After a historic but awkward comet landing, the robot probe Philae is now stable and sending pictures - but there are concerns about its battery life.
The lander bounced twice, initially about 1km back out into space, before settling in the shadow of a cliff, 1km from its intended target site.
It may now be problematic to get enough sunlight to charge its battery systems.
Launched in 2004, the European Space Agency (Esa) mission hopes to learn about the origins of our Solar System.
It has already sent back the first images ever taken from the crumbling, fractured terrain of a comet.
Philae got to the icy 67P/Churyumov-Gerasimenko on the back of Esa's Rosetta satellite after a 10-year, 6.4 billion-km (4bn-mile) journey, which reached its climax on Wednesday with a seven-hour drop to the surface.
After showing an image that indicates Philae's presumed location - on the far side of a large crater that was earlier considered but then rejected as a landing site - the head of the lander team, Stephan Ulamec, said: "We could be somewhere in the rim of this crater, which could explain this bizarre… orientation that you have seen."
Pictures taken by Philae of its surroundings show it pressed up against what appears to be a hard wall of some kind.
Telemetry indicates it is on a slope or perhaps even on its side.
Certainly, one of its three feet is not in contact with the surface.
The key issue vexing controllers right now is the lighting conditions.
Philae is receiving about 1.5 hours of illumination during every 12-hour rotation of the comet.
This will be insufficient to top up its battery system once the primary charge it had on leaving Rosetta runs out. That was some 60-plus hours.
It means Philae is unlikely to be operating in its present state beyond Saturday.
"We have estimations right now that go between Friday afternoon and Saturday afternoon," explained Paolo Ferri, the head of Esa's operations here in Darmstadt, Germany.
"It depends on the activities, of course. The more activities we do with the lander, the more power we will consume, and the less time we will have."
Engineers are examining how they might re-orientate the robot to maximise the light reaching its solar panels.
More extreme options being considered even include using some of the moving parts on the lander to try to make a hopping motion that would carry it clear of the shadows.
But, in truth, there is probably insufficient time to plan and then execute such a strategy.
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