The 260 - 580 metre wide asteroid 2003 UC5 will make a close pass (68.1 lunar distances, 0.1750 au), travelling at 35.80 km/second, to the Earth-Moon system on the 21st October, 2012 @ 02:01 UT ±00:01.
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The Lunar Distance (LD), the distance between Earth and the Moon, equals 384,401 km, (or 0.00256 AU).