Images Show Philae's First Bounce, Ulamec Optimistic Will Hear from It Again

The European Space Agency (ESA) today released new images taken by its Rosetta spacecraft of the Philae lander as it made a first landing on Comet 67P and then bounced on November 12.  Also today, the German Aerospace Center, DLR, issued a concise summary of very preliminary science results from Philae.  The fate of the lander, which bounced twice and landed three times, sparked interest around the world last week as its battery died and contact was lost.  Philae project manager Stephan Ulamec is optimistic, however, that communications will be restored next year.

Philae is funded by a consortium led by DLR (Deutsches Zentrum für Luft- und Raumfahrt) and was controlled and monitored by DLR’s Lander Control Center in Cologne, Germany.  The lander is part of ESA’s Rosetta mission.  Rosetta and Philae spent 10 years reaching Comet 67P/Churyumov-Gerasimenko, arriving in August 2014.  The two spacecraft separated on November 12.  Philae made its first landing on the comet about 7 hours later.  Harpoons that were intended to hold Philae in place on the surface did not fire, however, and the lander bounced twice. 

ESA still does not know where its final landing took place.  Rosetta serves as a communications link between Philae and Earth in addition to conducting its own science investigations as it orbits the comet.  It continues to look and listen for Philae.  Rosetta will stay with the comet as it journeys into toward the Sun, studying it as the ices melt and create the classic comet’s tail.   It is the first spacecraft to orbit a comet and Philae is the first spacecraft to land on a comet. 

Today ESA released a mosaic of images taken by the Osiris camera on Rosetta that shows Philae as it descended to the surface (minutes 15:14 to 15:23), touched down (minute 15:43), only to fly off again into space (minute 15:43 on far right).  It landed again about 2 hours later, bounced again, and landed a third time about 7 minutes after that.  Since the final landing site is not known, there are no images yet of those events.

Images of Philae as it landed on Comet 67P and bounced the first time.  November 12, 2014.  Times (hour:minute) are in GMT.
Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

The hope is that with these images ESA and DLR at least know the direction in which the lander headed and perhaps they will be able to locate it using Rosetta’s instruments.  All they know now is that Philae is surrounded by rocks that block sunlight from reaching Philae’s solar panels so its batteries can be recharged.  After 57 hours of work, its primary battery was depleted and the lander entered hibernation.   Planetary Society blogger Emily Lakdawalla was at ESA’s European Space Operations Center (ESOC) in Darmstadt, Germany as Philae gamely executed its commands despite dwindling energy — including an improvised lift-and-turn motion that rotated the lander’s body 35 degrees in the hope of getting more sunlight on the solar panels — and provides a compelling account of those last minutes.

Last minutes for now, that is.  Ulamec is optimistic that as the comet continues its journey in toward the Sun, lighting conditions will improve, the batteries will recharge, and Philae will be able to communicate again next year.  A DLR press release today says he “believes it is probable that in the spring of 2015” Philae will be heard from again.

Meanwhile, scientists are beginning to analyze data from the 57 hours of work Philae has already completed.   Data was received from all 10 of the instruments on the lander.  One instrument — Multi-Purpose Sensors for Surface and Sub-Surface Science (MUPUS) — hammered a probe into the surface, but it turned out to be a much harder surface than expected.  “Although the power of the hammer was gradually increased, we were not able to go deep into the surface,” said Tilman Spohn from DLR’s Institute of Planetary Research.  The comet “proved a tough nut to crack.”  Another instrument, SESAME (Surface Electrical, Seismic and Acoustic Monitoring Experiment) similarly found the comet was “not nearly as soft and fluffy as it was believed to be.” Brief initial results from all 10 instruments are provided in the DLR press release.   More are expected at the annual fall meeting of the American Geophysical Union (AGU) next month in San Francisco.