The Philae lander sitting on Comet 67P/Churyumov–Gerasimenko has run out of power after a successful last-ditch attempt to nudge it into better sunlight apparently came too late to charge its batteries and keep systems up and running.



Mission controllers for the Rosetta mission had said on Friday that they were preparing to “hop” the robotic probe in a hope it would settle in a sunnier spot on the comet’s surface.

Later came a promising announcement. “My rotation was successful (35 degrees). Looks like a whole new comet from this angle,” read a message posted on the lander’s official Twitter account. Earlier the scientists tweeted: “First comet drilling is a fact!”

But afterwards the Philae mission tweeted:

.@ESA_Rosetta I'm feeling a bit tired, did you get all my data? I might take a nap… #CometLanding — Philae Lander (@Philae2014) November 15, 2014

Philae had apparently been successful in shifting position to gives its shaded solar panels a better chance of catching sunlight. But the moment of success was followed by an announcement that it would have to use up its last battery power in sending a final burst of data back to Earth.



If the batteries are not charged the lander goes into hibernation. Without sufficient sunlight on the solar panels the mission shuts down.

The lander’s legs have a built-in spring action. Commands were uploaded on Friday night to fire them, scientists said, warning there was no guarantee of success. Another strategy under discussion was to spin up an internal flywheel that could make Philae cartwheel out of its predicament but also risked soaking up the last of its battery power.

Early on Saturday came an announcement that Philae was on the move:



I just started lifting myself up a little and will now rotate to try and optimize the solar power! — Philae Lander (@Philae2014) November 14, 2014

Since its triple touchdown on Wednesday the spacecraft had been resting on its side, lodged in the shadows of a cliff or large boulder. On Thursday the lander sent back historic first images taken from the surface of a comet. These showed that after its bumpy landing one of its legs was sticking up into space rather than in contact with the surface, raising doubts about whether there was enough spring in Philae’s step to achieve the hop.

The landing had left Philae surrounded by rocks with only a sliver of light reaching one of its smaller solar panels. Philae was receiving just 1.5 hours of sunlight instead of the expected 6-7 hours. “We are unlucky, in a corner, surrounded by rocks,” said Valentina Lommatsch from DLR’s lander team.

Despite the akward orientation, the lander’s science package deployed a 1.2 metre arm and a drill.

I confirm that my @RosettaSD2 went all the way DOWN and UP again!! First comet drilling is a fact! :) pic.twitter.com/eE3xL8CGk0 — Philae Lander (@Philae2014) November 14, 2014

Philae’s primary mission was always designed to last around 60 hours on its initial battery charge. But engineers covered the spacecraft in solar panels in the hope that sunlight could charge a set of secondary batteries and extend the mission for months.

Despite the awkward landing, by Friday Stephan Ulamec, Philae lander manager, estimated that 80% of the science Esa was hoping for had been achieved. If the drilling operation succeeded in delivering samples to onboard instruments it would rise to 90%, he said.

The COSAC (Cometary Sampling and Composition experiment) instrument was chosen to study the first samples rather than the UK-built PTOLEMY instrument. COSAC detects and identifies complex organic molecules from their elemental and molecular composition.

Ulamec said the choice was made because COSAC uses less power than PTOLEMY, and provided data that could be more easily compared to that taken from the Rosetta orbiter.

PTOLEMY still generated data by working in “sniffing” mode. Essentially the instrument detected and analysed molecules of gas that naturally drift off the surface of the comet.

“We juggled everything so that every instrument got to do a measurement, so we are very happy with the mission so far,” says Lommatsch.

Despite the lander shutting down for now, all might not be lost forever.

The comet is currently out beyond the orbit of Mars, heading for its closest approach to the sun in August 2015. This will bring it as close to the sun as Earth’s orbit. There the sunlight will be brighter and may just allow Philae to reboot and power up. To that end, the Philae mission tweeted:

My #lifeonacomet has just begun @ESA_Rosetta. I'll tell you more about my new home, comet #67P soon… zzzzz #CometLanding — Philae Lander (@Philae2014) November 15, 2014

“Cross your fingers, or press your thumbs if you are a German, that we hear something from the lander again,” said Lommatsch.