NASA’s Dawn Spacecraft Enters Orbit Around Asteroid Vesta

NASA's Dawn spacecraft, illustrated in this artist's concept, is propelled by ion engines. Image credit: NASA/JPL

NASA achieved a major milestone this past weekend. On Friday, July 15, the Dawn spacecraft became the first probe ever to enter orbit around an asteroid more than 100 million miles from earth. On Chicago Tonight at 7:00 pm, an astronomer from the Adler Planetarium tells Eddie Arruza what the spacecraft is looking for and what mysteries it might solve.

Dawn, which launched in September 2007, will be the first spacecraft to orbit two solar system destinations beyond Earth. Dawn will study the asteroid Vesta for one year before departing for a second destination, a dwarf planet named Ceres, in July 2012.

When Vesta captured Dawn into its orbit, there were approximately 9,900 miles between the spacecraft and asteroid. Engineers estimate the orbit capture took place at 10:00 pm on Friday, July 15 (PDT).

Vesta is 330 miles in diameter and the second most massive object in the asteroid belt. Ground- and space-based telescopes have obtained images of Vesta for about two centuries, but they have not been able to see much detail on its surface.

NASA's Dawn spacecraft obtained this image with its framing camera on July 17, 2011. It was taken from a distance of about 9,500 miles away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 0.88 miles. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

“We are beginning the study of arguably the oldest extant primordial surface in the solar system,” said Dawn principal investigator Christopher Russell from UCLA. “This region of space has been ignored for far too long. So far, the images received to date reveal a complex surface that seems to have preserved some of the earliest events in Vesta’s history, as well as logging the onslaught that Vesta has suffered in the intervening eons.”

Vesta is thought to be the source of a large number of meteorites that fall to Earth. Vesta and its new NASA neighbor, Dawn, are currently approximately 117 million miles away from Earth.

The Dawn team will begin gathering science data in August. Observations will provide unprecedented data to help scientists understand the earliest chapter of our solar system. The data also will help pave the way for future human space missions.

After traveling nearly four years and 1.7 billion miles, Dawn also accomplished the largest propulsive acceleration of any spacecraft, with a change in velocity of more than 4.2 miles per second due to its ion engines. The engines expel ions to create thrust and provide higher spacecraft speeds than any other technology currently available.

Core Structure of Dawn Spacecraft with Ion Propulsion System Installed. Image credit: Orbital Sciences Corporation

“Dawn slipped gently into orbit with the same grace it has displayed during its years of ion thrusting through interplanetary space,” said Marc Rayman, Dawn chief engineer and mission manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “It is fantastically exciting that we will begin providing humankind its first detailed views of one of the last unexplored worlds in the inner solar system.”

Although orbit capture is complete, the approach phase will continue for about three weeks. During approach, the Dawn team will continue a search for possible moons around the asteroid; obtain more images for navigation; observe Vesta’s physical properties; and obtain calibration data.

In addition, navigators will measure the strength of Vesta’s gravitational tug on the spacecraft to compute the asteroid’s mass with much greater accuracy than has been previously available. That will allow them to refine the time of orbit insertion.

Dawn will spend one year orbiting Vesta, then travel to a second destination, the dwarf planet Ceres, arriving in February 2015.

The following video from June 1, 2011 shows surface details beginning to resolve as NASA’s Dawn spacecraft closes in on the giant asteroid Vesta. The framing camera aboard NASA’s Dawn spacecraft obtained the images used for this animation from a distance of about 300,000 miles.

The following virtual video shows the scientists’ best guess from back in March of what the surface of Vesta might look like. It was created as part of an exercise for NASA’s Dawn mission involving mission planners at NASA’s Jet Propulsion Laboratory and science team members at the German Aerospace Center and the Planetary Science Institute.

The mission to Vesta and Ceres is managed by NASA’s Jet Propulsion Laboratory in Pasadena, Calif., for the agency’s Science Mission Directorate in Washington.

For more information about NASA’s Dawn mission, visit the links below.

 

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