37th DPS Meeting, 4-9 September 2005
Session 15 Asteroid Physical Studies
Poster, Monday, September 5, 2005, 6:00-7:15pm, Music Recital Room

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[15.21] Physical Modeling of Near-Earth Asteroids 2005EU2 and 2002HK12

S Scoles (NAIC), C Magri (University of Maine, Farmington), E Howell, M Nolan (NAIC)

Radar observations of near-Earth asteroid 2005~EU2 were obtained at Arecibo Observatory on March 26-27, 2005. Both continuous wave (CW) and delay-Doppler images were used to estimate the shape of 2005EU2 using the method of Hudson 1993). The delay-Doppler images are at a resolution of 7.5 m/pixel which reveals at least one crater-like feature on the asteroid surface. Even with this limited data set, we are able to create a three dimensional asteroid model, which provides new information about the rotation and size characteristics of 2005~EU2.

We combined the ephemerides and estimates of rotation rate, rotation poles, spin states, diameters, and scattering law parameters to provide initial model parameters. Shape tries to minimize chi-square, subject to various penalty functions, then outputs images of the 3D asteroid model.

2005EU2 was found to have approximately a period of 3.07 +/- 0.20 hours. The asteroid appears to be an elongated object with principal axes of 211 m by 167 m +/- 15.0 km. These observations cover only one hemisphere of the asteroid. By combining these figures and polarization properties of the asteroid, we will learn more about its surface and scattering properties. All calculations were done assuming equatorial view and principal axis rotation. We varied the initial input values and converged on a consistent model each time.

Preliminary results for another near-Earth asteroid, 2002HK12 indicate a double-lobed object with a rotation period of approximately 13 hours and a diameter of approximately 690 m. The SC/OC ratio (the ratio of same circular polarization to opposite circular polarization) is approximately 1, which, compared to the typical 0.1-0.2 ratio, indicates possible unusual surface material and scattering properties. The models and interpretations for these asteroids will be presented. Research was funded by NSF's REU program.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.