Canada is preparing to launch the first space mission ever to search for asteroids between Earth and the sun -- the type of asteroid most likely to slam into our planet.

Asteroids
©Unknown

Fittingly for this country, the Near Earth Object Surveillance Satellite is not a Hubble-sized monster. It's a 60-kilogram microsatellite, costing a mere $10 million, yet able to deliver science results never seen before.

NEOSSat will search for asteroids that are closer to the sun than Earth. These are nearly impossible to see from our planet's surface -- there's too much atmosphere and sunshine -- but easier to spot from space.

The suitcase-sized satellite is expected to launch in two years.

"This is the first space-based asteroid-searching telescope, period . . . Why shouldn't Canada be the leader in a field? And it happens in this case, we are," says Alan Hildebrand of the University of Calgary, one of two principal scientists for the satellite.

Canada's specialty is in shrinking the equipment that holds a satellite stable in space, which allows a very small satellite to aim a telescope without having its aim wobble.

"It happens that we're the world leaders in this technology," he added.

Instead of launching an 11-tonne Hubble, Canada can send up a 60-kilogram "microsatellite."

Astronomers have been watching asteroids for many years. Most are located in a belt on the far side of Mars, but others are scattered here and there through the solar system. Most of the ones we know are outside Earth's orbit.

"Most people are interested in the possibility that an asteroid may impact the Earth," Hildebrand said.

"What you can do from the space that you can't do from Earth is, if you have a baffle (to block sunlight), you can look close to the sun."

Asteroids from far out in the solar system sometimes swing past Earth, but they don't stay long. The ones between us and the sun hang around our neighbourhood permanently. And the most dangerous of these have an orbit that crosses ours at times.

As well, some of these asteroids match Earth's own speed fairly closely, making it relatively easy to fly to one and land there.

"I think the most exciting thing about this mission is we are going to find asteroids that are accessible from our planet," Hildebrand said.

"So I see it as leveraging other exploration, both manned and unmanned," to land on asteroids.

"We've been to the moon. There's always more you can do (there), but asteroids have so much more to teach us about the origins of the solar system."

Many asteroids are leftovers from the original material of the solar system, unlike the moon, which has evolved over time. And some have water and other materials of interest. As well, their weak gravity makes it easier to land, and escape again, than the moon and Mars allow.

No one has ever done a systematic survey for asteroids inside Earth's orbit. Estimates say there could be about 50 big ones -- more than a kilometre wide -- and perhaps thousands of little ones.

The mission is a partnership of agencies led by the Canadian Space Agency and Defence Research and Development Canada.