Rosetta mission: 'Game is on' for newly awake probe
20 January 2014 Last updated at 20:19 GMT
The successful "waking up" of the European Space Agency's comet-chasing spacecraft, Rosetta, means the craft is ready for the next stage of its mission.
A signal confirming its alert status was received by controllers in Darmstadt, Germany, at 18:16 GMT.
Rosetta has spent the past 31 months in hibernation to conserve power as it arced beyond the orbit of Jupiter on a path that should take it to Comet 67P/Churyumov-Gerasimenko in August.
Jonathan Amos reports.