July 14, 2011

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

Jia-Rui Cook/Priscilla Vega Jet Propulsion Laboratory, Pasadena, Calif 818-354-0850/4-1357 jccook@jpl nasa gov/priscilla r vega@jpl nasa gov

RELEASE: 11-228

NASA SPACECRAFT TO ENTER LARGE ASTEROID'S ORBIT ON JULY 15

PASADENA, Calif -- 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 26,000 miles (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

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, which is managed by NASA's Marshall Space Flight Center in Huntsville, Ala

UCLA is responsible for overall Dawn mission science Orbital Sciences Corp of 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 part of the mission team

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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