Like a groggy traveler after a long, cold night, the European Space Agency's comet-chasing Rosetta spacecraft woke up, warmed up and took stock of its surroundings early Monday as it prepared to phone home before setting off on the final leg of its journey.

At least, that's the hope of ESA controllers, who won't know exactly what happened in the dark reaches of our solar system until the spacecraft manages to shake off its 31 months of sleep, turn its antennas toward Earth and send a brief message that will take 45 minutes to arrive. The message isn't expected to arrive at the ESA's Darmstadt, Germany, operations center until at least 6:30 p.m. (12:30 p.m. ET).

That's about 5½ hours after the spacecraft's internal alarm was set to go off.

The spacecraft, launched in 2004, is some 497,000 miles (800,000 kilometers) from Earth, ESA says.