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A lonely spacecraft is nearing Pluto after a 3-billion-mile journey lasting almost 9 years. Nasa's New Horizons probe awoke from hibernation on December 6 and is preparing to explore the Solar System's mysterious "ninth planet".

Dr Hal Waver, the New Horizons project scientist from the Applied Physics Laboratory at Johns Hopkins University in Maryland, told Today's Justin Webb: "To get to Pluto we launched the fastest spacecraft ever to leave the earth on a beeline towards Pluto, we did get a gravity assist from giant Jupiter and cut 3 years off the travel time."

"In between Jupiter and Pluto we have been hibernating a lot. We put the spacecraft to sleep for roughly 10 months per year to save all the resources on the spacecraft ...for the big show in 2015."

"We're going to be flying just 12,500km above the surface of Pluto ...and we have the instruments to study Pluto as the spacecraft flies by."

First broadcast Today programme 5 January 2015.