1. Dissecting Space Debris Events
Dr. T.S. Kelso

2. Overview Three notable events Recognizing event triggers
IRIDIUM 47, 2014 Sep 26
IRIDIUM 91, 2014 Dec 3
DMSP 5D-2 F13, 2015 Feb 25
Recognizing event triggers
Performing orbital forensics
Conclusions

3. Event Trigger TLEs released via Space Track
Typically not added to their SATCAT for days/weeks
No event time or cause provided
Only identifies International Designator (launch)
U 97082H
Data posted to CelesTrak within 8 hours
Perform initial analysis and tweet results
Goal to provide awareness and starting point for other analysts

4. Post-Trigger Analysis
Obtain TLEs for all objects
Check debris for nodal drift & alignment with pre- existing objects
Refine event time by plotting range to parent
Generate relative velocity using STK Viewer
Provides insight into type of event
Can be limited by data quality and number of pieces

5. IRIDIUM 47 Event
First public TLEs: 2014 Sep 26
10 TLEs for

6. Debris aligned with IRIDIUM 47 and 49
Separation of debris planes correlated to time since event

7. Separation of debris planes, 2014 Mar 24 to Sep 25
Suggests event occurred around 2014 Jun 12

8. Separation of debris planes, 2014 Jun 5-18
Suggests event occurred around 2014 Jun 12

9. Debris range to IRIDIUM 47, 2014 Jun 5-19
Suggests event occurred around 2014 Jun 12

10. Debris range to IRIDIUM 47, 2014 Jun 11-14
Suggests event occurred on 2014 Jun 12

11. Debris range to IRIDIUM 47, 2014 Jun 12
Suggests event occurred around 1900 UTC

12. IRIDIUM 47 Results
TLE analysis suggests event time of 2014 Jun 12 around 1900 UTC
JSpOC-reported event time 2014 Jun 7, 0330 UTC
Shows limitations of TLE data for long propagation
No public statement from Iridium regarding event
Only stated IRIDIUM 47 still operational
Optical observations confirm stable attitude

13. Separation of debris planes from IRIDIUM 47, 2014 Jun 5-15
No clear event time apparent

14. IRIDIUM 47 and debris at JSpOC-predicted event time

15. IRIDIUM 91 Event
First public TLEs: 2014 Dec 3
4 TLEs for

16. 2002-005 orbits and debris at TLE release
Clear alignment with IRIDIUM 91 & 95

17. Debris range to IRIDIUM 91, 2014 Nov 28-Dec 3
Suggests event occurred on Nov 30

18. Debris range to IRIDIUM 91, 2014 Nov 30
Suggests event occurred on Nov 1615 UTC

19. IRIDIUM 91 and debris at predicted event time

20. IRIDIUM 91 Results
TLE analysis suggests event time of 2014 Nov 30 @ 1615UTC
JSpOC-reported event time agrees
No public statement from Iridium regarding event
Only stated IRIDIUM 91 still operational
Optical observations confirm stable attitude
IRIDIUM 91 was the spare moved into IRIDIUM 33’s slot after the collision with COSMOS 2251 on Feb 10

21. DMSP 5D-2 F13 Event First public TLEs: 2015 Feb 25
26 TLEs initially (eventually 160 objects)

22. 1995-015 orbits and debris at TLE release
Debris does not line up with known orbits

23. Separation of debris planes, 2015 Jan 24-Feb 26
Suggests event occurred around 2015 Feb 1

24. Separation of debris planes, 2015 Jan 29-Feb 5
Suggests event occurred around 2015 Feb 1

25. Debris range to DMSP 5D-2 F13, 2015 Jan 30-Feb 5
Suggests event occurred on 2015 Feb 3

26. Debris range to DMSP 5D-2 F13, 2015 Feb 3
Suggests event occurred on 2015 Feb 1723 UTC

27. DMSP 5D-2 F13 and debris at predicted event time

28. Gabbard plot of all 160 pieces of debris
Ranges from perigee of 350 km to apogee of 1,200 km

29. Relative Velocity of Debris
Use to further illuminate event circumstances
Start with all 160 debris objects
Propagate to event time and filter to within 100 km
Eliminates all but 52 objects
Calculate velocity of each debris piece relative to pre- event orbit of main payload

30. Distribution of 52 pieces of debris within 100 km

31. Relative velocity distribution in satellite frame

32. Largest components vertical and in velocity direction

33. DMSP 5D-2 F13 Results
Analysis showed event time of 2015 Feb ~1723 UTC
50th Space Wing Review Board stated: “Post event analysis indicated that a major kinetic event occurred at ~1720z.”
Attributed cause to Battery 1 rupture
Thermal runaway detected on pass prior to kinetic event at 1634 UTC
Successfully safed and decommissioned satellite

34. Conclusions No events attributed to collisions
All events occurred in high-density debris convergence zones near the poles
Analysis hampered by delayed release of orbital data and lack of transparency
Some suggestions this may be improving
Cases represent opportunities to improve safety of flight
Probably won’t be the last examples

35. Polar debris convergence zones
Correlated to inclination of large constellations

36. Polar debris convergence zones
Correlated to inclination of large constellations

37. Questions?