Canada is about to build technology that will be used to map an asteroid in 3D using lasers on an upcoming space mission.

The tool will fly aboard NASA's unmanned OSIRIS-REx spacecraft, which will visit the asteroid Bennu, collect a sample from its surface, and bring that back to Earth, Canadian Space Agency head Walter Natynzczk told a news conference in Toronto on Thursday.

The spacecraft will launch in September 2015, reach Bennu in November 2018 and return to Earth in 2023.

Canadian scientists will work with space technology firm MacDonald, Dettwiller and Associates Ltd. (MDA). The company is about to start building and testing the new tool, known as the OSIRIS-REx Laser Altimeter (OLA).

"They will be creating a 3D map of the asteroid. That will help the team choose the best site to land and collect the sample using advanced robotics," Treasury Board president Tony Clement said at the news conference.

Craig Thornton, general manager for robotics and automation for MDA, said the device will take 160 million measurements of Bennu, which is almost 500 metres in diameter, generating the most accurate map ever created of an asteroid.

Clement said the federal government pledged $61 million to the mission over the next 15 years, including a $9-million contract to MDA.

In return for its contribution the CSA will get four per cent of the asteroid sample for its scientists to study.

York University researcher Mike Daly, deputy principal investigator for the OLA team, said he thinks as a result of the mission, "we're going to learn things about these asteroids that we never, ever expected to learn."

In an interview with CBC News, retired Canadian astronaut Chris Hadfield said the operation will be very challenging because Bennu is constantly rotating.

"Imagine if you were trying to drive your car into a parking spot that is spinning," he said, adding that the OLA will help the spacecraft approach the the asteroid safely.

Bennu is a carbon-rich asteroid made up of material that is thought to be left over from the formation of the solar system and its rocky planets.

Hadfield thinks studying asteroids like Bennu will help scientists understand the origin of our planet. It may also help humans defend themselves against asteroids that threaten Earth.

"You kind of have to know truly what asteroids are made of," he said, "and are they something you could deflect, or is there valuable mineral wealth on them?"

The Canadian scientific team for the mission will be led by Alan Hildebrand at the University of Calgary, and include researchers from the: