1. Reference impact scenarios – an example
18 Feb 2013
Reference impact scenarios – an example
Gerhard Drolshagen, Detlef Koschny
Presented in ESOC, Darmstadt, 06 Feb 2014
Image credit: ESA
The SSA-NEO Segment, Feb 2013, D. Koschny - Page 4

2. Definitions/terminology
Near-Earth Object (NEO): Any asteroid coming closer than 0.3 AU to the Earth
1 AU = Astronomical Unit = distance Sun-Earth = Mio km
Threatening object: Any asteroid that may hit the Earth
Risk list: A list containing all threatening objects
NEO Itokawa (credit: JAXA)
500 m
SSA-NEO-ESA-HO-0150/1.0 – interface to emergency response, Sep 2013, - Page 4

3. The Tunguska Event Juni 1908 - 105 years ago
2000 km2 of Taiga were destroyed in Sibiria
SSA-NEO-ESA-HO-0150/1.0 – interface to emergency response, Sep 2013, - Page 4

4. NEO impacts: frequency and effects
Asteroids (and Comets) hit Earth with very high velocities.
typical: km/s, 20 times faster than a gun bullet!
NEO diameter
Impact energy [Megatons TNT] (1g TNT ≡ 4184 J)
Typical interval [Years]
Effect
2 mm
1 per hour
(visible for each location)
Nice meteor
3 m
0.002 1
Fireball, Sudan Event, Meteorites reach ground
10 m
0.08 10
Big fireball, fear, shock wave, 5-fold energy of Hiroshima bomb
40 m 5
500
Tunguska explosion or Crater
140 m
220
10,000
Regional destruction, Tsunami
500 m
200,000
Europe-wide destruction
1 km
80,000
700,000
Millions dead, global effects
10 km
80 million
100 million
End of human civilisation

5. ESA-centric view of a case study – detection of a threatening object – 05 Sep 2015…
ESA SSA-NEO survey telescope discovers moving object close to the celestial equator
Position measurements are sent to Minor Planet Center (MPC) in US as part of regular observation process
MPC checks orbit; object is potential NEO. Posted on ‘NEO Confirmation Page’

6. Case study – detection of a threatening object – 06 Sep 2015…
Other observers perform ‘follow-up’ observations
Object is confirmed after 24 hours – receives a ‘designation’
NEODyS computes detailed orbit – finds an impact solution. Impact risk: 1/10 => SSA-NEO managers are informed
Based on visual brightness: size estimate 20 m +/- 10 m => could generate ground effects
JPL Sentry impact monitoring system confirms
SSA Programme Manager is informed
news release is sent to an distribution list (triggered at impact probability of >1/100).
Notification to special distribution list (including civil protection specialists)
SSA-NEO-ESA-HO-0150/1.0 – interface to emergency response, Sep 2013, - Page 6

7. 06 Sep: 14 days before impact
Velocity: 18.7 km/s
Size: 20 m +/- 10 m
Density: 1 g/cm g/cm3
Impact probability: 1/10
Time of impact: 20 Sep 2015, 20:10 +/- 3 min
Kinetic energy:
min: 21.9 Kt
max: 4.87 Mt

8. Starting 06 Sep 2015 High-end amateur telescope
Observations continue (professional and amateur telescopes)
Special observations with infrared telescopes, radar systems (mostly US-based) => allows to constrain physical properties
Arecibo radar Puerto Rico
SSA-NEO-ESA-HO-0150/1.0 – interface to emergency response, Sep 2013, - Page 8

9. 07 Sep: 13 days before impact
18 Feb 2013
07 Sep: 13 days before impact
Velocity: 18.7 km/s
Size: 20 m +/- 10 m
Density: 1 g/cm g/cm3
Impact probability: 1
Time of impact: 20 Sep 2015, 20:10 +/- 1 min
Kinetic energy:
min: 21.9 Kt
max: 4.87 Mt
Background: Comet PanSTAARS C/2011 I4, 12 Mar 2013, D. Koschny
SSA-NEO-ESA-HO-0150/1.0 – interface to emergency response, Sep 2013, - Page 9

10. Possible press response
Reports on Alien invasions
Claim that Space Agencies are hiding information
Killer-asteroid on the way!
Deadly asteroid will destroy Berlin/New York /Tokyo /Moscow/Sidney/Bejing…
The SSA-NEO Segment, Feb 2013, D. Koschny - Page 4

11. 13 Sep: 7 days before impact
Velocity: 18.7 km/s
Size: 20 m +/- 3 m
Density: 1 g/cm g/cm3
Impact probability: 1
Time of impact: 20 Sep 2015, 20:10 +/- 10 sec
Kinetic energy:
min: Kt
max: 1.04 Mt
SSA-NEO-ESA-HO-0150/1.0 – interface to emergency response, Sep 2013, - Page 11

12. 20 Sep 2015
The SSA-NEO Segment, Feb 2013, D. Koschny - Page 4

13. For SMPAG Develop similar sample reference cases – e.g. 2011 AG5
Detected 2011
Impact probabilty up to 1/500 in 2040
But: ‘Keyhole’ passage in 2023
Difficult to get more observations to improve orbit
Solved by obserations with large telescope
SSA-NEO-ESA-HO-0150/1.0 – interface to emergency response, Sep 2013, - Page 13