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

Orbital debris: an introduction

History: Near Earth environment Courtesy: NASA/JSC

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

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

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

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

Orbital debris: KASI activities

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

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

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”

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

Orbital debris: the future

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

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

Near Earth Asteroids: NEAs

NEAs: an introduction

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.

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 December 08 2011 Near Earth Asteroids : 8,405 Potentially Hazardous Asteroids : 1,269

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

NEAs: impact records

Confirmed impact structures: 182

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

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.

The impact and recovery of asteroid 2008 TC3

NEAs: Mitigation measure

Terrestrial Impact: A scaling law Courtesy: LSST

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

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

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, 2010-2012 Interim Report of the Action Team on NEO, in preparation (will be released in Feb 2012)

NEAs: KASI activities

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

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

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

Questions?