Back in October 2012, a small (45-100 feet, or 15-30 m) asteroid known as 2012 TC4 had a close encounter with Earth. It passed our planet at a distance only a quarter of that between the Earth and the Moon. On October 12, 2017, this asteroid will make another close flyby of Earth. This encounter will be used by asteroid trackers around the world to test their ability to operate as a coordinated International Asteroid Warning Network.
2012 TC4 was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) on Hawaii back in 2012. However, it traveled out of the range of asteroid-tracking telescopes shortly after it was discovered.
Based on the observations asteroid trackers were able to make in 2012, they predicted that it should come back into view in the fall of 2017.
Observers with the European Space Agency and the European Southern Observatory were the first to recapture 2012 TC4, in late July 2017, using one of their large 8-m aperture telescopes.
According to the asteroid trackers, 2012 TC4 will fly safely past Earth on October 12 at a distance of about 26,000 miles (42,000 km), or a little over 1/10 the distance from Earth to the Moon.
Its closest approach to our planet will be over Antarctica at 1:40 a.m. EDT (5:40 a.m. GMT, 7:40 a.m. CEST, 10:40 p.m. PDT on October 11).
2012 TC4 poses no risk of impact with Earth. Nonetheless, its close approach to Earth is an opportunity to test the ability of a growing global observing network to communicate and coordinate their optical and radar observations in a real scenario.
This test of what has become a global asteroid-impact early-warning system is a…