The anticipated June 30 launch will carry the spaceprobe Dawn on a 3.2-million mile expedition to the primary asteroid belt between the planets Mars and Jupiter. On-orbit the Dawn spacecraft will be powered by ion propulsion system to visit and orbit first the 329-milewide asteroid Vesta and then on to the 597-milewide asteroid dwarf-planet Ceres where some scientists believe that water ice may exist.
After Dawn gets a gravity boost in a fly-by of Mars in March 2009, it will reach Vesta in late 2011 and Ceres in early 2015. In both cases, the spacecraft will survey the situation before beginning a polar orbit and bearing down for closer inspection. The spacecraft will circle both poles, while the body rotates to reveal its entire surface for mapping instruments on-board Dawn.