Dawn mission to asteroid belt launched

NASA's Dawn spacecraft blasted off today, aboard a United Launch Alliance Delta II rocket. The spacecraft left Cape Canaveral Air Force Station at 11:34 GMT (7:34 ET). The Dawn mission will explore Vesta, and later Ceres, because these two asteroid belt behemoths have been witness to so much of our solar system's history.

'Visiting both Vesta and Ceres enables a study in extraterrestrial contrasts,' said Dawn Principal Investigator Christopher Russell of the University of California, Los Angeles. 'One is rocky and is representative of the building blocks that constructed the planets of the inner solar system. The other may very well be icy and represents the outer planets. Yet, these two very diverse bodies reside in essentially the same neighbourhood. It is one of the mysteries Dawn hopes to solve.'

Using the same spacecraft to reconnoiter two different celestial targets makes more than fiscal sense. It makes scientific sense. By utilising the same set of instruments at two separate destinations, scientists can more accurately formulate comparisons and contrasts. Dawn's science instrument suite will measure mass, shape, surface topography and tectonic history, elemental and mineral composition, as well as seek out water-bearing minerals. In addition, the Dawn spacecraft itself and the way it orbits both Vesta and Ceres will be used to measure the celestial bodies' gravity fields.

'Understanding conditions that lead to the formation of planets is a goal of NASA's mission of exploration,' said David Lindstrom, Dawn program scientist at NASA Headquarters, Washington. 'The science returned from Vesta and Ceres could unlock many of the mysteries of the formation of the rocky planets including Earth.'

Before all this celestial mystery unlocking can occur, Dawn has to reach the asteroid belt and its first target - Vesta. This is a four-year process that begins with launch and continues with the firing of three of the most efficient engines in NASA's space motor inventory - ion propulsion engines. Employing a complex commingling of solar-derived electric power and xenon gas, these frugal powerhouses must fire for months at a time to propel as well as steer Dawn. Over their eight-year, almost 4-billion-mile lifetime, these three ion propulsion engines will fire cumulatively for about 50,000 hours (over five years) - a record for spacecraft.

The Dawn mission to asteroid Vesta and dwarf planet Ceres is managed by JPL, for NASA's Science Mission Directorate, Washington, DC. JPL is a division of the California Institute of Technology in Pasadena. The University of California, Los Angeles, is responsible for overall Dawn mission science. Other scientific partners include: Los Alamos National Laboratory, New Mexico; Max Planck Institute for Solar System Research, Katlenburg, Germany; and Italian National Institute of Astrophysics, Rome. Orbital Sciences Corporation of Dulles, VA, designed and built the Dawn spacecraft.