Jet Propulsion Laboratory (U.S.). Voyager Project Office.

The twin Voyager spacecraft, over a period of a dozen years, drew back the curtain on nearly half of the solar system. From launch in 1977 through the spectacular parting shots of Neptune at the outer reaches of the solar system in 1989, this pair of spacecraft explored four planets---Jupiter, Saturn, Uranus and Neptune-as well as dozens of moons, and the rings and magnetic environments of those planetary systems.

The Voyagers were designed to take advantage of a rare alignment of the outer planets that occurs only once every 176 years. This configuration allows a single spacecraft to swing by all four gas giants without the need for large onboard propulsion systems. The flyby of each planet both accelerates the spacecraft and bends its flight path. Without these gravity assists, the flight time to Neptune would have been 30 years.

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