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The European Space Agency's comet lander has gone silent again

Philae, phone home, please

ESA

The European Space Agency has lost contact with its comet lander, Philae, yet again. Today, the space agency said that Philae hasn’t made contact since July 9th; efforts to re-establish communication over the following weekend were unsuccessful.

It's possible that Philae has somehow moved.

ESA scientists also don’t know exactly where Philae is on the space rock. The space agency is exploring the possibility that Philae has somehow moved on 67P/Churyumov-Gerasimenko, the comet it landed on in November. Scientists believe that gas emissions from the comet may have altered Philae's orientation, meaning it might be in an area without sunlight.

It also means that Philae's antenna may no longer be pointed directly toward Rosetta — the spacecraft that carried Philae to the comet. Rosetta remains in orbit around 67P/Churyumov-Gerasimenko, and the research team has been moving the spacecraft to different locations in order to get a lock on Philae. So far, they haven't had any luck.

view of Philae in flight

67P/Churyumov-Gerasimenko is an object in the Kuiper Belt that is orbiting the Sun as fast as 84,000 mph. It was attractive to scientists as a landing target because its orbital path around the Sun made it easier for a prolonged survey and rendezvous with a spacecraft. Philae was the first spacecraft ever to land on a comet, as part of the ESA’s Rosetta mission (though we’ve slammed probes into comets before). But the landing wasn't exactly smooth; the lander suffered from a couple mechanical malfunctions, and Philae bounced off the comet's surface two to three times before coming to rest.

The area where Philae finally settled turned out to be in the shadow of a nearby cliff or crater, blocking the sunlight needed to power the lander's batteries. So shortly after landing on 67P/Churyumov-Gerasimenko, Philae lost power and went into hibernation mode. ESA scientists said the lander would eventually reboot as the comet moved closer to the Sun, allowing sunlight to shine on the spacecraft's solar panels.

The recent gap in contact suggests Philae isn’t receiving enough sunshine anymore.

In June, the ESA announced that it had finally regained contact with Philae; the lander's solar panels were getting energy again. The Rosetta spacecraft picked up data from the lander and transmitted more than 300 data packets back to ground control.

But the recent gap in contact suggests Philae isn’t receiving enough sunshine anymore. "The profile of how strongly the Sun is falling on which panels has changed from June to July, and this does not seem to be explained by the course of the seasons on the comet alone," said Philae’s project manager, Stephan Ulamec, in a statement.

It also looks like one of the two transmission units that Philae uses to send data is no longer working, and one of its two receiving transmission units is damaged. ESA is preparing several commands for Philae that will help the lander recommence operations with its faulty transmission units. But none of that will matter unless Rosetta can find Philae first.