Space Surveillance Contributions to the STS 107 Accident InvestigationSpace Surveillance
Space Flight Mechanics Conference
Authors
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
Overview
Satellite Breakup
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
*
Satellite Breakup
Debris Campaign
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
*
Flight Day 2 Piece
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
*
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
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
*
FD2 Piece: Event Timeline
Moved from tail-first to right wing-first orientation
17 Jan, 1517Z: Shuttle attitude reoriented
Returned to tail-first orientation
17 Jan, 1857Z: First confirmed SSN sensor track
19 Jan, 2146Z: Last confirmed SSN sensor track
20 Jan, 0145Z-0445Z: Piece decayed from orbit
*
FD2 Piece: Separation from Shuttle
Piece Separation
Shuttle Orbit
FD2 Piece: Characteristics
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
*
FD2 Piece: RCS Data
17 Jan – slow rotation
RCS varied from ~0.1 to ~0.7 m2
*
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
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
*
FD2 Piece: Object Types Examined
Items from inside Shuttle Bay
Thermal Blankets (beta cloth)
Thermal Blankets (FRSI, AFRSI)
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
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
*
Flight Day 5 Object
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
*
FD5 Object: COMBO Results
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
Illumination angles (beta angle)
*
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:
Optimal beta angle at ~08:42Z (43°)
Stable satellite attitude (steady light source)
Higher orbit—no possible conjunction with Columbia
FD5 Object: Summary
Video Animations:
Summary
Summary
Flight Day 5 Object Observed by STS 107 Crew
Contributed to NASA’s final determination of the cause of the accident
-1400
-1200
-1000
-800
-600
-400
-200
0
200
17-00:00:00
18-00:00:00
19-00:00:00
20-00:00:00
21-00:00:00
0
10
20
30
40
50
60
70
Seconds
RCS
0
5
10
15
20
25
30
Seconds
RCS
0
5
10
15
20
25
30
Seconds
RCS