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Voyager 2
Artist's rendering of the Voyager spacecraft, a small-bodied spacecraft with a large, central dish and multiple arms and antennas extending from the dish
Artist's rendering of the Voyager spacecraft design
Mission typePlanetary exploration
OperatorNASA / JPL[1]
COSPAR ID1977-076A[2]
SATCAT no.10271[2]
Websitescience.nasa.gov/mission/voyager/
Mission duration
  • 48 years, 3 months, 7 days elapsed
  • Planetary mission: 12 years, 1 month, 12 days
  • Interstellar mission: 36 years, 1 month, 26 days elapsed
Spacecraft properties
ManufacturerJet Propulsion Laboratory
Launch mass721.9 kilograms (1,592 lb)[3]
Power470 watts (at launch)
Start of mission
Launch dateAugust 20, 1977, 14:29:00 (1977-08-20UTC14:29Z) UTC
RocketTitan IIIE
Launch siteCape Canaveral LC-41
Flyby of Jupiter
Closest approachJuly 9, 1979
Distance570,000 kilometers (350,000 mi)
Flyby of Saturn
Closest approachAugust 26, 1981
Distance101,000 km (63,000 mi)
Flyby of Uranus
Closest approachJanuary 24, 1986
Distance81,500 km (50,600 mi)
Flyby of Neptune
Closest approachAugust 25, 1989
Distance4,951 km (3,076 mi)
Large Strategic Science Missions
Planetary Science Division
Heliocentric positions of the five interstellar probes (squares) and other bodies (circles) until 2030, with launch and flyby dates. Markers denote positions on 1 January of each year, with every fifth year labelled.
Plot 1 is viewed from the north ecliptic pole, to scale.
Plots 2 to 4 are third-angle projections at 20% scale.
In the SVG file, hover over a trajectory or orbit to highlight it and its associated launches and flybys.

Voyager 2 is a space probe launched by NASA on August 20, 1977, as a part of the Voyager program. It was launched on a trajectory towards the gas giants (Jupiter and Saturn) and enabled further encounters with the ice giants (Uranus and Neptune). The only spacecraft to have visited either of the ice giant planets, it was the third of five spacecraft to achieve Solar escape velocity, which allowed it to leave the Solar System. Launched 16 days before its twin Voyager 1, the primary mission of the spacecraft was to study the outer planets and its extended mission is to study interstellar space beyond the Sun's heliosphere.

Voyager 2 successfully fulfilled its primary mission of visiting the Jovian system in 1979, the Saturnian system in 1981, Uranian system in 1986, and the Neptunian system in 1989. The spacecraft is in its extended mission of studying the interstellar medium. It is at a distance of 139.26 AU (20.8 billion km; 12.9 billion mi) from Earth as of May 2025.[4]

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[5] and moving at a velocity of 15.341 km/s (34,320 mph)[4] relative to the Sun. Voyager 2 has left the Sun's heliosphere and is traveling through the interstellar medium, though still inside the Solar System, joining Voyager 1, which had reached the interstellar medium in 2012.[6][7][8][9] Voyager 2 has begun to provide the first direct measurements of the density and temperature of the interstellar plasma.[10]

Voyager 2 is in contact with Earth through the NASA Deep Space Network.[11] Communications are the responsibility of Australia's DSS 43 communication antenna, near Canberra.[12]

History

[edit]
Further information: Grand Tour program

Background

[edit]
Main article: Mariner Jupiter-Saturn

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. NASA began work on a Grand Tour, which evolved into a massive project involving two groups of two probes each, with one group visiting Jupiter, Saturn, and Pluto and the other Jupiter, Uranus, and Neptune. The spacecraft would be designed with redundant systems to ensure survival throughout the entire tour. By 1972 the mission was scaled back and replaced with two Mariner program-derived spacecraft, the Mariner Jupiter-Saturn probes. 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]: 263  As the program progressed, the name was changed to Voyager.[14]

The primary mission of Voyager 1 was to explore Jupiter, Saturn, and Saturn's largest moon, Titan. Voyager 2 was also to explore Jupiter and Saturn, but on a trajectory that would have the option of continuing on to Uranus and Neptune, or being redirected to Titan as a backup for Voyager 1. Upon successful completion of Voyager 1's objectives, Voyager 2 would get a mission extension to send the probe on towards Uranus and Neptune.[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. Hence the trajectory was designed for optimum Titan flyby.[15][16]

Spacecraft design

[edit]

Constructed by the Jet Propulsion Laboratory (JPL), Voyager 2, whose bus is shaped like a decagonal prism, included 16 hydrazine thrusters, three-axis stabilization, gyroscopes and celestial referencing instruments (a Sun sensor, and a Canopus star tracker) to maintain pointing of the high-gain antenna toward Earth. Collectively these instruments are part of the Attitude and Articulation Control Subsystem (AACS) along with redundant units of most instruments and 8 backup thrusters. The spacecraft also included 11 scientific instruments to study celestial objects as it traveled through space.[17]

Communications

[edit]

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. Communications are conducted over the S-band (about 13 cm wavelength) and X-band (about 3.6 cm wavelength) providing data rates as high as 115.2 kilobits per second at the distance of Jupiter, and then ever-decreasing as distance increases, because of the inverse-square law.[18] When the spacecraft is unable to communicate with Earth, the Digital Tape Recorder (DTR) can record about 64 megabytes of data for transmission at another time.[19]

Power

[edit]
Voyager RTG unit

Voyager 2 is equipped with three multihundred-watt radioisotope thermoelectric generators (MHW RTGs). Each RTG includes 24 pressed plutonium oxide spheres. At launch, each RTG provided enough heat to generate approximately 157 W of electrical power. Collectively, the RTGs supplied the spacecraft with 470 watts at launch (halving every 87.7 years). They were predicted to allow operations to continue until at least 2020, and continued to provide power to five scientific instruments through the early part of 2023. In April 2023 JPL began using a reservoir of backup power intended for an onboard safety mechanism. As a result, all five instruments had been expected to continue operation through 2026.[17][2][20][21] In October 2024 NASA announced that the plasma science instrument had been turned off, preserving power for the remaining four instruments.[22]

Attitude control and propulsion

[edit]

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. The propulsion module was jettisoned shortly after the successful Jupiter burn.

Sixteen hydrazine Aerojet MR-103 thrusters on the mission module provide attitude control.[23] Four are used to execute trajectory correction maneuvers; the others in two redundant six-thruster branches, to stabilize the spacecraft on its three axes. Only one branch of attitude control thrusters is needed at any time.[24]

Thrusters are supplied by a single 70-centimeter (28 in) diameter spherical titanium tank. It contained 100 kilograms (220 lb) of hydrazine at launch, providing enough fuel until 2034.[25]

Scientific instruments

[edit]
Main article: Voyager program
Instrument name Abr. Description
Imaging Science System
(disabled) 		(ISS) Utilized a two-camera system (narrow-angle/wide-angle) to provide imagery of the outer planets and other objects along the trajectory.
Filters
Narrow Angle Camera Filters[26]
Name Wavelength Spectrum Sensitivity
Clear 280–640 nm;
460 nm center
UV 280–370 nm;
325 nm center
Violet 350–450 nm;
400 nm center
Blue 430–530 nm;
480 nm center
' '
'
Green 530–640 nm;
585 nm center
' '
'
Orange 590–640 nm;
615 nm center
' '
'
Wide Angle Camera Filters[27]
Name Wavelength Spectrum Sensitivity
Clear 280–640 nm;
460 nm center
' '
'
Violet 350–450 nm;
400 nm center
Blue 430–530 nm;
480 nm center
CH4-U 536–546 nm;
514 nm center
Green 530–640 nm;
585 nm center
Na-D 588–590 nm;
589 nm center
Orange 590–640 nm;
615 nm center
CH4-JST 614–624 nm;
619 nm center
Radio Science System
(disabled) 		(RSS) Utilized the telecommunications system of the Voyager spacecraft to determine the physical properties of planets and satellites (ionospheres, atmospheres, masses, gravity fields, densities) and the amount and size distribution of material in Saturn's rings and the ring dimensions.
Infrared interferometer spectrometer and radiometer
(disabled) 		(IRIS) Investigates both global and local energy balance and atmospheric composition. Vertical temperature profiles are also obtained from the planets and satellites as well as the composition, thermal properties, and size of particles in Saturn's rings.
Ultraviolet Spectrometer
(disabled) 		(UVS) Designed to measure atmospheric properties, and to measure radiation.
Triaxial Fluxgate Magnetometer
(active) 		(MAG) Designed to investigate the magnetic fields of Jupiter and Saturn, the solar-wind interaction with the magnetospheres of these planets, and the interplanetary magnetic field out to the solar wind boundary with the interstellar magnetic field and beyond, if crossed.
Plasma Spectrometer
(disabled) 		(PLS) Investigates the macroscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV.
Low Energy Charged Particle Instrument
(disabled) 		(LECP) Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition.
Cosmic Ray System
(active) 		(CRS) Determines the origin and acceleration process, life history, and dynamic contribution of interstellar cosmic rays, the nucleosynthesis of elements in cosmic-ray sources, the behavior of cosmic rays in the interplanetary medium, and the trapped planetary energetic-particle environment.
Planetary Radio Astronomy Investigation
(disabled) 		(PRA) Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn.
Photopolarimeter System
(defective) 		(PPS) Utilized a telescope with a polarizer to gather information on surface texture and composition of Jupiter and Saturn and information on atmospheric scattering properties and density for both planets.
Plasma Wave Subsystem
(active) 		(PWS) Provides continuous, sheath-independent measurements of the electron-density profiles at Jupiter and Saturn as well as basic information on local wave-particle interaction, useful in studying the magnetospheres.
Images of the spacecraft
  • Voyager in transport to a solar thermal test chamber.
    Voyager in transport to a solar thermal test chamber.
  • Voyager in transport to a solar thermal test chamber
    Voyager 2 awaiting payload entry into a Titan IIIE/Centaur rocket.

Mission profile

[edit]
Images of Voyager 2's trajectory
  • Voyager 2's trajectory from the Earth, following the ecliptic through 1989 at Neptune and now heading south into the Pavo constellation
    Voyager 2's trajectory from the Earth, following the ecliptic through 1989 at Neptune and now heading south into the Pavo constellation
  • Path viewed from above the Solar System
    Path viewed from above the Solar System
  • Path viewed from side, showing distance below ecliptic in gray
    Path viewed from side, showing distance below ecliptic in gray
Timeline of travel
Date Event
1977-08-20 Spacecraft launched at 14:29:00 UTC.
1977-12-10 Entered asteroid belt.
1977-12-19 Voyager 1 overtakes Voyager 2. (see diagram)
1978-06 Primary radio receiver fails. The remainder of the mission flown using backup.
1978-10-21 Exited asteroid belt
1979-04-25 Start Jupiter observation phase
1981-06-05 Start Saturn observation phase.
1985-11-04 Start Uranus observation phase.
1989-06-05 Start Neptune observation phase.
1989-10-02 Begin Voyager Interstellar Mission.
Interstellar phase[28][29][30]
1998-11-13 Terminate scan platform and UV observations.
2007-09-06 Terminate data tape recorder operations.
2008-02-22 Terminate planetary radio astronomy experiment operations.
2011-11-07 Switch to backup thrusters to conserve power[31]
2018-11-05 Crossed the heliopause and entered interstellar space.
2023-07-18 Voyager 2 overtook Pioneer 10 as the second farthest spacecraft from the Sun.[32][33]
2024-10 Turned off the plasma science instrument.[34]
2025-03-24 Turned off the low-energy charged particle instrument.[35]

Launch and trajectory

[edit]

The Voyager 2 probe was launched on August 20, 1977, by NASA from Space Launch Complex 41 at Cape Canaveral, Florida, aboard a Titan IIIE/Centaur launch vehicle. Two weeks later, the twin Voyager 1 probe was launched on September 5, 1977. However, Voyager 1 reached both Jupiter and Saturn sooner, as Voyager 2 had been launched into a longer, more circular trajectory.[36][37]

Voyager 1's initial orbit had an aphelion of 8.9 AU (830 million mi; 1.33 billion km), just a little short of Saturn's orbit of 9.5 AU (880 million mi; 1.42 billion km). Whereas, Voyager 2's initial orbit had an aphelion of 6.2 AU (580 million mi; 930 million km), well short of Saturn's orbit.[38]

In April 1978, no commands were transmitted to Voyager 2 for a period of time, causing the spacecraft to switch from its primary radio receiver to its backup receiver.[39] Sometime afterwards, the primary receiver failed altogether. The backup receiver was functional, but a failed capacitor in the receiver meant that it could only receive transmissions that were sent at a precise frequency, and this frequency would be affected by the Earth's rotation (due to the Doppler effect) and the onboard receiver's temperature, among other things.[40][41]

  • Voyager 2 launch on August 20, 1977, with a Titan IIIE/Centaur
    Voyager 2 launch on August 20, 1977, with a Titan IIIE/Centaur
  • Animation of Voyager 2's trajectory from August 20, 1977, to December 30, 2000    Voyager 2  ·   Earth ·   Jupiter  ·   Saturn ·   Uranus  ·   Neptune  ·   Sun
    Animation of Voyager 2's trajectory from August 20, 1977, to December 30, 2000
       Voyager 2  ·   Earth ·   Jupiter  ·   Saturn ·   Uranus  ·   Neptune  ·   Sun
  • Trajectory of Voyager 2 primary mission
    Trajectory of Voyager 2 primary mission
  • Plot of Voyager 2's heliocentric velocity against its distance from the Sun, illustrating the use of gravity assists to accelerate the spacecraft by Jupiter, Saturn and Uranus.[A]
    Plot of Voyager 2's heliocentric velocity against its distance from the Sun, illustrating the use of gravity assists to accelerate the spacecraft by Jupiter, Saturn and Uranus.[A]

Encounter with Jupiter

[edit]
Further information: Exploration of Jupiter
Animation of Voyager 2's trajectory around Jupiter
  Voyager 2 ·   Jupiter ·   Io ·   Europa ·   Ganymede ·   Callisto
The trajectory of Voyager 2 through the Jovian system

Voyager 2's closest approach to Jupiter occurred at 22:29 UT on July 9, 1979.[3] It came within 570,000 km (350,000 mi) of the planet's cloud tops.[43] Jupiter's Great Red Spot was revealed as a complex storm moving in a counterclockwise direction. Other smaller storms and eddies were found throughout the banded clouds.[44]

Voyager 2 returned images of Jupiter, as well as its moons Amalthea, Io, Callisto, Ganymede, and Europa.[3] During a 10-hour "volcano watch", it confirmed Voyager 1's observations of active volcanism on the moon Io, and revealed how the moon's surface had changed in the four months since the previous visit.[3] Together, the Voyagers observed the eruption of nine volcanoes on Io, and there is evidence that other eruptions occurred between the two Voyager fly-bys.[36]

Jupiter's moon Europa displayed a large number of intersecting linear features in the low-resolution photos from Voyager 1. At first, scientists believed the features might be deep cracks, caused by crustal rifting or tectonic processes. 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".[36] Europa is internally active due to tidal heating at a level about one-tenth that of Io. Europa is thought to have a thin crust (less than 30 km (19 mi) thick) of water ice, possibly floating on a 50 km (31 mi)-deep ocean.[36][37]

Two new, small satellites, Adrastea and Metis, were found orbiting just outside the ring.[36] A third new satellite, Thebe, was discovered between the orbits of Amalthea and Io.[36]

Encounter with Saturn

[edit]
Further information: Exploration of Saturn

The closest approach to Saturn occurred at 03:24:05 UT on August 26, 1981.[45] When Voyager 2 passed behind Saturn, viewed from Earth, it utilized its radio link to investigate Saturn's upper atmosphere, gathering data on both temperature and pressure. In the highest regions of the atmosphere, where the pressure was measured at 70 mbar (1.0 psi),[46] Voyager 2 recorded a temperature of 82 K (−191.2 °C; −312.1 °F). Deeper within the atmosphere, where the pressure was recorded to be 1,200 mbar (17 psi), the temperature rose to 143 K (−130 °C; −202 °F).[47] 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[47] (see also Saturn Oppositions).

After its Saturn fly-by, Voyager 2's scan platform experienced an anomaly causing its azimuth actuator to seize. This malfunction led to some data loss and posed challenges for the spacecraft's continued mission. 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,[48] other elements, such as dissimilar metal reactions and a lack of relief ports, compounded the problem. Engineers on the ground were able to issue a series of commands, rectifying the issue to a degree that allowed the scan platform to resume its function.[49] Voyager 2, which would have been diverted to perform the Titan flyby if Voyager 1 had been unable to, did not pass near Titan due to the malfunction, and subsequently, proceeded with its mission to explore the Uranian system.[50]: 94 

Encounter with Uranus

[edit]
Further information: Exploration of Uranus

The closest approach to Uranus occurred on January 24, 1986, when Voyager 2 came within 81,500 km (50,600 mi) of the planet's cloudtops.[51] 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.[51] The length of a day on Uranus as measured by Voyager 2 is 17 hours, 14 minutes.[51] Uranus was shown to have a magnetic field that was misaligned with its rotational axis, unlike other planets that had been visited to that point,[52][55] and a helix-shaped magnetic tail stretching 10 million kilometers (6 million miles) away from the Sun.[52]

When Voyager 2 visited Uranus, much of its cloud features were hidden by a layer of haze; however, false-color and contrast-enhanced images show bands of concentric clouds around its south pole. This area was also found to radiate large amounts of ultraviolet light, a phenomenon that is called "dayglow". The average atmospheric temperature is about 60 K (−351.7 °F; −213.2 °C). The illuminated and dark poles, and most of the planet, exhibit nearly the same temperatures at the cloud tops.[52]

The Voyager 2 Planetary Radio Astronomy (PRA) experiment observed 140 lightning flashes, or Uranian electrostatic discharges with a frequency of 0.9-40 MHz.[56][57] The UEDs were detected from 600,000 km (370,000 mi) of Uranus over 24 hours, most of which were not visible.[56] However, microphysical modeling suggests that Uranian lightning occurs in convective storms occurring in deep troposphere water clouds.[56] If this is the case, lightning will not be visible due to the thick cloud layers above the troposphere.[57] Uranian lightning has a power of around 108 W, emits 1×10^7 J – 2×10^7 J of energy, and lasts an average of 120 ms.[57]

Detailed images from Voyager 2's flyby of the Uranian moon Miranda showed huge canyons made from geological faults.[52] One hypothesis suggests that Miranda might consist of a reaggregation of material following an earlier event when Miranda was shattered into pieces by a violent impact.[52]

Voyager 2 discovered two previously unknown Uranian rings.[52][53] Measurements showed that the Uranian rings are different from those at Jupiter and Saturn. The Uranian ring system might be relatively young, and it did not form at the same time that Uranus did. The particles that make up the rings might be the remnants of a moon that was broken up by either a high-velocity impact or torn up by tidal effects.[36][37]

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.[58][59]

  • Uranus as viewed by Voyager 2
    Uranus as viewed by Voyager 2
  • Departing image of crescent Uranus
    Departing image of crescent Uranus
  • Ariel as imaged from 130,000 km
    Ariel as imaged from 130,000 km
  • Ariel imaged from 130,000 km
    The rings of Uranus imaged by Voyager 2

Encounter with Neptune

[edit]
Further information: Exploration of Neptune

Following a course correction in 1987, Voyager 2's closest approach to Neptune occurred on August 25, 1989.[60][36] Through repeated computerized test simulations of trajectories through the Neptunian system conducted in advance, flight controllers determined the best way to route Voyager 2 through the Neptune–Triton system. Since the plane of the orbit of Triton is tilted significantly with respect to the plane of the ecliptic; through course corrections, Voyager 2 was directed into a path about 4,950 km (3,080 mi) above the north pole of Neptune.[61][62] Five hours after Voyager 2 made its closest approach to Neptune, it performed a close fly-by of Triton, Neptune's largest moon, passing within about 40,000 km (25,000 mi).[61]

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.[63] A plasma wave system (PWS) detected 16 electromagnetic wave events with a frequency range of 50 Hz – 12 kHz at magnetic latitudes 7˚–33˚.[56][64] These plasma wave detections were possibly triggered by lightning over 20 minutes in the ammonia clouds of the magnetosphere.[64] During Voyager 2's closest approach to Neptune, the PWS instrument provided Neptune’s first plasma wave detections at a sample rate of 28,800 samples per second.[64] The measured plasma densities range from 10–3 – 10–1 cm–3.[64][65]

Voyager 2 discovered previously unknown Neptunian rings,[66] and confirmed six new moons: Despina, Galatea, Larissa, Proteus, Naiad and Thalassa.[67][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.[68] 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.[69]

Interstellar mission

[edit]
Voyager 2 left the heliosphere on November 5, 2018.[9]
Voyager 1 and 2 speed and distance from Sun

Once its planetary mission was over, Voyager 2 was described as working on an interstellar mission, which NASA is using to find out what the Solar System is like beyond the heliosphere. As of September 2023 Voyager 2 is transmitting scientific data at about 160 bits per second.[70] Information about continuing telemetry exchanges with Voyager 2 is available from Voyager Weekly Reports.[71]

Official NASA map of the Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2 spacecraft's trajectories through the Solar System.
NASA map showing trajectories of the Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2 spacecraft.

In 1992, Voyager 2 observed the nova V1974 Cygni in the far-ultraviolet, first of its kind. The further increase in the brightness at those wavelengths helped in the more detailed study of the nova.[72][73]

In July 1994, an attempt was made to observe the impacts from fragments of the comet Comet Shoemaker–Levy 9 with Jupiter.[72] 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.[72] Voyager 2 failed to detect anything, with calculations showing that the fireballs were just below the craft's limit of detection.[72]

On November 29, 2006, a telemetered command to Voyager 2 was incorrectly decoded by its on-board computer—in a random error—as a command to turn on the electrical heaters of the spacecraft's magnetometer. 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.[74]

On August 30, 2007, Voyager 2 passed the termination shock and then entered into the heliosheath, approximately 1 billion mi (1.6 billion km) closer to the Sun than Voyager 1 did.[75] This is due to the interstellar magnetic field of deep space. The southern hemisphere of the Solar System's heliosphere is being pushed in.[76]

On April 22, 2010, Voyager 2 encountered scientific data format problems.[77] On May 17, 2010, JPL engineers revealed that a flipped bit in an on-board computer had caused the problem, and scheduled a bit reset for May 19.[78] On May 23, 2010, Voyager 2 resumed sending science data from deep space after engineers fixed the flipped bit.[79]

In 2013, it was originally thought that Voyager 2 would enter interstellar space in two to three years, with its plasma spectrometer providing the first direct measurements of the density and temperature of the interstellar plasma. 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.[10] Finally, in December 2018, Stone announced that Voyager 2 reached interstellar space on November 5, 2018.[8][9]

The position of Voyager 2 in December 2018. Note the vast distances condensed into a logarithmic scale: Earth is one astronomical unit (AU) from the Sun; Saturn is at 10 AU, and the heliopause is at around 120 AU. Neptune is 30.1 AU from the Sun; thus the edge of interstellar space is around four times as far from the Sun as the last planet.[9]

Maintenance to the Deep Space Network cut outbound contact with the probe for eight months in 2020. Contact was reestablished on November 2, when a series of instructions was transmitted, subsequently executed, and relayed back with a successful communication message.[80] On February 12, 2021, full communications were restored after a major ground station antenna upgrade that took a year to complete.[12]

In October 2020, astronomers reported a significant unexpected increase in density in the space beyond the Solar System as detected by the Voyager 1 and Voyager 2; this implies that "the density gradient is a large-scale feature of the VLISM (very local interstellar medium) in the general direction of the heliospheric nose".[81][82]

On July 18, 2023, Voyager 2 overtook Pioneer 10 as the second farthest spacecraft from the Sun.[32][33]

On July 21, 2023, a programming error misaligned Voyager 2's high gain antenna[83] 2 degrees away from Earth, breaking communications with the spacecraft. By August 1, the spacecraft's carrier signal was detected using multiple antennas of the Deep Space Network.[84][85] A high-power "shout" on August 4 sent from the Canberra station[86] successfully commanded the spacecraft to reorient towards Earth, resuming communications.[85][87] As a failsafe measure, the probe is also programmed to autonomously reset its orientation to point towards Earth, which would have occurred by October 15.[85]

Reductions in capabilities

[edit]

As the power from the RTG slowly reduces, various items of equipment have been turned off on the spacecraft.[88] The first science equipment turned off on Voyager 2 was the PPS in 1991, which saved 1.2 watts.[88]

Year End of specific capabilities as a result of the available electrical power limitations[89]
1998 Termination of scan platform and UVS observations[88]
2007 Termination of Digital Tape Recorder (DTR) operations (It was no longer needed due to a failure on the High Waveform Receiver on the Plasma Wave Subsystem (PWS) on June 30, 2002.)[89]
2008 Power off Planetary Radio Astronomy Experiment (PRA)[88]
2019 CRS heater turned off[90]
2021 Turn off heater for Low Energy Charged Particle instrument[91]
2023 Software update reroutes power from the voltage regulator to keep the science instruments operating[21]
2024 Plasma Science instrument (PLS) turned off[92]
2025 Low-Energy Charged Particles (LECP) instrument terminated[93]
2030 approx Can no longer power any instrument[94]
2036 Out of range of the Deep Space Network[47]

Concerns with the orientation thrusters

[edit]

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.[95] 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. Before uploading the software update on the Voyager 1 computer, NASA will first try the procedure with Voyager 2, which is closer to Earth.[95]

Future of the probe

[edit]

The probe is expected to keep transmitting weak radio messages until at least the mid-2020s, more than 48 years after it was launched.[89] NASA says that "The Voyagers are destined—perhaps eternally—to wander the Milky Way."[96]

Voyager 2 is not headed toward any particular star. The nearest star is 4.2 light-years away, and at 15.341 km/s, the spacecraft travels one light-year in about 19,541 years — during which time the nearby stars will also move substantially. In roughly 42,000 years, Voyager 2 will pass the star Ross 248 (10.30 light-years away from Earth) at a distance of 1.7 light-years.[97] If undisturbed 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.[98]

Golden record

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Main article: Voyager Golden Record
A child's greeting in English recorded on the Voyager Golden Record
Voyager Golden Record

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.[99][100] The record, made under the direction of a team including Carl Sagan and Timothy Ferris, includes photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from people such as the Secretary-General of the United Nations, and a medley, "Sounds of Earth", that includes the sounds of whales, a baby crying, waves breaking on a shore, and a collection of music spanning different cultures and eras including works by Wolfgang Amadeus Mozart, Blind Willie Johnson, Chuck Berry and Valya Balkanska. Other Eastern and Western classics are included, as well as performances of indigenous music from around the world. The record also contains greetings in 55 different languages.[101] 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.[100][102]

See also

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Notes

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References

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Further reading

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Voyager 2

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Voyager 2 is an American robotic space probe launched by NASA on August 20, 1977, as part of the Voyager program to explore the outer Solar System and beyond. It is the only spacecraft to have conducted close-up observations of all four giant planets—Jupiter, Saturn, Uranus, and Neptune—and their major moons and ring systems. After completing its planetary tour, Voyager 2 entered interstellar space on November 5, 2018, becoming the second human-made object to reach this region beyond the Sun's heliosphere. The mission's primary objectives included detailed flyby encounters with the gas giants to study their atmospheres, magnetospheres, rings, and satellites, utilizing a suite of 11 scientific instruments such as cameras, spectrometers, and particle detectors. Voyager 2's trajectory allowed it to leverage gravitational assists from and Saturn to reach in January 1986 and in August 1989, providing unprecedented data on these distant worlds. Key discoveries include complex ring structures around and , and Neptune's dynamic , which revealed the planet's stormy atmosphere. As of November 2025, Voyager 2 continues its interstellar mission, traveling at approximately 9.6 miles per second (15.4 kilometers per second) and located over 13 billion miles (21 billion kilometers) from , with signals taking about 19.6 hours to reach . To conserve dwindling power from its radioisotope thermoelectric generators, several instruments have been powered down, including the plasma science instrument in 2024 and others in early 2025, yet core instruments remain active to measure cosmic rays, , and plasma waves in the . The probe is expected to continue transmitting data until at least the late , contributing to our understanding of the heliosphere's boundary and the galaxy's interstellar environment.

Development and Launch

Background and Objectives

The Voyager 2 mission originated as part of NASA's ambitious , which evolved from the earlier Mariner series of planetary probes during the height of the efforts amid the ongoing War-era competition in space achievements. Conceived in the mid-1960s, the program initially drew on Mariner-class designs for efficient, cost-effective interplanetary travel, with Voyager originally designated as Mariner 11 and Mariner 12 until their renaming in March 1977. This evolution reflected NASA's shift toward grand-scale outer solar system exploration following the successes of Mariner missions to , Mars, and Mercury, aiming to extend robotic reconnaissance to the gas giants. The primary scientific objectives of Voyager 2 centered on conducting detailed investigations of the outer planets' atmospheres, magnetospheres, ring systems, and moons to enhance understanding of their formation, evolution, and potential for . Specifically, the mission sought to characterize , composition, and dynamics; map and plasma environments; analyze ring structures and compositions; and survey moons for geological features that might indicate subsurface oceans or other conditions conducive to life, such as on Europa or Titan during earlier flybys shared with Voyager 1. These goals built on preliminary data from and 11, prioritizing comparative planetology to reveal how the giant planets shaped the solar system's architecture. Planning for Voyager 2 capitalized on a rare once-in-175-years alignment of the outer planets in the late , enabling a "grand tour" trajectory that used gravity assists to visit , Saturn, , and with minimal . This alignment, occurring roughly every 175 years, opened a narrow from 1976 to 1980, allowing efficient multi-planet exploration that would otherwise require decades or advanced unavailable at the time. To mitigate risks, decided to launch Voyager 2 first on August 20, 1977, positioning it for the full grand tour, while followed on September 5, 1977, on a shorter path; this order permitted to be retargeted for the grand tour if Voyager 2 failed during launch or early operations. The Voyager program's development timeline spanned from initial concept studies in to approval in 1972, with spacecraft construction and testing completed by 1977 under a total budget of approximately $360 million for both Voyagers, later adjusted to around $320 million due to scaled-back ambitions from the original grand tour proposal. Key personnel included , who served as project scientist from 1972 to 2022, overseeing scientific planning and operations from 's (JPL). Additionally, approved the inclusion of a gold-plated , known as the Golden Record, on both spacecraft as a symbolic message to potential , curated by a committee led by and containing sounds, images, and greetings from Earth to convey humanity's diversity and location.

Spacecraft Construction

The Voyager 2 spacecraft was assembled at NASA's in , from 1975 to 1977, following the approval of the in 1972. JPL engineers designed and integrated the core structure, subsystems, and scientific components into a cohesive unit capable of withstanding the harsh conditions of deep space travel. The assembly process included rigorous testing for radiation exposure, thermal extremes ranging from -200°C to +200°C, and conditions to ensure reliability over decades. These tests simulated the environments encountered during planetary flybys and beyond, validating the spacecraft's durability before shipment to for launch preparation. The central element of the was a ten-sided polygonal bus constructed from aluminum panels, providing a lightweight yet robust framework weighing approximately 721.9 kilograms at launch, including fuel and scientific instruments. This structure measured about 1.78 meters across the flats and 0.46 meters in height, with overall dimensions expanding to roughly 3.7 meters by 3.2 meters by 2.1 meters when including deployed booms for the and plasma instruments. Key integrations included the 3.7-meter diameter high-gain antenna, mounted directly on the bus for high-speed data transmission back to , and the scan platform—a motorized, two-axis system extending up to 3 meters that allowed precise pointing of cameras and other sensors toward planetary targets without altering the spacecraft's orientation. The aluminum material, combined with blankets, protected internal electronics from micrometeoroids, cosmic radiation, and temperature fluctuations. Voyager 2's onboard computing relied on three dual-redundant systems: the Command Computer Subsystem for sequencing commands, the Flight Data Subsystem for instrument data handling, and the Attitude and Articulation Control Subsystem for orientation and platform control, totaling 68 kilobytes of plated-wire memory across all units. These 18-bit and 16-bit processors executed custom software, enabling autonomous fault detection, sequence execution, and attitude adjustments with minimal ground intervention to conserve power and bandwidth. The power for these systems came from three radioisotope thermoelectric generators using plutonium-238. The entire , encompassing both spacecraft, cost $865 million from 1972 through the encounter in 1989.

Launch and Initial Trajectory

Voyager 2 was launched on , , at 14:29:44 UT from Launch Complex 41 at Air Force Station, , aboard a Titan IIIE- rocket designated TC-7. This launch preceded that of by 16 days to provide additional time for potential adjustments, as Voyager 2 followed a more complex path enabling visits to all four outer planets if the mission parameters allowed. The rocket's Centaur upper stage imparted an initial heliocentric velocity of approximately 17.1 km/s to the , sufficient to escape 's and place it on a toward the outer solar system. Post-launch, the separated from the stage about 260 seconds after ignition, achieving Earth escape energy and beginning its outbound journey. Early flight operations included initial communication checks via NASA's Deep Space Network, which successfully acquired the spacecraft's signal shortly after launch and confirmed nominal performance of its systems. The first trajectory correction maneuver (TCM-1) occurred on October 11, 1977, refining the path to with high precision, achieving the desired delta-v to within one percent. Subsequent maneuvers, such as TCM-2 on May 3, 1978, further aligned the trajectory, ensuring the spacecraft's hyperbolic approach to the gas giants. No major anomalies were reported during this initial phase, though routine checks verified the activation of scientific instruments, which began collecting preliminary data on cosmic rays, plasma waves, and particles as Voyager 2 traversed the inner solar system. The mission's trajectory relied on the gravity assist technique, where the spacecraft uses a planet's gravitational field to alter its velocity and direction without expending fuel, effectively "slingshotting" it toward subsequent targets. This method enabled Voyager 2's grand tour by converting some of the planet's orbital momentum into additional speed for the probe. The path consisted of a series of hyperbolic orbits around each planet, with the Jupiter encounter planned for a closest approach of approximately 645,000 km on July 9, 1979, providing the initial boost for the Saturn flyby while allowing detailed observations. Later assists at Saturn, Uranus, and Neptune extended the trajectory into interstellar space, demonstrating the efficiency of this propulsion strategy for deep space exploration.

Design and Systems

Structure and Propulsion

Voyager 2's structural framework centers on a ten-sided polygonal bus, approximately 1.8 meters across and constructed from , which serves as the core platform for mounting electronics, instruments, and subsystems. This bus is integrated with a that supports the 3.7-meter high-gain antenna, ensuring stable communication orientation throughout the mission. Extending from the bus are several deployable booms, including a 13-meter boom made of for low-magnetic-field measurements and a 2.3-meter graphite- that positions the scan platform away from spacecraft interference. The scan platform itself, a two-axis articulated mechanism weighing 103 kilograms, enables precise of remote-sensing instruments such as cameras and spectrometers, achieving an accuracy of 2.5 milliradians (approximately 0.14 degrees) to capture detailed planetary imagery. The system relies on a monopropellant setup for both adjustments and attitude maintenance, comprising 16 low-thrust engines each delivering 0.889 newtons of force. These thrusters are distributed across the : three primary units dedicated to major correction maneuvers (TCMs), eight for fine attitude control, and five as backups to enhance reliability over the long mission duration. At launch, the system carried 104 kilograms of fuel, stored in four spherical tanks pressurized by , enabling a blowdown mode operation without complex regulators. This configuration provided the necessary impulse for interplanetary course corrections without the need for larger engines post-launch. Attitude and articulation control is managed by the three-axis stabilized system, which uses a combination of inertial and celestial references to maintain the high-gain antenna's Earth-pointing accuracy within 0.05 degrees. Key components include three redundant two-axis gyroscopes for short-term stability, Canopus star trackers for precise angular measurements against the star Canopus, and coarse sun sensors that detect solar position through slots in the antenna dish to provide coarse attitude updates. Following early mission anomalies, such as sensor degradations, the system incorporated built-in redundancies, including backup trackers and gyros, allowing seamless switching to preserve orientation control as the spacecraft ventured farther from the Sun. The overall for propulsion maneuvers totals approximately 190 meters per second, sufficient to support multiple TCMs across the mission's planetary flybys and interstellar extension. For instance, post-launch corrections near involved burns on the scale of several meters per second to refine the trajectory for subsequent encounters, demonstrating the system's efficiency in conserving fuel for long-term operations. Thermal management addresses extreme environmental variations, from near-Earth solar intensities to deep-space , using a passive-active hybrid approach. Radioisotope heater units (RHUs), each generating 1 watt from decay without producing electricity, are strategically placed on sensitive components like the boom, sun sensors, and scan platform to prevent freezing. Complementing these are four sets of louvers on the electronics bays and mini-louvers on the scan platform and cosmic ray instrument, which automatically adjust to radiate excess heat or retain warmth, maintaining internal temperatures within operational limits despite swings from -79°C to 100°C and external conditions dropping to around -160°C near Saturn.

Power and Communications

Voyager 2's electrical power is supplied by three Multi-Hundred Watt radioisotope thermoelectric generators (MHW-RTGs) fueled by plutonium-238, which convert the heat from radioactive decay into electricity through thermoelectric conversion. At launch in 1977, the RTGs generated approximately 470 watts of electrical power at 30 volts DC on an unregulated bus. This power is distributed to subsystems via DC-DC converters that step down to regulated 5-volt and other low-voltage supplies for electronics and instruments. The initial usable power budget was about 420 watts, supporting all operations during the early planetary encounters. Due to the half-life of plutonium-238 (approximately 87.7 years), the RTGs' output decays by roughly 4 watts per year, reducing the total available power to around 225 watts by April 2024 and an estimated 220 watts by late 2025. The enables Voyager 2 to transmit scientific and receive commands across vast distances using a 23-watt X-band amplifier operating at 8.4 GHz for downlink . is directed through a 3.7-meter high-gain , which provides focused transmission and reception capabilities. At the distance of the flyby in 1989 (about 30 AU from ), the typical data rate was 160 bits per second under normal engineering constraints, though higher rates up to 115 kilobits per second were possible during close encounters with burst transmissions. As of 2025, with the spacecraft at approximately 141 AU (over 21 billion kilometers) from , one-way signal travel time exceeds 19.5 hours, necessitating careful command sequencing. Ground communication relies on NASA's Deep Space Network (DSN), comprising three primary complexes in Goldstone, California; , Spain; and , Australia, which provide continuous tracking, command uplink via S-band at 2.3 GHz, and data downlink reception with large dish antennas up to 70 meters in diameter. To ensure reliable transmission over noisy deep-space channels, data employs convolutional coding with a rate of 1/2 and constraint length 7, often concatenated with Reed-Solomon outer codes for error correction, achieving low bit error rates even at faint signal strengths. Over the mission's duration, NASA developed adaptive compression techniques, such as for images and , to maximize data return within the constrained bit rates as power and distance limited bandwidth.

Scientific Instruments

Voyager 2 carried a suite of 11 scientific instruments designed to investigate the outer planets, their satellites, magnetospheres, and the interplanetary medium, as part of 11 investigations including radio science. These instruments were mounted on the spacecraft's science deck and scan platform, enabling comprehensive remote sensing and in-situ measurements. The payload emphasized multispectral imaging, particle detection, and field measurements to capture data across electromagnetic spectra and particle energies. The instruments include the Imaging Science System (ISS), consisting of two vidicon cameras—a narrow-angle camera with 1500 mm and f/8.5 , and a wide-angle camera with 200 mm and f/3 —each equipped with an 800 × 800 pixel vidicon tube and multiple filters for visible and near-infrared imaging to resolve planetary surfaces and atmospheres at scales down to kilometers per pixel during close encounters. The Infrared Interferometer Spectrometer (IRIS) measured thermal emissions and atmospheric compositions in the 2.5–50 μm range, providing spectra to analyze temperature profiles and trace gases. The Ultraviolet Spectrometer (UVS) observed emissions from 40–180 nm to study upper atmospheres, aurorae, and ionospheres through high-resolution grating . The Triaxial Fluxgate Magnetometer (MAG) detected magnetic fields with dual sensors, covering ranges from 0.006 nT to 20 gauss to map planetary magnetospheres and interplanetary fields with high temporal resolution. The Plasma Spectrometer (PLS) analyzed low-energy ions and electrons (up to 10 keV) using Faraday cup detectors to measure solar wind parameters like density, velocity, and temperature. The Low-Energy Charged Particle (LECP) instrument employed scanning telescopes to detect ions and electrons from 10 eV to 40 MeV, characterizing energetic particle populations in planetary environments and the heliosphere. The Cosmic Ray Subsystem (CRS) measured high-energy particles (electrons 3–110 MeV, nuclei 1–500 MeV/nuc) with solid-state detectors and scintillation counters to study galactic cosmic rays and solar energetic particles. Additional instruments included the Planetary Radio Astronomy (PRA) system, which used dual antennas to detect radio emissions from 20.4 kHz to 40.5 MHz, investigating planetary magnetospheric radio sources and interactions. The Plasma Wave Subsystem (PWS) recorded waves from 10 Hz to 56 kHz via long antennas, analyzing plasma densities, wave modes, and dust impacts. The Photopolarimeter System (PPS) featured a 0.2 m to measure polarization and intensity from 235–750 nm, probing atmospheric and ring structures. Radio investigations utilized the spacecraft's telecommunications system as a probe for gravity fields, atmospheres, and ionospheres during flybys. An Optical Calibration Target (OCT) provided a known reference for in-flight of scan platform instruments. Pre-mission calibration and testing occurred at NASA's (JPL), including vibration, thermal vacuum, and tests to ensure performance under space conditions. Instruments underwent evaluations, such as proton and electron exposure simulations using facilities like the JPL Dynamitron, to withstand Jupiter's intense belts (up to 10^8 rads total dose). The total science mass was approximately 105 kg, with power consumption around 100 W for electronics plus 10 W for heaters at nominal operation. Most instruments featured a dual-string design, with parallel electronics chains switchable via ground command to enhance reliability against single-point failures.

Planetary Encounters

Jupiter Flyby

Voyager 2 began its encounter on April 24, 1979, approaching the planet for a series of targeted observations that culminated in its closest approach on July 9, 1979, when it passed within 570,000 kilometers (350,000 miles) of the cloud tops. The spacecraft conducted an intense observation period over approximately 48 hours around closest approach, capturing high-resolution images and data on the planet's atmosphere, , and satellites using its suite of instruments. This flyby provided the second detailed survey of the Jovian system following Voyager 1's earlier passage, building on initial findings with complementary trajectories that allowed for outbound observations of features missed inbound. Key observations included detailed imaging of the , revealing it as a vast, system with turbulent internal dynamics and surrounding smaller vortices interacting with the planet's banded cloud layers. Voyager 2 also confirmed and expanded on the discovery of active on Io, observing multiple plumes during a dedicated 10-hour monitoring sequence from a distance of about 1.1 million kilometers (702,200 miles), marking the first extraterrestrial volcanic activity verified beyond . These plumes were later identified as ejecting sulfur-rich material, contributing to Io's colorful surface and tenuous atmosphere. The spacecraft's instruments further mapped Jupiter's , detecting its vast extent with a tail stretching over 600 million kilometers toward the outer solar system, influenced by interactions with the and Io's plasma torus. During the encounter, Voyager 2 performed close flybys of several moons, obtaining detailed images of Amalthea at 559,000 kilometers (347,000 miles), revealing its irregular, potato-shaped form; Europa at 206,000 kilometers (127,900 miles), showing a cracked, icy surface suggestive of subsurface processes; Ganymede at 62,100 kilometers (38,600 miles), highlighting cratered terrains and possible tectonic features; and Callisto at 215,000 kilometers (133,600 miles), displaying heavily cratered, ancient crust. Io was observed from afar but with focus on its dynamic surface changes due to ongoing eruptions. Atmospheric measurements indicated zonal winds reaching speeds of up to 540 kilometers per hour (335 miles per hour) in the equatorial regions, driven by the planet's rapid rotation, with a composition dominated by approximately 90% and 10% by volume. An early anomaly during the approach involved the failure of Voyager 2's primary radio receiver in April 1978, necessitating a switch to the backup system, which performed reliably throughout the flyby without impacting data return. No major imaging issues were reported specific to the encounter, allowing for the successful transmission of over 16,000 images from Voyager 2 alone.

Saturn Flyby

Voyager 2's encounter with Saturn began with long-range observations starting on June 5, 1981, from a distance of 41 million miles, following trajectory adjustments made after its Jupiter flyby in 1979 to optimize the path for the Saturn targeting and subsequent outer planet encounters. The spacecraft achieved its closest approach to Saturn on August 25, 1981, passing 161,000 km from the planet's , or approximately 41,000 km above the cloud tops. Observations continued until September 28, 1981, providing a comprehensive dataset during the four-month period. The flyby revolutionized understanding of Saturn's , revealing thousands of narrow ringlets within the main rings and transient spoke-like features in the B ring, imaged from about 2.5 million miles away on August 22, 1981. Voyager 2 also identified the roles of small , such as and , which orbit approximately 1,800 km apart and gravitationally confine the narrow F ring through their influence on ring particles. These discoveries highlighted the dynamic, moon-driven structure of the rings, with embedded bodies creating gaps and density waves. A dedicated flyby of Saturn's largest moon, Titan, occurred on August 24, 1981, at a distance of 413,000 miles, where Voyager 2 probed its thick atmosphere composed primarily of with traces of and hydrocarbons. The dense haze layers obscured the surface, presenting Titan as a featureless orange globe, but and data suggested the presence of methane-driven processes, including potential liquid hydrocarbon reservoirs. In Saturn's atmosphere, Voyager 2 captured evidence of a persistent hexagonal encircling the , a unique wave pattern in the , alongside zonal bands and high-altitude clouds. Measurements indicated intense zonal winds, with equatorial speeds reaching up to 1,800 km/h eastward, five times stronger than those on and driven by internal heat sources. Voyager 2 provided high-resolution images of several inner moons during the encounter, including close passes by at 54,000 miles and Tethys at 58,000 miles on August 25, 1981, revealing cratered terrains and tectonic features. It also imaged , showcasing its distinctive large , and contributed confirmatory observations of the small moon Atlas, first discovered by , highlighting its position near the A ring.

Uranus Flyby

Voyager 2's encounter with marked the first and only close-up exploration of the , providing unprecedented data on its atmosphere, , rings, and moons during a brief flyby in early 1986. Launched on a enabled by a rare alignment of the outer planets—occurring approximately once every 175 years—the spacecraft capitalized on this singular opportunity to study after its prior visits to and Saturn. Observations commenced on November 4, 1985, with the encounter phase concluding on February 25, 1986, yielding insights into a world previously known only through ground-based telescopes. The timeline of the flyby culminated in Voyager 2's closest approach to on January 24, 1986, at 17:59 UT, when it passed approximately 81,500 kilometers (50,640 miles) above the planet's cloud tops. About 11 hours prior, the spacecraft entered 's , initiating a compressed period of intense data collection over roughly six hours around periapsis. This geometry allowed Voyager 2 to traverse the Uranian system from the dayside to the nightside, capturing images and measurements of the planet, its rings, and major moons in sequence. The mission's design ensured all scientific instruments operated simultaneously during this window, though the faint sunlight—only 25% as intense as at Saturn—necessitated careful imaging strategies. Atmospheric observations revealed a dynamic yet featureless upper layer dominated by and , with comprising about 2% of the composition and responsible for the planet's characteristic pale hue through absorption of wavelengths. A global of submicron particles, likely hydrocarbons, scattered blue light and contributed to the bland appearance, while Voyager 2's instruments detected no prominent cloud bands or storms, unlike those at or Saturn. Winds in the reached speeds of up to 250 meters per second (about 900 km/h), driven by seasonal and solar influences, and temperature profiles indicated frigid conditions, with the at approximately -224°C (49 K). These findings highlighted Uranus's quiescent atmosphere, possibly due to its extreme and weak internal heat source. The proved highly unusual, with Voyager 2 measuring a tilted 59° relative to the planet's rotation axis and offset from the center by nearly one-third of Uranus's . This obliquity results in the rotating with the planet every 17.2 hours, periodically reconnecting with the and generating asymmetric plasma flows that produce unique, low-energy auroras confined to the magnetic poles. Instruments detected intense plasma waves and low-energy charged particles, but the overall magnetotail was compressed and dynamic, reflecting the system's youth and interaction with the tenuous at 19 AU. Voyager 2 expanded knowledge of Uranus's ring-moons system by discovering 10 new moons, including the small inner satellites Puck (diameter ~160 km), (~40 km), and (~40 km), which act as shepherds confining the outermost epsilon ring. The rings themselves—previously detected from —were found to be dark, diffuse, and variable in density, composed of micrometer-sized particles with low , and two additional faint rings were identified near the planet. Among the five classical moons, Miranda received the closest scrutiny at 29,000 km, revealing a fractured surface with chevron-shaped terrains, layered cliffs up to 20 km high, and chaotic regions suggestive of past and geological resurfacing, possibly indicating cryovolcanism or collisional disruption. The flyby presented significant operational challenges from Uranus's intense radiation environment, where high-energy electrons in the —second only to Jupiter's in intensity—damaged the spacecraft's scan platform bearings and temporarily blinded the imaging system. Peak fluxes exceeded 10^8 electrons per square centimeter per second, necessitating real-time command uploads from Earth to recalibrate instruments and prioritize non-imaging data collection. Engineers at NASA's averted potential mission loss by adjusting Voyager 2's attitude control and instrument pointing, ensuring the recovery of critical scientific returns despite the belts' unexpected ferocity.

Neptune Flyby

Voyager 2 conducted its final planetary encounter on August 25, 1989, achieving closest approach to at approximately 4,800 kilometers above the cloud tops. The spacecraft captured its highest-resolution images of the from about 4.4 million kilometers away, revealing a deep blue world with a dynamic atmosphere. This flyby marked the only close-up exploration of to date, providing unprecedented data on its gaseous envelope and satellite system. Neptune's atmosphere proved highly active, featuring the Great Dark Spot, a massive roughly the size of , observed as a dark, oval-shaped vortex in the . This storm, analogous to Jupiter's , rotated counterclockwise and was accompanied by bright white clouds. Voyager 2 measured winds of more than 2,000 kilometers per hour (1,200 miles per hour), the fastest in the solar system, driven by the planet's internal heat source that generates more energy than it receives from the Sun. These high-speed zonal winds, moving both eastward and westward, sculpted cloud features and highlighted Neptune's turbulent weather patterns. Following the Neptune encounter, Voyager 2 flew past Triton on August 25, 1989, at a distance of about 40,000 kilometers, imaging nearly half of the moon's surface. Triton orbits in a retrograde direction, opposite to the planet's rotation, suggesting it was captured from the rather than forming in place. The flyby revealed active geysers erupting plumes up to 8 kilometers high, driven by solar heating or subsurface processes, which deposit dark streaks on the icy surface. Triton's south polar region features a thin , while its overall surface appears surprisingly young, with few impact craters indicating recent geological resurfacing. The observations also uncovered evidence of an internal heat source on Triton, inferred from and cryovolcanic activity, which may sustain a subsurface ocean beneath its icy crust. Voyager 2 discovered six new moons around , including the irregularly shaped , the largest at about 400 kilometers across. Additionally, the spacecraft confirmed a faint with four rings, notably the Adams ring featuring clumpy, localized arcs confined by gravitational influences from nearby moons like Galatea.

Interstellar Phase

Heliopause Crossing

Voyager 2 crossed the heliopause on November 5, 2018, at a distance of approximately 119 from the Sun, marking its transition from the to . This boundary separates the region influenced by the from the , where charged particles from beyond the solar system dominate. The crossing was confirmed by a dramatic jump in plasma density, from about 0.002 electrons per cm³ in the heliosheath to roughly 0.039 electrons per cm³ in the , indicating compression at the interface. The Plasma Wave System (PWS) detected this sudden increase in electron through plasma oscillations, while the (MAG) recorded a strengthening of the , with its magnitude rising by a factor of about three just before the boundary and the field direction rotating slightly afterward. These observations provided direct evidence of the spacecraft entering a cooler, denser plasma environment beyond the Sun's influence. Unlike , which crossed the in 2012 at 122 AU using indirect plasma measurements due to the earlier failure of its Plasma Science instrument, traversed the boundary in the of the and benefited from a functional Plasma Science (PLS) instrument for direct plasma velocity and density readings. Earlier, on August 30, 2007, had crossed the termination shock at 84 AU, where the slows from supersonic to subsonic speeds, entering the heliosheath—a turbulent region of heated, compressed plasma that the navigated for over a decade. The heliosheath's thickness along 's trajectory was about 35 AU, thinner than in the northern direction probed by , reflecting the 's asymmetric, squashed shape due to interstellar magnetic field interactions. The heliopause's position varies directionally, generally around 120 AU from the Sun, influenced by solar activity and the interstellar medium's pressure.

Ongoing Operations and

As of November 2025, Voyager 2 is approximately 142 AU (21.2 billion kilometers) from the Sun, traveling at a speed of about 15.4 km/s relative to the Sun. The spacecraft continues to operate in interstellar space, providing ongoing measurements of the local interstellar medium, which consists of low-density plasma, , and cosmic rays beyond the heliopause. Three scientific instruments remain active: the magnetometer (MAG), which measures interstellar magnetic fields; the plasma wave subsystem (PWS), which detects plasma waves and electron density; and the cosmic ray subsystem (CRS), which monitors cosmic ray fluxes and their interactions with the interstellar environment. Other instruments, such as the low-energy charged particle (LECP) instrument, were powered down in March 2025, and the plasma science (PLS) instrument in October 2024, to conserve dwindling radioisotope thermoelectric generator power. These active instruments contribute to key data themes, including mapping variations in interstellar magnetic fields, tracking cosmic ray intensities and anisotropies, and analyzing plasma wave emissions that reveal density fluctuations near the heliopause boundary. Representative observations include periodic detections of electron plasma oscillations, which help characterize the interstellar plasma's thermal properties. Voyager 2's commanding and data return are managed through NASA's Deep Space Network (DSN), with one-way light travel time exceeding 20 hours due to the 's distance. Engineers conduct routine checkups, including annual command sequences for instrument health and trajectory adjustments, while recent software updates—such as the 2023 fault protection patch—enhance onboard autonomy to mitigate potential anomalies without ground intervention. is transmitted continuously at a reduced rate of 160 bits per second, prioritizing telemetry and science packets from the active instruments. A notable achievement was the 2023 implementation of a backup power distribution strategy, which reallocates radioisotope generator output to sustain operations through at least 2026 by avoiding unnecessary loads during non-critical periods. This approach, combined with earlier shifts to redundant thruster systems for attitude control, ensures the spacecraft maintains its high-gain antenna pointed toward for reliable communications.

Challenges and Adaptations

Power Management Strategies

Voyager 2's power supply relies on three radioisotope thermoelectric generators (RTGs) fueled by , which convert decaying radioactive heat into electricity. At launch in 1977, the RTGs collectively provided approximately 470 watts of electrical power. Due to the natural decay of , the power output has declined steadily, reaching about 225 watts as of 2023, with an ongoing loss of roughly 4 watts per year. This decay necessitates careful management to ensure the spacecraft can continue scientific operations in . To conserve power, engineers have progressively shut down non-essential instruments, prioritizing those focused on studies such as s and . Early shutdowns included the ultraviolet spectrometer (UVS) in 1998 and the planetary (PRA) instrument in 2008. More recent deactivations encompass the plasma science (PLS) instrument on September 26, 2024, saving several watts by eliminating its operational draw. Following the PLS shutdown, four instruments remain active as of November 2025: the subsystem (CRS), (MAG), plasma wave subsystem (PWS), and low-energy (LECP) instrument. The LECP is planned to be powered down in 2026. These decisions reflect a strategic shift toward sustaining a core set of instruments into the late 2020s or early 2030s. Power budgeting strategies have evolved to optimize the limited supply, including the of low-power modes for remaining instruments since the post-planetary phase. In 2023, engineers reconfigured the to access reserve power, reclaiming approximately 4 watts and delaying an instrument shutdown from 2023 to 2026. This approach reduces reliance on primary RTG output and minimizes heater usage for thermal control, further extending operational life without compromising key . Contingency measures include fault protection systems that automatically adjust loads if power levels drop critically, preventing system-wide failures. For instance, the spacecraft's software can trigger backups or partial shutdowns to maintain essential functions like communication. Over the mission's interstellar phase, these combined strategies have conserved power, allowing Voyager 2 to prioritize high-impact science despite the RTG's inexorable decline. These power trade-offs have directly influenced scientific output, such as the deactivation of the imaging science subsystem (ISS), including its scan platform, shortly after the 1989 Neptune encounter to save about 6 watts. While this ended planetary imaging capabilities, it preserved resources for long-term measurements of interstellar plasma and particles, underscoring the mission's adaptation from solar system exploration to .

Attitude Control and Thruster Issues

Voyager 2 utilizes 16 hydrazine-fueled MR-103 thrusters for maintaining its three-axis stabilization and orientation, with 12 dedicated to attitude control (arranged in two redundant branches of six for pitch, yaw, and roll adjustments) and four for correction maneuvers. The primary attitude control thrusters have accumulated over 300,000 firings by 2025, enabling precise pointing of the high-gain antenna toward and the instruments during the spacecraft's 48-year mission. Degradation of these thrusters began accumulating in the due to silicone residue—specifically byproduct—from the rubber diaphragm in the propellant tank, leading to inconsistent and the need for increasingly frequent pulses to achieve stable orientation. This buildup narrows fuel lines over time, risking complete failure of attitude control and potential loss of communication with . By 2019, the issue had escalated to a near-loss of reliable pointing capability, prompting engineers to assess the thrusters' untenable pulse rates. To mitigate the degradation, mission controllers in successfully switched Voyager 2 to its backup trajectory correction maneuver thrusters for attitude control duties—specifically roll adjustments—a role these thrusters had not performed since the 1989 Neptune encounter. This transition preserved the primary thrusters by reducing their usage while maintaining stability. In January 2020, following heating maneuvers to warm the fuel lines and prevent freezing, the experienced an anomaly during a commanded 360-degree roll for instrument calibration, entering fault protection mode and halting science operations temporarily. Engineers resolved the issue within days, restoring normal functions without long-term damage. Ongoing maintenance includes annual "bake-out" procedures, where thrusters are fired in longer bursts to vaporize and expel residue, combined with a 2023 software patch that optimized firing patterns for fewer but more effective pulses across both Voyager . This patch addressed proactive concerns over primary thruster reliability, activating underused backups and extending operational life by an estimated three years. Although no acute primary thruster failure occurred in 2023, the updates prevented imminent risks from residue accumulation. These challenges have resulted in intermittent impacts, such as a brief data gap in early when science instruments were powered down during the anomaly recovery, limiting plasma and particle measurements for several days. Attitude control is now monitored continuously using celestial references like star trackers and the sun sensor, following the deactivation of mechanical gyroscopes in to conserve power. This hybrid approach ensures redundancy against thruster inconsistencies while prioritizing antenna alignment for data return.

Scientific Legacy

Key Discoveries from Encounters

Voyager 2's planetary encounters revolutionized our understanding of the outer solar system, providing the first data that challenged existing models of planetary formation, dynamics, and atmospheric processes. These flybys confirmed dynamic geological activity on moons, revealed complex ring systems influenced by electromagnetic and gravitational interactions, and supplied compositional insights that prompted revisions to theories on origins and captured bodies from distant reservoirs. The mission's observations underscored the role of tidal forces and migration in shaping these worlds, laying foundational data for subsequent modeling of solar system evolution. During its 1979 Jupiter flyby, Voyager 2 captured definitive evidence of active volcanism on Io, building on Voyager 1's initial detection by imaging multiple eruptions and sulfur plumes that demonstrated from Jupiter's gravitational pull as the driver of this unprecedented extraterrestrial activity. The spacecraft's high-resolution images of Europa revealed a remarkably smooth, cracked surface with few impact craters, hinting at a dynamic icy crust possibly overlying a subsurface of liquid water, a concept later bolstered by subsequent missions but first suggested by these early observations of resurfacing processes. The 1981 Saturn encounter yielded breakthroughs in ring dynamics and , with Voyager 2 imaging transient "spokes" in the B ring—radial, dark features attributed to electromagnetic forces charging dust particles and levitating them above the ring plane, a invisible from Earth-based telescopes. On Titan, the probe's and spectrometers detected a thick nitrogen-methane atmosphere rich in organic molecules like and , along with complex haze layers of tholins—refractory organics formed by photochemical reactions—that evoked prebiotic conditions akin to early Earth's chemistry, transforming views of Titan as a potential for life's building blocks. Voyager 2's 1986 and 1989 flybys provided the sole in-situ data for ice giants, prompting major revisions to formation theories by revealing unexpectedly low internal heat and atmospheric compositions that favored models of inward-then-outward migration during the solar system's early , rather than static in-situ accretion. At , the retrograde orbit and icy, Pluto-like surface of Triton—imaged in detail showing geysers and nitrogen ice—strongly supported its capture from the , implying disruptive dynamical events that scattered planetesimals and influenced outer solar system architecture. Across its encounters, Voyager 2 updated models by demonstrating asymmetric plasma distributions shaped by planetary rotation and interactions, as seen in Uranus's offset field and Neptune's tilted . Ring systems were shown to form and evolve through moon disruptions, with Voyager detecting arc-like structures at likely from shepherding by embedded moonlets and diffuse rings at composed of debris from collisional grinding of small satellites. Overall, the Voyager missions transmitted approximately 67,000 images and more than 5 trillion bits of data, with Voyager 2 providing extensive contributions from its encounters with all four giant , enabling comprehensive mapping and spectral analysis that continue to inform comparative planetology. The Voyager Imaging Team's archival datasets, hosted in NASA's Planetary Data System, have facilitated ongoing reanalysis with advanced computational techniques, including studies of Uranus's using modern computing methods, yielding new insights decades after the flybys. As of , Voyager 2's data continues to inform interstellar research, including heliopause models integrated with missions like .

The Golden Record and Cultural Impact

The is a 12-inch gold-plated disc designed to communicate the diversity of life and culture on to any potential extraterrestrial finders. It contains 115 analog images encoded in format, depicting subjects ranging from Earth's landscapes and to human , , and daily activities, along with a calibration image for a total of 116 visuals. The audio component spans approximately 90 minutes and includes natural sounds such as whale songs, bird calls, , thunder, and surf; spoken greetings in 55 languages from around the world; and musical selections from various cultures and eras, including classical pieces by composers like Johann Sebastian Bach, (such as the opening of his Fifth Symphony), and , as well as traditional music from regions like , , and . A and cartridge are included in a protective assembly attached to the record's aluminum cover for playback, while the protective aluminum cover features etched symbolic instructions, including a of the atom's hyperfine transition (frequency 1420 MHz, corresponding to the 21 cm line) to provide a standard for determining the playback speed of 16 2/3 and a pulsar map showing the position of the solar system relative to 14 s with their periods encoded for locating Earth's origin. The record's creation was overseen by a committee led by astronomer at , commissioned by in 1977 to assemble content for both Voyager spacecraft as a intended to endure for up to a billion years in space. Sagan's team, including his wife and musicologist Timothy Ferris, curated the selections to represent humanity's scientific achievements, artistic expressions, and peaceful intentions, drawing from global contributors to ensure cultural breadth; the project was completed under tight deadlines just before the Voyager launches, with the records hand-etched and plated for durability. Etched on the cover alongside the hydrogen diagram and pulsar map—elements adapted from the earlier Pioneer plaques—is a message in stating "To the makers of music – all worlds, all times," underscoring the record's universal aspirational tone. Both and Voyager 2 carry identical Golden Records, launched in 1977 for redundancy in case one spacecraft failed to reach , ensuring that at least one copy of 's message would venture beyond the solar system. This duplication reflects the mission's dual emphasis on scientific exploration and symbolic outreach, with Voyager 2's record now traveling along a trajectory that will take it toward the constellation Telescopium. The Golden Record has profoundly influenced and interstellar communication efforts, inspiring the Search for (SETI) by demonstrating how to encode knowledge for alien audiences and prompting discussions on active messaging protocols like METI (Messaging Extraterrestrial Intelligence). It served as a in the 1997 science fiction film Contact, directed by and based on Sagan's novel, where a similar record symbolizes humanity's quest for cosmic connection. In 2017, a Kickstarter-funded project by Ferris and others rereleased the record's audio contents commercially for the first time, making the sounds accessible to audiences and reigniting . By 2025, NASA's digital archives have expanded to include high-resolution scans and interactive reconstructions of the record's images and etchings, facilitating educational outreach and virtual playback simulations. Philosophically, the record embodies a message of global peace and diversity, with greetings emphasizing unity and curiosity, yet it has sparked ethical debates about the inclusion of images—particularly nude figures—raising concerns over cultural biases, consent for representation, and the risks of portraying humanity in potentially vulnerable ways to unknown recipients.

Future Prospects

Expected Operational Lifespan

Voyager 2's operational lifespan is primarily limited by the diminishing power output from its three multi-hundred watt radioisotope thermoelectric generators (MHW-RTGs), which convert heat from the of into electricity. These RTGs initially produced about 470 watts of electrical power at launch in 1977 but have degraded at a rate of approximately 4 watts per year due to decay and thermocouple degradation, reaching around 225 watts as of April 2024. NASA engineers have implemented power-saving measures, such as tapping into reserve electrical capacity discovered in 2023 and turning off the low-energy instrument in March 2025, to sustain full scientific operations until at least 2026, with projections indicating the RTGs could support limited instrument functionality through the late 2020s to early 2030s. Scientific data collection is expected to cease when available power falls below the threshold needed to operate the remaining instruments—currently the cosmic ray subsystem (CRS), (MAG), and plasma wave subsystem (PWS)—potentially forcing all instruments offline by the mid-2030s. The MAG and PWS, which require relatively low power, could continue functioning until around 2036 absent component failures, allowing continued measurements of and plasma waves in the . Communication with Earth is projected to end around the same period or by approximately 2040 at the latest, as the spacecraft's faint 23-watt transmitter signal weakens further with increasing distance (as of November 2025, over 140 AU), becoming undetectable even by the Deep Space Network's 70-meter antennas. Key risk factors threatening the mission include cumulative damage from cosmic rays, which can induce bit flips or electronic faults in aging systems, and potential depletion of the remaining propellant for attitude control thrusters, essential for keeping the high-gain antenna pointed toward . As a contingency, if power becomes insufficient for transmission, Voyager 2 could enter a "," where onboard systems persist without sending data, preserving the as a passive interstellar artifact. The mission aims to sustain interstellar observations at least until the 2040s, when the probe may provide complementary outer data as Voyager's capabilities wane. NASA's Voyager Interstellar Mission (VIM) is reviewed and extended annually, with the fiscal year 2025 budget request of $25.4 billion including allocations within the Science Mission Directorate to support ongoing operations, instrument management, and Deep Space Network (DSN) tracking. This funding ensures continued command uplinks and data downlinks from the three global DSN sites, prioritizing Voyager's unique interstellar science despite competing priorities.

Long-Term Trajectory and End State

Voyager 2 is on a hyperbolic escape from the Solar System, inclined at approximately 31° to the ecliptic plane toward the south, carrying it into the at a heliocentric speed of 15.4 km/s. Currently directed toward the constellation Pavo, the spacecraft's path has been modeled using JPL's Horizons ephemerides system, which integrates short-term dynamics up to the year 2900 before extrapolating longer-term motion through a simulated Galactic potential incorporating stellar perturbations from DR2 data. Over the coming millennia, Voyager 2 will traverse the local interstellar medium without any close stellar encounters for at least the next 40,000 years. Its nearest approach will be to the red dwarf star Ross 248 (Gliese 905), passing within 1.7 light-years (0.529 parsecs) approximately 42,000 years from now at a relative speed of 72.3 km/s. Earlier, in about 20,300 years, it will come within 2.9 light-years (0.878 parsecs) of Proxima Centauri, though this remains a distant flyby. These projections account for the relative motions of nearby stars and indicate no encounters closer than 1 light-year within the next million years. At its current velocity, Voyager 2 is expected to reach a distance of 1 light-year from the Sun in roughly 19,400 years. In the far future, Voyager 2 will continue its eternal drift through the galaxy, influenced gradually by galactic tides and stellar encounters that may alter its path over millions of years. The spacecraft, including its attached Golden Record—a gold-plated disc containing sounds, images, and greetings from —serves as a passive designed to endure for up to a billion years in the vacuum of space, potentially available for discovery by should any civilization intercept it during its boundless journey.

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