南半球近地小行星（163899）2003 SD220的双基地雷达观测
Bistatic Radar Observations of Near-Earth Asteroid (163899) 2003 SD220 from the Southern Hemisphere
摘要：
我们报告了堪培拉-ATCA多普勒连续波（CW）雷达对近地小行星（163899）2003 SD 220的观测结果，接收频率为7159 MHz（4.19 cm），于2018年12月20日，21日和22日在0.019 au（7.4月球距离）内接近。回波功率谱提供的证据表明，形状是显着拉长，不对称，并有至少一个相对较大的弯曲。每个航迹的平均频谱产生的OC（圆极化相反方向）雷达截面分别为0.39、0.27和0.25 km $^{2}$，不确定度为35%。在这三天里，肢体到肢体的带宽变化大约为2倍，这表明细长物体的旋转。我们得到一个圆偏振比为0.21 $\pm$ 0.07，这是一致的，但略低于，在其他S级近地小行星的雷达观测的平均值。
英文摘要：
We report results of Canberra-ATCA Doppler-only continuous wave (CW) radar observations of near-Earth asteroid (163899) 2003 SD220 at a receiving frequency of 7159 MHz (4.19 cm) on 2018 December 20, 21, and 22 during its close approach within 0.019 au (7.4 lunar distances). Echo power spectra provide evidence that the shape is significantly elongated, asymmetric, and has at least one relatively large concavity. An average spectrum per track yields an 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 \%. Variations by roughly a factor of two in the limb-to-limb bandwidth over the three days indicate rotation of an elongated object. We obtain a circular polarization ratio of 0.21 $\pm$ 0.07 that is consistent with, but somewhat lower than, the average among other S-class near-Earth asteroids observed by radar.
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