Sep 5, 2012 12:55 PM by Matt Stafford
LOS ANGELES (AP) - After spending a year circling the giant asteroid Vesta, NASA's Dawn spacecraft is poised to travel to an even bigger target.
For more than a month, Dawn has been spiraling away from Vesta. The departure is so slow and gradual that engineers won't know until Wednesday how it went.
Its next destination is Ceres, the largest asteroid in the asteroid belt between Mars and Jupiter. It's so large - about the size of Texas - that it's also known as a dwarf planet.
Unlike the dry and rocky Vesta, Ceres is icy and may have frost-covered poles. Dawn is scheduled to arrive there in early 2015.
The spacecraft is powered by ion propulsion, which provides gentle yet constant acceleration, making it possible to visit two celestial bodies.