NASA's Dawn Asteroid Probe Tests Ion Engine

NASA?s Dawn spacecraft bound for the solar system's two largest asteroids has aced the first test of its ion propulsion system, the space agency said.

The system will enable Dawn to make the eight-year, three billion-mile (4.9 billion-kilometer) trek to the asteroid Vesta and dwarf planet Ceres.

"Dawn is our baby and over the weekend it took some of its first steps," said Dawn project manager Keyur Patel of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "We have two months more checkout and characterization remaining before Dawn is considered mission operational, but this is a great start."

Spacecraft controllers fired up Dawn's ion drive on Oct. 6 and continued monitoring the system?s performance over the next 27 hours. The ion engines consumed less than 10 ounces (0.28 kilograms) of xenon propellant – not even the equivalent of a can of soda – compared to the 937 pounds (425 kilograms) of Dawn?s onboard fuel supply. That energy efficiency will permit the three ion engines to fire continuously for more than five years, a record for spacecraft, mission managers have said.

The ion engines were tested at five different throttle levels and performed ?flawlessly? according to Jon Brophy, the Dawn project's ion propulsion manager at JPL, in an official statement. Charged ion particles shoot out of the engines at 90,000 miles per hour (144,840 kph) to slowly accelerate the spacecraft over time.

Dawn is slated to arrive at Vesta in 2011 and spend about a year studying the space rock before meeting the dwarf planet Ceres in 2015. The spacecraft will measure the asteroids' shape, surface topography, tectonic history, elemental and mineral composition, and look for water-bearing minerals. Scientists will also use Dawn?s orbit around Vesta and Ceres to gauge mass and gravity fields.

NASA's Dawn mission launched on Sept. 27 from Cape Canaveral, Florida.

• VIDEO: Dawn's Mission to Asteroids Vesta and Ceres
• GALLERY: Asteroids
• VIDEO: The Asteroid Paradox