sciencehabit writes "The European comet-chasing probe Rosetta is up and running again today after it successfully roused itself from a 2½-year sleep and signaled anxious controllers on the ground. The spacecraft had been put into hibernation during the most distant part of its 10-year journey in pursuit of comet 67 P/Churyumov-Gerasimenko because sunlight was too dim to keep its solar-powered systems running. Dozing in a slow stabilizing spin, Rosetta could not receive signals from the ground, so there was a risk that some problem might prevent it from responding to its preset alarm call at 10:00 GMT. Even then, there were many processes to go through before news reached Earth: The spacecraft's heaters would need to warm up its systems, its startrackers get a fix, boosters halt the spin, solar arrays turn towards the sun, and, finally, its communications antenna would need to point at Earth. It was not till 18:18 GMT that the signal was picked up by NASA's ground stations at Goldstone, California, and Canberra in Australia, and transmitted to the European Space Agency's (ESA's) control center at Darmstadt in Germany."