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Philae attached to the Rosetta mothership
Philae attached to the Rosetta mothership. Artwork credit: ESA

Philae is a 100kg lander, currently riding piggy-back on the European Rosetta spacecraft, which will rendezvous with Comet 67P/Churyumov-Gerasimenko in August 2014 and go into orbit around it. In November, after a period of mapping by Rosetta, Philae will self-eject from the main craft and unfold its three legs, ready for a gentle touchdown at the end of the ballistic descent. On landing, the legs will damp out most of the kinetic energy to reduce the chance of bouncing, and tcan rotate, lift, or tilt to return the lander to an upright position. Immediately after touchdown, a harpoon will fired to anchor the lander to the icy surface and prevent it escaping from the comet's extremely weak gravity. The minimum mission target is one week, but surface operations may continue for many months.

Philae was successfully reactivated, as its mothership had been earlier, on March 28, 2014, after a three-year period of hibernation in deep space.

Philae on the surface of the comet
Philae on the surface of Comet 67P/Churyumov-Gerasimenko. Artwork credit: ESA

Lander design

The lander structure consists of a baseplate, an instrument platform, and a polygonal sandwich construction, all made of carbon fiber. Some of the instruments and subsystems are beneath a hood that is covered with solar cells.

An antenna will transmit data from the surface of the comet to Earth via the Rosetta orbiter. The lander carries nine experiments, with a total mass of about 21 kg. It also carries a drilling system to take samples of subsurface material.

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