Arecibo and Goldstone radar images of near-Earth Asteroid (469896) 2005 WC1

We report radar observations of near-Earth asteroid (469896) 2005 WC1 that were obtained at Arecibo (2380 MHz, 13 cm) and Goldstone (8560 MHz, 3.5 cm) on 2005 December 14–15 during the asteroid's approach within 0.020 au The asteroid was a strong radar target. Delay-Doppler images with resolutions as fine as 15 m/pixel were obtained with 2 samples per baud giving a correlated pixel resolution of 7.5 m. The radar images reveal an angular object with 100 m-scale surface facets, radar-dark regions, and an estimated diameter of 400 ± 50 m. The rotation of the facets in the images gives a rotation period of ∼2.6 h that is consistent with the estimated period of 2.582 h ± 0.002 h from optical lightcurves reported by Miles (private communication). 2005 WC1 has a circular polarization ratio of 1.12 ± 0.05 that is one of the highest values known, suggesting a structurally-complex near-surface at centimeter to decimeter spatial scales. It is the first asteroid known with an extremely high circular polarization ratio, relatively low optical albedo, and high radar albedo.