Race against time to save Philae comet probe

The landing site has caused worries for the ESA as Philae is thought to be sitting beneath a cliff which is preventing much needed solar power from reaching the lander. Picture: PA
The landing site has caused worries for the ESA as Philae is thought to be sitting beneath a cliff which is preventing much needed solar power from reaching the lander. Picture: PA
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SCIENTISTS racing against time to save the Philae comet probe are actively considering taking a last-ditch gamble and “hopping” the lander into a sunnier spot.

Mission controllers have less than 24 hours before the craft’s primary battery power runs out.

Because the lander is shrouded in shadow, it will not be able to recharge the batteries using electricity generated by its solar panels.

A risky solution would be to use the probe’s landing gear to perform the unorthodox mano­euvre and “hop” to a sunnier spot, or shift the craft by activating moving parts linked to its instruments.

British scientist Professor Ian Wright, lead investigator for Philae’s “Ptolemy” instrument that is designed to analyse the composition of surface and dust samples, said: “The hopping idea is being actively considered. There’s no manual for this. We’re having to respond to what we think we’re dealing with. The balance we have to strike is using power to rescue the craft and using power to do some science.


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“There’s no rule book for this stuff. People are very tired and thinking about it as well as they can. Clearly, we’re potentially heading towards the end, but if we could get it out into a bit more sunlight then things will improve.

“In actual fact, these movements don’t take up a lot of power. There is a slight worry that if you try to move something, it might make things worse. It might topple over. But clearly, if you’re getting to the end there’s no harm in having a go.

“It’s a complete unknown but we should be taking risks. There’s no point in not doing that.”

The dishwasher-sized craft made a dramatic landing on comet 67P/Churyumov-Gerasimenko on Wednesday after an epic ten-year, four billion-mile journey through space aboard its Rosetta mothership.

Two harpoons that were supposed to anchor Philae to the surface failed to deploy, and the probe bounced 0.6 miles into space, floating above the comet for nearly two hours.

Eventually, gravity drew it down and it bounced again, coming to rest close to the wall of a large crater more than half a mile from the original landing site.

Scientists believe it is positioned at an angle with one of its three spidery legs suspended in space. The cliff-like crater wall has cast a dark shadow on the probe.

Instead of the expected six or seven hours of sunlight per 12-hour day, Philae is only receiving one-and-a-half.

It is still unclear precisely where the lander is, and how it is orientated.

“The working assumption is that it’s tilted,” said Prof Wright, of the Open University.

“There’s some talk about it having tumbled or something, but I don’t think that can be right because it would have caused more damage.”

Despite its roller-coaster landing, Philae’s radio antenna is operating normally and most of its package of ten scientific instruments is functional. A question mark lies over whether to risk using its drill, which is designed to bore out surface samples to a depth of nine inches.

The samples were to be heated and vaporised in ovens so they could be analysed by instruments including Ptolemy.

But with Philae not properly tethered to the surface, turning on the drill could cause the craft to rotate and become unstable.

“We can’t possibly at this point in time contemplate doing the kind of experiments we set out to do,” said Prof Wright.

Ptolemy has already been sending back data on dust and gas “sniffed” from the environment.

Scientists are working on a way to carry out the instrument’s primary function: measuring ratios of isotopes – atomic “strains” – of different elements. The ratios will be telltale indicators of where and how comets are created.

While scientists, including Doctor Matt Taylor from London, try to save Philae, attention will turn to Rosetta, which has to manoeuvre from its post-separation path back into orbit. Next year, as the comet grows more active, Rosetta will step further back and fly unbound “orbits”, making brief fly-bys to within five miles of the comet.

The comet will reach its closest point to the sun on 13 August next year at a distance of about 115 million miles.


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