Nasa's New Horizons spacecraft has begun its long-awaited, historic encounter with Pluto.
The spacecraft is entering the first of several approach phases that culminate on July 14 with the first close-up flyby of the dwarf planet - 7.5 billion km from the Earth, the US space agency said in a statement.
"Nasa first mission to distant Pluto will also be humankind's first close-up view of this cold, unexplored world in our solar system," said Jim Green, director of Nasa's planetary science division at the agency's headquarters in Washington, DC.
New Horizons lifted off in January 2006. It awoke from its final hibernation period last month and will soon pass close to Pluto, inside the orbits of its five known moons.
In preparation for the close encounter, the mission's team configured the piano-sized probe for distant observations of the Pluto system that start January 25 with a long-range photo shoot.
The images captured by New Horizons' telescopic Long-Range Reconnaissance Imager (Lorri) will give mission scientists a continually improving look at the dynamics of Pluto's moons.
The images also will play a critical role in navigating the spacecraft as it covers the remaining 220 million kms to Pluto.
"We have completed the longest journey any spacecraft has flown from Earth to reach its primary target," added Alan Stern, New Horizons principal investigator.
Eventually, the spacecraft will obtain images good enough to map Pluto and its moons more accurately than achieved by previous planetary reconnaissance missions.