Voyager 2 is a space probe launched by NASA on August 20, 1977, as part of the Voyager program. It was sent on a path toward the gas giants (Jupiter and Saturn) and later reached the ice giants (Uranus and Neptune). It is the only spacecraft to have visited either of the ice giant planets. Voyager 2 was the third of five spacecraft to reach Solar escape velocity, which allowed it to leave the Solar System. Launched 16 days before its twin, Voyager 1, the main goal of Voyager 2 was to study the outer planets. Its extended mission is to explore interstellar space beyond the Sun’s heliosphere.

Voyager 2 completed its primary mission by visiting the Jovian system in 1979, the Saturnian system in 1981, the Uranian system in 1986, and the Neptunian system in 1989. The spacecraft is now in its extended mission, studying the interstellar medium. As of February 2026, it is 143.05 AU (21.4 billion km; 13.3 billion mi) from Earth.

The probe entered the interstellar medium on November 5, 2018, at a distance of 119.7 AU (11.1 billion mi; 17.9 billion km) from the Sun. It moves at a speed of 15.341 km/s (34,320 mph) relative to the Sun. Voyager 2 has left the Sun’s heliosphere and is traveling through the interstellar medium, still within the Solar System. It now joins Voyager 1, which entered the interstellar medium in 2012. Voyager 2 is providing the first direct measurements of the density and temperature of interstellar plasma.

Voyager 2 communicates with Earth through the NASA Deep Space Network. Australia’s DSS 43 communication antenna, near Canberra, is responsible for these communications.

History

In the early days of space exploration, scientists noticed that the outer planets would line up in a special pattern in the late 1970s. This alignment allowed a single spacecraft to visit Jupiter, Saturn, Uranus, and Neptune by using a new method called gravity assists. NASA started planning a mission called the Grand Tour, which later became a large project with two groups of two spacecraft. One group would visit Jupiter, Saturn, and Pluto, while the other would visit Jupiter, Uranus, and Neptune. The spacecraft were built with backup systems to ensure they could survive the long journey. By 1972, the mission was changed to use two spacecraft from the Mariner program, called Mariner Jupiter-Saturn. These spacecraft would only fly by Jupiter and Saturn, but the possibility of continuing the Grand Tour remained. The mission was later renamed Voyager.

Voyager 1's main goal was to study Jupiter, Saturn, and Titan, Saturn's largest moon. Voyager 2 was also sent to explore Jupiter and Saturn, but its path allowed it to continue to Uranus and Neptune or return to Titan as a backup for Voyager 1. After Voyager 1 completed its mission, Voyager 2 was given a new task to travel to Uranus and Neptune. Titan was chosen because earlier images from Pioneer 11 in 1979 showed that Titan had a thick and complex atmosphere. This influenced the design of the spacecraft’s path to ensure a close flyby of Titan.

Built by the Jet Propulsion Laboratory (JPL), Voyager 2 has a shape like a 10-sided prism. It includes 16 thrusters, tools to keep the spacecraft stable, and instruments to track the Sun and stars. These tools help direct the spacecraft’s large antenna toward Earth. The spacecraft also has 11 scientific tools to study space objects.

Designed for a journey beyond our solar system, Voyager 2 uses a large, 3.7-meter (12-foot) parabolic antenna to send and receive data through the Deep Space Network on Earth. It communicates using radio waves with wavelengths of about 13 cm (S-band) and 3.6 cm (X-band). At Jupiter’s distance, data can be sent at up to 115.2 kilobits per second, but the speed decreases as the spacecraft moves farther from Earth. If the spacecraft cannot communicate directly, it stores data on a digital recorder and sends it later.

Voyager 2 uses three power sources called radioisotope thermoelectric generators (RTGs). Each RTG contains 24 spheres of plutonium oxide. At launch, each RTG produced about 157 watts of power, totaling 470 watts for the spacecraft. This power decreases by half every 87.7 years. These power sources were expected to last until at least 2020 and continued to operate five scientific instruments through 2023. In April 2023, backup power was used for a safety system, allowing the instruments to operate until 2026. In October 2024, NASA turned off one instrument to save power for the remaining four.

To reach Jupiter with its heavy payload, Voyager 2 used a propulsion module with a solid-rocket motor and eight hydrazine thrusters. These thrusters helped control the spacecraft’s direction and were removed after the Jupiter mission. Sixteen hydrazine thrusters on the spacecraft help control its movement. Four are used for course corrections, and the others are in two backup groups to stabilize the spacecraft.

The thrusters are powered by a single spherical titanium tank holding 100 kilograms (220 pounds) of hydrazine. This fuel was expected to last until 2034.

Mission profile

The Voyager 2 probe was launched on August 20, 1977, by NASA from Space Launch Complex 41 at Cape Canaveral, Florida, using a Titan IIIE/Centaur launch vehicle. Two weeks later, on September 5, 1977, its twin, Voyager 1, was launched. Voyager 1 reached Jupiter and Saturn faster because Voyager 2 followed a longer, more circular path around the Sun.

Voyager 1’s initial orbit had an aphelion (the farthest point from the Sun) of 8.9 AU (830 million miles; 1.33 billion kilometers), slightly less than Saturn’s orbit of 9.5 AU (880 million miles; 1.42 billion kilometers). Voyager 2’s initial orbit had an aphelion of 6.2 AU (580 million miles; 930 million kilometers), which was much shorter than Saturn’s orbit.

In April 1978, no commands were sent to Voyager 2 for a time, causing it to switch from its main radio receiver to a backup. Later, the main receiver stopped working completely. The backup receiver could still receive signals but only at a specific frequency. This frequency changed due to Earth’s rotation (Doppler effect) and the receiver’s temperature.

Voyager 2’s closest approach to Jupiter occurred on July 9, 1979, at 22:29 UT. It passed within 570,000 km (350,000 miles) of Jupiter’s cloud tops. The Great Red Spot was observed as a large, counterclockwise-moving storm. Smaller storms and eddies were also seen in Jupiter’s banded clouds.

Voyager 2 captured images of Jupiter and its moons: Amalthea, Io, Callisto, Ganymede, and Europa. During a 10-hour observation period, it confirmed active volcanoes on Io, as seen by Voyager 1, and showed changes on Io’s surface since the previous visit. Together, the Voyagers observed nine volcanic eruptions on Io, with evidence of other eruptions between the two flybys.

Voyager 1’s low-resolution images of Europa showed intersecting linear features, which scientists first thought might be deep cracks caused by tectonic activity. Higher-resolution images from Voyager 2 showed the features lacked depth, leading one scientist to say they “might have been painted on with a felt marker.” Europa is thought to have a thin ice crust (less than 30 km thick) over a 50 km-deep ocean, due to tidal heating.

Two small new moons, Adrastea and Metis, were discovered orbiting just outside Saturn’s ring. A third, Thebe, was found between Amalthea and Io.

Voyager 2’s closest approach to Saturn occurred on August 26, 1981, at 03:24:05 UT. As it passed behind Saturn from Earth’s perspective, it used its radio link to study Saturn’s upper atmosphere, measuring temperature and pressure. At 70 mbar (1.0 psi), the temperature was 82 K (−191.2 °C; −312.1 °F). At 1,200 mbar (17 psi), the temperature rose to 143 K (−130 °C; −202 °F). The north pole was about 10 °C (18 °F) cooler than mid-latitudes at 100 mbar (1.5 psi), possibly due to seasonal changes.

After its Saturn flyby, Voyager 2’s scan platform had a malfunction that caused its azimuth actuator to stop working. This led to data loss and mission challenges. The issue was caused by a design flaw, corrosion, and debris buildup. Engineers fixed the problem, allowing the scan platform to resume function. Voyager 2 did not visit Titan due to the malfunction and instead continued to explore the Uranian system.

Voyager 2’s closest approach to Uranus occurred on January 24, 1986, at 81,500 km (50,600 miles) from the planet’s cloud tops. It discovered 11 new moons: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck, and Perdita. It studied Uranus’s tilted atmosphere and ring system. A day on Uranus lasts 17 hours and 14 minutes. Uranus has a magnetic field misaligned with its rotation axis and a magnetic tail stretching 10 million km (6.2 million miles) from the Sun.

During its Uranus visit, haze hid many cloud features, but false-color images revealed concentric cloud bands around the south pole. This area emitted strong ultraviolet light, called “dayglow.” The average atmospheric temperature was about 60 K (−351.7 °F; −213.2 °C). Temperatures at the cloud tops were nearly the same across the planet.

Voyager 2’s Planetary Radio Astronomy experiment detected 140 lightning flashes (Uranian electrostatic discharges) with frequencies of 0.9–40 MHz. Modeling suggests these lightning events occur in deep troposphere water clouds, hidden by thick cloud layers. Each lightning flash released about 10 W of power and 1×10^7–2×10^7 J of energy, lasting 120 ms on average.

Images of Uranus’s moon Miranda showed large canyons formed by geological faults. One theory suggests Miranda may have reassembled after being shattered by a violent impact.

Voyager 2 discovered two new Uranian rings. These rings differ from those at Jupiter and Saturn and may be relatively young, formed from debris of a moon broken by an impact or tidal forces.

In March 2020, NASA scientists reported detecting a large magnetic bubble, called a plasmoid, released from Uranus, based on reanalyzed data from the 1986 flyby.

After a course correction in 1987,

Interstellar mission

After completing its planetary mission, Voyager 2 began an interstellar mission to study the space beyond the heliosphere. As of September 2023, the spacecraft sends scientific data at a rate of about 160 bits per second. Details about ongoing communication with Voyager 2 can be found in the Voyager Weekly Reports.

In 1992, Voyager 2 observed the nova V1974 Cygni using far-ultraviolet light, which was the first such observation of its kind. The increased brightness at those wavelengths allowed scientists to study the nova in greater detail.

In July 1994, Voyager 2 attempted to observe impacts from fragments of Comet Shoemaker–Levy 9 colliding with Jupiter. Its position allowed it to view the impacts directly, with observations made in the ultraviolet and radio spectrum. However, Voyager 2 did not detect the impacts, as the fireballs were too faint for its instruments to see.

On November 29, 2006, a command sent to Voyager 2 was incorrectly interpreted by its computer as an instruction to activate the spacecraft’s magnetometer heaters. These heaters remained on until December 4, 2006, causing temperatures above 130°C (266°F), which was much hotter than the magnetometers were designed to handle. During this time, a sensor on the spacecraft rotated out of its correct position.

On August 30, 2007, Voyager 2 crossed the termination shock and entered the heliosheath, about 1 billion miles (1.6 billion kilometers) closer to the Sun than Voyager 1. This difference is due to the magnetic field in deep space, which is pushing the southern part of the Solar System’s heliosphere inward.

On April 22, 2010, Voyager 2 experienced problems with its data format. Engineers at JPL discovered that a flipped bit in the spacecraft’s computer caused the issue. A reset was performed on May 19, 2010, and science data resumed on May 23, 2010.

In 2013, scientists initially expected Voyager 2 to enter interstellar space in two to three years. Its plasma spectrometer would have measured the density and temperature of interstellar plasma. However, scientists lacked evidence of a key sign of interstellar space: a change in the direction of the magnetic field. In December 2018, Voyager project scientist Edward C. Stone announced that Voyager 2 entered interstellar space on November 5, 2018.

In 2020, maintenance on the Deep Space Network disrupted communication with Voyager 2 for eight months. Contact was restored on November 2, 2020, after instructions were sent and confirmed. Full communication was reestablished on February 12, 2021, following a major upgrade to a ground station antenna that took one year to complete.

In October 2020, astronomers reported a large, unexpected increase in the density of space beyond the Solar System, as detected by Voyager 1 and Voyager 2. This suggests that the density change is a large-scale feature of the very local interstellar medium in the direction of the heliospheric nose.

On July 18, 2023, Voyager 2 became the second farthest spacecraft from the Sun, surpassing Pioneer 10.

On July 21, 2023, a programming error caused Voyager 2’s high gain antenna to misalign by 2 degrees from Earth, disrupting communication. By August 1, the spacecraft’s signal was detected using multiple antennas of the Deep Space Network. A high-power signal sent on August 4 from the Canberra station successfully reoriented the spacecraft toward Earth, restoring communication. As a backup, the spacecraft is programmed to automatically reset its orientation to face Earth, which would have occurred by October 15.

Reductions in capabilities

As the power from the RTG decreases, some equipment on the spacecraft has been turned off. The first science instrument turned off on Voyager 2 was the PPS in 1991, which saved 1.2 watts of power.

Some thrusters, which help control the spacecraft’s direction and point its high-gain antenna toward Earth, are no longer working because of blockages in their hydrazine injectors. The spacecraft no longer has backup thrusters, and all systems now operate with no backup, as stated by Suzanne Dodd, Voyager project manager at JPL, in an interview with Ars Technica. NASA plans to update the spacecraft’s software to change how the remaining thrusters work, which may help reduce further blockages in the small hydrazine injector jets. Before sending the software update to Voyager 1, NASA will first test the process on Voyager 2, which is closer to Earth.

Future of the probe

The probe is expected to continue sending weak radio signals until at least the mid-2020s, more than 48 years after it was launched. NASA states, "The Voyagers are destined—perhaps eternally—to wander the Milky Way."

Voyager 2 is not traveling toward any specific star. The nearest star is 4.2 light-years away, and the spacecraft moves at a speed of 15.341 kilometers per second. At this speed, it would take about 19,541 years to travel one light-year. During this time, nearby stars will also move significantly. In about 42,000 years, Voyager 2 will pass the star Ross 248 (10.30 light-years from Earth) at a distance of 1.7 light-years. If not disturbed for 296,000 years, Voyager 2 should pass by the star Sirius (8.6 light-years from Earth) at a distance of 4.3 light-years.

Golden record

Each Voyager space probe carries a special gold-covered disc that includes a collection of images, sounds, and messages. This disc was created to share information about Earth's life and culture if either probe is ever discovered by an alien being. A group of scientists, including Carl Sagan and Timothy Ferris, helped design the disc. It contains pictures of Earth and its living creatures, scientific facts, greetings from people like the United Nations Secretary-General, and a mix of sounds called "Sounds of Earth." These sounds include whale calls, a baby's cry, ocean waves, and music from many cultures and time periods, such as pieces by Wolfgang Amadeus Mozart, Blind Willie Johnson, Chuck Berry, and Valya Balkanska. The disc also includes traditional music from various regions around the world and greetings in 55 languages. The goal of the project was to show the variety of life on Earth and to share human creativity and the wish to connect with the universe.