Launched on March 2, 2004, the European Space Agency’s Rosetta spacecraft has become the first probe to orbit a comet after arriving at its destination at Comet 67P/Churyumov- Gerasimenko on August 6. On November 12, Rosetta will deploy a second robotic probe to explore the comet’s surface, which has also never been done before. Rosetta will separate from the comet after chasing it across the galaxy for 10 years as it sends Philae, the smaller robotic probe, to investigate the surface of the comet. If successful, Philae will become the first craft to land on a comet. Philae will take pictures of the mother ship Rosetta as it embarks on its 7- hour descent to the comet’s surface.
Scientists from NASA and the European Space Agency hope to learn more about the composition of comets and how they interact with solar winds. Many people believe that water may have been brought to Earth by comets, as well as the chemicals that make up the building blocks of life. This mission may provide information on these theories as Philae has the ability to detect organic chemicals on the comet’s surface. But engineers say that the landing scheduled on November 12 will be a very difficult endeavor. Engineers will not be able to steer Philae once it departs from the Rosetta mother ship. The trajectory has to be programmed into the probe before it is deployed to the comet’s surface. The comet’s surface is also very rocky and irregular, making it difficult for the scientists and engineers to find a suitable landing spot that also receives enough light to allow Philae’s solar panels to recharge its batteries. The comet’s gravity is very weak and scientists say there is a chance that Philae could bounce off the comet upon impact. In preparation for this problem, Philae has been designed to grip the comet’s surface when it lands. At the moment of touchdown, Philae will fire two harpoons into the surface of the comet and the attached cords will rewind to help anchor the craft. Then, a thruster will fire from the top of the probe to push Philae downwards as screws from each foot of the craft imbed themselves into the surface of the comet. While this process sounds complicated, all of these actions will occur in a 15 second period of landing. If successful, Philae will have an initial 65 hours of battery life before it will need to recharge its solar batteries. But, scientists hope to continue working on the comet’s surface for 3 months. After this 3-month period, scientists believe that the comet will travel too close to the sun, causing intense heat that Philae will not be able to operate under. The Philae landing could break new ground in the study of comets and may be one of the most important space missions of the early 21st century.
http://www.cnn.com/2014/11/10/world/philae-comet-lander/index.html?hpt=hp_t2