NASA's Dawn probe is about to go into orbit around the Vesta asteroid, the second largest in an asteroid belt lying between Mars and Jupiter, in the culmination of a nearly four year journey.

The satellite will spend a year revolving around Vesta, a lopsided and cratered gray orb with a circumference of about 260 miles, before moving on to the dwarf planet Ceres. Dawn traveled about 117 million miles to get there.

Our latest tests and check-outs show that Dawn is right on target and performing normally, said Robert Mase, Dawn project manager at Nasa's Jet Propulsion Laboratory in Pasadena, California.

Scientists believe the images and information collected about Vesta will illuminate what happened in the early days of the universe, since the asteroid is believed to be the detritus left over after the formation of the solar system.