By Paul Rincon
Science reporter, BBC News
Nasa's New Horizons spacecraft, launched from Earth just over a year ago, has flown past the giant planet Jupiter.
The flyby was intended to test the probe's instruments before it is hurled away by Jupiter's gravity toward the distant target of Pluto and its moons.
The plutonium-powered spacecraft made its closest approach to Jupiter at 0543 GMT (0043 EST) on Wednesday.
This gravity "kick" accelerated the probe by 14,000km/h (9,000mph).
This should send it hurtling towards Pluto at 84,000km/h (52,000mph).
With closest approach coming 13 months after launch, New Horizons has completed the fastest ever crossing by a spacecraft travelling from Earth to Jupiter.
"Jupiter's just a waypoint to take us to our ultimate destination, which is, of course, the planet Pluto," said John Spencer, deputy chief of the Jupiter encounter science team.
The pass provided the spacecraft with the first close-up look at Jupiter and its moons since the Galileo mission, which reached the planetary system in 1995.
It will also be the last look at the Jovian system until Nasa's Juno system arrives in 2016.
The speed boost will shave three years off the probe's travel time to Pluto.
Even so, the half-tonne spacecraft will take eight more years to reach the distant dwarf planet. It will arrive in July 2015, when Pluto will be five billion km (three billion miles) from Earth.
The spacecraft threaded its path through an "aim point" which lies 2.3 million km (1.4 million miles) from the centre of Jupiter.
The pass is also letting mission controllers test drive the spacecraft, putting its systems and science instruments through their paces before the crucial encounter with Pluto.
"We want to test the spacecraft hard enough that we turn up any small vulnerabilities," said Dr Alan Stern, the mission's prinicpal investigator, from the Southwest Research Institute in Colorado.
"With our high technology instruments, we are going to produce some stunning data sets, and we can't wait to get them on the ground."
During its encounter with Jupiter, the probe will make more than 700 observations of the gas giant and its four largest moons by June.
It will scan the planet's stormy atmosphere and its magnetic shell, or magnetosphere; make a detailed survey of its rings, including a search for any small moons which have lain undiscovered within them; and map Jupiter's large moons such as Europa and Callisto.
New Horizons will study volcanic activity on Jupiter's moon Io
New Horizons will also carry out a survey of volcanic activity on Jupiter's moon Io and take a close-up look at the "little red spot", a nascent storm south of Jupiter's famous great red spot.
In addition, the flight plan also calls for the first ever trip down the long "tail" of Jupiter's magnetosphere, a wide stream of charged particles that extends tens of millions of kilometres beyond the planet.
After the eight-year cruise from Jupiter across the Solar System's expanse, New Horizons will conduct a five month study of Pluto and its three moons in 2015, characterising their geology, structure and composition.
The spacecraft uses plutonium in a radioisotope thermal generator (RTG) to power its science instruments, computers and other flight systems.