Rosetta answers her wake-up call

Rosetta's alarm clock went off at 1000 UTC, but the craft needed six hours to power up - and the signal had to traverse roughly 800 million kilometers (500 million miles) to Earth - so the European Space Agency (ESA) didn't hear anything from the comet-chaser until the early evening. The signal was first heard at the US space agency NASA's tracking dish in Goldstone, California, at 1818 UTC.

"It was a fairy-tale ending to a tense chapter in the story of the Rosetta space mission this evening as ESA heard from its distant spacecraft for the first time in 31 months," the European agency announced in a statement on its website.

The ESA launched Rosetta into space in 2004 with the goal of carrying out tests on the comet 67/Churyumov-Gerasimenko. The spacecraft will now fly toward the small icy celestial body, enter its orbit and eventually land on its surface, with a targeted touchdown of November. Scientists hope to gather samples from the rock with its 220-pound (100 kg) lander Philae, which could reveal more about the make-up of the solar system at its earliest stages.

'A new level'

In the time since it was thrust into space, the comet-chaser has been gathering speed to put it on the right trajectory toward comet 67/Churyumov-Gerasimenko. It has traveled past Earth three times and Mars once.

In mid-2011, ESA scientists shut down all of its operating systems except for its computer and several heaters. Rosetta has been running on solar power since that time on its journey toward Jupiter's orbit.

"We have our comet-chaser back," ESA Science and Robotic Exploration Director Alvaro Gimenez said in the agency's statement. "With Rosetta, we will take comet exploration to a new level. This incredible mission continues our history of ‘firsts' at comets, building on the technological and scientific achievements of our first deep space mission Giotto, which returned the first close-up images of a comet nucleus as it flew past Halley in 1986."

mkg/tj (AFP, AP, Reuters)