The 18 - 39 metre wide asteroid 2015 SS2 made a close pass (19.9 LD, 0.0512 AU) travelling at 5.10 km/second, to the Earth-Moon system on the 20th September 2015 @ 15:47 UT ±01:14.
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The Lunar Distance (LD), the distance between Earth and the Moon, equals 384,401 km, (or 0.00256 AU).