[meteorite-list] NASA's Dawn Spacecraft Begins Science Orbits of Vesta

[Ron Baalke]

August 01, 2011

Dwayne C. Brown 
Headquarters, Washington 
202-358-1726 
dwayne.c.brown at nasa.gov 

Priscilla Vega 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-1357 
priscilla.r.vega at jpl.nasa.gov   


RELEASE: 11-254

NASA'S DAWN SPACECRAFT BEGINS SCIENCE ORBITS OF VESTA

WASHINGTON -- NASA's Dawn spacecraft, the first ever to orbit an 
object in the main asteroid belt, is spiraling toward its first of 
four intensive science orbits. That initial orbit of the rocky world 
Vesta begins Aug. 11, at an altitude of nearly 1,700 miles (2,700 
kilometers) and will provide in-depth analysis of the asteroid. Vesta 
is the brightest object in the asteroid belt as seen from Earth and 
is thought to be the source of a large number of meteorites that fall 
to Earth. 

The Dawn team unveiled the first full-frame image of Vesta taken on 
July 24: 

http://go.nasa.gov/ohdkyh 

This image was taken at a distance of 3,200 miles (5,200 kilometers). 
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, since the giant asteroid turns on its axis once every 
five 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 a unique and fascinating 
place," said Marc Rayman, Dawn's chief engineer and mission manager 
at NASA's Jet Propulsion Laboratory in Pasadena, Calif. 

After traveling nearly four years and 1.7 billion miles (2.8 billion 
kilometers), Dawn has been captured by Vesta's gravity, and there 
currently are 1,800 miles (2,900 kilometers) between the asteroid and 
the spacecraft. The giant asteroid and its new neighbor are 
approximately 114 million miles (184 million kilometers) away from 
Earth. 

"We have been calling Vesta the smallest terrestrial planet," said 
Chris Russell, Dawn's principal investigator at the UCLA. "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 9:47 p.m. PDT on July 15 (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 very 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, planetary division director at NASA Headquarters in 
Washington. 

Dawn launched in September 2007. Following a year at Vesta, the 
spacecraft will depart in July 2012 for Ceres, where it will arrive 
in 2015. Dawn's mission to Vesta and Ceres is managed by JPL for 
NASA's Science Mission Directorate in Washington. Dawn is a project 
of the directorate's Discovery Program, managed by NASA's Marshall 
Space Flight Center in Huntsville, Ala. 

UCLA is responsible for overall Dawn mission science. Orbital Sciences 
Corp. in Dulles, Va., designed and built the spacecraft. The German 
Aerospace Center, the Max Planck Institute for Solar System Research, 
the Italian Space Agency and the Italian National Astrophysical 
Institute are international partners on the mission team. 

For more information about Dawn, visit: 

http://www.nasa.gov/dawn   
	
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