Asteroid 1950 DA
http://neo.jpl.nasa.gov/1950da/
Asteroid (29075) 1950 DA was discovered on 23 February 1950. It was observed for 17 days and then faded from view for half a century. Then, an object discovered on 31 December 2000 was recognized as being the long-lost 1950 DA. (As an aside, this was New Century's Eve and exactly 200 years to the night after the discovery of the first asteroid, Ceres.)
Radar observations were made at Goldstone and Arecibo on 3-7 March 2001, during the asteroid's 7.8 million km approach to the Earth (a distance 21 times larger than that separating the Earth and Moon). Radar echoes revealed a slightly asymmetrical spheroid with a mean diameter of 1.1 km. Optical observations showed the asteroid rotated once every 2.1 hours, the second fastest spin rate ever observed for an asteroid its size.
Detection of A Potential Hazard
When high-precision radar meaurements were included in a new orbit solution, a potentially very close approach to the Earth on March 16, 2880 was discovered to exist.
Would that be am or pm?