Space visi­tor phones home

Comet lan­der Phi­lae awak­ens af­ter months of no con­tact with Earth

Los Angeles Times - - THE WORLD - By Lau­ren Raab and Deb­o­rah Net­burn lau­ren. raab@ latimes. com Twit­ter: @raablau­ren deb­o­rah. net­burn @ latimes. com Twit­ter: @ Deb­o­rahNet­burn

Phi­lae, the first space­craft to land on a comet, re­cently de­lighted sci­en­tists by wak­ing up and reestab­lish­ing con­tact with Earth seven months af­ter run­ning out of power.

It “spoke” for more than a minute, ac­cord­ing to the Euro­pean Space Agency, and it is ex­pected to be able to con­tinue gath­er­ing in­for­ma­tion and send­ing it home.

Here’s a look at what the lan­der has done so far and what will hap­pen next. What is Phi­lae?

Phi­lae is a mo­bile lab­o­ra­tory the size of a wash­ing ma­chine. It was launched in March 2004 from the Guiana Space Cen­ter in French Guiana, strapped to the side of the ESA’s Rosetta or­biter. The pair were tasked with study­ing the moun­tain- sized comet 67P/ Churyu­mov- Gerasi­menko as it made its way to­ward the sun.

To­gether, they f lew a loop­ing tra­jec­tory through the in­ner so­lar sys­tem that lasted 10 years and cov­ered nearly 4 bil­lion miles. In Au­gust, they fi­nally met up with 67P, which or­bits the sun once ev­ery 6.5 years along a path that takes it roughly be­tween Earth and Jupiter.

Rosetta spent a few months cir­cling the comet, send­ing back im­ages that would help sci­en­tists de­ter­mine the best place for Phi­lae to land. Af­ter a site was se­lected, Phi­lae de­scended onto the comet’s sur­face in Novem­ber. Is Phi­lae’s awak­en­ing a sur­prise? Some­what. Af­ter Phi­lae’s touch­down on the sur­face of the comet, it bounced twice be­fore even­tu­ally set­tling into a shady spot where its so­lar pan­els were not able to re­ceive suf­fi­cient sun­light to keep the lan­der op­er­at­ing. Sci­en­tists hoped that as the comet ap­proached the sun, the lan­der would charge enough through its so­lar pan­els, but they didn’t know when or whether that would hap­pen. Why did Phi­lae wake up now?

The comet fi­nally brought it close enough to the sun. If Phi­lae had landed at its in­tended site, it prob­a­bly would have over­heated and be­come use­less by March, ac­cord­ing to the ESA. But be­cause Phi­lae is in a shad­owy spot, be­ing nearer to the sun is what’s en­abling it to power up.

The comet will con­tinue trav­el­ing closer to the sun un­til Au­gust, when its or­bit will pull it away again. Where is Phi­lae?

The lan­der’s ex­act lo­ca­tion on the comet’s sur­face is un­clear. Phi­lae is so small that im­ages taken by its mother ship, Rosetta, which is or­bit­ing the comet, have not re­vealed its po­si­tion. What has Phi­lae ac­com­plished?

Dur­ing its first 60 hours on the comet, when it was op­er­at­ing on bat­tery power, Phi­lae scooped up ma­te­rial from the comet’s sur­face, took its tem­per­a­ture, sent ra­dio waves through its nu­cleus and hunted for hints of or­ganic ma­te­rial.

Be­cause comets are be­lieved to be relics from our so­lar sys­tem’s ear­li­est days, they can pro­vide clues about the so­lar sys­tem’s for­ma­tion. Sci­en­tists won­der, for ex­am­ple, how big a role mag­netic fields played in caus­ing the gas and dust that sur­rounded the young sun to clump to­gether into ob­jects such as plan­ets and moons.

Mea­sure­ments from Phi­lae helped sci­en­tists find that the nu­cleus of 67P is not mag­ne­tized. If that’s rep­re­sen­ta­tive of all comets, they con­cluded, “mag­netic forces are un­likely to have played a role in the ac­cu­mu­la­tion of plan­e­tary build­ing blocks greater than one me­ter in size,” ac­cord­ing to a study pub­lished in the jour­nal Science in April.

Phi­lae also took the first panoramic im­ages from the sur­face of a comet. What did sci­en­tists find re­cently?

This month, Phi­lae com­mu­ni­cated for 85 sec­onds with the ESA team, send­ing a mes­sage to the Rosetta or­biter, which in turn beamed it across 190 mil­lion miles of space to Earth. How­ever, the lan­der must have come out of hi­ber­na­tion be­fore then, be­cause there are more than 8,000 data pack­ets in its mem­ory, ac­cord­ing to the space agency.

Phi­lae phoned home again the next day, but this time the com­mu­ni­ca­tion was just a few sec­onds long and less sta­ble. Still, mis­sion of­fi­cials said this brief con­tact was enough to con­firm that the lan­der is in good con­di­tion.

“Phi­lae is do­ing very well,” Stephan Ulamec, the space agency’s Phi­lae pro­ject man­ager, said in a state­ment. “The lan­der is ready for oper­a­tions.” What’s next?

ESA of­fi­cials are work­ing on new or­bit tra­jec­to­ries for Rosetta that will op­ti­mize its abil­ity to hear from Phi­lae. Sci­en­tists also hope to find out ex­actly where on the comet it’s lo­cated.

Af­ter the health of the lan­der has been fully an­a­lyzed, engi­neers will slowly start turn­ing on in­stru­ments, be­gin­ning with those that use the least energy and send the small­est bits of data back to Earth. In­stru­ments that ham­mer and drill into the comet will be last on the list.

As it turns out, Phi­lae’s un­planned bounce may have a sil­ver lin­ing: The lan­der should be op­er­a­tional dur­ing the time the comet is clos­est to the sun, a point called per­i­he­lion.

Jac­ques Brinon Pool Photo

FRENCH PRES­I­DENT Fran­cois Hol­lande, cen­ter, and as­tro­physi­cist Fran­cis Ro­card look at a model of the comet lan­der Phi­lae in Paris in Novem­ber.

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