Rosetta will release its Philae lander when approximately 22 kilometres from the centre of the comet. A signal confirming the separation will arrive at ground stations on Earth 28 minutes and 20 seconds later while the lander’s descent to the surface will take seven hours. On the way down, Philae will take a series of images and onboard instruments will sample the dust, gas and plasma close to the comet’s surface and measure any magnetic field.
Philae’s three lander legs will absorb the momentum of impact and use it to drive an ice screw in each foot into the surface. At the same time two harpoons will fire to lock the probe onto the surface and a small thruster on top will counteract the impulse. Once anchored to the nucleus, Philae will begin its primary science mission, based on its initial battery lifetime of 64 hours.
The SESAME experiment - which contains three instruments - includes one called CASSE, located in the lander’s feet. Harald KRUEGER, Principal Investigator of Rosetta’s SESAME experiment, explains how CASSE will use acoustic waves to determine properties of the comet’s soil.
Within hours of landing, we also hope to see the first ever images of a comet from its surface.
More about the Rosetta mission: http://rosetta.esa.int
