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Healthy comet lander Philae is ready to get back to work

Paul Sutherland, Feature writer
Jun 17, 2015, 19:02 UTC

Sen—Rosetta’s little comet lander Philae is in good health and ready to start work immediately, the operations engineer responsible for the reawakened probe said today.

Barbara Cozzoni, of the German Aerospace Centre (DLR), confirmed that Philae came out of hibernation well before the first contact with Earth was made on June 13 after seven months asleep.

She told a European Space Agency (ESA) briefing at the Paris Air Show: “Most of the telemetry received was historical. This means the lander did not switch on on the 13th, but probably days before.”

The probe’s internal temperature was a relatively warm -36°, she said, compared to the minimum of -45° at which it can operate. She added: “The other good news is that its solar panels are collecting energy. So it looks like Philae is ready for operation now.”

But Cozzoni added that more telemetry was needed to tell the ground team when it would be able to establish a communications link to Rosetta, so that they could plan a strategy for carrying out its science experiments on the surface of Comet 67P/Churyumov-Gerasimenko.

Rosetta itself will be brought closer to the comet, to a distance of 180 km (112 miles) from its surface, to help communications, though it has to be kept safe from the dust that is now spewing from the highly active nucleus.

She said Philae was able to tell when it was day and night at the location where it unexpectedly ended up after bouncing twice from its planned touchdown point on Nov. 12, 2014. So it would be able to switch itself on and off as required.

She added that communication with Rosetta was not necessary every comet day, and Philae could store its data for some time before it was all downloaded to the mothership.

Cozzoni said science operations would resume with the simpler, low-risk experiments and then move on to more complex, risky ones. She concluded: “That’s it. Philae’s back and we are all very happy!”

Philippe Gaudon, of the French space agency (CNES) reminded the briefing that Philae was on its side and not anchored to the comet. He said that because the day and night cycle was different in its new location, the sequence of activities had to change.

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The many instruments aboard Rosetta's little lander Philae: Image credit: ESA

He added that, although it was not possible to be 100 per cent certain, the latest data from Philae was compatible with the lander being in the spot where ESA said they believed they had imaged it last week.

The good news was that it was getting four times more energy from the Sun now to keep it powered up than when it landed in November, and by August when the comet will be at perihelion (closest to the Sun) it will be receiving nearly six times as much.

First of Philae’s science operations to start will be Sesame, Romap and Mupus, followed by Consert, Civa and Rolis, and then finally the more complex, risky and power-hungry ones. 

Jean-Pierre Bibring, lead lander scientist at the Institut d’Astrophysique Spatiale, Université Paris Sud, France, said that Philae’s unexpected landing site, in the shadow of what has been dubbed Perihelion Cliff, had given it the chance to study the comet during its most active phase.

It had not been expected to survive past March because it would have got too hot in the direct sunlight. Bibring told the briefing: “I would like to thank the comet for cooperating with us and for being fundamentally different from what we expected!

“The frustration we had after November has changed to a new excitement. Not only has Philae woken up, but we have the chance to complete the mission and go beyond it. Thanks to the cliff, we have compatibility for long-term activity. Essentially we are now able to resume science beyond expectations.”

Bibring said scientists were already learning more about the pristine materials from which the outer Solar System formed. The comet was not 80 per cent ice, as had been thought, but much more complex than that. Its surface was covered with grains of organic matter, with not a single spot of ice on the surface.

“It was the grains that cemented the comet as the Solar System formed from a condensing molecular cloud. Now we have the possibility to measure the compositions of the material.”

Bibring concluded: “The dream is being pursued. And if it is a dream, then I would prefer not to wake up!”

Nothing was heard from Philae last night, but that was as expected. Following first resumed contact on June 13, three 10-second bursts of communication were picked up and relayed by Rosetta on June 14.