After seven months of unintended hibernation, the European Space Agency's comet lander Philae has awakened and called home.
Signals from the lander, which touched down on Comet 67P/Churyumov-Gerasimenko on November 15, were received at the European Space Operations Center in Darmstadt, Germany.
Philae's landing – after being released from its Rosetta comet probe mothership – did not go quite as planned. The lander ended up bouncing away from its intended landing spot, coming to rest in a deep cleft on the comet's surface.
This kept sunlight from reaching its solar panels, and the lander's batteries ran out after about 60 hours.
Philae's controllers had remained hopeful that as Comet 67P came closer to the sun, there would be enough sunlight to recharge the landers' batteries — something that the renewed communications have borne out.
Using Rosetta as a relay, Philae transmitted an initial "hello" that lasted 85 seconds and consisted of more than 300 data packets, which are being analyzed at the German Aerospace Center's Lander Control Center.
Researchers there said they are eagerly awaiting an estimated 8,000 more data packets stored in Philae's mass memory.
"Philae is doing very well. It has an operating temperature of -35ºC (-31ºF) and has 24 watts available," said Philae project manager Stephan Ulamec. "The lander is ready for operations."
"I'm not really surprised it happened, but if you wait for several months and then suddenly in the middle of the night you get a call saying 'we have a signal from Philae,' it's exciting," he added.
The ESA Rosetta twitter account first carried the news.
- ESA Rosetta Mission (@ESA_Rosetta) June 14, 2015
There is evidence the lander may have been awake for some time and collecting information before making its first contact with Rosetta and through it its control center on Earth, scientists posited.
"I think we're optimistic now that it's awake that we'll have several months of scientific data to pore over," said ESA scientist Mark McCaughrean.
Twitter was alive with exchanges between Philae and Rosetta, as posted by ESA.
"Hello @ESA_Rosetta! I'm awake! How long have I been asleep? #Lifeonacomet," came the tweet from Philae's handle.
"Hello @Philae2014! You've had a long sleep, about 7 months!" came a response from Rosetta.
"Wow @ESA_Rosetta! That's a long time... time for me to get back to work! #Lifeonacomet"
As Comet 76P makes its closest approach to the sun in August, ESA scientists are hoping Philae can give them a ringside seat.
"I think we are going to see some amazing images at that point," said lander system engineer Laurence O'Rourke.