The asteroid, called 2015 FF, is expected to come within 0.02864 astronomical units, or around 2.6 million miles, from the Earth's surface, at 08:09 UTC (09:09 BST). .
2015 FF is also 'potentially hazardous' because it comes within 0.05 astronomical units (4.65 million miles) of Earth, although it's much smaller than other potentially hazardous objects (PHOs). .
Although 2015 FF – which can be tracked on NASA's website – is at a distance of 2.6 million miles away, this is relatively close in astronomical terms. .
NEOs are an asteroid or comet whose orbit brings it into or through a zone between approximately 91 million and 121 million miles (195 million km) from the sun, meaning that it can pass within about 30 million miles (50 million km) of Earth’s orbit. .
Although 2015 FF is at a distance of 2.6 million miles away, this is relatively close in astronomical terms (file photo)
On average, Earth is hit by a football pitch-sized rock every 5,000 years, and a civilisation-ending asteroid every one million years, according to NASA's Near-Earth Object Program.
While neither asteroid poses a threat to Earth, DART's kinetic impact will prove that a spacecraft can autonomously navigate to a target asteroid and kinetically impact it
The DART technique could prove useful for altering the course of an asteroid years or decades before it bears down on Earth with the potential for catastrophe
Deflecting an asteroid such as Bennu, which has a small chance of hitting Earth in about a century and a half, could require multiple small impacts from some sort of massive human-made deflection device, according to experts
The space agency upgraded the risk of Bennu impacting Earth at some point over the next 300 years to one in 1,750
Scientists have been seriously considering how to stop an asteroid from ever hitting Earth since the 1960s, but previous approaches have generally involved theories on how to blow the cosmic object into thousands of pieces
A more recent approach, called kinetic impact deflection (KID), involves firing something into space that more gently bumps the asteroid off course, away from Earth, while keeping it intact.
Therefore, around 160 years in the future – when Bennu is most likely to collide with Earth, according to NASA – a KID device would have to give it a series of gentle nudges to prevent it from breaking up and sending dangerous splinter fragments flying towards Earth
'Although the chances of it hitting Earth are very low, Bennu remains one of the two most hazardous known asteroids in our solar system, along with another asteroid called 1950 DA,' NASA said in a statement.