Rosetta: Comet lander Philae now stable4 min read

The robot probe Philae that made a historic comet landing is now stable after initially failing to attach to the surface, and is sending pictures.

Efforts are now being made to locate the precise position of the European Space Agency probe on the comet.

A brand new image shows the view from the Philae lander of the surface of the comet

A brand new image shows the view from the Philae lander of the surface of the comet

Engineers say it may have bounced hundreds of metres back off the surface after first touching down.

Scientists hope the probe will analyse the comet’s surface to yield insights into the origins of our Solar System.

The first pictures indicate that the lander is sitting at an angle – perhaps on a slope, or maybe even on its side. But the team is continuing to receive “great data” from Philae.

Esa’s Rosetta satellite carried Philae on a 6.4 billion-km (4bn-mile) journey to Comet 67P/Churyumov-Gerasimenko.

Signals from the landing are still being analysed - but this is the team's current best guess at how events unfolded

Signals from the landing are still being analysed – but this is the team’s current best guess at how events unfolded

he robot probe, the size of a washing machine, was dropped from the satellite on Wednesday and spent seven hours travelling down to the icy body.

News of the “first” landing was confirmed at about 16:05 GMT.

Ebullient mood

Controllers re-established radio communication with the probe on cue on Thursday after a scheduled break, and are retrieving pictures from it.

These show the feet of the lander and the wider cometscape.

But there is still concern about the longer-term stability of Philae because it 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.

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David Shukman, BBC science editor

Touching down on a comet is mind-blowing in itself, but try picturing how the tiny Philae lander has then bounced around its new home.

From what we know, the lander rose hundreds of metres above the surface at one stage and remained in flight for nearly two hours. One might say it was airborne, except that the comet has no air.

In any event, it may have risen vertically or drifted sideways – we should hear later. Either way, while Philae was off the surface, the comet will have rotated beneath it. Each rotation takes about 12 hours which means the lander may effectively travelled across one-sixth of the comet’s surface.

By the time it came down again, the original landing zone – chosen for its relative safety and ideal amount of sunshine – was left far behind. The lander is now in different, undetermined area that may prove far more hazardous.

The first picture is confusing, but suggests Philae is sitting at an angle. Everyone here is hungry for more news.

One of the cameras on Philae sent this image of the comet during the descent

One of the cameras on Philae sent this image of the comet during the descent

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.

He also has worries about drilling into the comet because this too could affect the stability of the lander.

“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.

“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.”

The mood at Esa’s operations centre in Darmstadt, Germany, this morning is very ebullient following the historic touchdown.

When it became clear just after landing that the contact was not clean, there was considerable worry. That has changed noticeably.

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 controllers understand where the probe came to rest after its bouncing.

If the probe remains stable, it will engage in several months of science experiments on 67P.

It will take pictures of the cometscape and analyse the surface chemical composition to test several hypotheses about the origins of life and the universe.

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 life.

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Mission facts:

Philae lander

  • Travelled 6.4 billion km (four billion miles) to reach the comet
  • Journey took 10 years
  • Planning for the journey began 25 years ago

Comet 67P

  • More than four billion years old
  • Mass of 10 billion tonnes
  • Hurtling through space at 18km/s (40,000mph)
  • Shaped like a rubber duck
Sebastien Clarke
Sebastien Clarke

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