Voyager 2 Uranus Encounter
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| Artist’s impression of Voyager passing Uranus, created for NASA in 1981. Credit: NASA/JPL/Don Davis |
Voyager 2 flew by Uranus on January 24, 1986. At the closest approach, at 17:58:51 UT, the spacecraft came within 81,500 km of the planet's cloudtops. The probe discovered new rings, eleven previously unknown moons, and a magnetic field tilted at 55° off-axis and off-center. Voyager 2 remains the only spacecraft to explore Uranus. After the encounter the probe proceeded on its journey to Neptune.
The spacecraft's observations at the distance of Uranus and Neptune were hampered by the need to take images in low light conditions. The intensity of sunlight on Uranus is about 360 times lower, and on Neptune about 900 times lower, than on Earth. This forced the spacecraft to take images of passing bodies using long exposure times, which risked blurring the images due to the spacecraft's own motion and vibrations. At the same time, the decreasing power of the spacecraft's radio signals reaching Earth limited the data transfer rate — the strength of radio signals received on Earth from the vicinity of Uranus was four times lower, and from the vicinity of Neptune about ten times lower, than during the flyby of Saturn.
During the flight towards Uranus, engineers reprogrammed Voyager 2's computers. New, more efficient image compression and data encoding algorithms were implemented. During the flyby, a camera motion compensation technique was used using the spacecraft's thrusters. Communication with the spacecraft was maintained by Deep Space Network (DSN) stations located in California, Australia, and Spain, equipped with antennas with 64-meter diameter dishes. The incoming signal power was 10−16 W. Signals amplified at the DSN stations were retransmitted via satellite links to the Jet Propulsion Laboratory in California, where a 200-person team of scientists awaited data about Uranus.
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| Voyager 2 trajectory in Uranus System, January 24, 1986. Credit: NASA/JPL |
The first navigational images of the planet were taken in June 1985. The Uranus observation phase began on November 4, 1985, when the probe was 103.5 million km away. On that day, a signal from Earth activated the probe's observation equipment and confirmed its operation. The probe reached Uranus along a curved, kinked path from Earth, covering a distance of 4.8 billion kilometers. At the time of Voyager 2's flyby, the Earth-Uranus distance was approximately 2.96 billion kilometers, resulting in a one-way radio signal travel time of 2 hours and 45 minutes.
Voyager 2 approached from the planet's south pole, almost perpendicular to the plane in which Uranus's ring system and natural satellites orbit. Closest approach to the planet occurred on January 24, 1986, at 17:58:51 UTC, at a distance of 107,100 km from Uranus' center and about 81,500 km from the cloud tops. This was 68 seconds ahead of schedule for the expedition, which began 8.5 years earlier. Voyager reached a speed of 67,820 km/h (41,820 mph). About ten hours earlier, the spacecraft had reached the limits of the planet's magnetosphere. The radio eclipse resulting from the spacecraft's disappearance behind the planet lasted about 1 hour 22 minutes. Most of the close-up observations of the moons and rings were made within 6 hours (from 4 hours before to 2 hours after closest approach). Voyager 2 captured and transmitted to Earth about 6,000 images of Uranus's surface. The spacecraft approached the five previously known moons to the following distances (predicted distances in parentheses): Titania at 365,300 km (372,000 km), Oberon at 471,500 km (472,000 km), Ariel at 130,400 km (127,000 km), Miranda at 28,000 km (29,000 km), and Umbriel at 325,100 km (325,000. km).
On January 29, the spacecraft finally exited the planet's magnetosphere. On February 14, a trajectory correction maneuver lasting over 2.5 hours was performed, which, together with a gravity assist performed during the Uranus flyby, placed Voyager 2 on a hyperbolic orbit toward Neptune. On February 25, 1986, the Uranus observation phase concluded.
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| Uranus in true color compiled from images returned Jan. 17, 1986, by the narrow-angle camera of Voyager 2. Credit: NASA/JPL |
Voyager 2 discovered the planet's magnetic field and radiation belts, studied the structure of its magnetosphere, and discovered auroras. The structure and dynamics of the atmosphere, its helium content, and the content of many chemical compounds were analyzed. The planet's rotation period was determined. Concentric cloud systems were discovered around the south pole, where Uranus faced the Sun and Earth. These were tinged orange — in contrast to the greenish-blue hue of the rest of the planet. This confirmed the assumption that the planet's atmosphere was composed primarily of hydrogen, helium, methane, and ammonia. The probe revealed, for the first time, detailed surface morphology and geology of the planet's largest moons. The most unusual moon turned out to be Miranda, whose surface displays a vast diversity of geology.
Voyager discovered two new rings for the planet and numerous dust lanes in the ring plane, visible only in forward-scattered light. During the flyby, ten of the planet's small moons were discovered. These are: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, and Puck. In 1999, images taken by Voyager 2 revealed another moon, which was named Perdita.
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| Voyager 2 picture of Uranus' rings taken on January 22, 1986, from a distance of 2.52 million kilometers. Nine rings are visible in this image, a 15-second exposure through a clear filter. Credit: NASA/JPL |
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| Miranda, a moon of Uranus, from Voyager 2 on Jan. 24, 1986, around its close approach to the Uranian moon. At least three terrain types of different age and geologic style are evident at this resolution of about 700 meters. Credit: NASA/JPL |
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| This picture is part of the highest-resolution Voyager 2 imaging sequence of Ariel, a moon of Uranus about 1,300 kilometers in diameter. The clear-filter, narrow-angle image was taken Jan 24, 1986, from a distance of 130,000 km. Credit: NASA/JPL |
© 2026, Andrew Mirecki
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