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Philae lander completes its main mission, then falls silent

The first-ever comet lander – Philae – made history this week by spending some 57 hours gathering data on the surface of Comet 67P/Churyumov–Gerasimenko.

This animated GIF shows the Philae comet lander's first touchdown point, as seen by the Rosetta mothership's NavCam.  After touching down the first time, the lander bounced nearly a kilometer back to space, before touching down again two more times on its comet.  Image via ESA

This animated GIF shows the Philae comet lander’s first touchdown point, as seen by the Rosetta mothership’s NavCam. After touching down the first time, the lander bounced nearly a kilometer back to space, before touching down again two more times on its comet. Image via ESA

After nearly 57 hours on Comet 67P/Churyumov–Gerasimenko, the Rosetta mission’s Philae lander had completed its main science mission on November 15, 2014, when its batteries failed and the lander went silent. The Rosetta mothership was able to regain contact with Philae at 22:19 UTC (4:22 p.m. CST) Friday night (November 14). ESA says the signal was:

… initially intermittent, but quickly stabilized and remained very good until 00:36 UTC this morning [6:36 p.m. CST Friday evening].

In that last communication between the mothership and lander, Philae returned all its “housekeeping” data, as well as science data from targeted instruments. ESA said:

This completed the measurements planned for the final block of experiments on the surface.

Check out this page: Where is Rosetta today?

The data returned from the comet’s surface will no doubt give scientists something to chew on for years.

The Rosetta mission made history on November 12 by sending the first-ever probe down to soft-land on the surface of a comet. That landing took place a few months after the Rosetta mothership became first spacecraft to rendezvous with – that is, begin moving side by side with – a comet, on August 6, 2014. The comet and spaceraft were more than 300 million miles (500 million km) away on November 12, when the Philae lander sent confirmation of its own successful touchdown on the surface of Comet 67P/Churyumov-Gerasimenko. There was some nail-biting when the lander initially failed to attach to the surface. However, as of Thursday morning, November 13, Philae appeared stable and was sending back data.

The lander set down not once, but three times, in the weak gravitational field of its comet. It essentially bounced in the comet’s weak gravity to two unintended landing sites. Its final touchdown was apparently not in a sunlit area, as planned, but in the shade of a cliff wall. The reduced sunlight meant its solar panels could not recharge the lander’s batteries as was originally hoped by mission planners. ESA said on November 15:

From now on, no contact would be possible unless sufficient sunlight falls on the solar panels to generate enough power to wake it up …

However, given the low recharge current available from the solar cells, it is considered unlikely that contact with Philae will be established in the coming days.

Rosetta mission scientist describes the difference between the initial landing site - Site J, shown as a red square - and the area where the lander is now, shown as a blue diamond.  Image is a screen grab from ESA live video.

Rosetta mission scientist describes the difference between the initial landing site – Site J, shown as a red square – and the area where the lander is now, shown as a blue diamond. The lander apparently came down in the shadow of a cliff, meaning its solar panels could not re-charge as hoped. Still, it operated for 57 hours via its batteries and completed its main mission. Image is a screen grab from ESA live video.

There was talk last week of the lander’s mission reviving some months from now, as the comet continues moving around the sun, causing its “season” to change and the sun to move across the sky visible from the comet’s surface. We will see if that revival comes to pass. I wouldn’t put anything past this great mission! In the meantime, the fascinating Rosetta mission will continue, as the mother spacecraft keeps on moving in tandem with Comet 67P/Churyumov–Gerasimenko on its journey to its July 2015 perihelion, or closest point to the sun.

Rosetta is the first spacecraft to rendezvous with and orbit a comet. It has already returned incredible scientific data, and it has blown all our minds with its amazing images of what comets actually look like up close!

Follow the mission on Twitter via @ESA_Rosetta or at the Rosetta mission’s blog.

One of the first-ever images from the surface of a comet.  It's a view of a shadowed low cliff from the comet's surface after landing. Read more about this image from Andrew R. Brown

One of the first-ever images from the surface of a comet. It’s a view of a shadowed low cliff from the comet’s surface after landing. Read more about this image from Andrew R. Brown

The Philae lander has returned the first panoramic image from the surface of a comet. The view, unprocessed, shows a 360º view around the point of final touchdown. The three feet of Philae’s landing gear can be seen in some of the frames.  Superimposed on top of the image is a sketch of the Philae lander in the configuration the lander team currently believe it is in.   Image via ESA

First panoramic image from the surface of a comet. The view, unprocessed, shows a 360º view around the point of final touchdown of the Philae lander. The three feet of Philae’s landing gear can be seen in some of the frames. Superimposed on top of the panorama is a sketch of the Philae lander in the configuration the lander team currently believe it is in. Image via ESA

Bottom line: The Rosetta mission’s Philae lander has fallen silent after completing the main part of its mission.

Deborah Byrd

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