On October 12, a 30-metre is set to make a 'close' flyby of Earth.

The asteroid, named 2012 TC4, will pass just 4,200 miles (6,800 kilometres) from Earth for the first time since it went out of range in 2012.

Nasa is using this opportunity to test it's 'planetary defence system' put in place to protect Earth from a doomsday asteroid threat.

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On October 12, the 2012 TC4 asteroid will be just 4,200 miles (6,800 kilometres) from Earth for the first time since it went out of range in 2012. Nasa is using the opportunity to test its 'planetary defence system'

THE PLANETARY DEFENCE SYSTEM Nasa hopes to use its international network of observatories to recover, track and characterise asteroid 2012 TC4. As it starts to approach Earth in the coming months, large telescopes will be used to detect it and establish the asteroid's precise trajectory. The new observations are expected to help refine knowledge about its orbit, narrowing the uncertainty about how far it will be from Earth at its closest approach in October. Advertisement

Asteroid 2012 TC4 is estimated to be between 10 and 30 metres in size.

Michael Kelley, a scientist working on the Nasa TC4 observation campaign, said: 'Scientists have always appreciated knowing when an asteroid will make a close approach to and safely pass the Earth because they can make preparations to collect data to characterise and learn as much as possible about it.

'This time we are adding in another layer of effort, using this asteroid flyby to test the worldwide asteroid detection and tracking network, assessing our capability to work together in response to finding a potential real asteroid threat.'

Nasa hopes to use its international network of observatories to recover, track and characterise 2012 TC4.

Professor Vishnu Reddy, who is leading the campaign, said: '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.

'This effort will exercise the entire system, to include the initial and follow-up observations, precise orbit determination, and international communications.'

Based on predictions made at Nasa's Centre for Near-Earth Object Studies, 2012 TC4 will pass no closer than 4,200 miles from Earth, although it will more likely pass much farther away, as far as 170,000 miles (270,000 kilometres).

Based on predictions made at Nasa's Centre for Near-Earth Object Studies in Pasadena, California, 2012 TC4 will pass no closer than 4,200 miles from Earth, although it will more likely pass much farther away, as far as 170,000 miles (270,000 kilometres)

ASTEROID 2012 TC4 The asteroid was first discovered in 2012, when it sped past Earth, but it has been too distant and faint to see over the last five years. It is is estimated to be between 10 and 30 metres in size. Based on predictions made at Nasa's Centre for Near-Earth Object Studies in Pasadena, California, 2012 TC4 will pass no closer than 4,200 miles from Earth, although it will more likely pass much farther away, as far as 170,000 miles (270,000 kilometres). Advertisement

The asteroid was first discovered in 2012, when it sped past Earth, but it has been too distant and faint to see over the last five years.

But as it starts to approach Earth in the coming months, large telescopes will be used to detect it and establish the asteroid's precise trajectory.

The new observations are expected to help refine knowledge about its orbit, narrowing the uncertainty about how far it will be from Earth at its closest approach in October.

Paul Chodas, a manager working on the project, said: '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.

'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.'