(Photo : NASA/JPL-Caltech)

Originally launched in 2007, NASA's Dawn Spacecraft has entered an approach phase, as it moves closer to Ceres, a Texas-sized dwarf planet never before visited by a spacecraft. Dawn is scheduled to enter orbit of the dwarf planet in the asteroid belt in March 2015.

Dawn is approximately 640,000 kilometers from Ceres and is approaching the dwarf planet at 725 kilometers per hour. The arrival of Dawn at Ceres will mark the first time a spacecraft has ever orbited two bodies in the solar system. The spacecraft previously explored the protoplanet Vesta for 14 months beginning in 2011 and completing its survey in 2012. During that time, Dawn captured detailed images and collected data about the body.

"Ceres is almost a complete mystery to us," principal investigator for the Dawn mission, based at the University of California, Los Angeles, Christopher Russell says. "Ceres, unlike Vesta, has no meteorites linked to it to help reveal its secrets. All we can predict with confidence is that we will be surprised."

The two planetary bodies are thought to differ in a few important ways. Ceres is believed to have formed later than Vesta, and with an interior far cooler when compared to Vesta. Current evidence suggests Vesta retained only a small amount of water because it formed during a period when more radioactive material was available producing more heat. Ceres, on the other hand, has a thick ice mantle and is the largest body in the asteroid belt with an average diameter of 950 kilometers.

The Dawn spacecraft has already completed five years of accumulated thrust time, more than any other spacecraft. The Dawn utilizes ion propulsion allowing it to travel through space more efficiently compared to traditional chemical propulsion. In an ion propulsion engine, an electrical charge is applied to xenon gas, and charged metal grids accelerate these xenon particles out of the thruster.

Dawn has recently emerged from solar conjunction, meaning the spacecraft was on the opposite side of the Sun, limiting communication between the craft and Earth. Now that it can reliably communicate with Earth, mission controllers have programmed the necessary maneuvers for its rendezvous with Ceres.

As Dawn approaches Ceres over the next couple of months, the views of Ceres should continue to improve. By the end of January, scientists hope to view some of the best images and data ever taken of this relatively unknown dwarf planet in our solar system.

NASA's Dawn Spacecraft Begins Approach Toward Dwarf Planet Ceres [VIDEO]