Dawn probe reaches asteroid belt between Mars, Jupiter

Jul 16, 2011, 5:30 GMT

Washington - The Dawn space probe was expected to go into orbit Saturday around a rocky object in the asteroid belt between Mars and Jupiter and signal that it had reached its first goal in a 5-billion-kilometre journey.

Dawn, which was launched in 2007 by the US space agency, is to offer insights into the beginning of the universe by examining rocky objects that date to the time when planets were forming in the solar system.

The 1.6-metre-long, 747-kilogramme craft was to have begun circling the asteroid Vesta early Saturday. Both Vesta and another Dawn target, the dwarf planet Ceres, are significantly smaller than Earth's moon.

NASA's Jet Propulsion Laboratory in California, which is monitoring Dawn's progress, said its cameras had already sent back images of Vesta's surface, taken from about 41,000 kilometres away.

'It has taken nearly four years to get to this point,' said Robert Mase, the Dawn project manager. 'Our latest tests and checkouts show that Dawn is right on target and performing normally.'

Vesta and Ceres were discovered more than 200 years ago, and NASA chose them for their completely different characteristics.

Vesta, which Dawn had not been expected to reach until October, is a hot, volcanic asteroid and, at about 500 kilometres in diameter, the brightest asteroid in the solar system. It can be seen from Earth as a small point of light above the Scorpius constellation.

In six months, Dawn is to leave Vesta for icy Ceres. The dwarf planet is 950 kilometres in diameter, and its coat of ice is believed to be 100 kilometres thick.

Dawn is the first US mission for which primary components originated in Europe. Two multispectral cameras that allow the craft to capture images were made in Germany, and the Italian space agency provided the craft's spectrometer.