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Asteroid rendezvous nears

Dawn and Hubble images of Vesta

Already, Dawn's images of Vesta (left) are better even than the Hubble Space Telescope can obtain (right). The protoplanet Vesta is the second-most massive object in the main asteroid belt.

NASA’S DAWN SPACECRAFT is on track to begin the first extended visit to a large asteroid. The mission expects to go into orbit around Vesta on July 16 and begin gathering science data in early August.

Vesta is considered a protoplanet, or body that didn’t quite become a full-fledged planet. It lives in the main asteroid belt between Mars and Jupiter, and is thought to be the source of a large number of meteorites that fall to Earth.

After travelling nearly four years and 2.7 billion kilometres, Dawn is approximately 150,000 kilometres away from Vesta. When Vesta captures Dawn into its orbit on July 16, there will be approximately 16,000 kilometres between them. When orbit is achieved, they will be approximately 188 million kilometres away from Earth.

Artist's impression of the Dawn spacecraft

Artist's impression of the Dawn spacecraft

“The spacecraft is right on target,” said Robert Mase, Dawn project manager at NASA’s Jet Propulsion Laboratory. “We look forward to exploring this unknown world during Dawn’s one-year stay in Vesta’s orbit.”

Peeling back the layers

After Dawn enters Vesta’s orbit, engineers will need a few days to determine the exact time of capture. Unlike other missions where a dramatic, nail-biting propulsive burn results in orbit insertion around a planet, Dawn has been using its placid ion propulsion system to subtly shape its path for years to match Vesta’s orbit around the Sun.

Images from Dawn’s framing camera, taken for navigation purposes, show the slow progress toward Vesta. Made into a movie (below), they are about twice as sharp as the best images of Vesta from NASA’s Hubble Space Telescope, but the surface details Dawn will obtain are still a mystery.

“We can’t wait for Dawn to peel back the layers of time and reveal the early history of our Solar System,” said Christopher Russell, Dawn principal investigator, at UCLA.

During the initial reconnaissance orbit, at a distance of approximately 2,700 kilometres, the spacecraft will get a broad overview of Vesta with colour pictures and data in different wavelengths of reflected light.

The spacecraft will then move drop lower into a mapping orbit about 680 kilometres above the surface to systematically map the parts of Vesta’s surface illuminated by the Sun.

It will collect stereo images to see topographic highs and lows, acquire higher-resolution data to map rock types at the surface; and learn more about Vesta’s thermal properties.

Up close and personal

Dawn then will move even closer, to a low-altitude mapping orbit approximately 200 kilometres above the surface. The primary science goals of this orbit are to detect the by-products of cosmic rays hitting the surface and help scientists determine the many kinds of atoms there, and probe the protoplanet’s internal structure.

“We’ve packed our year at Vesta chock-full of science observations to help us unravel the mysteries of Vesta,” said Carol Raymond, Dawn’s deputy principal investigator at JPL.

Following a year at Vesta, the spacecraft will depart for its second destination, the dwarf planet Ceres, in July 2012.

As Dawn spirals away from Vesta, it will pause again at the high-altitude mapping orbit. Because the Sun’s angle on the surface will have progressed, scientists will be able to see previously hidden terrain while obtaining different views of surface features.

Dawn was launched in September 2007.

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Adapted from information issued by NASA / JPL-Caltech. Images courtesy NASA / JPL-Caltech / UCLA / MPS / DLR / PSI and NASA / ESA / STScI / Umd.

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2011: The year in space

Artist's impression of the Juno spacecraft at Jupiter

Artist's impression of the Juno spacecraft investigating Jupiter. Juno is set for launch later this year.

THERE ARE LOTS OF EXCITING happenings coming up in space this year. Here’s just a sample of what we can expect.

On February 14-15, NASA’s Stardust probe will do a fly-by of comet Tempel 1. It’ll be looking for damage done by the Deep Impact spacecraft, which fired a projectile into the comet back in 2005.

Also there’ll be the launch of Glory, an Earth-orbiting spacecraft that’ll make readings of black carbon and aerosols in the atmosphere, and measure the amount of incoming sunlight. Plus there’ll be the final flight of the space shuttle Discovery, on a mission to the space station.

March will see NASA’s MESSENGER spacecraft go into orbit around Mercury, the first probe to do so. A largely unknown world, the closest planet to the Sun is sure to hold some surprises. That month will also mark 25 years since Europe’s Giotto probe gave us our first close-up look at a comet, the famous Halley.

In April there’ll be a bunch of anniversaries, the 30th of the first space shuttle launch, the 40th of the first space station launch (which was the Soviet’s Salyut 1), and the biggie, the 50th anniversary of the flight of Vostok 1, carrying Yuri Gagarin, the first person to go into outer space.

Artist's impression of Salyut 1

Artist's impression of Salyut 1, the world's first space station.

April will also see the last flight of space shuttle Endeavour. And it could be the final shuttle mission of all. An extra flight by Atlantis in June has been approved but not yet funded, so we’ll just have to wait and see. Also in June, some parts of Australia will catch a short glimpse of a lunar eclipse.

July will see the second flight of the new, private Dragon spacecraft, designed to take cargo and eventually people to the International Space Station. Its first short test flight last year went perfectly. Dragon could end up being the replacement for the space shuttle.

Also in July, NASA’s Dawn spacecraft will sidle up to the 530km-wide asteroid Vesta, and go into orbit. It’ll spend a year investigating it before heading off to do the same thing with the even larger asteroid Ceres, which is actually known as a dwarf planet these days.

Artist's impression of the Dawn spacecraft

Artist's impression of the Dawn spacecraft studying asteroid Vesta

August will see the launch of Juno, NASA’s new unmanned mission to study the planet Jupiter. It’ll take about five years to get there. And the following month will see NASA launch GRAIL, a pair of satellites that’ll orbit the Moon and map its gravitational field, which will help scientists work out its inner structure.

In November, Russia will launch Fobos-Grunt, a mission to the larger of the two Martian moons, Phobos. All going well, it’ll touch down, grab some samples, and blast off back to Earth with them. The Chinese are piggybacking a small satellite too, which will orbit Mars and study its atmosphere, ionosphere and surface.

Finally, in December, there’ll be another launch of that Dragon capsule, plus the first launch of its competitor, called Cygnus. And to top it off, we’ll have another lunar eclipse.

Image credits: NASA / JPL-Caltech.

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