[AstroNet] Dawn Spacecraft To Enter Large Asteroid's Orbit On July 15

[Maciej Soltynski]

On July 15, NASA's Dawn spacecraft will begin a 
prolonged encounter with the asteroid Vesta, making the mission the 
first to enter orbit around a main-belt asteroid. 

The main asteroid belt lies between the orbits of Mars and Jupiter. 
Dawn will study Vesta for one year, and observations will help 
scientists understand the earliest chapter of our solar system's 
history. 

As the spacecraft approaches Vesta, surface details are coming into 
focus, as seen in a recent image taken from a distance of about 
41,000 kilometers. The image is at: 

http://www.nasa.gov/mission_pages/dawn/multimedia/dawn-image-070911.html 

Engineers expect the spacecraft to be captured into orbit at 
approximately 10 p.m. PDT Friday, July 15. They expect to hear from 
the spacecraft and confirm that it performed as planned during a 
scheduled communications pass that starts at approximately 11:30 p.m. 
PDT on Saturday, July 16. When Vesta captures Dawn into its orbit, 
engineers estimate there will be approximately 9,900 miles (16,000 
kilometers) between them. At that point, the spacecraft and asteroid 
will be approximately 117 million miles (188 million kilometers) from 
Earth. 

"It has taken nearly four years to get to this point," said Robert 
Mase, Dawn project manager at NASA's Jet Propulsion Laboratory in 
Pasadena, Calif. "Our latest tests and check-outs show that Dawn is 
right on target and performing normally." 

Engineers have been subtly shaping Dawn's trajectory for years to 
match Vesta's orbit around the sun. Unlike other missions, where 
dramatic propulsive burns put spacecraft into orbit around a planet, 
Dawn will ease up next to Vesta. Then the asteroid's gravity will 
capture the spacecraft into orbit. However, until Dawn nears Vesta 
and makes accurate measurements, the asteroid's mass and gravity will 
only be estimates. The Dawn team will refine the exact moment of 
orbit capture over the next few days. 

Launched in September 2007, Dawn will depart for its second 
destination, the dwarf planet Ceres, in July 2012. The spacecraft 
will be the first to orbit two bodies in our solar system. 

For an image of Vesta and more information about the Dawn mission, 
visit: http://www.nasa.gov/dawn and http://dawn.jpl.nasa.gov 
You also can follow the mission on Twitter at: http://www.twitter.com/NASA_Dawn 
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