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Today’s finding of the Philae comet lander is great news for the ESA. It was close to a perfect mission when it touched down on the comet 67P/Churyumov-Gerasimenko in November 2014, but the spikes fired into the surface failed to hold the lander to the surface and it bounced away. The Daily Mail UK has a clear basic article of the landing, and Universe Today has descriptions of the coping with the problems.

An artists representation of the landing site.

This is what the landing site on Philae was expected to look like.

A photograph of the resting place of Philae

This is what the jagged landing place looked like where Philae stopped bouncing.

The photo clearly shows Philae on its side, stuck in between rocks where it is usually in shadows of the sun. Now that the exact location is known it will be possible to know when it will be in sunshine and possibly be generating enough electricity for radio communication.

A photo of Philae in space.

This is a photo from ESA showing the Philae immediately after being released from its comet orbiter.

What is obvious when looking at this lander is how top-heavy it is, and how narrow the gear is for landing on an unknown place. The descent speed was intended to be about one meter per second for this one hundred kilogram vehicle. There was a gyroscope on board to help with stabilizing the orientation, but in addition to the narrow landing gear, there would probably be some transverse movement which would tend to topple the whole device over onto its side. Also, if it was moving sideways and the surface was irregular, the feet would snag and that too could topple the whole thing over.

Comet lander Philae with struts

Philae with long and light-weight stabilizing struts added.

If the lander was descending very slowly vertically on its touchdown it could be stabilized with light struts even on very irregular ground, as seen in the photo above. The struts are not intended to hold the weight, but to orient the vehicle so the main landing gear would be in a more appropriate position. When the vehicle is stabilized the gear struts could have motors to level the vehicle perfectly to the local gravity. These ideas are not available to this lander, but

A future lander on a low gravity object would benefit from long stabilizing struts. 

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