The Dawn craft was launched on September 27, 2007 and has a twofold primary mission: To travel to the asteroid belt and study two of its massive residents, Vesta and Ceres. Both objects are thought to have formed early on in the solar system's history.
By examining these celestial bodies, scientists hope to uncover details about how the solar system came to be. It is science's way of stepping back to the beginnings of our universe and learning the processes that brought us to where we are. This artist's concept illustration depicts the spacecraft heading toward the dwarf planet Ceres. It is the only man-made object to explore one solar body, orbiting it for a year before traveling on to orbit another.
The Dawn mission is part of NASA's Discovery Program, which began in 1992. In an effort to unlock the secrets of the solar system, the program has been focusing on smaller missions to complement NASA's continued planetary exploration. NASA/JPL-Caltech
Vesta and Ceres are the two largest surviving protoplanets -- bodies that nearly became planets. By studying them with the same equipment (the first time two celestial bodies will have been closely explored by the same instruments), scientists hope to compare how each protoplanet developed, and in turn deduce how the early solar system came to be.
Despite Vesta's being known as a giant asteroid, it's tiny -- as is Ceres -- compared with other small bodies like Mars, Mercury and our moon.NASA/JPL-Caltech/UCLA
Like something out of a sci-fi plot, the spacecraft uses an ion propulsion system, pictured left, for traveling through deep space. Without this technology, the mission would have required 10 times more propellant and a much larger spacecraft in order to reach the asteroid belt.
In terms of equipment on board, Dawn, pictured on the right ahead of launch, carries cameras for taking detailed imagery, helping the study of minerals on the surface, as well as for navigation. To detect the elemental composition of the two celestial bodies, a gamma ray and neutron detector has been installed. Finally, to examine the surface mineralogy, a visible and infrared mapping spectrometer has been fitted. This particular piece of equipment is a modification of a similar version currently flying on the European Space Agency's Rosetta.NASA/JPL
Journeying to the asteroid belt, a region located between Mars and Jupiter and populated with numerous misshapen bodies, Dawn was tasked first with studying the asteroid known as Vesta. Arriving in July 2011, Dawn spent 14 months orbiting the giant asteroid gathering data and imagery. Its findings indicated that Vesta is "the only intact layered planetary building block with an iron core known to be remaining since the early days of the solar system." Due to its composition, it is actually more similar to terrestrial planets and the Earth's moon than other asteroids. Upon completion of this phase in July 2012, the probe began traveling toward Ceres, the first dwarf planet ever found and one of the largest objects in the asteroid belt.
This full view of Vesta was taken by NASA's Dawn spacecraft, as part of a rotation characterization sequence, on July 24, 2011, at a distance of 3,200 miles (5,200 kilometers). The resolution of this image is about 500 meters per pixel.NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
This image taken on October 20, 2011 from an altitude of about 420 miles (680 kilometers) shows Vesta's crater "Canuleia." About 6 miles (10 kilometers) in diameter, it is notable for the rays of bright material that seem to emanate from it. To the northeast, scientists also identified a presently unnamed crater of about the same size. NASA/JPL-Caltech/UCLA/MPS/DLR/PSI/Brown
The second phase of the primary mission is to document Ceres, a object first spotted by Sicilian astronomer Giuseppe Piazzi in 1801. On December 1, 2014 as Dawn continued its solitary flight through space, early glimpses of the dwarf planet were attained by the craft's on-board cameras. Because Ceres is so much brighter than the stars surrounding it, the photograph required a long exposure time to make the stars visible in the shot. It was snapped using the probe's framing camera and using a clear spectral filter, from a distance of around 740,000 miles (1.2 million kilometers).NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
By the time Dawn, pictured in this artist concept illustration, reaches Ceres on March 6, the spacecraft will have made an epic journey of 3 billion miles (4.9 billion kilometers). We know Ceres is roughly the size of Texas in diameter and has an almost spherical exterior. And according to NASA, astronomers believe water ice may be buried under the dust-covered surface. Little else is known at present.