Rosetta’s job is to monitor a comet, 67P/Churyumov-Gerasimenko, by placing an orbiter around it and a lander on it! It will do this as the comet races toward the inner Solar System.
To conserve power while coasting through space, Rosetta’s been ‘sleeping.’ Here’s how they list it on the mission timeline.
July 2011 Aphelion/Enter Hibernation
Today Rosetta gets its wake-up call! It needs to start processing data. It needs to prepare for its May meet-up with Comet 67P/Churyumov-Gerasimenko.
This is another unbelievably complex and intricate engineering challenge that should be impossible. What could possibly be more difficult than this?