Voyager 1 visited Jupiter and Saturn. Voyager 2 visited Jupiter, Saturn, Uranus and Neptune.
Both probes took detailed photographs and made other measurements of the gas giants and their moons. Their many discoveries included erupting volcanoes on Jupiter's moon Io, "spokes" in Saturn's rings and wind speeds of more than 700mph (1,100km/h) on Neptune.
Photo: Voyager 2 lifts off (NASA/JPL)
Two probes visit the outer planets on their long journey.
Images of Jupiter's moon reveal evidence of a new type of volcanism.
Images from the Galileo and Voyager missions (launched in 1989 and 1977 respectively) showed scientists that Europa is a relatively smooth icy moon with a network of fractures that may erupt liquid water from an ocean beneath the surface.
Earth is a tiny blue dot when viewed from the edge of the Solar System.
In 1990, 13 years after leaving the Earth and at a distance of 3.7 billion miles, Voyager 1 turned around to face the Sun and captured images of most of the planets, including the Earth. Voyager scientist Carl Sagan described our planet as a "blue dot".
Miranda lifts scientists' spirits after disappointment at Uranus.
Despite the careful work of engineers, Voyager 2 saw only impenetrable cloud at Uranus. Uranus's moon Miranda, with its fractured surface, proved more interesting to scientists. The Voyager probes were launched in 1977.
Backwards Triton falls under Voyager's gaze.
The Voyager 2 probe, launched in 1977, flew by Triton in 1989. The moon's unexpected, miles-high nitrogen geysers proved that geologic activity is possible in the coldest outer reaches of the Solar System.
Pioneer 10 and 11 discover hazards facing the Voyager probes.
The Pioneer 10 and 11 spacecraft, launched in 1972 and 1973 respectively, survived the asteroid belt and Jupiter's radiation belt and magnetic field. These probes fed crucial information to scientists designing the Voyager 1 and 2 spacecraft.
The Voyager program is an American scientific program that launched two unmanned space missions, the probes Voyager 1 and Voyager 2. These were launched in 1977 to take advantage of a favorable alignment of the planets during the late 1970s. Although they were designated officially to study just the planetary systems of Jupiter and Saturn, the space probes were able to continue their mission into the outer solar system, and they are expected to push through the heliosheath in deep space.
These two space probes were built at the Jet Propulsion Laboratory in Southern California, and they were paid for by the National Aeronautics and Space Administration (NASA), which also paid for their launchings from Cape Canaveral, Florida, their tracking, and everything else concerning the space probes.
As of April 2013, Voyager 1 is the farthest manmade object that has ever been sent from the Earth. On 15 June 2012, scientists at NASA reported that Voyager 1 might be very close to entering interstellar space and becoming the first manmade object to leave the Solar System.
Both of these scientific missions into outer space have gathered large amounts of data about the gas giants of the solar system, and their orbiting satellites, about which little had been previously known. In addition, the trajectories of the two spacecraft have been used to place limits on the existence of any hypothetical trans-Neptunian planets.