Comet-chasing probe calls home

The spacecraft Rosetta was launched by the European Space Agency on March 2, 2004, for a 10-year mission to catch comet 67P/Churyumov-Gerasimenko. After taking pictures of Earth, Mars and asteroids, Rosetta was put into hibernation in May 2011 after it reached the outer part of the solar system. Mission managers will wake it up on January 20.

Rosetta will be the first spacecraft to deploy a robot for a soft landing on a comet. It also will be the first probe to escort a comet into our inner solar system. This drawing shows how Rosetta will drop its robotic lander, Philae, onto the comet.

Rosetta is named after the Rosetta Stone, the black basalt that provided the key to deciphering Egyptian hieroglyphs. Scientists hope the mission will give them new clues about the origins of the solar system and life on Earth. The mission is spearheaded by the European Space Agency with key support from NASA.

Traveling through space can be bumpy. Workers put Rosetta through vibration tests before wrapping it in thermal blankets before its launch.

Rosetta's solar wings are unfurled and checked out at the European Space Agency's test facilities.

A European Ariane 5 rocket, carrying Rosetta, lifts off from Kourou, French Guiana, on March 2, 2004.

Rosetta snapped this image of Earth in November 2009. The spacecraft was 393,328 miles from Earth.

After its closest approach to Earth in November 2007, Rosetta captured this image.

Rosetta took this image of Mars as it looped through the solar system.

This image was taken by an instrument on Rosetta's Philae lander just minutes before the spacecraft made its closest approach to Mars. Part of Rosetta and its solar arrays are visible.

Rosetta passed asteroid Steins in September 2008, giving scientists amazing close-ups of the asteroid's huge crater. The asteroid is about 3 miles in diameter.

On July 10, 2010, Rosetta flew about 1,864 feet from asteroid Lutetia, which is 10 times larger than asteroid Steins.

Look closely at the top of this picture. See that dot? That's Saturn. Rosetta snapped the picture of asteroid Lutetia and captured Saturn in the background.

On January 20, Rosetta will wake up, fire its engine and chase after comet 67P/Churyumov Gerasimenko as it hurtles by. This drawing shows how Rosetta will orbit the comet.

A drawing of the comet's nucleus. The nucleus, or rocky part of the comet, is thought to be about 2.5 miles miles wide.

Rosetta will release its robot lander Philae for a soft landing on the comet in November. It will fire harpoons to anchor itself to the comet. Scientists expect the lander to send back data to Earth for at least a week and possibly for many months as the comet heads toward the sun.

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• NEW: ESA's comet probe Rosetta wakes up, beams a signal back to Earth


• The spacecraft is nearly 500 million miles from the Sun, angling to rendezvous with a comet


• Scientist must now learn how to maneuver the craft around the environment of the comet


• Rosetta is set to meet up with the comet in August, follow it for two years

(CNN) -- Like a groggy traveler after a long, cold night, the European Space Agency's comet-chasing Rosetta spacecraft woke up, warmed up and called home Monday before setting off on the final leg of its journey.

Rosetta shook off 31 months of sleep, during which it traveled into the dark reaches of the solar system, and contacted its operators Monday evening. Cheers erupted in the ESA mission control center in Darmstadt, Germany, when a signal from Rosetta arrived shortly after 7 p.m. (1 p.m. ET).

"The spacecraft is there, it's awake, and I think we are all overwhelmed," mission manager Gerhard Schwehm told reporters. Now, he said, controllers will have "two busy years ahead of them" as it approaches its target, Comet 67P/Churyumov-Gerasimenko, and follows it around the sun.

There was only an hour window for the signal to reach Earth, putting scientists on pins and needles.

"The spacecraft decided to make us suffer after two and half year," Paolo Ferri, head of ESA Mission Operations told CNN. "We came almost to the end of the window, we were very tense," he said.

The unmanned probe was launched in 2004 and is now nearly 500 million miles (800 million kilometers) from the Sun -- a distance that puts it just past the orbit of Jupiter. At that distance, the message it beamed back took 45 minutes to arrive.

When the signal finally arrived there were cheers of relief.

Comet-chasing spacecraft 'wakes up'

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Comet-chasing probe wakes up after 2 years

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Wake up Rosetta: You have a date with a comet

If all goes well, Rosetta will rendezvous with the comet in August and fly with it for two years. Scientists now have to learn how to maneuver the craft around a comet.

"It's flying in a very unusual environment for space flight with gas and dust and not much gravity to keep your obit stable," Ferri said.

Rosetta is also supposed to send a small lander to the surface of the comet in November. The mission will give scientists unprecedented insight into the makeup and structure of these ancient residents of the solar system, ESA officials say.

"This is groundbreaking science," Rosetta project scientist Matt Taylor told ESA television. "We're looking at where we came from, the evolution of our own solar system. And comets are looked upon as kind of a time capsule back to the beginning of the solar system."

Scientists believe comets, composed of rock and ice, may have brought water and maybe even the primitive building blocks of life to Earth.

Rosetta carries 11 scientific instruments; its lander has 10 more.

ESA controllers ordered Rosetta to shut down most of its systems in June 2011 to save on power as it sailed through the darkest reaches of the solar system. The amount of sunlight reaching the solar-powered probe is only 4% that on Earth, according to ESA.

READ: 5 things we know about ISON

READ: ESA's Rosetta factsheet

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