Exploration of Neptune

[1] NASA, ESA, and independent academic groups have proposed future scientific missions to visit Neptune.

[3] Voyager 2's observation phase proper of Neptune began 5 June 1989, the spacecraft officially reached the Neptunian system on 25 August, and data collection ceased on 2 October.

[5] On 25 August, in Voyager 2's last planetary encounter, the spacecraft swooped only 4,950 km (3,080 mi) above Neptune's north pole, the closest approach it had made to any body since it left Earth in 1977.

[6] The Neptunian system had been studied scientifically for many years with telescopes and indirect methods, but the close inspection by the Voyager 2 probe settled many issues[example needed] and revealed a plethora of information that could not have been obtained otherwise.

[4][8] The fly-by of the Neptunian system provided the first accurate measurement of Neptune's mass, which was found to be 0.5 percent less than previously calculated.

[4] Voyager 2 discovered six new small moons orbiting Neptune's equatorial plane, dubbed Naiad, Thalassa, Despina, Galatea, Larissa and Proteus.

The closest approach to Triton, the last solid world Voyager 2 would explore close by, was about 40,000 km (25,000 mi).

NASA, ESA and independent academic groups have proposed and developed concept missions to visit Neptune.

After the Voyager flyby, NASA's next step in scientific exploration of the Neptune system was considered to be a flagship orbiter mission.

With the new Space Launch System (SLS) technology in development at Boeing, deep space missions with heavier payloads could potentially be propelled at much greater speeds (200 AU in 15 years) and missions to the outer planets could be launched independently of gravity assistance.

Since 1997, adaptive optics technology has also allowed for detailed scientific observations of Neptune and its atmosphere from ground-based telescopes.