Sub-km sized Asteroids Near the Earth & SDSS data

Bae Young Ho & Byun Yong IkDept. of Astronomy, Yonsei University

SDSS Korean Scientist Group WorkshopFeb. 20, 2007 YongPyung

Near-Earth Objects (NEOs)

NECs (Near-Earth Comets) NEAs (Near-Earth Asteroids)

Atens Apollos Amors PHAs (Potentially Hazardous Asteroids)

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

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

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…

Near-Earth Asteroids q ≤ 1.3AU, Q ≥ 0.983AU Potentially Hazardous Asteroids(PHAs)

MOID < 0.05AU ~ 20DL

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

The Number of Detected NEAs

http://neo.jpl.nasa.gov

Size & Magnitude Distribution of Main Belt Asteroids(2)

F.Yosida et. al., Science, 2004, 33

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

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

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

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°

YSTAR-NEOPATSouth Africa Station

Fast Movers in SDSS data

http://www.sdss.org

Stereo Observation(1)

Two or more telescopes away from each other

Observing same sky area simultaneously

Measure Parallax / streak on images

Stereo Observation(2)

Captured by RAPTOR, Fall 2003

Earth

Detection of the Sub-km sized Asteroids near the Earth

A B

Stereo Observation(3)

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