Dawn’s day has finally come

Dawn image of Vesta

NASA's Dawn spacecraft obtained this image of the 'protoplanet' Vesta with its framing camera on July 9, 2011. It was taken from a distance of about 41,000 kilometres. Each pixel in the image corresponds to roughly 3.8 kilometres on the surface of Vesta.

NASA’S DAWN SPACECRAFT is about to begin a prolonged encounter with the asteroid Vesta, making it the first mission to enter orbit around a body in the main asteroid belt between Mars and Jupiter.

As the spacecraft approaches the 530-kilometre-wide Vesta, surface details are coming into focus, as seen in a recent image taken from a distance of about 41,000 kilometres (above).

Engineers expect the spacecraft to be captured into orbit at approximately 3:00pm Saturday, July 16, Sydney time (1:00am US EDT Saturday, July 16). They expect to hear from the spacecraft and confirm that it performed as planned during a scheduled communications pass that starts approximately an hour and a half later.

When Vesta captures Dawn into its orbit, engineers estimate there will be approximately 16,000 kilometres between them. At that point, the spacecraft and asteroid will be approximately 188 million kilometres 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. “Our latest tests and check-outs show that Dawn is right on target and performing normally.”

The following video shows a series of images of Vesta during Dawn’s approach, and includes comparisons with the best Vesta images taken by the Hubble Space Telescope:

Two for the price of one

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. So the Dawn team will need a few days to refine the exact moment of orbit capture.

Launched in September 2007, Dawn will stay in orbit around Vesta for one year, conducting studies of the ‘protoplanet’ before departing for its second destination, the dwarf planet Ceres, in July 2012. Upon reaching Ceres, the spacecraft will become the first to orbit two Solar System destinations beyond Earth.

Finally, here’s another video, showing how Dawn has slowly crept up on Vesta from behind, how it will go in to orbit, and the way in which it will study the small rocky world:

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 Centre in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. designed and built the spacecraft. The German Aerospace Centre, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are part of the mission team.

Adapted from information issued by NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.

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