Philae Works Hard To The End — And it May Not Be The End – UPDATE

Philae Works Hard To The End — And it May Not Be The End – UPDATE

UPDATED throughout on November 15, 2014 (originally published November 14)

Despite the odds, the European Space Agency (ESA) was able to restore contact with its Philae lander on the surface of Comet 67P Friday evening (November 14, Eastern Standard Time).  Not only were they able to retrieve data obtained previously, but new commands were sent, new data acquired, and they succeeded in rotating the lander so more sunlight will fall on one of the solar panels.  That gives hope that contact could be restored again as the comet moves closer to the Sun.

Philae (pronounced fee-LAY) spent 10 years travelling to Comet 67P/Churyumov-Gerasimenko aboard its Rosetta mothership.  The two spacecraft separated on November 12 and Philae landed on the surface of the comet, the first time such a feat has been achieved.  But two systems that were intended to ensure that the lander stayed put in the very low gravity environment did not work and Philae bounced twice, landing three times.   Unfortunately, the final landing spot is surrounded by rocks, preventing sunlight from recharging the lander’s batteries.

Philae has two batteries and one of them was sufficiently charged to complete the probe’s primary scientific goals, but the hope was that it, plus a secondary battery, could be recharged to allow an extended mission lasting months rather than days.   Earlier on Friday, prospects seemed grim that even one more communications session could take place.

Philae landed for the first time at 10:34 am EST on November 12.  It bounced and remained aloft for almost two hours, bounced again and then landed 7 minutes later.  From then until approximately 7:30 pm EST Friday, its 10 scientific instruments collected a great amount of data, including drilling into the comet.  Scientists are still analyzing the data collected during the 57 hours it operated.

But with battery levels falling precipitously, at 7:28 pm EST, ESA’s operations center tweeted (@esaoperations) that the lander had switched to standby mode due to low power: “All instruments off.  Comm link still active.”  A few minutes later “Lander now sending only housekeeping data at very low rate.  All instruments off.  Comm link alive.” Soon thereafter: “our lander’s asleep.  Good night.”  ESA reports that the last contact was at 00:36 GMT November 15 (7:36 pm EST November 14).

Project manager Stephan Ulamec said “we are happy.  We can even watch it falling asleep, which is a little bit sad but it can give us data that we want to have,” according to a tweet from The Planetary Society’s Emily Lakdawalla (@elakdawalla) who has been reporting from the European Space Operations Center (ESOC) in Germany throughout the lander’s mission.

Scientists are ecstatic at all the data the lander was able to acquire in that short time, and from Rosetta, which continues to orbit the comet and will collect and send back data until it runs out of fuel in 2016.   Rosetta project scientist Matt Taylor said yesterday that some results will be presented at the fall meeting of the American Geophysical Union (AGU) next month.

Cameras on Rosetta continue to try to locate Philae.   ESA does not know where it is.  The first touchdown was exactly where it was supposed to land, but where the bounces took it is unknown.  (ESA released a set of images from Rosetta’s NavCam taken of the original landing spot over a period of 3 minutes and 34 seconds as Philae approached the surface and then after it bounced, apparently leaving a dark spot of disturbed dust behind.)

Rosetta serves as a relay between Philae and Earth, so communications are only possible when Rosetta is in the correct position to serve that function.  A communications opportunity opened at 10:00 UTC (5:00 am EST) on November 15, but Philae did not respond.   Rosetta is now being moved into a different orbit around the comet to continue its own science program, but will continue listening — and looking — for Philae.

Comet 67P is on its way in towards the Sun and Rosetta will be able to study it as it becomes active with its ices melting from the Sun’s heat creating the familiar comet’s tail.  

Scientists have some hope that they may hear again from Philae if the solar panel becomes more illuminated as the comet travels inward.  During the session last night, commands were sent such that Philae lifted its body 4 centimeters and turned 35 degrees in the hope its solar panels would get more sunlight to recharge the batteries.   Between now and whenever that happens, Philae will hibernate. 

Whatever happens in the future, ESA has achieved several firsts that will go into the space exploration record books, including the first spacecraft to orbit a comet, the first spacecraft to land on a comet, and the first spacecraft to drill into the surface of a comet.

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