[12] In the early space age, it was realized that a periodic alignment of the outer planets would occur in the late 1970s and enable a single probe to visit Jupiter, Saturn, Uranus, and Neptune by taking advantage of the then-new technique of gravity assists.

To keep apparent lifetime program costs low, the mission would include only flybys of Jupiter and Saturn, but keep the Grand Tour option open.

[13] Titan was selected due to the interest developed after the images taken by Pioneer 11 in 1979, which had indicated the atmosphere of the moon was substantial and complex.

[15][16] Constructed by the Jet Propulsion Laboratory (JPL), Voyager 2 included 16 hydrazine thrusters, three-axis stabilization, gyroscopes and celestial referencing instruments (Sun sensor/Canopus Star Tracker) to maintain pointing of the high-gain antenna toward Earth.

[17] Built with the intent for eventual interstellar travel, Voyager 2 included a large, 3.7 m (12 ft) parabolic, high-gain antenna (see diagram) to transceive data via the Deep Space Network on Earth.

[22] Because of the energy required to achieve a Jupiter trajectory boost with an 825-kilogram (1,819 lb) payload, the spacecraft included a propulsion module made of a 1,123-kilogram (2,476 lb) solid-rocket motor and eight hydrazine monopropellant rocket engines, four providing pitch and yaw attitude control, and four for roll control.

[34] Jupiter's moon Europa displayed a large number of intersecting linear features in the low-resolution photos from Voyager 1.

Closer high-resolution photos from Voyager 2, however, were puzzling: the features lacked topographic relief, and one scientist said they "might have been painted on with a felt marker".

[45] The spacecraft also observed that the north pole was approximately 10 °C (18 °F) cooler at 100 mbar (1.5 psi) than mid-latitudes, a variance potentially attributable to seasonal shifts[45] (see also Saturn Oppositions).

The anomaly was traced back to a combination of issues, including a design flaw in the actuator shaft bearing and gear lubrication system, corrosion, and debris build-up.

While overuse and depleted lubricant were factors,[46] other elements, such as dissimilar metal reactions and a lack of relief ports, compounded the problem.

[49] Voyager 2 also discovered 11 previously unknown moons: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck and Perdita.

[B] The mission also studied the planet's unique atmosphere, caused by its axial tilt of 97.8°; and examined the Uranian ring system.

[50] The Voyager 2 Planetary Radio Astronomy (PRA) experiment observed 140 lightning flashes, or Uranian electrostatic discharges with a frequency of 0.9-40 MHz.

[34][35] In March 2020, NASA astronomers reported the detection of a large atmospheric magnetic bubble, also known as a plasmoid, released into outer space from the planet Uranus, after reevaluating old data recorded during the flyby.

[59] In 1989, the Voyager 2 Planetary Radio Astronomy (PRA) experiment observed around 60 lightning flashes, or Neptunian electrostatic discharges emitting energies over 7×108 J.

[62][63] Voyager 2 discovered previously unknown Neptunian rings,[64] and confirmed six new moons: Despina, Galatea, Larissa, Proteus, Naiad and Thalassa.

[65][C] While in the neighborhood of Neptune, Voyager 2 discovered the "Great Dark Spot", which has since disappeared, according to observations by the Hubble Space Telescope.

[66] The Great Dark Spot was later hypothesized to be a region of clear gas, forming a window in the planet's high-altitude methane cloud deck.

[70] The craft's position meant it had a direct line of sight to the impacts and observations were made in the ultraviolet and radio spectrum.

These heaters remained turned on until December 4, 2006, and during that time, there was a resulting high temperature above 130 °C (266 °F), significantly higher than the magnetometers were designed to endure, and a sensor rotated away from the correct orientation.

But the Voyager project scientist, Edward C. Stone and his colleagues said they lacked evidence of what would be the key signature of interstellar space: a shift in the direction of the magnetic field.

Contact was reestablished on November 2, when a series of instructions was transmitted, subsequently executed, and relayed back with a successful communication message.

[32][33] On July 21, 2023, a programming error misaligned Voyager 2's high gain antenna[81] 2 degrees away from Earth, breaking communications with the spacecraft.

[82][83] A high-power "shout" on August 4 sent from the Canberra station[84] successfully commanded the spacecraft to reorient towards Earth, resuming communications.

[86] Some thrusters needed to control the correct attitude of the spacecraft and to point its high-gain antenna in the direction of Earth are out of use due to clogging problems in their hydrazine injector.

The spacecraft no longer has backups available for its thruster system and "everything onboard is running on single-string" as acknowledged by Suzanne Dodd, Voyager project manager at JPL, in an interview with Ars Technica.

[92] NASA has decided to patch the computer software in order to modify the functioning of the remaining thrusters to slow down the clogging of the small diameter hydrazine injector jets.

[95] Both Voyager space probes carry a gold-plated audio-visual disc, a compilation meant to showcase the diversity of life and culture on Earth in the event that either spacecraft is ever found by any extraterrestrial discoverer.

[98] The project aimed to portray the richness of life on Earth and stand as a testament to human creativity and the desire to connect with the cosmos.