1. Sub-km sized Asteroids Near the Earth & SDSS data Bae Young Ho & Byun Yong Ik Dept. of Astronomy, Yonsei University SDSS Korean Scientist Group Workshop Feb. 20, 2007 YongPyung

2. Near-Earth Objects (NEOs)  NECs (Near-Earth Comets)  NEAs (Near-Earth Asteroids) Atens Apollos Amors PHAs (Potentially Hazardous Asteroids)

3. Orbit diagram of NEAs  Aten and Apollo cross Earth’s orbit.  Difficult to observe them with ground based telescopes.  But, potentially very dangerous!!! UK NEO Task Force Report, 2000

4. Goals of NEO Investigation  Study of dynamics and evolution of the Solar System  Study of statistics and dynamics of near- earth asteroids  Detection & tracking of NEO  Contribution to world-wide effort to protect Earth from NEO impacts

5. Current NEO Search Programs ; International Effort  Lincoln Near-Earth Asteroid Research (LINEAR)  Near-Earth Asteroid Tracking (NEAT)  Spacewatch  Lowell Observatory Near-Earth Object Search (LONEOS)  YSTAR-NEOPAT  Japanese Spaceguard  etc…

6. Near-Earth Asteroids  q ≤ 1.3AU, Q ≥ 0.983AU  Potentially Hazardous Asteroids(PHAs) MOID < 0.05AU ~ 20D L H < 22 About 20% of NEAs  NEAs > 3km : completed  NEAs > 1km : about 55% by early 2004  NEAs less than km-sized : ??? C.R.Chapman, Earth and Planetary Science Letters, 222, 2004

7. The Number of Detected NEAs http://neo.jpl.nasa.gov

8. Size & Magnitude Distribution of Main Belt Asteroids(2) F.Yosida et. al., Science, 2004, 33

9. Sub-km sized Asteroids Near the Earth ; The Characteristics  Most of these are of UNKNOWN nature But, we can guess these are  Very Fast !!! Streaks (tangential direction) Large parallax during exposure time (direction of sight → stereo observation)  High (apparent) Brightness

10. SDSS data & YSTAR-NEOPAT  SDSS data Sky coverage : 8,000 sq. deg.(DR5) Single-shot & Multi-band Observation  Detection Streak : More Effective to define orbital elements & velocity & distance  Study of Statistics & Velocity Distribution of Sub- km sized Asteroids around the Earth

11. SDSS data & YSTAR-NEOPAT  YSTAR-NEOPAT Stereo Observation  More effective on Detection & Define of Orbital Elements & Velocity & Distance Automatic Steak Detection Algorithm  Already developed, and presently being tested for SDSS image archive SDSS Mirror Site

12. YSTAR-NEOPAT System  Small Optics : 0.5m  Shallow Photometric Depth : 17 R at 5σ  Fast Telescope & Open-Type Enclosure  Very Wide FOV : 1.75°X 1.75°

13. YSTAR-NEOPAT South Africa Station

14. Fast Movers in SDSS data http://www.sdss.org

15. Stereo Observation(1)  Two or more telescopes away from each other  Observing same sky area simultaneously  Measure Parallax / streak on images

16. Stereo Observation(2) Captured by RAPTOR, Fall 2003 Earth Detection of the Sub-km sized Asteroids near the Earth AB

17. Stereo Observation(3)

18. Summary  Characteristics of sub-km sized asteroids near the Earth are UNKNOWN !!!  Massive data of SDSS Streak Detection → study of statistics & velocity distribution  YSTAR-NEOPAT South African Extension Dedicated Stereo Observations  More effective to define orbital elements  study of statistics & velocity distribution