1. Threat from the Space : Orbital Debris and NEAs
Hong-Kyu Moon
Korea Astronomy and Space Science Institute

2. Orbital debris: an introduction

3. History: Near Earth environment
Courtesy: NASA/JSC

4. Mission-related debris
The Debris Family
Nat'l Academies Press (modified)
10 m
100 m
10 cm
1 m
10 m
1 mm
1 cm
Size
R/Bs, S/C
Breakup fragments
Mission-related debris
Al2O3 slag
Al2O3
Meteoroids
NaK
Paint flakes
MLI pieces
Orbital Debris

5. How much junk is up there?
Softball size or larger ≥10 cm:
~22,000
Marble size or larger ≥1 cm:
~500,000
A grain of salt or larger ≥1 mm:
~100,000,000
Total mass: ~6300 t LEO-to-GEO (~2700 t in LEO)
Debris of 0.2 mm in size pose a realistic threat to Human Space Flight

6. Potential shuttle damage
Nat'l Academies Press
0.5
1.5
2.5
3.5
4.5
5.5
6.5
0.01
0.1 1 10
100
1000
Window Replacement
EVA Suit Penetration
Radiator Penetration
Debris Diameter in cm
RCC Penetration
TPS Tile Penetration
Cabin Penetration
Cargo Bay Damage

7. Growth: cataloged pops
National Academies Press
Iridium-Cosmos
FY-1C ASAT Test

8. Orbital debris: KASI activities

9. NAP: Optical Wide-field Patrol
A World-wide Network of o.5 m telescopes
Optics: 0.5 m Richey-Cretien
Detector: 4K CCD, 1º.75 FOV
Primary objectives
Tracking domestic LEOs
Monitoring GEO-belt
Collision risk management
Locations: TK, MN, KZ, NZ, ZA
Start operations: 2013
NAP: National Agenda Project

10. NAP: Optical Wide-field Patrol
2-m class Space Debris Telescope, Big-OWL
currently in requirements analysis
Primary objectives
GEO debris: down to < 10 cm
LEO debris: low inclination & high eccentricity
Near Earth Asteroids
Location: TBD
Expected operations: 2016

11. NAP: ROSAT reentry monitoring
To be ready for reentry of the defunct German X-ray
space telescope ROSAT in Oct 2011, MEST installed &
operated a situation room at KASI.
Monitored orbit decay: TLE
Orbit analysis and prediction: STK – modeling
Dissemination of info.;
and …
Ready for reentry of “Phobos-Grunt”

12. NAP: ROSAT reentry monitoring
Daily reports 6; spot report 12
Web news 7; Twitts 36
Press releases 3; press coverage 113
Reponses: The Blue House; ministries and
gov’t offices, AF, and Korean Air

13. Orbital debris: the future

14. The Worst Case Scenario
Courtesy: NASA/JSC
The Worst Case Scenario
Regular launches, No mitigation measures

15. Preserve the environment for future
2011
2211 ?
Passive and active measures: global coordination
Observing – cataloging – modeling (KASI - KARI)
Collision predictions – alert – avoidance (KARI - KASI)
Controlled reentry - active removal

16. Near Earth Asteroids: NEAs

17. NEAs: an introduction

18. Definition of NEO Near-Earth Objects
Asteroids and comets that cross or approach the orbit of the Earth.
About 90% of NEO population is NEAs.
PHAs have orbits that come to within 0.05 AU of Earth’s.
If a NEO’s orbit intersects that of Earth, a collision is possible.
Depends on phasing
Annual meteor showers are caused by Earth passing through the paths of comets.

19.                                                                                                                                                                                             
                                                                                                                                                                                            
                                                                                                                                                                                            
                                                                                                                                                                                            
                                                                                                                                                                                            
December Near Earth Asteroids : 8,405 Potentially Hazardous Asteroids : 1,269

20. Composition Asteroid composition classifications:
Wide variety of spectral classifications,
but there are three main groups:
S-group
Silicaceous, majority of inner asteroid belt
Iron mixed with iron- and magnesium-silicates
X-group
M: Metallic iron, E: high albedo, P: low albedo
C-group
Carbonaceous, dark, 75% of known asteroids

21. NEAs: impact records

22. Confirmed impact structures: 182

23. Impact is still occurring!
Task Force Report on the Potentially Hazardous Near Earth Asteroids 2000, UK

24. Impact Earth: examples
Upper atmosphere bolides (several/year):
Stony and icy objects smaller than 50 m will burn up or explode in the upper atmosphere.
There are numerous historical examples extending up to present day.
1998: A small meteorite hit the ground 1 meter from
a man playing golf in Ontario.
2002: A ~10 m object exploded over Mediterranean
Sea, releasing ~26 Kt.

25. The impact and recovery of
asteroid 2008 TC3

26. NEAs: Mitigation measure

27. Terrestrial Impact: A scaling law
Courtesy: LSST

28. MND and NEO risks
NEO risks are best compared with the risks of Major Natural Disasters (MND)
- The causes are similarly natural
- The NEO risks ~ 1/10 of MND risk
- NEO risks can be substantially reduced by
research and actions

29. Explosively growing discovery rate
NASA’s Spaceguard Goal: identify 90% of NEOs larger than 1 km within a decade.
Spaceguard Project
initiated in 1998
Courtesy: NASA/JPL

30. Findings and conclusions:
Recommendations for the OECD gov’t (Apr 2003)
1. Acknowledging the problem
2. Enabling a policy-level response
3. Assessing risk at the national level
4. Strengthening risk assessment through R&D
5. Supporting exploratory R&D for mitigation
UN COPUOS Action Team 14 on NEO
Near Earth Object, Interim Report of the Action
Team on NEO, in preparation (will be released in Feb 2012)

31. NEAs: KASI activities

32. Assessment and mitigation
Detection & characterization (planned project)
- Discovery and follow-up
- Orbit and impact risk analysis
- Physical characterizations
Deflection methods
Optimal impulsive NEO deflection
Mitigation mission design

33. KMTNet: secondary science - proposed
24-hour uninterrupted monitoring of the southern NEAs in 3 different time zones.
- D = 1.6 m prime focus
- 4 x 9K chips, 4□°FOV
- High QE ~ 90 %
- Cousins and SDSS filters
- Australia, Chile & S. Africa

34. Physical characterizations
During "off-season" for exoplanets search we will investigate bulk properties of NEAs
- mass, ρ, and porosity
- internal structure and composition
- surface chemical composition
- spin state
Physical characterization is very much in need for risk assessment for NEA impacts

35. Questions?