Launched in 1977, Voyager 2 reached Uranus after flybys of Jupiter and Saturn, an eight-and-a-half-year journey. In a few hours of close approach it discovered ten new moons and two new rings, measured a magnetic field tilted about 60 degrees from the planet's spin axis and photographed the tortured surface of the moon Miranda. Its findings came four days before the Challenger disaster, which pushed the news off front pages.
Uranus had been a pale, featureless dot in telescopes since William Herschel spotted it in 1781. Voyager 2 was never designed to go there: its primary mission ended at Saturn in 1981, and reaching Uranus meant reprogramming a spacecraft whose radio signals now took more than two and a half hours to arrive. Engineers taught it to compress images and to compensate for its own jitter during the long exposures needed in the dim light so far from the Sun.
The close encounter on January 24, 1986, lasted only hours. Voyager found a planet knocked on its side, rolling around the Sun with its poles in turn facing the light, and a magnetic field bizarrely offset from the planet's center. Among its ten new moons was Puck, and the images of Miranda showed cliffs taller than any on Earth, set in a patchwork of terrain that looked as if the moon had been smashed apart and reassembled.
Four days later, Challenger broke apart after launch, and Voyager's findings were largely lost in the national grief. No spacecraft has returned to Uranus since.
Key people: Edward C. Stone