The Philae probe is a ESA (European Space Agency) probe which is the first ever to achieve a landing on a comet. It was attached to the Rosetta spacecraft, and was launched in 2004. After 10 years of travel, it finally landed on the comet on November 12, 2014. It is named after the Philae Obelisk, which was used along with the Rosetta Stone to decipher Ancient Egyptian hieroglyphics.
The probe's main mission was to land on a comet, attach itself to the surface and transmit information about its composition back to Earth. Unlike the probe Deep Impact, which actually impacted the nucleus of the comet Tempel-I, Philae was designed to land on the comet and stay there, transmitting information back all the time. An Ariane 5G+ rocket carried the spacecraft and lander on a ten-year-long journey to the comet Churyumov–Gerasimenko. (Right): An illustration of Philae.
The probe is expected to function for about 4-5 months, after which it will run out of power completely. A secondary rechargeable battery exists, but there is too less sunlight falling on Philae's panels to fill them up. However, by August 2015, the comet will be close enough to the Sun to refill the panels and maybe jumpstart the probe.
Philae actually did not touch down as planned. There were harpoons in each of its legs, but they did not fire of, and the craft bounced twice, almost to a height of a kilometre, before finally staying put. Copenhagen Suborbitals showed that the nitrocellulose which was employed to fire off the harpoons is unreliable in a vacuum. On 15th November, all electrical power had been used up, and Philae shut down and ceased all communications. (Above right): A depiction of the landing of Philae.