It was brought to life to chase comets but has been asleep for 31 months, drifting beyond the orbit of Jupiter. Yesterday (Jan. 20), the European spacecraft Rosetta successfully turned itself on. The craft had been powered down to save energy, but is now closer to the sun and the comet that it was designed to approach and land on later this year, Comet 67P/Churyumov-Gerasimenko. After turning itself it called home to signal that all was well. It also tweeted, "Hello, world!" 

“This was one alarm clock not to hit snooze on, and after a tense day we are absolutely delighted to have our spacecraft awake and back online,” said Rosetta mission manager Fred Jansen, from the European Space Agency.  

But it's fair to say that it did "hit the snooze button" before phoning home. Mission scientists told New Scientist that it didn't wake up when its first programmed alarm went off, and had to wait for a second reboot, causing 18 minutes of delay that frayed engineers' nerves.