Dawn spacecraft begins science orbits of Vesta
The first images from orbit show that a variety of processes were once at work on the asteroid’s surface.
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NASA/JPL —
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August 2, 2011 NASA's Dawn spacecraft obtained this image of the giant asteroid Vesta with its framing camera on July 24, 2011.
Photo by NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Images from Dawn's framing camera, taken for navigation purposes and as preparation for scientific observations, are revealing the first surface details of the giant asteroid. These images go all the way around Vesta, as the giant asteroid turns on its axis once every 5 hours and 20 minutes.
"Now that we are in orbit around one of the last unexplored worlds in the inner solar system, we can see that it's an unique and fascinating place," said Marc Rayman from NASA's Jet Propulsion Laboratory in Pasadena, California.
After traveling nearly 4 years and 1.7 billion miles (2.8 billion km), Dawn has been captured by Vesta's gravity, and there currently are 1,800 miles (2,900 km) between the asteroid and the spacecraft. The giant asteroid and its new neighbor are approximately 114 million miles (184 million km) away from Earth.
"We have been calling Vesta the smallest terrestrial planet," said Chris Russell from University of California, Los Angeles. "The latest imagery provides much justification for our expectations. They show that a variety of processes were once at work on the surface of Vesta, and provide extensive evidence for Vesta's planetary aspirations."
Engineers still are working to determine the exact time that Dawn entered Vesta's orbit, but the team has reported an approximate orbit insertion time of 12:47 a.m. EDT on July 16.
In addition to the framing camera, Dawn's instruments include the gamma-ray and neutron detector and the visible and infrared mapping spectrometer. The gamma-ray and neutron detector uses 21 sensors with a wide field of view to measure the energy of subatomic particles emitted by the elements in the upper yard (meter) of the asteroid's surface. The visible and infrared mapping spectrometer will measure the surface mineralogy of both Vesta and Dawn's next target, the dwarf planet Ceres. The spectrometer is a modification of a similar one flying on the European Space Agency's Rosetta and Venus Express missions.
Dawn also will make another set of scientific measurements at Vesta and Ceres using the spacecraft's radio transmitter in tandem with sensitive antennas on Earth. Scientists will monitor signals from Dawn, and later Ceres, to detect subtle variations in the objects' gravity fields. These variations will provide clues about the interior structure of these bodies by studying the mass distributed in each gravity field.
"The new observations of Vesta are an inspirational reminder of the wonders unveiled through ongoing exploration of our solar system," said Jim Green from NASA’s Headquarters in Washington, D.C.
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