The Dawn spacecraft is heading toward the dwarf planet Ceres, one of the least-understood of all bodies in the inner solar system.
Ceres is the largest member of the asteroid belt, approximately the size of Texas, and has never before been explored by a spacecraft.
Dawn was launched into space in 2007, and is expected to arrive at Ceres in March 2015. Images taken of Ceres by the spacecraft continue to improve as the vehicle approaches its target. By the end of January 2015, pictures captured by Dawn are expected to be the most-detailed ever taken of the dwarf planet.
Ceres was recently placed on the opposite side of the Sun, hindering communications between the vehicle and mission engineers. That segment of the mission is now complete, and Dawn has entered the Ceres approach phase. Engineers have uploaded commands to the spacecraft, ordering the observatory to prepare for its long-awaited rendezvous.
Dawn is currently 400,000 miles away from Ceres, approaching the body at a relatively slow speed of just 450 miles per hour. Before heading off the Ceres, Dawn spent 14 months orbiting and exploring the asteroid Vesta, recording images and data from 2011 to 2012.
"Ceres is almost a complete mystery to us. Ceres has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised," Christopher Russell, principal investigator for the Dawn mission, said.
Ceres is covered in frozen water ice, and may even be home to an ocean, deep beneath the ice. Vesta was found to be largely lacking in water, and astronomers believe radioactivity may have created heat, driving the substance from the asteroid, during the earliest days of our solar system. Ceres is believed to be younger than Vesta, possibly explaining the presence of water on the body.
Dawn uses ion propulsion for thrust, a far more efficient system than traditional chemical rockets. These engines operate by applying an electrical charge to a storehouse of xenon gas. This material then accelerates between a pair of charged metal plates, and out a thruster. The equal and opposite reaction provided according to Newton's laws of motion then drive the spacecraft forward. During its flight from Earth, the ion engines have set a new record, completing five years of thrust to the vehicle.
"Orbiting both Vesta and Ceres would be truly impossible with conventional propulsion. Thanks to ion propulsion, we're about to make history as the first spaceship ever to orbit two unexplored alien worlds," Marc Rayman, chief engineer and mission director for the Dawn program, said.
