Philae, short for Philae Lander, is ESA’s (European Space Agency) lander that accompanied the Rosetta spacecraft until it landed on comet 67P/Churyumov-Gerasimenko on November 12, 2014. Philae gathered hugely important data throughout the following 60 hours, which will be studied for years to come. Unfortunately however, its batteries ran out of power. Philae was designed to recharge itself with solar power, yet it landed in what seemed to be the shadow of a crater rim which blocked most of the sunlight.
On November 15, 2014, Philae went into hibernation due to reduced sunlight. The ESA expressed hoped that additional sunlight would reach Philae’s solar panels by August 2015 since Churyumov-Gerasimenko is still heading towards the sun, with closest approach on August 13. With sufficient sunlight, Philae could reboot.
Orbital changes could give a few advantages. Comets have seasons too, and if Churyumov-Gerasimenko’s tilt turned Philae’s location towards the sun, it would be able to get more hours of light in a day. Additionally, solar intensity is increasing as the comet comes closer to the sun. Finally, since comets sublime away as they reach the inner solar system, the ridge blocking the sun’s rays might shrink.
As of December, Philae’s lead scientist Jean-Pierre Bibring was telling a news conference that “Pessimistically [a wake up] will be after Easter,” yet that one early this year was a strong possibility. The ESA additionally proclaimed that if Philae could sufficiently get just enough sunlight to function, its location would be an advantage, permitting it to study the ground beneath its feet, as well as the bits of the comet now concealing the sun.
However, as the days passed, the public became cynical. Mission scientists did not lost hope. Just three days back, analysis of pictures taken by Rosetta a year ago alluded Philae’s exact landing site, which was something unsubstantiated until recently. Dr. Stephen Ulamec announced that “the conditions for Philae’s wake-up are becoming more and more favorable as the comet approaches the sun.”
Now indeed, Philae woke up on June 14, 2015. And just after noontime Greenwich Mean Time, Philae’s Twitter account, after seven months of silence, tweeted “Hello Earth! Can you hear me? #WakeUpPhilae”. This was followed by a brief interchange with @ESA_Rosetta.
Philae’s awakening seem to last for only eighty-five seconds, with the last tweet that reads “Oh, OK @ESA_Rosetta! I’m still a bit tired anyway…talk to you later! Back to #lifeonacomet!”
Lander control had acquired 300 data packets from the spacecraft a couple of hours earlier, but verified their reliability before releasing the information to the world.
Ulamec reported that “Philae is doing very well: It has an operating temperature of -35ºC and has 24 Watts available.” He also said that “the lander is ready for operations.”
Ulamec likewise reported that the messages revealed that Philae had woken up previously, but signals had not got through. “We have also received historical data,” he said. Also in the messages is the fact that there were significant amount of data gathered in the few days after Philae landed, but it was not yet received on Earth. It will remain in Philae’s mass memory until in wakes up again in the future.