"Lander" is maybe not a good job description for the Rosetta sub probe Philae. I understand that there is no practically useful gravity there. Philae will try to hook itself onto the comet surface in order to get stationary.

When it has completed its primary mission on one surface site, could it unhook itself and float (fall? hop?) to another location and do new science there? Within its battery life.

EDIT:Could Philae just detach itself and tumble but still make use of its instruments on another part of the comet?

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    $\begingroup$ The two harpoons and the ice screws on each of its legs would make that unfeasible. Well, at least they hope it won't bounce off or sink too deep into the surface dust, that's the plan. Also other sites might not be as suitable as the one they're gonna decide to go for. It does need sunlight for power, but also some shadow to cool down. Hopping might also stir up too much dust that could cover its solar panels. So while technically possible, actually it would be a very likely outcome if they wouldn't deploy harpoons and ice screws, each new hop just adds to the risk of failure. $\endgroup$
    – TildalWave
    Aug 25, 2014 at 19:40
  • $\begingroup$ @TidalWave But if a failure as in landing on a too steep a surface (in a gravitational meaning which I don't understand) then the failure would be a "hop". And that might end up in a better place. I don't think it would fall towards the "neck", because there the mass of the two lobes should cancel each other out. A bounce would probably give it escape velocity for the few days it's got battery power. And maybe it won't have any ice to drill into, but just sink through a slush. We'll see. $\endgroup$
    – LocalFluff
    Aug 25, 2014 at 20:20

1 Answer 1


During development, the team discussed the possibility of hopping Philae if that became necessary or desirable. It would be done by activating various mechanical devices. This was explained briefly during the Philae descent video coverage. They tried to do it a bit when the lander ended up in an unfavorable position, but were not successful.


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