For more than 10 years, the spacecraft has looped around the inner solar system, gathering speed by slingshotting past Earth three times and Mars once. Propelled by its final pass by Earth, Rosetta began a five-year loop to align itself with the orbit of the comet, setting the stage for a rendevous this past August and a landing Wednesday. Rosetta’s journey A tricky landing 2.4 miles 1.5 miles 3.1 miles The primary landing sitefor Rosetta’s lander Philaewas chosen from fiveoptions in September. ThrusterpushesPhilaedown. Ice screws oneach foot drillinto the cometsurface. Landinggear willabsorbthe impact. Harpoonswill lock Philaeto the surface. PRIMARY LANDING SITE THE SCALE OF THE COMET Sideview Sideview Imperial Star Destroyer Smallendview If all goes well at the moment of touchdown on the comet (11 a.m. Wednesday), the landing gear will absorb the forces of landing, then ice screws in each of the probe’s feet and a harpoon system will lock Philae to the surface. At the same time a thruster on top of the lander will push down to counteract the impulse of the harpoon. 2004, March 2Launch 2005, March 4First Earth flyby 2007, Nov. 13Second Earth flyby 2009, Nov. 13Third Earth flyby 2014, Nov. 12Scheduled landing on 67P/C-G 2007, Feb. 24Mars flyby Sun Sun 2011, June 8 Placed in hibernation for 31 months 2014, Aug. 6 Arrival at comet67P/C-G 4:03 a.m. Wednesday Philae lander separatesfrom the Rosetta orbiter.

SOURCE: European Space Agency.