Whether a potential asteroid strike is a Chelyabinsk chaos-causer or a Cretaceous world-ender, it's definitely an advantage to have some forewarning. NASA has been working towards that goal for years, establishing the Planetary Defense Coordination Office to detect and track potentially hazardous space rocks and coordinate response plans with the US government if an impact threat arises. Now, NASA will test out its detection equipment on a known asteroid that's due to buzz Earth in October.

This won't be asteroid 2012 TC4's first visit: it was discovered in 2012 when it whipped past at about a quarter of the distance between Earth and the Moon. Soon after, it vanished into the inky darkness of space, too small and faint to be detected again in the years since. But for the week or so that it was visible, its orbit was plotted out, telling us that TC4 will swing by again on October 12, 2017.

The data isn't complete though, and astronomers can't be sure of its exact path, only knowing it will brush past within 4,200 to 170,000 miles (6,760 to 274,000 km) of Earth. While NASA stresses that the asteroid will not collide with the Earth, narrowing that window is important and serves as a great learning opportunity and test run for the entire international network.

"This is the perfect target for such an exercise because while we know the orbit of 2012 TC4 well enough to be absolutely certain it will not impact Earth, we haven't established its exact path just yet," said Paul Chodas, manager of NASA's Center for Near-Earth Object Studies (CNEOS). "It will be incumbent upon the observatories to get a fix on the asteroid as it approaches, and work together to obtain follow-up observations than make more refined asteroid orbit determinations possible."

As the asteroid approaches Earth over the next few months, astronomers will detect it with large telescopes and take more precise measurements of its path. This task will give the whole system a solid workout before any actual hazards are found hurtling towards us.

"This is a team effort that involves more than a dozen observatories, universities and labs across the globe so we can collectively learn the strengths and limitations of our near-Earth object observation capabilities," says Vishnu Reddy, leader of the 2012 TC4 observation campaign. "This effort will exercise the entire system, to include the initial and follow-up observations, precise orbit determination, and international communications."

TC4 measures between 30 and 100 ft (9 and 30 m) wide, meaning it's roughly the same size or larger than the 66-ft (20-m) Chelyabinsk meteor that caused widespread damage and injury in 2013. That event highlighted how vital it is to spot any potentially hazardous objects early enough to intervene – and NASA is currently working on how we might deflect such a threat.

Source: JPL

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