A European spacecraft racing through the asteroid belt skimmed past a 10-kilometre (six-mile) space rock on Friday to carry out its first scientific work in a decade-long trek into the Solar System, mission controllers said.

In a minutely choreographed operation, the one-billion-euro (1.45-billion-dollar) unmanned probe Rosetta -- launched in 2004 by the European Space Agency (ESA) -- came within around 800 kilometres (500 miles) of an unusual asteroid called (2867) Steins, a distance that is a hair's breadth in space terms.

Its goal was to get rare, close-up photographs and surface scanning of an asteroid, part of the intriguing debris left over from the building of the Solar System.

The encounter took place 360 million kilometres (225 million miles) from home as Rosetta zipped through the asteroid belt between Mars and Jupiter, on its way to a rendezvous with Comet 67P/Churyumov-Gerasimenko in 2014.

Rosetta switched on 11 instruments to scan the rock as it flashed by at 8.6 kms (5.2 miles) per second, or 30,720 kph (19,200 mph), using an optical navigation system to keep automatically on course, ESA said in a live blog of the operation.

The spacecraft had been instructed to make a flip so as to get the best view of the asteroid and this caused a planned break in radio contact of around 80 minutes.

When a NASA ground station relayed the message that it had picked up signals from Rosetta after the flyby, the entire team at mission control "let out a huge cheer," blog editor Daniel Scuka wrote.

Rosetta is four and a half years into a 6.5-billion-kilometre (4.06-billion-mile) journey that will cause it to loop Earth three times and Mars once, using the planet's gravity as a slingshot to build up speed so that it can make the meeting with the comet.

It had been roused from hibernation for the meeting with Steins.

Asteroids are a source of deep scientific interest because of the clues they offer into the physical composition of the planets and the impact of the harsh environment of space.

Understanding their structure, density, orbit and spin is also useful for helping Earth to defend itself against any rogue rock that is deflected onto a collision course with our planet.

Scientists will have to determine whether it will be safer to nudge any potential threat out of harm's way or to blow it up, and accurate knowledge will be crucial for making this decision.

Steins falls into a so-called Type E asteroid, composing mainly silicates and basalts, but about which very little is known in detail.

In addition to scanning Steins' shape and reflectivity with powerful cameras, Rosetta used infrared spectrometry to get a fix on the chemical composition of its surface and monitored whether the asteroid was leaving any dust or emitting gas.

The first pictures of the flyby were expected to arrived back at mission control in Darmstadt, Germany, around noon (1000 GMT) on Saturday, followed by data from other instruments.

"It will take approximately four weeks for all of the acquired data from all instruments to be down-linked," ESA said.

Rosetta is due to carry out a second asteroid flyby in July 2010, skimming past a 100-kilometre (62-mile) rock called 21 Lutetia.

The comet-chasing project was approved in 1993 and launched in 2004.

If all goes well, Rosetta will meet up with Churyumov-Gerasimenko in May 2014 and then send down a small lander, Philae, that will hook onto the comet's crusty surface and carry out nine experiments.