A network of astronomers will test an astroid early-warning system tomorrow when a lump of rock up to 30 metres wide passes within 42,000km of Earth.
The asteroid, known as 2012 TC4 has been tracked continuously since July and offers an opportunity for Nasa to evaluate the capability of professional and amateur astronomers to identify and follow objects that could one day pose a risk to Earth.
Co-ordinated by Nasa, the astroid early-warning system comprises dozens of professional facilities around the world who will report their observations centrally. Amateur astronomers can also contribute although the space agency warns that 2012 TC4 will be difficult to see because of its size, speed and distance from the Earth.
Nasa says it has not identified any asteroids that could hit our planet in the next 100 years.