Things have gone from bad to worse for Philae, the comet lander sent up to land on Comet 67P/Churyumov-Gerasimenko in 2014 as part of the European Space Agency's Rosetta mission. After a pretty much last-ditch attempt to contact the lander over the weekend, the German Aerospace Center (DLR) reports no signs of life.
I asked Philae project manager Stephan Ulamec if he expected to hear from the lander again. "One has to be realistic," he said. "The chances go very, very low now in the next few days."
Philae has been silent since July 2015 and now the chances of it ever reawakening look slim indeed. The comet reached perihelion—its closest pass by the Sun—in August, and now it's only getting further away. That means the temperature on the comet is dropping, and an ESA blog explains it expects conditions to be too cold for Philae to function by the end of January. At that point it'll be some 300 million kilometres from the Sun, with temperatures expected to drop to a lander-killing -51 Celsius.
The Philae team tried to send a command to the lander on Sunday in an effort to move its flywheel and perhaps push it into a better position or rattle it enough to shake some dust off its solar panels. But the DLR tweeted that though the commands were executed, no signal was received from the lander.
"Unfortunately, after these commands have been sent, we did not receive any signal from the lander, so we also do not really know what happened," said Ulamec.
It's impossible to tell if Philae received the commands but was unable to act on them, possibly because it didn't have enough power, or if it didn't get them in the first place.
"I have to say, this was a low-chance, kind of last activity we tried, with some risk involved," added Ulamec. The risk was that if the lander did move, it could have fallen on its antennas or incurred other damage.
Since Sunday, Ulamec said the researchers had tried to turn instruments such as Philae's radar instrument on, but also had no success.
Philae has had a tumultuous journey so far. After successfully touching down on the comet surface—no mean feat—the lander bounced into a less-than-ideal position. Tucked away in shadow, it went into hibernation when its batteries ran out and its solar panels couldn't get enough Sun. Further efforts to restore contact with Rosetta, the comet orbiter, were fruitless until it woke up in June 2015. But it soon fell silent once more.
Rosetta's researchers will keep listening for Philae, but with the clock ticking, it seems highly unlikely that the lander will again be resurrected.
"The situation is getting worse; if we do not hear anything from it today, there is little reason we should get a signal a few weeks from now," said Ulamec. "It's all getting worse due to the increasing heliocentric distances."
Meanwhile, Rosetta will carry on until September 2016, continuing to gather further data before making a kamikaze dive into the comet itself. Only then will Rosetta and Philae find themselves once more united.