NASA counts down to Pluto encounter
NASA has marked the 25th anniversary of Voyager 2's fly-past of Neptune in 1989 as the space agency prepares to get up close and personal with Pluto.
This picture of Neptune, above, was taken on 20 August 1989, at a range of 4.4 million miles from the planet. Voyager 2's closest approach to Neptune came four days later on 25 August.
The picture shows the Great Dark Spot and its companion bright smudge; on the west limb the fast moving bright feature called "Scooter" and the little dark spot are visible. North of these, there is a bright cloud band similar to the south polar streak.
NASA is also using the anniversary to set the scene for the climax another mission to the outermost edges of the Solar System in a little under a year when the New Horizons space craft does a similar fly-by of Pluto.
By coincidence, New Horizons passes the orbit of Neptune, its last orbit crossing before beginning its historic exploration of Pluto on the exact 25th anniversary of the Voyager 2 spacecraft’s encounter with the planet.
New Horizons will begin its Pluto exploration in January but the best pictures will come a little later when the spacecraft is at its closest.
New Horizons' Pluto encounter on July 14, 2015, will not be a replay of Voyager but more of a sequel and a reboot, with a new and more technologically advanced spacecraft and, more importantly, a new cast of characters. Those characters are Pluto and its family of five known moons, all of which will be seen up close for the first time next summer.