Space Surveillance Contributions to the STS 107 Accident

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. ) § R. F. Morris, G. T. De. Vere, J. C. Randolph, B. R. Bowman, R. A. Racca, N. L. Ericson § 1 st Space Control Squadron § R. G. Thurston 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 2

Overview § Analysis Contributions § § Satellite Breakup Debris Campaign Flight Day 2 Piece Flight Day 5 Object § Summary 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 3

Satellite Breakup 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 4

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 -048 A) source of breakup § 62º inclination, apogee height 7, 439 km, perigee height 94 km § 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 280 km, perigee height 263 km § Out of phase—no close approaches less than 1, 000 km 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 5

Satellite Breakup 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 6

Debris Campaign 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 7

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) 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 8

Flight Day 2 Piece 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 9

FD 2 Piece § Worked with 1 SPCS to discover unexpected piece had separated from Columbia on Flight Day 2 (FD 2, 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 FD 2 piece by NASA, CAIB, and DCIST § Searched for additional objects in shuttle orbit—none found 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 10

FD 2 Piece (cont) § Used SSN data to form initial orbit on FD 2 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 FD 2 piece § Obtained data during sensor downtimes § Obtained data below normal thresholds § Extensive work done to recover & process raw radar data 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 11

FD 2 Piece: Event Timeline § 17 Jan, 1442 Z: Shuttle attitude reoriented § Moved from tail-first to right wing-first orientation § 17 Jan, 1517 Z: Shuttle attitude reoriented § Returned to tail-first orientation § § 17 Jan, 1500 Z-1615 Z: Piece separates 17 Jan, 1857 Z: First confirmed SSN sensor track 19 Jan, 2146 Z: Last confirmed SSN sensor track 20 Jan, 0145 Z-0445 Z: Piece decayed from orbit 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 12

FD 2 Piece: Separation from Shuttle Orbit Piece Separation Piece Track grouping shows CONUS overflights 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 13

FD 2 Piece: Characteristics § Ballistic coefficient (B = (Drag Coefficient * Area)/Mass) near 0. 10 m 2/kg § Suggests a relatively lightweight piece § Physical size of piece estimated to be ~0. 4 m by ~0. 3 m § Object was non-spherical § Wavelength of UHF radars (0. 7 m) 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 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 14

FD 2 Piece: RCS Data 17 Jan – slow rotation RCS varied from ~0. 1 to ~0. 7 m 2 18 Jan – 7 sec rotation period 19 Jan – 3 sec rotation period 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 15

FD 2 Piece: Separation § Generated best possible orbit on piece using highaccuracy special perturbation (SP) theory and SSN observations § Determined separation time/velocity using COMBO (Computation Of Miss Distance Between Orbits) § Separation time window between 1500 Z and 1615 Z § Results favor 1530 Z– 1600 Z 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 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 16

FD 2 Piece: Continued Analysis § Initial results on FD 2 piece generated much interest at NASA, CAIB, and DCIST § Further analysis performed to determine if FD 2 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 FD 2 piece from SSN data § AFRL was involved to conduct radar tests of candidates § Compared candidate radar cross sections with SSN data 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 17

FD 2 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 NASA photo • 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) 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 NASA photo 18

FD 2 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 FD 2 piece § Damage to Reinforced Carbon-Carbon (RCC) wing leading edge panel would almost certainly result in wing burnthrough during reentry § FD 2 piece probably associated with left wing problems § CAIB used data—along with many other data sources— to formulate final conclusions and report 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 19

Flight Day 5 Object 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 20

FD 5 Object: Background § Review of NASA log entries prompted request § Flight Day 5 (21 Jan) at 08: 51: 30 Z, 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: 39 Z to 08: 54 Z (16 -minute span) 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 21

FD 5 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 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 22

FD 5 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: 42 Z (43°) § Stable satellite attitude (steady light source) § Higher orbit—no possible conjunction with Columbia 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 23

FD 5 Object: COMBO Visualization Trailing Perspective Video Animations: 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 Top-Down Perspective Shuttle from ORBCOMM 24

Summary 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 25

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 14 th AAS/AIAA Space Flight Mechanics Conference, 2003 February 9 26