In 2002, NASA launched Contour (Comet Nucleus Tour), a U.S. unmanned satellite on a mission to get within 60 miles of a comet nucleus to study frozen samples of the solar system from its infancy. It was launched aboard a Boeing Delta 2 rocket from Cape Canaveral. After orbiting Earth until 15 Aug 2002, the satellite's onboard rockets sent it toward an encounter with Comet Enke in 2003, then Comet Schwassman- Wachman 3 in 2006. It is equipped with a special debris shield so it can navigate closer to the comets and survive bombardment from the minute particles of dust and frozen water that form a comet's most distinctive feature, the tail. The shield includes a layer of Kevlar, the material used in bullet-proof vests.