In the final hours, Philae's science team hurried to squeeze as much science out of the small lander as possible. But the deep sleep was inevitable, Rosetta's lander has slipped into hibernation after running its batteries dry.
In its final hour, the official Philae Twitter feed conversed with the official Rosetta account, saying, "I'm feeling a bit tired, did you get all my data? I might take a nap."
"My #lifeonacomet has just begun @ESA_Rosetta. I'll tell you more about my new home, comet #67P soon... zzzzz," it tweeted before falling silent just as the European Space Agency confirmed that Philae had run so low on battery power that it had to drop into hibernation, ceasing all science operations.
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"Prior to falling silent, the lander was able to transmit all science data gathered during the First Science Sequence," said Stephan Ulamec, Philae Lander Manager. "This machine performed magnificently under tough conditions, and we can be fully proud of the incredible scientific success Philae has delivered."
Contact with the lander was lost at 01:36 CET (7:36 p.m. EST), which is around the time the Rosetta spacecraft orbited beyond the comet's horizon, severing the communications link with its lander.
According to the ESA Rosetta mission blog, reestablishing communications will not be possible unless enough sunlight falls on the lander's solar array to charge up its batteries.
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Earlier Friday evening, mission scientists sent commands to the lander to turn its body so that the small amount of sunlight Philae does receive (only 1.5 hours of light per 20 hour comet rotation) will hit more of the solar panels, boosting the possibility of a recharge. But there is only a very slim chance that this operation will bring Philae out of hibernation.
Although this likely spells the end of Rosetta's surface mission with Philae, as the comet continues its journey around the sun with spacecraft in tow, the solar angle may change, casting more light on the rover in coming weeks - but this is a long-shot.
Regardless, Rosetta will listen out for Philae when the next communication window opens, on Saturday (Nov. 15) at 11:00 CET (5:00 a.m. EST).
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This may be the end of Philae's short and trailblazing mission on the surface of Comet 67P, but a huge amount of data - including data from a drilling operation that, apparently, was carried out despite concerns that Philae wasn't positioned correctly - was streamed to Rosetta mission control, potentially revolutionizing our understanding about the nature of comets.
And Rosetta will continue orbiting its comet as 67P drops closer to the sun, providing us with a unique and historic perspective on an icy body that could hold the secrets to the formation of our solar system.