Philae is a 100kg lander that rode piggy-back on the European Rosetta spacecraft, which rendezvoused with Comet 67P/Churyumov-Gerasimenko in August 2014 and is currently go in orbit around it. On November 12, after a period of mapping by Rosetta, Philae self-ejected from the main craft and unfolded its three legs, ready for a gentle touchdown at the end of the ballistic descent. Immediately after touchdown, a pair of harpoons were supposed to fire to anchor the lander to the surface and prevent it escaping from the comet's extremely weak gravity. In the event, the comet initially struck the comet within 100 meters of the chosen target point. However, the harpoons failed to fire and the craft bounced away from the comet on a trajectory that lasted for about two hours and carried it laterally about 1 km from the first landing site. Upon making contact for a second time, it rebounded at about 2 cm per second, bouncing up for about 7 seconds before landing and staying put the third time.
The minimum mission target is one week, but surface operations may continue for many months.
Lander designThe 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 transmits 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.
Related category SATELLITES AND SPACE PROBES
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