Artist rendition of the Philae lander on Comet 67P/Churyumov-Gerasimenko. Credit: DLR
It was just a few months ago that, in a historic first, we landed on a comet.
It all started more than 10 years ago. The Philae lander was launched on March 2nd, 2004. It traveled for 3,907 days (over ten and a half years) in order to reach its goal: Comet 67P/Churyumov–GerasimenkoIt. The lander traveled across the solar system on the Rosetta spacecraft, an its journey went as expected. It reached its target on the 12th of November, 2014.
It touched down mostly as planned, but unfortunately, the lander bounced twice before finally settling down. During its rebound, it traveled upwards around 38 cm/s (15 in/s). That may not sound all that fast, but remember, we are talking about a comet, which means that the escape velocity (the speed needed to escape a massive object and "launch" into space) is a lot less. Ultimately, if Philae had been traveling just a little faster, 44 cm/s (17 in/s), it would have soared out into space. Scientists estimated it could have bounced as high as 3.2 kilometers (2 miles) during its rebounds.
Fortunately, the lander settled back onto the comet. Unfortunately, it landed in an area that doesn't receive much sunlight. This means that Philae lost power just days after landing (as opposed to the weeks that it was supposed to run). Still, landing on a comet is an amazing accomplishment, and things went very well, all things considered. The big question now, the one that is on everyone's mind, is where is the Philae lander and will it wake up?
Those are the questions the team at the DLR Lander Control Center will be trying to answer starting tomorrow. Thursday, March 12 provides the first possible opportunity to receive a signal from Philae, Rosetta’s lander, which is still resting (somewhere) on Churyumov-Gerasimenko.
“It could be that the lander has already woken up from its winter sleep 500 million kilometers away, but does not yet have sufficient power to inform the team on Earth,” said Koen Geurts from the German Aerospace Center in a
blog post yesterday.
There are high hopes, as the comet marches ever closer to the Sun, as Philae needs to receive enough solar energy in order to activate a few systems before it can wake up and send signals back to Earth. And the closer it is to the Sun, the more likely that it is to receive the necessary sunlight. Ultimately, the lander must be able to generate at least 5.5 watts in order to wake up. In addition to this, the interior of the lander must be at least at minus 45 degrees Celsius (-49F).
In the event that the rechargeable battery on board Philae did not survive the intense cold of its hibernation, the engineers have worked our a few tricks to help it continue its mission: “We are working to ensure that we can operate the lander and its instruments at least during the comet’s daytime, when it is in direct sunlight.” The scientists sent new commands to Philae in an attempt to optimize the heating and use energy saving tactics in order to improve its chances of communication with Earth. Even if Philae does not have enough energy to answer (yet), scientists assert that the lander could still receive the commands and execute them.
However, despite its ever increasing proximity to the Sun, some think that the lander is likely out for the count, at least for the time being. “Philae currently receives about twice as much solar energy as it did in November last year,” said Lander Project Manager Stephan Ulamec from DLR. “Comet 67P/Churyumov-Gerasimenko and its companion, Philae, are now only 300 million kilometers from the Sun. It will probably still be too cold for the lander to wake up, but it is worth trying. The prospects will improve with each passing day.”
But this does not mean that the lander is really gone. Chances improve each passing say and scientists will keep working until March 20. Throughout this time, Rosetta will be transmitting to the lander and listening for a response. “If we cannot establish contact with Philae before 20 March, we will make another attempt at the next opportunity,” said Ulamec. “Once we can communicate with Philae again, the scientific work can begin.”
But for now—until tomorrow, at least—we're just playing the waiting game...
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