After two and a half years in hibernation, the European Space Agency's Rosetta spacecraft emerged from its slumber while cruising nearly 418 million miles (673 million kilometers) from the sun. The wakeup call, which was due to begin at 5 a.m. ET (1000 GMT), took hours as Rosetta switched on heaters to warm itself after its long night in the cold depths of space.

"We made it!" Andrea Accomazzo, Rosetta's spacecraft operations manager, shouted in exultation in a webcast. "We can definitely see a signal from Rosetta!" 

The first signal from Rosetta was received by NASA's Deep Space Network at 1:18 p.m. ET (1818 GMT) and relayed to ESA's Space Operations Center in Darmstadt, Germany, which erupted in cheers and applause as the signal was confirmed.

Rosetta's first message home via Twitter: "Hello, world!"

The signal came after 18 minutes of tense silence as Rosetta's mission team awaited word from the spacecraft.

"We have our comet-chaser back," said Alvaro Giménez, ESA's Director of Science and Robotic Exploration, in a statement. "With Rosetta, we will take comet exploration to a new level."