By Jonathan Amos
Science correspondent, BBC News
The US space agency says its Dawn probe should go into orbit around the Asteroid Vesta early on Saturday (GMT).
The robotic satellite will be spending a year at the 530km-wide body before moving on to the "dwarf planet" Ceres.
New pictures on Dawn's approach to Vesta show the giant rock in unprecedented detail.
The asteroid looks like a punctured football, the result of a colossal collision sometime in its past that knocked off its south polar region.
Dawn's encounter is occurring about 188 million km (117 million miles) from Earth. Engineers have put the spacecraft on a course to be captured in the gravitational field of Vesta.
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more:
http://www.bbc.co.uk/news/science-environment-14160135http://dawn.jpl.nasa.gov/