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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[15.19] Radar Observations of Itokawa in 2004 and Improved Shape Estimation

S. J. Ostro, L. A. M. Benner (JPL/CalTech), C. Magri (U. Maine Farmington), J. D. Giorgini, R. Rose, R. F. Jurgens, D. K. Yeomans (JPL/CalTech), A. A. Hine, M. C. Nolan (Arecibo Obs.), D. J. Scheeres, S. B. Broschart (U. Michigan), M. Kaasalained (U. Helsinki and U. Oulu), J. L. Margot (Cornell)

June 2004 radar images of the Hayabusa (MUSES-C) sample-return target asteroid improve upon the longitude-latitude coverage of images obtained in 2001 by Ostro et al. (2004, MAPS 39, 407-424), and we have used the 2001-2004 images to refine that paper's constraints on Itokawa's shape. The 2004 images, the first of the asteroid's southern side, look distinctly different from the 2001 images. While the 2001 images showed a nearly ellipsoidal shape devoid of noteworthy topographic relief, the 2004 images are replete with intriguing topographic structure. Dark portions of many images suggest subtle concavities, and the irregularity of many images' trailing edges suggests structure at several-decameter scales. The object's leading edges seen at southern subradar latitudes in 2004 are much more curved and rugged than the nearly convex leading edges seen in at northern latitudes in 2001. Although Itokawa's topography is not monumental, it certainly is not as subtle as it appeared to be from the 2001 investigation. Itokawa is shaped like a slightly asymmetrical, bent, lumpy ellipsoid with dimensions along the principal axes within 10% of 594 x 320 x 288 m. Hayabusa's imaging of Itokawa will let us assess the accuracy of shape estimation using Hudson's shape reconstruction technique in situations with suboptimal orientational coverage by a radar data set. It also will let us compare the merits of inferences about physical properties from radar images vs. photometry.

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