Japan spacecraft sends rovers to asteroid

Japan is about to land two robotic rovers on a far-away asteroid in the hope of finding out more about the origin and evolution of the solar system.

Japanese spacecraft Hayabusa2 is launching robotic rovers onto an asteroid. (AAP)

Two small robotic rovers released from a Japanese spacecraft are set to land on an asteroid 300 million kilometres away from Earth.

Space probe Hayabusa2 arrived near the 900-metre-wide asteroid known as Ryugu in late June after a three-and-a-half-year trip, with the rovers among its cargo, Japan's space agency said on Friday.

After the landing, the two rovers - measuring just 18 centimetres across - will make small hops on the asteroid and capture images of the surface and measure temperatures, the Japan Aerospace Exploration Agency (JAXA) said.

The asteroid is believed to contain organic substances and hydrated minerals, and the agency hopes the readings will help find out more about the origin and evolution of the solar system.

Hayabusa2 carries four payloads - three rovers and the 10kg lander, the Mobile Asteroid Surface Scout (MASCOT) built by the German Aerospace Centre (DLR) and the French space agency (CNES).

Hayabusa means falcon in Japanese, while the word Ryugu is an undersea place for a dragon king in Japanese folklore.

The explorer was launched at the Tanegashima Space Centre in southern Japan in December 2014. It is expected to return at the end of 2020 with rock and soil samples, the agency said.