Explanation:
Shortly
after sunrise on Thursday at
Cape Canaveral
Air Force Station, the
Dawn
spacecraft began its journey to the asteroid belt,
arcing eastward into a blue and cloudy sky.
Dawn's voyage began on a conventional,
chemically
fueled Delta II
rocket, but will continue with an
innovative
ion propulsion system.
The spacecraft's extremely
efficient
ion engines will use electricity
derived from solar power to ionize xenon atoms and generate
a gentle but continuous thrust.
After a four year interplanetary cruise, Dawn will orbit
two small worlds, first Vesta and then Ceres.
Vesta is one of the largest main belt asteroids, while nomenclature
introduced by the International Astronomical Union in 2006 classifies
nearly spherical Ceres as a dwarf planet.
