NASA is preparing to harness the power of the Earth’s gravity ahead of plans to slingshot a mineral-collecting spacecraft towards a distant asteroid.

The OSIRIS-REx will be visible to observatories and amateur astronomers as it uses Earth to propel itself to a rendezvous with mountain-sized asteroid Bennu in October 2018.

Once there, the jeep-sized spacecraft will begin mapping and studying the rock ahead of its July 2020 landing date to collect rock and dust samples.

On Friday, OSIRIS-Rex is expected approach Earth at a speed of 19,000 miles per hour (30,000kmph) before the Earth’s momentum ratchets up its speed to more than 27,000 miles per hour (43,000kmph) – nearly double the speed of a fuel-based propulsion method.

Michael Moreau, a flight engineer at NASA’s Goddard Space Flight Center, said the ‘gravity assist’ method is essential if the spacecraft is to meet Bennu in time.

“We’re targeting the spacecraft to fly by the Earth at a very specific point and time,” Moreau told the Verge.

Launched last year from Cape Canaveral, OSIRIS-REx is scheduled to return to Earth’s orbit in September 2023 when a special capsule designed with a parachute and heat shield will detach from the spacecraft and enter our atmosphere.

Bennu was chosen for its size rare and proximity to Earth. As a B-type asteroid, it is seen as carbon-rich, meaning its surface is expected to have organic compounds and water-bearing minerals like clay.