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Space Surveillance Contributions to the STS 107 Accident Investigation

Space Surveillance Contributions to the STS 107 Accident Investigation. A Presentation to the AAS/AAIA Space Flight Mechanics Conference 8-12 February 2004 R. Morris, HQ AFSPC/XPY. Authors. HQ AFSPC Space Analysis Division T.S. Kelso, Col USAF retired (now with Analytical Graphics, Inc.)

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Space Surveillance Contributions to the STS 107 Accident Investigation

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  1. Space Surveillance Contributions to the STS 107 Accident Investigation A Presentation to the AAS/AAIA Space Flight Mechanics Conference 8-12 February 2004 R. Morris, HQ AFSPC/XPY

  2. Authors • HQ AFSPC Space Analysis Division • T.S. Kelso, Col USAF retired (now with Analytical Graphics, Inc.) • R.F. Morris, G.T. DeVere, J.C. Randolph, B.R. Bowman, R.A. Racca, N.L. Ericson • 1st Space Control Squadron • R.G. Thurston

  3. Overview • Analysis Contributions • Satellite Breakup • Debris Campaign • Flight Day 2 Piece • Flight Day 5 Object • Summary

  4. Satellite Breakup

  5. Satellite Breakup • NASA requested details of satellite breakup on 29 Jan • Processed data on satellite breakup during STS 107 mission to help NASA determine risk of impact to Columbia • Russian COSMOS 1849 (1987-048A) source of breakup • 62º inclination, apogee height 7,439km, perigee height 94km • Recovered and processed all SSN debris observations • Used specialized in-house processing algorithms & software • Generated element sets for 51 debris objects • Analysis showed breakup debris not close to Columbia • 39º inclination, apogee height 280km, perigee height 263km • Out of phase—no close approaches less than 1,000km

  6. Satellite Breakup

  7. Debris Campaign

  8. Debris Campaign • NASA requested analysis of data collected during Inter-Agency Space Debris Coordination Committee (IADC) Debris Campaign for close approaches to STS 107 • Supported 2003 IADC Debris Campaign on 20 Jan 2003 using Cobra Dane (L-band radar) at high power • Collected added data on objects not in satellite catalog • Processed several thousand metric observations • Generated over 900 new element sets • No debris assessed to present serious collision threat • Only 9 objects had orbits crossing STS 107 orbit regime • None were found to have close approaches (out of phase)

  9. Flight Day 2 Piece

  10. FD2 Piece • Worked with 1 SPCS to discover unexpected piece had separated from Columbia on Flight Day 2 (FD2, 17 Jan 2003) • Sensors and 1 SPCS did not process piece in real time • Common practice to use NASA vectors exclusively • Eliminated need for manual scrutiny by sensor operators • Limited sensor data–few tracks initially sent to Space Control Center • Cape Cod and Eglin down on parts of 17 Jan • Post-processing discovered a small object in shuttle orbit • High interest in the FD2 piece by NASA, CAIB, and DCIST • Searched for additional objects in shuttle orbit—none found

  11. FD2 Piece (cont) • Used SSN data to form initial orbit on FD2 piece • Determined that orbit was very similar to shuttle • No other satellites or objects in similar orbit • 39º inclination, 90-minute period • Collected data from additional sensor tracks • Requested sites to recover any/all data on FD2 piece • Obtained data during sensor downtimes • Obtained data below normal thresholds • Extensive work done to recover & process raw radar data

  12. FD2 Piece: Event Timeline • 17 Jan, 1442Z: Shuttle attitude reoriented • Moved from tail-first to right wing-first orientation • 17 Jan, 1517Z: Shuttle attitude reoriented • Returned to tail-first orientation • 17 Jan, 1500Z-1615Z: Piece separates • 17 Jan, 1857Z: First confirmed SSN sensor track • 19 Jan, 2146Z: Last confirmed SSN sensor track • 20 Jan, 0145Z-0445Z: Piece decayed from orbit

  13. Shuttle Orbit Piece FD2 Piece: Separation from Shuttle Piece Separation Track grouping shows CONUS overflights

  14. FD2 Piece: Characteristics • Ballistic coefficient (B = (Drag Coefficient * Area)/Mass) near 0.10 m2/kg • Suggests a relatively lightweight piece • Physical size of piece estimated to be ~0.4m by ~0.3m • Object was non-spherical • Wavelength of UHF radars (0.7m) is very close to piece size • Introduces uncertainty in size assessment • Piece was initially semi-stable or in a slow rotation on 17 Jan • Approximately 24 hours later, piece was in a tumble

  15. FD2 Piece: RCS Data RCS varied from ~0.1 to ~0.7 m2 17 Jan – slow rotation 18 Jan – 7 sec rotation period 19 Jan – 3 sec rotation period

  16. FD2 Piece: Separation • Generated best possible orbit on piece using high-accuracy special perturbation (SP) theory and SSN observations • Determined separation time/velocity using COMBO (Computation Of Miss Distance Between Orbits) • Separation time window between 1500Z and 1615Z • Results favor 1530Z–1600Z timeframe as most likely • Separation velocity was between 0 and 1.5 m/s • Low separation velocity makes exact separation direction and time more uncertain • Results favor ~0.3 m/sec

  17. FD2 Piece: Continued Analysis • Initial results on FD2 piece generated much interest at NASA, CAIB, and DCIST • Further analysis performed to determine if FD2 piece was from the left wing and possibly associated with the accident • Examined many candidate pieces from the shuttle to understand their area/mass ballistic characteristics • Compared candidate B terms with that generated on FD2 piece from SSN data • AFRL was involved to conduct radar tests of candidates • Compared candidate radar cross sections with SSN data

  18. FD2 Piece: Object Types Examined • Items from inside Shuttle Bay • Thermal Blankets (beta cloth) • Thermal Blankets (aluminized) • Beta Cloth, logo panels • Items from exterior of Shuttle • Thermal Blankets (FRSI, AFRSI) • Heat Tiles (HRSI) • Items from Shuttle wing • RCC panel (wing leading edge) • Ear muff (space under RCC panel) • Carrier panel + Horse Collar seal (surface of wing, behind leading edge) • RCC T-seal (wing leading edge) • RCC segment (wing leading edge) NASA photo NASA photo

  19. FD2 Piece: Conclusions • SSN Area/Mass Analysis integrated with AFRL RCS test data (candidate must pass both tests) • RCS testing further narrowed candidate list • RCC panel fragment is leading candidate for FD2 piece • Damage to Reinforced Carbon-Carbon (RCC) wing leading edge panel would almost certainly result in wing burn-through during reentry • FD2 piece probably associated with left wing problems • CAIB used data—along with many other data sources—to formulate final conclusions and report

  20. Flight Day 5 Object

  21. FD5 Object: Background • Review of NASA log entries prompted request • Flight Day 5 (21 Jan) at 08:51:30Z, crew saw a “bright object that seems to be moving with them… at a long distance.” • JSC-DM submitted request for a COMBO analysis • COMBO: Computation Of Miss Distance Between Orbits • Identify all objects within a NASA specified “box” around Columbia • Compute miss-distances • Time period of analysis: 08:39Z to 08:54Z (16-minute span)

  22. FD5 Object: COMBO Results • Performed COMBO Analysis • Used the complete elset catalog to identify all candidate objects • 250+ objects identified within “box” during specified time interval • Minimum miss distance for all objects: ~370 km (Cerise debris) • More than 75% were in box for less than 5 minutes • Only 6 objects were in box for 10 minutes or greater • 5 candidates identified based on: • Object size • Visibility from Columbia (accounting for shuttle attitude) • Illumination angles (beta angle) • Orbit trajectory • Length of time in specified box

  23. FD5 Object: Summary TOP 5 COMBO CANDIDATES • Most likely candidate is the ORBCOMM satellite • Paralleled shuttle trajectory for duration of time interval • Visible from overhead windows in crew cabin • Bright reflection likely: • Two 42” solar arrays that follow the sun • Optimal beta angle at ~08:42Z (43°) • Stable satellite attitude (steady light source) • Higher orbit—no possible conjunction with Columbia

  24. FD5 Object: COMBO Visualization Trailing Perspective Top-Down Perspective Shuttle from ORBCOMM Video Animations:

  25. Summary

  26. Summary • Conducted various analyses: • COSMOS 1849 breakup • IADC 24-hour Debris Campaign • Flight Day 2 Piece • Flight Day 5 Object Observed by STS 107 Crew • Contributed to NASA’s final determination of the cause of the accident

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