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We report results of Canberra-ATCA Doppler-only continuous wave (CW) radarobservations of near-Earth asteroid (163899) 2003 SD220 at a receivingfrequency of 7159 MHz (4.19 cm) on 2018 December 20, 21, and 22 during itsclose approach within 0.019 au (7.4 lunar distances). Echo power spectraprovide evidence that the shape is significantly elongated, asymmetric, and hasat least one relatively large concavity. An average spectrum per track yieldsan OC (opposite sense of circular polarisation) radar cross section of 0.39,0.27, and 0.25 km$^{2}$, respectively, with an uncertainty of 35 \%. Variationsby roughly a factor of two in the limb-to-limb bandwidth over the three daysindicate rotation of an elongated object. We obtain a circular polarizationratio of 0.21 $\pm$ 0.07 that is consistent with, but somewhat lower than, theaverage among other S-class near-Earth asteroids observed by radar.

Bistatic Radar Observations of Near-Earth Asteroid (163899) 2003 SD220 from the Southern Hemisphere