In Astrotech's Payload Processing Facility, an overhead crane lifts the Dawn spacecraft from its transporter. Dawn will be moved into clean room C for unbagging and further processing. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate in Washington, D.C

In Astrotech's Payload Processing Facility, technicians help secure the Dawn spacecraft onto a moveable stand. Dawn will be moved into clean room C for unbagging and further processing. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate in Washington, D.C.

In clean room C of Astrotech's Payload Processing Facility, a worker wearing a "bunny suit," or clean-room attire, looks over the Dawn spacecraft after removing the protective cover, at bottom right. In the clean room, the spacecraft will undergo further processing. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate in Washington, D.C.

The Dawn spacecraft is seen here in clean room C of Astrotech's Payload Processing Facility. In the clean room, the spacecraft will undergo further processing. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate in Washington, D.C.

In clean room C of Astrotech's Payload Processing Facility, a worker wearing a "bunny suit," or clean-room attire, begins removing the protective cover surrounding the Dawn spacecraft. In the clean room, the spacecraft will undergo further processing. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate in Washington, D.C.

In clean room C of Astrotech's Payload Processing Facility, technicians dressed in "bunny suits," or clean-room attire, begin working on the Dawn spacecraft. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate in Washington, D.C.

In clean room C of Astrotech's Payload Processing Facility, a worker wears a "bunny suit," or clean-room attire, next to the Dawn spacecraft, which will be unbagged and undergo further processing. Dawn's mission is to explore two of the asteroid belt's most intriguing and dissimilar occupants: asteroid Vesta and the dwarf planet Ceres. The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate in Washington, D.C.

Artist rendition of NASA Dawn spacecraft, part of the Dawn Mission Art series. http://photojournal.jpl.nasa.gov/catalog/PIA19376

NASA Dawn spacecraft being assembled.

NASA Dawn spacecraft in thermal vacuum chamber.

This illustration shows an inside view of the NASA Dawn spacecraft.

Workers secure the attachments of NASA Dawn spacecraft onto the upper stage booster.

Artist concept of Earth reflection in Dawn spacecraft.

Artist concept of Dawn spacecraft leaving Earth.

Artist concept of the Dawn spacecraft orbiting Ceres.

Artist concept of the Dawn spacecraft with Vesta and Ceres.

Exposed interior of NASA Dawn spacecraft showing ion propulsion system xenon feed system.

This image shows NASA Dawn spacecraft Xenon tank -- composite overwrapped pressure vessel with titanium liner.

Artist rendering of NASA's Dawn spacecraft approaching Mars. Dawn, part of NASA's Discovery Program of competitively selected missions, was launched in 2007 to orbit the large asteroid Vesta and the dwarf planet Ceres. The two bodies have very different properties from each other. By observing them both with the same set of instruments, Dawn will probe the early solar system and specify the properties of each body. http://photojournal.jpl.nasa.gov/catalog/PIA18152

Artist concept of NASA Dawn spacecraft. The giant asteroid Vesta, Dawn next destination, is on the lower left. Another larger asteroid and Dawn second destination, Ceres, is on the upper right.

NASA Dawn spacecraft after installation of high gain antenna.

NASA Dawn spacecraft being moved into thermal vacuum chamber for bake-out.

NASA Dawn spacecraft after installation of high gain antenna.

Against a backdrop of clouds on the horizon, the Delta II rocket carrying NASA's Dawn spacecraft rises from the smoke and fire on the launch pad to begin its 1.7-billion-mile journey through the inner solar system to study a pair of asteroids. Liftoff was at 7:34 a.m. EDT from Pad 17-B at Cape Canaveral Air Force Station. Dawn is the ninth mission in NASA's Discovery Program. The spacecraft will be the first to orbit two planetary bodies, asteroid Vesta and dwarf planet Ceres, during a single mission. Vesta and Ceres lie in the asteroid belt between Mars and Jupiter. It is also NASA's first purely scientific mission powered by three solar electric ion propulsion engines.

This illustration shows the core structure with ion propulsion system installed aboard NASA Dawn spacecraft.

Artist concept of the Dawn spacecraft gathering spectral data from Vesta.

Technician helps guide the second half of the fairing for installation around NASA Dawn spacecraft.

NASA Dawn spacecraft solar array wings are folded to fit inside nose section of protective fairing.

This image is a blinking of two 14-minute exposures of NASA Dawn spacecraft from 600,000 miles from Earth. Bill Dillon, a regular advanced user of Sierra Stars Observatory.

This image from NASA Dawn spacecraft is located in asteroid Vesta Caparronia quadrangle.

The rim of Ezinu Crater is seen in this view from NASA Dawn spacecraft.

These images from NASA Dawn spacecraft show Caparronia crater on asteroid Vesta.

These images from NASA Dawn spacecraft show Sextilia crater on asteroid Vesta.

This image from NASA Dawn spacecraft shows Dawn visible and infrared spectrometer image, overlain on top of a framing camera image of the same region on asteroid Vesta.

This artist concept shows NASA Dawn spacecraft orbiting the giant asteroid Vesta. The depiction of Vesta is based on images obtained by Dawn framing cameras.

This side-perspective view of Ceres mysterious mountain Ahuna Mons was made with images from NASA Dawn spacecraft. Dawn took these images in December 2015.

This artist concept shows NASA Dawn spacecraft heading toward the dwarf planet Ceres. When Dawn arrives, it will be the first spacecraft to go into orbit around two destinations in our solar system beyond Earth.

This image, taken by NASA Dawn spacecraft, shows a variety of small craters in the northern hemisphere of Ceres. The majority of Ceres images from Dawn show heavily cratered terrains such as this.

Tupo Crater on Ceres is seen in this view from NASA Dawn spacecraft. This crater, located in the southern hemisphere of Ceres, was named for the Polynesian god of turmeric. Dawn captured the scene on Dec. 24, 2015.

This artist concept shows NASA Dawn spacecraft arriving at the dwarf planet Ceres, the most massive body in the asteroid belt. Dawn is the first mission to visit a dwarf planet.

The shadowy outlines of the terrain in Vesta northern region are visible in this image from NASA Dawn spacecraft. The image comes from the last sequence of images Dawn obtained of the giant asteroid Vesta as it departed the giant asteroid.

This image shows the first, unprocessed image obtained by NASA Dawn spacecraft of the giant asteroid Vesta in front of a background of stars. It was obtained by Dawn framing camera on May 3, 2011.

NASA Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011. Dawn entered orbit around Vesta on July 15, and will spend a year orbiting the body.

This image from NASA Dawn spacecraft shows a part of Vesta northern hemisphere, which is mostly in darkness. Since Dawn arrival at asteroid Vesta the sun has not illuminated Vesta most northerly latitudes.

NASA Dawn spacecraft has spiraled closer and closer to the surface of the giant asteroid Vesta. These images were obtained by Dawn framing camera in the three phases of its campaign since arriving at Vesta in mid-2011.

NASA Dawn spacecraft flys over dwarf planet Ceres which Dawn has been orbiting for mre than a year, providing us with fascinating views of an alien world.

These images from NASA Dawn spacecraft are located in asteroid Vesta Oppia quadrangle, just south of Vesta equator; Claudia was chosen to anchor the coordinate system for Vesta used in the scientific investigations of the Dawn team.

NASA Dawn spacecraft flys over dwarf planet Ceres which Dawn has been orbiting for mre than a year, providing us with fascinating views of an alien world.

Vesta is the largest asteroid visited by a spacecraft. It is currently being observed by NASA Dawn spacecraft, which has entered orbit around Vesta.

This artist concept shows NASA Dawn spacecraft arriving at the dwarf planet Ceres. Dawn travels through space using a technology called ion propulsion, with ions glowing with blue light are accelerated out of an engine, giving the spacecraft thrust.

Craters in the northern hemisphere of dwarf planet Ceres are seen in this image taken by NASA's Dawn spacecraft on June 6, 2015. This is among the first snapshots from Dawn's second mapping orbit, which is 2,700 miles (4,400 kilometers) in altitude. The resolution is 1,400 feet (410 meters) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA19570

These images from NASA Dawn spacecraft are located in asteroid Vesta Sextilia quadrangle, in Vesta southern hemisphere.

NASA Dawn spacecraft shows the central area of the south polar basin. This view is rotated by approximately 60°.

These images from NASA Dawn spacecraft are located in asteroid Vesta Lucaria Tholus quadrangle, in Vesta northern hemisphere.

NASA Dawn spacecraft obtained this albedo image of asteroid Vesta with its framing camera on August 11th 2011.

NASA Dawn spacecraft took images of Haulani Crater at a distance of 240 miles 385 kilometers from the surface of Ceres.

These images from NASA Dawn spacecraft show an old, heavily cratered terrain around asteroid Vesta equator.

This frame from a movie presents a series of animations showing NASA Dawn spacecraft traveling to and operating at the giant asteroid Vesta.

These images from NASA Dawn spacecraft are located in asteroid Vesta Numisia quadrangle, a few degrees below Vesta equator.

This composite image from NASA Dawn spacecraft is a simulated true color image of asteroid Vesta northern and equatorial regions.

NASA Dawn spacecraft shows the central area of the south polar basin. This view is rotated by approximately 90°.

These images from NASA Dawn spacecraft are located in asteroid Vesta Tuccia quadrangle, in Vesta southern hemisphere.

This is the first image obtained by NASA Dawn spacecraft after successfully entering orbit around Vesta.

This image, taken by NASA Dawn spacecraft, shows a knobby surface on Ceres. The region is adjacent to the giant impact crater Urvara.

These images from NASA Dawn spacecraft are located in Vesta Numisia quadrangle, in Vesta northern hemisphere.

This image shows NASA Dawn spacecraft flying above Vesta, based on an artist concept of the surface of the giant asteroid.

These images from NASA Dawn spacecraft are located in asteroid Vesta Sextilia quadrangle, in Vesta southern hemisphere.

These images from NASA Dawn spacecraft are located in asteroid Vesta Pinaria quadrangle, in Vesta southern hemisphere.

This Ceres scene captured by NASA Dawn spacecraft shows an ancient crater wall that has been disrupted, possibly by a landslide.

These images from NASA Dawn spacecraft are located in Vesta Sextilia quadrangle, in asteroid Vesta southern hemisphere.

These images from NASA Dawn spacecraft are located in asteroid Vesta Tuccia quadrangle, in Vesta southern hemisphere.

Scientists believe a large number of the meteorites that are found on Earth originate from the protoplanet Vesta. This image is from NASA Dawn spacecraft.

This mosaic depicts a portion of asteroid Vesta imaged by NASA Dawn spacecraft where pockets of bright materials are visible.

These apparent brightness and topography images from NASA Dawn spacecraft are located in asteroid Vesta Floronia quadrangle, in Vesta northern hemisphere.

This image from NASA Dawn spacecraft shows some of the undulating terrain in asteroid Vesta southern hemisphere.

These images from NASA Dawn spacecraft are located in asteroid Vesta Tuccia quadrangle, in Vesta southern hemisphere.

This high-resolution geological map of Vesta is derived from NASA Dawn spacecraft data.

This view from NASA Dawn spacecraft shows a sinuous canyon in the southern hemisphere of Ceres, south of Yalode Crater.

This image from NASA Dawn spacecraft shows the crater Numisia, located just south of the equator in the Numisia quadrangle on asteroid Vesta.

These images from NASA Dawn spacecraft are located in asteroid Vesta Numisia quadrangle, in Vesta southern hemisphere.

NASA Dawn spacecraft shows Oxo Crater is unique because of the relatively large lump in its crater rim.

This view from NASA Dawn spacecraft shows a fresh crater among older terrain on Ceres, typical of the terrain of the dwarf planet.

These images from NASA Dawn spacecraft are located in asteroid Vesta Bellicia quadrangle, in Vesta northern hemisphere.

These images from NASA Dawn spacecraft are located in Urbinia quadrangle, in Vesta southern hemisphere.

These images from NASA Dawn spacecraft show the brightness/darkness of asteroid Vesta surface. These images are located in Vesta Marcia quadrangle.

These images from NASA Dawn spacecraft are located in asteroid Vesta Urbinia quadrangle, in Vesta southern hemisphere.

These apparent brightness and topography images from NASA Dawn spacecraft are located in asteroid Vesta Bellicia quadrangle, in Vesta northern hemisphere.

This image from NASA Dawn spacecraft shows a rough surface covered with ejecta and fine grooves on the giant asteroid Vesta.

This image from NASA Dawn spacecraft shows craters in various states of degradation on the asteroid Vesta.

This view of Ceres, taken by NASA Dawn spacecraft on December 10, 2015, shows an area in the southern mid-latitudes of the dwarf planet.

This image from NASA Dawn spacecraft of asteroid Vesta shows Eusebia crater, which is the large crater in the top right of the image.

This view from NASA Dawn spacecraft features the sharp rim of a steep-walled crater on Ceres.

This view from NASA Dawn spacecraft shows the rim of a crater near the south pole of Ceres, taken on Feb. 8, 2016.

These images from NASA Dawn spacecraft are located in asteroid Vesta Urbinia quadrangle, in Vesta southern hemisphere.

These images from NASA Dawn spacecraft are located in asteroid Vesta Lucaria Tholus quadrangle, in Vesta southern hemisphere.

These apparent brightness and topography images from NASA Dawn spacecraft are located in asteroid Vesta Sextilia quadrangle, in Vesta southern hemisphere.

This view from NASA Dawn spacecraft shows two medium-sized craters at high northern latitudes on Ceres.

This image of asteroid Vesta from NASA Dawn spacecraft shows a large crater with an irregularly shaped, reasonable sharp, fresh rim.

These apparent brightness and topography images from NASA Dawn spacecraft are located in asteroid Vesta Gegania quadrangle, in Vesta southern hemisphere.

This image from NASA Dawn spacecraft shows a detailed view of three craters, informally nicknamed Snowman by the camera team members.