1 inches. You can see th
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 76 and 77:
Table 2-2. Weekly summary of IOC ac
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
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 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
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-
Page 184 and 185: Furthermore, a fourth electronic sy
Page 186 and 187: positive thermal connections betwee
Page 188 and 189: astrophysics/cosmology. Many of the
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 208 and 209:
Figure 7-7. Magnitude of the roll r
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
Page 246 and 247:
gaFigure 8-15. Aft -X Thruster Temp
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
Page 258 and 259:
Figure 8-23. Solar Array Temperatur
Page 260 and 261:
8.3.10 ConclusionThe electrical pow
Page 262 and 263:
8.4.1 TDRSS OperationsFigure 8-28.
Page 264 and 265:
Figure 8-30. Xpndr-A STDN (green),
Page 266 and 267:
Figure 8-32. Plot of TDRS AGC vs Te
Page 268 and 269:
The FSW also met its subsystem leve
Page 270 and 271:
Appendix E, Flight Software Applica
Page 272 and 273:
Table 8-4. SCRs Addressed in On-orb
Page 274 and 275:
The software and macro changes resu
Page 276 and 277:
Figure 8-38 below is an excerpt fro
Page 278 and 279:
Figure 8-40. A-side CCCA Single Bit
Page 280 and 281:
Figure 8-43. A-side CCCA Single Bit
Page 282 and 283:
When single MBEs did not result in
Page 284 and 285:
256 March 2007 Chapter 9 — Gyro S
Page 286 and 287:
9.1 GSS Hardware DescriptionFigure
Page 288 and 289:
significantly reduces and thus pres
Page 290 and 291:
9.1.11 Clock synchronizationThe aft
Page 292 and 293:
Figure 9-8. Block diagram of the LQ
Page 294 and 295:
direction (transverse to the space
Page 296 and 297:
9.2.2.2 Spin-up SuspensionDuring sp
Page 298 and 299:
Figure 9-16. Predicted and measured
Page 300 and 301:
Figure 9-18. The GSS passes rotor c
Page 302 and 303:
Figure 9-20. Representative drag-fr
Page 304 and 305:
Table 9-1. GSS Science Mission Mode
Page 306 and 307:
Table 9-3. GSW application source l
Page 308 and 309:
The Design and Testing of the Gravi
Page 310 and 311:
282 March 2007 Chapter 10 — SQUID
Page 312 and 313:
ate uncertainty). Although we have
Page 314 and 315:
All of the GP-B electronics have be
Page 316 and 317:
10.3 Pre-Launch Ground-Based TestsW
Page 318 and 319:
Figure 10-6. AC Magnetic Shielding
Page 320 and 321:
Figure 10-8. Temperature Error of S
Page 322 and 323:
Figure 10-10. Quiescent SQUID Noise
Page 324 and 325:
Analog control loops on the electro
Page 326 and 327:
The science support applications ru
Page 328 and 329:
Table 10-7. SSW application source
Page 330 and 331:
Page 332 and 333:
Page 334 and 335:
Page 336 and 337:
308 March 2007 Chapter 11 — Teles
Page 338 and 339:
Figure 11-1. Block diagram of TRE a
Page 340 and 341:
Additionally, the warm electronics
Page 342 and 343:
Figure 11-3. CLL switch states duri
Page 344 and 345:
Table 11-3. Dates and UTC times whe
Page 346 and 347:
Figure 11-7. Low Gamma Angle Data S
Page 348 and 349:
s N+w i= sign+w i++−+−w i−w i
Page 350 and 351:
expression, which otherwise on a po
Page 352 and 353:
Figure 11-14. Y axis, B side RMS po
Page 354 and 355:
Figure 11-17. X axis, B side curren
Page 356 and 357:
Figure 11-20. Pointing angle differ
Page 358 and 359:
Figure 11-24. Scaled summed current
Page 360 and 361:
Figure 11-26 through Figure 11-29 s
Page 362 and 363:
334 March 2007 Chapter 12 — Cryog
Page 364 and 365:
12.2 Temperature / pressure control
Page 366 and 367:
control the space vehicle without t
Page 368 and 369:
Figure 12-3. Helium flow rate predi
Page 370 and 371:
helium at 1.8 K. It does not appear
Page 372 and 373:
Figure 12-6. Flow meter and ATC flo
Page 374 and 375:
were generally within a day or so o
Page 376 and 377:
shields) and subsequent instability
Page 378 and 379:
350 March 2007 Chapter 12 — Cryog
Page 380 and 381:
352 March 2007 Chapter 13 — Other
Page 382 and 383:
Figure 13-2. ECU-operated heaters i
Page 384 and 385:
13.1.3.1 Vatterfly Valve Operations
Page 386 and 387:
13.1.3.7 Payload MagnetometersThe E
Page 388 and 389:
Figure 13-11. ECU performance durin
Page 390 and 391:
As we entered the second month of o
Page 392 and 393:
During the last month of IOC, prepa
Page 394 and 395:
Figure 13-19. ECU heater activity d
Page 396 and 397:
Table 13-1. Proton monitor channel
Page 398 and 399:
Figure 13-21. Proton Monitor data i
Page 400 and 401:
In November, 2004 there was a large
Page 402 and 403:
Figure 13-28 shows a correlation th
Page 404 and 405:
13.3.1 About the MagnetometersFigur
Page 406 and 407:
13.3.2 Other Applications for Paylo
Page 408 and 409:
Figure 13-35. GPS Antennae Field of
Page 410 and 411:
Figure 13-37. Master Antenna Switch
Page 412 and 413:
Figure 13-39. Time difference betwe
Page 414 and 415:
13.4.6 On-Orbit ResultsThe GPS comp
Page 416 and 417:
and velocity values erroneously cal
Page 418 and 419:
E. G. Lightsey, C. E. Cohen, B. W.
Page 420 and 421:
Figure 13-45. A Bottom View of the
Page 422 and 423:
Figure 13-48. The GMA configuration
Page 424 and 425:
Table 13-10. Summary for Helium Gas
Page 426 and 427:
398 March 2007 Chapter 14 — Data
Page 428 and 429:
a relatively slow data rate, so we
Page 430 and 431:
Figure 14-4. NASA ground stations a
Page 432 and 433:
electronic components to recover fr
Page 434 and 435:
By a process of elimination, the GP
Page 436 and 437:
A special room in the GP-B Mission
Page 438 and 439:
Starting on 3 December 1725, Bradle
Page 440 and 441:
seemed that aberration of starlight
Page 442 and 443:
14.1.6 Telescope Dither—Correlati
Page 444 and 445:
14.1.6.3 The Telescope Dither Patte
Page 446 and 447:
amplifications. Thus, in addition t
Page 448 and 449:
14.2.2 Independent Data Analysis Te
Page 450 and 451:
monthly time scales. Though only sh
Page 452 and 453:
424 March 2007 Chapter 15 — Preli
Page 454 and 455:
Figure 15-2. A diagram of the GP-B
Page 456 and 457:
15.4 The Two Surprises and Their Im
Page 458 and 459:
Near Zeroes.) The exception that we
Page 460 and 461:
Figure 15-8. A slide from the GP-B
Page 462 and 463:
Figure 15-9. A poster on the effect
Page 464 and 465:
electrostatic patches, located at o
Page 466 and 467:
Last summer (2006), Mac Keiser devi
Page 468 and 469:
440 March 2007 Chapter 15 — Preli
Page 470 and 471:
442 March 2007 Chapter 16 — Lesso
Page 472 and 473:
16.1.1.3 Flight science downlink da
Page 474 and 475:
Description of the GP-B experience:
Page 476 and 477:
Lessons:1. Perform all tests with a
Page 478 and 479:
Page 480 and 481:
Figure 16-1. Six interacting transl
Page 482 and 483:
16.1.3.2 Training and certification
Page 484 and 485:
Page 486 and 487:
Below is an edited summary of six a
Page 488 and 489:
460 March 2007 Chapter 16 — Lesso
Page 490 and 491:
462 March 2007 Appendix A — Gravi
Page 492 and 493:
Apogee altitude659.1 km (409.6 mile
Page 494 and 495:
466 March 2007 Chapter B — Spacec
Page 496 and 497:
Gravity Probe B — Post Flight Ana
Page 498 and 499:
470 March 2007 Appendix C — Weekl
Page 500 and 501:
16 April 2004—Vehicle is Prepared
Page 502 and 503:
The electrical power system is full
Page 504 and 505:
4 JUNE 2004—MISSION UPDATE: DAY 4
Page 506 and 507:
SQUIDs to detect their rotation spe
Page 508 and 509:
17 JULY 2004—MISSION UPDATE: DAY
Page 510 and 511:
indicate that we have reduced the t
Page 512 and 513:
C.4 Science Mission Phase: 8/27/04
Page 514 and 515:
• GP-B also has an independent da
Page 516 and 517:
free suspension parameters to de-tu
Page 518 and 519:
We have received inquiries about a
Page 520 and 521:
One of the effects of geomagnetic s
Page 522 and 523:
egan transmitting, one-by-one, stat
Page 524 and 525:
28 JANUARY 2005—GRAVITY PROBE B M
Page 526 and 527:
magnetic pole. This event triggered
Page 528 and 529:
8 APRIL 2005—GRAVITY PROBE B MISS
Page 530 and 531:
On Tuesday afternoon (19-April), GP
Page 532 and 533:
Norway or through the NASA space ne
Page 534 and 535:
Dewar Temperature: 1.82 kelvin, hol
Page 536 and 537:
visitors on a tour of the GP-B faci
Page 538 and 539:
test, we are planning on running fi
Page 540 and 541:
contractor at the Goddard Space Fli
Page 542 and 543:
On Wednesday, we visited the star H
Page 544 and 545:
Gyro Suspension System (GSS): All 4
Page 546 and 547:
The helium in the dewar has now sur
Page 548 and 549:
the all the spacecraft status data.
Page 550 and 551:
522 March 2007 Appendix D — Summa
Page 552 and 553:
Figure D-2 below shows the distribu
Page 554 and 555:
DateSeveritySubtypeTitle Descriptio
Page 556 and 557:
DateSeverity24 26-Apr-04 Obs F Nois
Page 558 and 559:
DateSeverity40 11-May-04 Obs T Dwel
Page 560 and 561:
Page 562 and 563:
DateSeverity68 16-Jun-04 Medium Dec
Page 564 and 565:
DateSeverity84 13-Jul-04 Obs F Slig
Page 566 and 567:
Page 568 and 569:
DateSeverity116 26-Sep-04 Obs F SG3
Page 570 and 571:
DateSeverity132 20-Dec-04 Obs F Unc
Page 572 and 573:
DateSeverity149 5-Mar-05 Obs T Few
Page 574 and 575:
DateSeverity169 04-Jun-05 Obs F MBE
Page 576 and 577:
DateSeverity191 04-Oct-05 Obs A GSS
Page 578 and 579:
550 March 2007 Appendix E — Fligh
Page 580 and 581:
ReqIDLevel 1CSCDMP DataMgmtProcessi
Page 582 and 583:
ReqIDLevel 1CSCLevel2 CSC Level 3 C
Page 584 and 585:
Page 586 and 587:
Page 588 and 589:
ReqIDLevel 1CSCSRM Solid StateRecor
Page 590 and 591:
Page 592 and 593:
Page 594 and 595:
ReqIDLevel 1CSCSRP SafemodeResponse
Page 596 and 597:
ReqIDLevel 1CSCGUP GSS Processing g
Page 598 and 599:
570 March 2007 Appendix F — Acron
Page 600 and 601:
AcronymDefinitionAcronymDefinitionB
Page 602 and 603:
AcronymDefinitionAcronymDefinitionD
Page 604 and 605:
AcronymDefinitionAcronymDefinitionF
Page 606 and 607:
AcronymDefinitionIRUInertial Refere
Page 608 and 609:
AcronymDefinitionAcronymDefinitionM
Page 610 and 611:
AcronymPMPMAPMCPMEPMETPMSPMSUPNPoPO
Page 612 and 613:
AcronymSCMOSCMTSCNSCPASCPMSCRSCSASC
Page 614 and 615:
AcronymDefinitionAcronymDefinitionT
Page 616:
588 March 2007 Appendix F — Acron
show all

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

Create successful ePaper yourself

Delete template?

Save as template?