The Philae lander, the first probe to ever touch down on a comet, hasn’t made a peep in 11 days, prompting fears that it has shifted its position, and not for the better.

Above: Comet 67P/Churyumov-Gerasimenko on July 7, 2015

Since it emerged from hibernation on June 14, 2015, Philae has made intermittent and sporadic contact with Rosetta mission controllers on Earth. The lander’s last transmission was on July 9th, when it sent measurement data from its COmet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) instrument. But since that time it has gone completely silent, and efforts to reach the probe have failed.

Philae, is that you?

Back in November, Philae made history by landing on comet 67P/Churyumov-Gerasimenko, but because it landed in a shaded area, its solar panels were unable to recharge its power supply. It sprang back to life in June as the comet moved closer to the Sun. But now there are fears that something—possibly a gas emission—may have jostled the probe and moved it again. With its orientation changed, its antenna position may have also changed with respect to its surroundings. Its current position may not be ideal for communications.

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“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,” noted Philae’s project manager, Stephan Ulamec at DLR, in a statement.

Making matters worse, two transmission units of the lander aren’t working properly, and one of them is damaged. The probe is programmed to switch back-and-forth between these two units. ESA scientists are now trying to contact the lander and make it work with just one transmitter. Assuming it can acquire some sunlight, Philae might be able to execute a transmission command.

The lander’s current status remains uncertain, but further commands are being prepared and tested on a duplicate probe in hopes that Philae will once again commence operations.

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“Philae is obviously still functional, because it sends us data, even if it does so at irregular intervals and at surprising times,” added Ulamec. “Several times we were afraid that the lander would remain off—but it has repeatedly taught us otherwise”.

As for Philae’s mothership, Rosetta, it’s being moved to a more distant orbit. Because the comet is becoming increasingly active, there’s worry that dust particles could damage the spacecraft. Rosetta is currently moving to a safer distance of about 105 to 118 miles (170 to 190 km) from the comet.

[ ESA Rosetta Blog ]


Contact the author at george@io9.com and @dvorsky. Images by ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0