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Rosetta: concerns for comet lander after uneven landing Rosetta: concerns for comet lander after uneven landing
(35 minutes later)
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.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.
After two bounces, the first one about 1km back out into space, the lander settled in the shadow of a cliff, 1km from its target site. 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 be problematic to get enough sunlight to charge its batteries. 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.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 on the surface of a comet. It has already sent back the first images ever taken from the crumbling, fractured terrain of a comet.
Esa's Rosetta satellite carried Philae on a 10-year, 6.4 billion-km (4bn-mile) journey to Comet 67P/Churyumov-Gerasimenko, which reached its climax on Wednesday. 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 location - on the far side of a large crater that was considered but rejected as a landing site - the head of the lander team Dr Stephan Ulamec said: "We could be somewhere in the rim of this crater, which could explain this bizarre… orientation that you have seen." 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, Dr Stephan Ulamec, said: "We could be somewhere in the rim of this crater, which could explain this bizarre… orientation that you have seen."
Figuring out the orientation and location is a difficult task, Dr Ulamec said. Pictures taken by Philae of its surroundings show it pressed up against what appears to be a hard wall of some kind.
"I can't really give you much more than you interpret yourself from looking at these beautiful images." Telemetry indicates it is on a slope or perhaps even on its side.
But the team is continuing to receive "great data" from several different instruments on board Philae. Certainly, one of its three feet is not in contact with the surface.
It may be possible to reconfigure Philae's landing gear and "hop" to a new location, but Dr Ulamec said there may not be enough time to do the analysis required for such a risky strategy. The key issue vexing controllers right now is the lighting conditions.
"There is a limited amount of battery power there and the solar panels are not really illuminated, so we don't know precisely how long it's going to last," said Rosetta mission manager Dr Fred Jansen. Philae is receiving about 1.5 hours of illumination during every 12-hour rotation of the comet.
The robot probe, the size of a washing machine, was dropped from the Rosetta satellite on Wednesday and spent seven hours travelling down to the icy body. 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.
News of the "first" landing was confirmed at about 16:05 GMT. It means Philae is unlikely to be operating in its present state beyond Saturday.
Ebullient mood "We have estimations right now that go between Friday afternoon and Saturday afternoon," explained Paolo Ferri, the head of Esa's operations.
Controllers re-established radio communication with the probe on cue on Thursday after a scheduled break, and began pulling of the new pictures. "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."
These show the feet of the lander and the wider cometscape. One of the three feet is not in contact with the ground. Engineers are examining how they might re-orientate the robot to maximise the light reaching its solar panels.
Philae is stable now, but there is still concern about the longer-term situation because the probe is not properly anchored - the harpoons that should have hooked it into the surface did not fire on contact. Neither did its feet screws get any purchase. 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.
Lander project manager Stephan Ulamec told the BBC that he was very wary of now commanding the harpoons to fire, as this could throw Philae back off into space. But, in truth, there is probably insufficient time to plan and then execute such a strategy.
Dr Ulamec also has worries about drilling into the comet to get samples for analysis because this too could affect the overall stability of the lander. The priority right now is to use Philae to acquire as much information as possible about the comet.
"We are still not anchored," he said. "We are sitting with the weight of the lander somehow on the comet. We are pretty sure where we landed the first time, and then we made quite a leap. Some people say it is in the order of 1 km high. In this regard, researchers are thrilled by the performance of the probe.
"And then we had another small leap, and now we are sitting there, and transmitting, and everything else is something we have to start understanding and keep interpreting." However, they would dearly love to use the lander's drill. This was one of the key objectives of the mission - to pull up sub-surface material for chemical analysis in onboard labs.
Another very important concern is the amount of sunlight available to Philae. But the team currently cannot contemplate such an operation with the probe so delicately positioned on only two feet. The drill's rotational forces could destabilise Philae.
The probe set off from Rosetta with 60-plus hours of battery life, and will need at some point to recharge using its solar panels. Controllers will see what they can do to lower the third foot to the surface.
But early reports indicate that in its present position, the robot is receiving only one-and-a-half hours of sunlight during every 12-hour rotation of the comet. If that is not possible, drilling may be commanded towards the end of the primary battery window. By then, scientists would have little to lose anyway.
This will not be enough to sustain operations. "This is a very typical operational decision," said Paolo Ferri. "You gather everything you can first, and then the risky things - you only do them at the end."
As a consequence, controllers here are discussing using one of Philae's deployable instruments to try to launch the probe upwards and away to a better location. But this would be a last-resort option. Whatever happens in the hours ahead, the mission is already assured of its place in history.
First, the team really needs to fully understand where Philae is on the surface and what lies around it. Its data - and that from Rosetta which continues to observe from overhead - will transform what we know about comets, and enable researchers to test several hypotheses about the formation of the Solar System and the origins of life.
Holger Sierks, the principal investigator of the science cameras on Philae's mothership, Rosetta, which is circling the comet overhead, said his team was now trying to take pictures of the robot on the surface.
These pictures will show very little detail because Rosetta is many tens of kilometres away, but they will help pinpoint the place the little probe came to rest after its bouncing.
Even if Philae does not live beyond its initial battery life, scientists will be delighted with the data they have already got.
This information will transform what we know about these objects, and enable researchers to test several hypotheses about the formation of the Solar System and the origins of life.
One theory holds that comets were responsible for delivering water to the planets. Another idea is that they could have "seeded" the Earth with the chemistry needed to help kick-start biology.One theory holds that comets were responsible for delivering water to the planets. Another idea is that they could have "seeded" the Earth with the chemistry needed to help kick-start biology.
"It has been an absolutely magnificent two days," said Esa mission manager Fred Jansen.
"I never thought when I got this job a year and a half ago that this would be the impact.
"Of course, when you're successful, like the lander now is, taking measurements on the surface, you'd like to continue this for as long as possible. But reality tells us there is a limited amount of battery power."
Mission facts:Mission facts:
Philae landerPhilae lander
Comet 67PComet 67P
Can you land on a comet?Can you land on a comet?
'More black swan than yellow duck''More black swan than yellow duck'
Brief encounters with cometsBrief encounters with comets