Far from Earth, a robot spacecraft has been prodded from deep slumber to make a rare encounter with an asteroid, the intriguing orbital debris that could offer clues into the making of the Solar System.
The pride of the European Space Agency (ESA), the probe Rosetta has been ordered out of hibernation four and a half years into a 10-year trek that will take it into the dark chill of deep space.
Rosetta is due to rendezvous in 2014 with Comet 67P/Churyumov-Gerasimenko, sending down a refrigerator-sized lab to examine its crusty surface.
But its 6.5-billion-kilometre odyssey will be interrupted on Friday, when the craft will get down to some serious science as it zooms through the asteroid belt between Mars and Jupiter.
Some 360 million kilometres from home, Rosetta will carry out a flip to let its array of cameras and scanners snatch what could be a stunning view of a 10-kilometre-long space rock called Steins.
It will aim to get unprecedented high-resolution data of Steins’ shape, size and spin, and maybe also tease out clues about its density and composition.
These could add useful knowledge about how asteroids – hypothesised as primordial rubble left from the building of the Solar System – weather during their aeons in orbit, said Rosetta’s mission manager, Gerhard Schwehm.
“It’s an E-type [asteroid], which is a silicate asteroid with a dark surface, and has not been looked at before from a spacecraft,” he told AFP.
Impact with Earth?
And experts in monitoring space rocks that are a potential threat to Earth will also be looking closely, said Schwehm.
“There’s a lot of scientific interest in asteroids as primitive objects, but there’s also interest in them as hazards, as Near-Earth Objects,” he said.
“It’s always useful to see their different composition, shape and size. By looking at them close-up and then comparing them with ground-based data, you can see how your classification and measurement systems perform.”
At the closest point, expected at 6.58pm GMT on Friday, the craft will flash past Steins at a distance of 800 km and with a speed of 8.6 km per second (30 720 km/h).
Rosetta is due to carry out a second asteroid flyby, skimming past a 100-km behemoth called 21 Lutetia in July 2010.
Costing a billion euros, Rosetta is the most ambitious mission ever undertaken by ESA.
The project was approved in 1993 and launched in 2004 from ESA’s base at Kourou, French Guiana.
Since then, the spacecraft has looped twice around the Earth and once around Mars, using planetary gravity as a slingshot to help it build up speed.
A third gravitational “assist” by Earth is due in November 2009.
If all goes well, Rosetta will meet up with Churyumov-Gerasimenko in May 2014 and then send down a lander, known as Philae, that will anchor to the comet’s surface and analyse samples in a tiny onboard lab.
Friday’s flyby of asteroid Steins coincides by accident with another big date for ESA, when its truck-sized robot freighter, Jules Verne, is scheduled to detach from the orbital International Space Station (ISS) after a five-month maiden mission.