Recently read that power was lost in the Philae probe. Did the team under estimate how the probe would recharge or is it in a spot where it doesn't get enough sun. And since this was supposed to transmit data back for months.. what is going to happen now?


1 Answer 1


Nothing will happen with the Philae lander now for some undetermined time. How much time is not exactly clear though, but ESA operations said not to expect the lander to wake up in a couple of days or so. From Rosetta blog:

From now on, no contact would be possible unless sufficient sunlight falls on the solar panels to generate enough power to wake it up.

Problem is, that its batteries are now depleted and Philae is receiving only roughly 1.5 hours of illumination during every 12-hour rotation period of the comet. The comet is still on its approach to perihelion, closest point in its orbit to the Sun, so while the period of sunlight won't change, at least not by much since 67P isn't a very active comet and outgassing shouldn't change its rotation rate by much, total insolation (sunlight intensity) will increase as the comet comes closer to the Sun and the lander might be able to partially charge its batteries in the meantime too. Increased sunlight intensity will also increase intensity of comet's albedo (reflected light) and that might also help it a bit.

Philae operators have tried to reposition its solar panels to receive more incident sunlight before the lander run out of battery juice, so that might have help it a bit and is yet to be established for how much, but it will most likely be an on-and-off adventure. From the same linked blog article:

However, given the low recharge current available from the solar cells, it is considered unlikely that contact with Philae will be established in the coming days.

And here's this sad graph showing Philae's battery systems' charge levels (source: Philae Lander on Twitter):

    enter image description here

From another of its tweets:

.@ESA_Rosetta I'm feeling a bit tired, did you get all my data? I might take a nap… #CometLanding

Marking success of its main mission objectives and then falling into deep sleep (hibernation) as its batteries run out of free electrons.

  • $\begingroup$ So why won't the 1.5 hours of sunlight every 12 hours add up over several days and mean that after weeks or days or whatever it will have fully charged the battery to wake up? I mean it seems like people are saying it will only turn on when there is more sunlight or longer in the sunlight, as if it was powered directly by the solar panels with no battery to store charge from the previous days. $\endgroup$
    – Jonathan.
    Nov 18, 2014 at 2:25
  • $\begingroup$ @Jonathan. It probably will, but 1.5 out of 12 hour rotation period also means that the lander is most of the day on the comet (half the rotation period or 6 hours - 4x more than what Philae gets) in a shadow. Latest news from DLR is that they managed to align the angle of the largest solar panel more optimally (perpendicular to the Sun) by rotating the lander, but "Now we are somewhat in shadow, we will need more time to charge." $\endgroup$
    – TildalWave
    Nov 18, 2014 at 2:34
  • $\begingroup$ Yes, but say philae only gets 1.5 out of 12 hours of sunlight forever, would it every turn on? As in do we have to wait for the 1.5 hours to more, or wait for the battery to charge which will take a while because it only get 1.5 hours out of every 12? $\endgroup$
    – Jonathan.
    Nov 18, 2014 at 18:02
  • $\begingroup$ @Jonathan. I'm not sure I follow. Do you mean if it can recharge batteries to their maximum capacity using only 1.5 out of ever 12 hour charge cycles? Probably, we'll have to wait and see. Batteries would lose some of the charge by self-discharge in between even when not used and they're at the minimum 10+ years old so their ability to recharge and to what level might be affected too. Lander could power some of its equipment directly through photovoltaics but not all of them are optimally positioned and what current it would use that's available to it won't be used to recharge the batteries. $\endgroup$
    – TildalWave
    Nov 18, 2014 at 18:12
  • $\begingroup$ I mean they keep saying "we have to wait for more sunlight on the panels before it will turn on" rather than "we have to wait for the battery to charge before it will turn on" $\endgroup$
    – Jonathan.
    Nov 18, 2014 at 19:10

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.