Revisiting the ice giants: NASA considers missions to Uranus and Neptune

If you look up Uranus and Neptune in an encyclopedia, there's a good chance the pictures you see will be about 30 years old. In the late 1970s, the twin Voyager spacecraft launched on a grand tour of the solar system, taking advantage of a rare planetary alignment that only happens every 175 years. Voyager 2 flew past Uranus in January 1986, and Neptune in August 1989. The probe was traveling too fast, and lacked the fuel, to slow down and enter orbit.
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