A Blog by

After a 7-Month Sleep, Philae Phones Home

Philae, the little lander sent to explore a comet, has woken up after seven dark months of hibernation.

Late in the evening of June 13, the European Space Agency’s operations center in Darmstadt, Germany received an 85-second long transmission from Philae — the first sign of life from a lander that last phoned home in mid-November.

So far, Philae has sent more than 300 data packets back to Earth. The next communications pass is scheduled for 22:00 CEST tonight, and scientists are optimistic they will hear more from the robot. Then, it’s time to see if Philae is ready to go back to work.

“Philae is doing very well,” says Philae’s project manager Stephan Ulamec in a blog post from ESA. “The lander is ready for operations.”

In November, the European Space Agency’s Rosetta spacecraft sent Philae to the surface of duck-shaped comet 67P/Churyumov-Gerasimenko (see this adorable YouTube video for an overview). Rosetta had been orbiting the comet for three months, and it was time for Philae to gather some data from the strangely shaped interplanetary traveler.

Jets of gas and dust erupt from Comet 67P/Churyumov-Gerasimenko in this image from June 5. (ESA/Rosetta/NavCam)
Jets of gas and dust erupt from Comet 67P/Churyumov-Gerasimenko in this image from June 5. (ESA/Rosetta/NavCam)

The mission team had selected a nice spot for Philae to touch down – somewhere near the head of the duck – and gently sent the robot on its way. But instead of sticking its landing, Philae bounced. And then it bounced again. When it finally came to rest, Philae was nowhere near the targeted landing spot. Early images shot by the lander suggested that instead of settling in a sunny spot, it was perilously close to shade. That was terrible news for its solar-powered batteries.

One of Philae's three feet can be seen in this image.  (ESA/Rosetta/Philae/CIVA)
One of Philae’s three feet can be seen in this image. (ESA/Rosetta/Philae/CIVA)

Over the next 60 hours, Philae frantically gathered and transmitted data; then, as the unrelenting shadows starved its batteries, Philae fell into hibernation. 

Scientists hoped Philae would awaken as 67P approached the sun, yet no one knew when (or even if) that might happen. Until last night. Now, it appears as though Philae has been awake for a little while, but had been unable to contact Earth until now. “We have also received historical data – so far, however, the lander had not been able to contact us earlier,” Ulamec said in a statement.

Over the last seven months, the team (and others on the internet) have searched and searched for the little robot, but even the best images from Rosetta haven’t yet revealed the lander’s location. Perhaps, with more data coming back from Philae, we will now be able to pinpoint its exact comet-spot.

“With more contact, that may help us to zero in,” says ESA project scientist Matt Taylor. “But ultimately, we need to get in close to take images.”

Philae, are you in these images? (ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)

Scientists are now working on optimizing Rosetta’s trajectory around 67P for communication with Philae. And the timing is a bit ironic. “We were in Rome for a science meeting last week talking about optimising trajectories to ensure we hear,” Taylor says. “Then this happens before we do that. So we are working even harder to get that optimisation in place.”