The European Space Agency's Philae lander has woken up following seven months in hibernation mode. Controllers at the agency received a signal from the lander at 22.28 CET on 13 June, and are now hopeful that the mission will soon be able to restart science operations.

Philae was part of the Rosetta mission that was launched in 2004 to study Comet 67P/Churyumov–Gerasimenko. While Philae successfully landed on the comet last year, it touched down in an awkward position, meaning that its solar panels could not charge. The craft still managed to carry out experiments using its onboard instruments, but after around 60 hours of observations – with the battery fully depleted – it entered hibernation mode on 15 November.

As the comet moved closer to the Sun this year, researchers were hopeful that Philae would slowly emerge from the shadows, allowing its solar panels to charge its battery. It is only when Philae receives around 19 W of power that it can start to reboot and then make contact. Since 12 March, the communication unit on orbiter Rosetta has been turned on to listen for the lander.

Late on Saturday, the Lander Control Center at the German Aerospace Center announced it had received a signal from Philae, when around 300 "data packets" were sent from the probe during an 85 s period. "Philae is doing very well: it has an operating temperature of –35 °C and has 24 W available," Philae project manager Stephan Ulamec said in a statement. "The lander is ready for operations."

Starting science

The Rosetta researchers will now try to piece together what happened to the lander in the past few days, as Philae would have woken a couple of days before it sent the signal. Indeed, there are still more than 8000 data packets in Philae's memory that will give the team crucial information about the status of the lander. "We have only had brief interaction with the lander, but it seems in very good shape," Matt Taylor, Rosetta project scientist, told physicsworld.com.

Taylor adds that the first priority is to get Rosetta in the best location for it to be able to communicate with Philae. "This is a major challenge, given that the comet is active and the dusty environment is challenging to navigate safely," says Taylor. "Once we optimize things, then we can start lander science."

With Philae receiving around three hours of sunlight each day, it is hoped that the craft will be able to spend this time doing experiments. In particular, a high priority will be drilling into the surface of the comet to obtain a sample that can then be analysed.

Taylor adds that he is hopeful that Philae can then spend a couple of months doing science before the comet starts heading back towards the outer solar system. "We will have to see how things evolve in the next days from the analysis of housekeeping data from the lander," he says. "But I hope for a few months [of measurements]."

  • The Rosetta mission was awarded the Physics World 2014 Breakthrough of the Year, for being the first to land a spacecraft on a comet. Watch the Google Hangout video below, where physicsworld.com editor Hamish Johnston talks to Rosetta Mission manager Fred Jansen