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Asteroid Pallas
The close approach of FU 162 was no reason for alarm among scientist given that it is estimated to be about 10 m across and would have burned up before plunge very deep into Earth’s atmosphere. It would take an asteroid in excess of 100 m in diameter to impact Earth’s surface. Prior to the approach by FU 162, the closest asteroid had been 2004 FH, which came within 50,000 km of our atmosphere.
FU 162 was detected by the LINEAR survey system in New Mexico. Tim Spahr of the Minor Planet Center contacted the NASA NEO Program Office at JPL to extract an orbit, even though there was only 44 minutes of data available to study. No pre-recovery data were found, and indeed this asteroid is so small that it could not be seen by survey telescopes except when it was very close to Earth. Orbit calculations, however, did show that this asteroid had come closer than any previously discovered NEA. Based on this orbit, the asteroid was given an official designation.
The Lincoln Near-Earth Asteroid Research (LINEAR) is a cooperation between NASA, MIT, and the American Air Force. It has been operating a near-Earth object discovery facility using a one-meter aperture Ground-based Electro-Optical Deep Space Surveillance(GEODSS). The GEODSS instruments used by the LINEAR program are located at the Lincoln Laboratory’s experimental test site in Socorro, New Mexico. Between March and July 1997 four near Earth objects(NEOs) were discovered. In October 1997, a large format CCD, covering the telescope’s 2 square degree field of view, was added and discovered 9 new NEOs. There are multiple telescopes in use at the sight today. The LINEAR telescopes observe each patch of sky 5 times per night, but most of the efforts are concentrated along the ecliptic plane where most NEOs would be expected. The sensitivity of their CCDs, and the relatively rapid read out rates, allow LINEAR to cover large areas of sky each night. LINEAR is responsible for the majority of NEO discoveries.
The discovery of the closest asteroid was proof that LINEAR could be used as an early warning system if need be. The program continues to find new NEOs every month, but none have come closer than FU 162.
There is a good article on the NASA website about the closest asteroid. Universe Today has an article on asteroid near misses and Astronomy Cast has a good episode on sky surveys.
Sources:
http://impact.arc.nasa.gov/news_detail.cfm?ID=145
http://neo.jpl.nasa.gov/missions/linear.html
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