BERLIN (AP) — Waking up after almost three years of hibernation, a comet-chasing spacecraft sent its first signal back to Earth on Monday, prompting cheers from scientists who hope to use it to land the first space lander onto a comet.

The European Space Agency received the all-clear message from its Rosetta spacecraft at 7:18 p.m. (1818 GMT; 1:18 p.m. EST) — a message that had to travel some 800 million kilometers (500 million miles).