407 © Meteoritical Society, 2004. Printed in USA. Radar observations of asteroid 25143 Itokawa (1998 SF36)

Abstract–We observed 25143 Itokawa, the target of Japan’s Hayabusa (MUSES-C) sample-return mission, during its 2001 close approach at Arecibo on twelve dates during March 18–April 9 and at Goldstone on nine dates during March 20–April 2. We obtained delay-Doppler images with range resolutions of 100 ns (15 m) at Arecibo and 125 ns (19 m) at Goldstone. Itokawa’s average circular polarization ratio at 13 cm, 0.26 ± 0.04, is comparable to that of Eros, so its cm-to-m surface roughness probably is comparable to that on Eros. Itokawa’s radar reflectivity and polarization properties indicate a near-surface bulk density within 20 % of 2.5 g cm−3. We present a preliminary estimate of Itokawa’s shape, reconstructed from images with rather limited rotation-phase coverage, using the method of Hudson (1993) and assuming the lightcurve-derived spin period (12.132 hr) and pole direction (ecliptic long., lat. = 355°, −84°) of Kaasalainen et al. (2003). The model can b