Comet lander Philae communicates again

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The comet lander Philae has finally woken up after seven months

By Rachel Feltman June 14 at 8:25 AM

Good news! After seven months of hibernation, the first object ever landed on a comet has come back to life. On Sunday morning, the European Space Agency announced that it was back in contact with little Philae.

The Philae lander, which the European Space Agency's Rosetta orbiter dropped onto Comet 67P/Churyumov-Gerasimenko on Nov. 12, enjoyed only about 60 hours of life the first time around. The lander was supposed to have months, but a bumpy landing left it in the shade and without enough sunlight to keep working.

Scientists on the ground regretfully put it to bed, but hoped that as the comet approached perihelion — its closest pass with the sun — the increase in light would give Philae a second chance.

Until recently, we weren't even sure where the lander had landed. Scientists knew it was a shady area, probably the edge of a crater. But without more data from Philae, they were left searching for the lander in photos taken by its orbiter.

On June 11, ESA announced that it had a good candidate for Philae in one of Rosetta's images. But because the orbiter's mission wouldn't bring it close enough to take more detailed pictures anytime soon, the spotting was unconfirmed.

But in a lovely coincidence, Philae beat everyone to the punch June 13. About 4:28 p.m. Eastern time, the lander — which has apparently been awake and collecting data for some time — "spoke" to ground control for 85 seconds. The team members have already analyzed more than 300 data packets from the lander, and they say Philae is ready to do science again. And the social media teams behind Rosetta and Philae's Twitter accounts have jumped right into making us cry over them again, too.

"Philae is doing very well: It has an operating temperature of -35ºC and has 24 Watts available," Philae Project Manager Stephan Ulamec said in a statement. "The lander is ready for operations."

Now that we know that Philae survived its hibernation, we can actually consider its bumpy landing a fortunate mistake. Philae's intended landing site would have given it enough sunlight to power its operations for months, it's true. But the lander probably would have been dead by now, growing too hot as its host comet approached an August rendezvous with the sun.

In its accidentally shady spot, Philae will get to make observations on the comet as the sun heats it up, which is the most volatile time in its life cycle. Things are melting, gasses are off-gassing and new clues about the way comets form and evolve are being revealed. With Philae back on the case, there's no telling what we could learn.

The comet lander Philae has finally woken up after seven months - The Washington Post

 

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Rosetta spacecraft to change orbit in bid to strengthen Philae communication

Monday 15 June 201512.43 EDT Last modified on Monday 15 June 201513.42 EDT

The European Rosetta spacecraft will swoop into a closer orbit around its comet this week to help the mothership talk to its Philae lander, which emerged from a seven month hibernation at the weekend.

Scientists are set to change Rosetta’s orbit as soon as Tuesday to bring the spacecraft within 180 kilometres of the comet’s surface before the end of the week. The change in orbit should give Rosetta stronger and longer communication links with the lander, and allow scientists to send commands to the robot.

The lander made its first brief contact with Rosetta on Saturday night, when the little robot beamed up 300 of 8000 packets of housekeeping data it had saved onboard. On Sunday night, the lander made contact again, but the signal was weaker and more fleeting, relaying only five more packets of data. After the second contact was made, scientists at the French Space Agency, CNES, declared the lander was now “completely awake”.

European Space Agency staff in Darmstadt had been listening for the lander since 12 March when they switched on Rosetta’s communications unit. The orbiting spacecraft can only receive signals when Philae is bathed in sunlight and has a direct line of sight.

The signals are the first to come from the washing machine-sized Philae since 15 November 2014, when its batteries ran out and the probe fell silent. The lander came out of standby mode and used its transmitter to call home after its solar panels received enough sunlight to power the systems up.

The lander is expected to gain more power over the coming weeks and months as comet 67P/Churyumov-Gerasimenko gets closer to the sun. The comet reaches its closest approach to the sun in August, before heading back out beyond the orbit of Mars.

The data received so far only hold information on Rosetta’s status, but they have given scientists good reason to be optimistic about the lander’s chances of doing more work on the comet. “Sunday’s data are telling us that Philae is at -5C, and that is really good news, because it is warm enough to start recharging the batteries,” said Stephan Ulamec, Philae lander manager at the German Aerospace Center. “It’s an indication that in the coming weeks and months we’ll be able to recharge the lander and do more demanding science with the instruments,” Ulamec said.

Changing Rosetta’s orbit is not without risks. If Rosetta gets too close to the comet, the star-tracking instruments it uses to determine its position could become confused by dust tracks, causing the probe to go into temporary shutdown. But if all goes to plan, scientists could send their first commands to Philae next week, to see if the robotic lander responds.

The Philae team has drawn up a list of operations that will be sent to the lander when it has the power to perform the tasks. The first will be simple actions such as taking the outside temperature and more magnetic measurements. With a little more power, Philae will take pictures of its surroundings, to see if the terrain has changed since it landed, or if new features are visible now the comet is basking in more sunlight. Next, the lander will try to “sniff” the environment for volatile chemicals.

“Most demanding, but most interesting, will be getting a sample with the drill and investigating it with instruments like Ptolemy, but that’s not something we’ll do soon, because it needs fully recharged batteries,” Ulamec said.

The Ptolemy instrument can take samples drilled from the comet’s surface and infer their composition by analysing gases given off when the material is baked. Dust from the comet has probably already swept into the ovens, and this could be analysed if Philae can muster enough power to turn the ovens on.

Monica Grady, professor of planetary sciences at the Open University, who works on Philae’s Ptolemy instrument, said: “We are so happy Philae has woken up. We were hoping that this was going to happen. It’s a really exciting time.”

Before deciding whether to use Ptolemy’s ovens, mission controllers must find out whether Philae’s drill can still reach the comet’s surface. “We don’t know yet whether the drill can deliver anything. It was supposed to drill vertically down, but as far as we’re aware, Philae is on its side,” Grady said.

Mission scientists said there was only a slim chance of hearing from Philae on Tuesday night, but hope to hear from the lander again on Wednesday or Thursday.

The Rosetta spacecraft flew more than six billion kilometres on its 11-year mission to rendezvous with the comet, which orbits the sun at 135,000 kilometres per hour. The Philae lander touched down on the comet seven months ago, and after seveal bounces, came to rest against a cliff face, where much of the craft was in shadow. The comet is now 215 million kilometres from the sun and 305 million km from Earth.

Rosetta spacecraft to change orbit in bid to strengthen Philae communication | Science | The Guardian