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Is the Philae Comet Lander Dead? We’ll Find Out Soon

Can you hear us, Major Philae?
March 12, 2015, 5:25pm
​Concept drawing of Philae landing. Credit: DLR

The Rosetta mission's successful landing on Comet 67P/Churyumov-Gerasimenko last November was widely hailed as the biggest science story of 2014.

But as momentous as the achievement was, it was hampered somewhat by the loss of the Philae lander, which ran out of power two days after its bumpy touchdown. On November 15, the European Space Agency (ESA) announced that Philae ran out of power, and would be placed in sleep mode until its solar panels received enough sunlight to recharge.

Comet campout. Credit: ESA/YouTube

Now, four months later, the Rosetta team hopes that Philae is finally booting up again. Attempts to contact the lost lander began early this morning, and will continue until March 20. The Rosetta team thinks the probe is in a better position to soak up some rays, as Comet 67P/C-G is barreling ever closer the Sun. It is currently 320 million kilometers away from the star, and will make its closest approach this August.

I asked Rosetta project scientist Matt Taylor how this increasing proximity to the Sun might affect Philae's environment. "Basically, there would have been more sunlight on the area we believe the lander to be located," he told me.

"There could also be more dust in the environment, as the comet has become more active as it has been approaching the Sun," Taylor said.

According to an ESA blog post about the renewed contact attempts, the lander is expected to be receiving about twice as much solar energy as it did in November—good news, as the lander's internal temperature has to rise above –45ºC to wake up.

"It will probably still be too cold for the lander to wake up, but it is worth trying," said Stephan Ulamec, project manager for Philae, in the post. "The prospects will improve with each passing day."

In order to reboot, the lander will need to collect 5.5 watts of power, plus another 3.5 watts to run its receiver, allowing it to hear the Rosetta orbiter calling out to it. It needs 19 watts to transmit information back to the orbiter, which will then forward its reports along to Earth.

It's impressive that Philae is this thrifty when it comes to power, requiring much less to run than most incandescent lightbulbs. If it is able to boot itself up within the next eight days, Rosetta will be in a perfect position to rekindle communication with the lander. If not, there are plenty of upcoming opportunities to repeat the attempts.

"We listen when we are in range, roughly below 100 kilometers" from the comet's surface, Taylor told me.

"We carry out these flybys every two weeks or so," he continued. "So it may be that we listen again in two weeks, or [we will] wait four weeks. It is something the lander control centre will decide and let us know."

An adorable cartoon summary of the Rosetta/Philae love story. Credit: ESA/YouTube

This is only the latest exciting development in the ongoing cometary soap opera that is the Rosetta mission. When the lander made first contact with the comet on November 12, its harpoons failed to anchor it, resulting in it rebounding almost a full kilometer back into space.

In fact, it nearly hurtled out of orbit completely, but fortunately, the comet's gravity reeled it back an hour later.

After another bounce, lasting seven minutes, Philae settled in a shady spot about a half mile from the target landing site, sending back about 60 hours worth of valuable data before shutting down.

"I'm actually flabbergasted," said Ulamec, who is based at the German Aerospace Center, in a piece published two days after the landing. "Somehow, the German gods were looking [over the mission]."

Perhaps the German gods still are looking out for Philae, and we'll hear it finally reporting back for duty sometime over the next week. The plucky little lander has already overcome some pretty incredible odds, and may have more surprises up its robotic sleeve.