Heliocentric positions of the fiveinterstellar probes (squares) and other bodies (circles) until 2020, with launch and flyby dates. Markers denote positions on1 January of each year, with every fifth year labelled. Plot 1 is viewed from thenorth ecliptic pole, to scale. Plots 2 to 4 arethird-angle projections at 20% scale. Inthe SVG file, hover over a trajectory or orbit to highlight it and its associated launches and flybys.
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 theSun[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'sheliosphere and is traveling through theinterstellar medium, though still inside theSolar System, joiningVoyager 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 interstellarplasma.[10]
In the early space age, it was realized that aperiodic alignment of the outer planets would occur in the late 1970s and enable a single probe to visitJupiter,Saturn,Uranus, andNeptune by taking advantage of the then-new technique ofgravity assists.NASA began work on aGrand 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 twoMariner 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 ofVoyager 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 forVoyager 1. Upon successful completion ofVoyager 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 byPioneer 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]
Constructed by theJet Propulsion Laboratory (JPL),Voyager 2, whosebus is shaped like a decagonal prism, included 16hydrazine thrusters,three-axis stabilization,gyroscopes and celestial referencing instruments (a Sun sensor, and aCanopusstar tracker) to maintain pointing of thehigh-gain antenna toward Earth. Collectively these instruments are part of theAttitude 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]
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 theDeep Space Network on Earth. Communications are conducted over theS-band (about 13 cm wavelength) andX-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 theinverse-square law.[18] When the spacecraftis unable to communicate with Earth, the Digital Tape Recorder (DTR) can record about 64 megabytes of data for transmission at another time.[19]
Voyager 2 is equipped with threemultihundred-watt radioisotope thermoelectric generators (MHW RTGs). Each RTG includes 24 pressedplutonium 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]
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 hydrazinemonopropellant rocket engines, four providing pitch and yawattitude control, and four for roll control. The propulsion module was jettisoned shortly after the successful Jupiter burn.
Sixteenhydrazine 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]
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.
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 inSaturn's rings.
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.
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.
Utilized a telescope with apolarizer to gather information on surface texture and composition of Jupiter and Saturn and information on atmospheric scattering properties and density for both planets.
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.
TheVoyager 2 probe was launched on August 20, 1977, by NASA fromSpace Launch Complex 41 atCape Canaveral, Florida, aboard aTitan IIIE/Centaurlaunch vehicle. Two weeks later, the twinVoyager 1 probe was launched on September 5, 1977. However,Voyager 1 reached both Jupiter and Saturn sooner, asVoyager 2 had been launched into a longer, more circular trajectory.[36][37]
Voyager 1's initial orbit had anaphelion 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 toVoyager 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 theDoppler effect) and the onboard receiver's temperature, among other things.[40][41]
Animation ofVoyager 2's trajectory from August 20, 1977, to December 30, 2000 Voyager 2· Earth·Jupiter·Saturn·Uranus·Neptune·Sun
Trajectory ofVoyager 2 primary mission
Plot ofVoyager 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]
Animation ofVoyager 2's trajectory around Jupiter Voyager 2· Jupiter· Io· Europa· Ganymede· CallistoThe trajectory ofVoyager 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'sGreat 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 moonsAmalthea,Io,Callisto,Ganymede, andEuropa.[3] During a 10-hour "volcano watch", it confirmedVoyager 1's observations of activevolcanism 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 moonEuropa displayed a large number of intersecting linear features in the low-resolution photos fromVoyager 1. At first, scientists believed the features might be deep cracks, caused by crustal rifting or tectonic processes. Closer high-resolution photos fromVoyager 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 andMetis, were found orbiting just outside the ring.[36] A third new satellite,Thebe, was discovered between the orbits of Amalthea and Io.[36]
The closest approach to Saturn occurred at 03:24:05 UT on August 26, 1981.[45] WhenVoyager 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 alsoSaturn 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 ifVoyager 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
The closest approach to Uranus occurred on January 24, 1986, whenVoyager 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 andPerdita.[B] The mission also studied the planet's unique atmosphere, caused by itsaxial tilt of 97.8°, and examined theUranian ring system.[51] The length of a day on Uranus as measured byVoyager 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]
WhenVoyager 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]
TheVoyager 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 fromVoyager 2's flyby of the Uranian moonMiranda showed huge canyons made fromgeological 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 ortorn up by tidal effects.[36][37]
In March 2020, NASA astronomers reported the detection of a large atmospheric magnetic bubble, also known as aplasmoid, released intoouter space from the planetUranus, after reevaluating old data recorded during the flyby.[58][59]
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 routeVoyager 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 afterVoyager 2 made its closest approach to Neptune, it performed a close fly-by ofTriton, Neptune's largest moon, passing within about 40,000 km (25,000 mi).[61]
In 1989, theVoyager 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] DuringVoyager 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 unknownNeptunian rings,[66] and confirmed six new moons:Despina,Galatea,Larissa,Proteus,Naiad andThalassa.[67][C] While in the neighborhood of Neptune,Voyager 2 discovered the "Great Dark Spot", which has since disappeared, according to observations by theHubble 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]
Voyager 2 left the heliosphere on November 5, 2018.[9]Voyager 1 and2 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 theSolar System is like beyond theheliosphere. As of September 2023[update]Voyager 2 is transmitting scientific data at about 160bits per second.[70] Information about continuing telemetry exchanges withVoyager 2 is available from Voyager Weekly Reports.[71]
In 1992,Voyager 2 observed the novaV1974 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 cometComet 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 toVoyager 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 thetermination shock and then entered into theheliosheath, approximately 1 billion mi (1.6 billion km) closer to the Sun thanVoyager 1 did.[75] This is due to theinterstellar 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 thatVoyager 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 thatVoyager 2 reached interstellar space on November 5, 2018.[8][9]
The position ofVoyager 2 in December 2018. Note the vast distances condensed into alogarithmic 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 thespace beyond theSolar System as detected by theVoyager 1 andVoyager 2; this implies that "the density gradient is a large-scale feature of theVLISM (very localinterstellar medium) in the general direction of theheliospheric nose".[81][82]
On July 18, 2023, Voyager 2 overtookPioneer 10 as the second farthest spacecraft from the Sun.[32][33]
On July 21, 2023, a programming error misalignedVoyager 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 theDeep Space Network.[84][85] A high-power "shout" on August 4 sent from theCanberra 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]
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 onVoyager 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 ofDigital Tape Recorder (DTR) operations (It was no longer needed due to a failure on theHigh Waveform Receiver on thePlasma Wave Subsystem (PWS) on June 30, 2002.)[89]
2008
Power offPlanetary Radio Astronomy Experiment (PRA)[88]
Somethrusters 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 theirhydrazine 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 atJPL, in an interview withArs 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 theVoyager 1 computer, NASA will first try the procedure withVoyager 2, which is closer to Earth.[95]
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 starRoss 248 (10.30 light-years away from Earth) at a distance of 1.7 light-years.[97] If undisturbed for296,000 years,Voyager 2 should pass by the starSirius (8.6 light-years from Earth) at a distance of 4.3 light-years.[98]
A child's greeting in English recorded on theVoyager Golden RecordVoyager Golden Record
Both Voyager space probes carry a gold-platedaudio-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 anyextraterrestrial discoverer.[99][100] The record, made under the direction of a team includingCarl Sagan andTimothy Ferris, includes photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from people such as theSecretary-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 byWolfgang Amadeus Mozart,Blind Willie Johnson,Chuck Berry andValya 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]
^To observeTriton,Voyager 2 passed over Neptune's north pole, resulting in an acceleration out of the plane of the ecliptic, and, as a result, a reduced velocity relative to the Sun.[42]
^Some sources cite the discovery of only 10 Uranian moons byVoyager 2,[52][53] butPerdita was discovered inVoyager 2 images more than a decade after they were taken.[54]
^One of these moons,Larissa, was first reported in 1981 from ground telescope observations, but not confirmed until theVoyager 2 approach.[67]
^abButrica, Andrew.From Engineering Science to Big Science. p. 267.Archived from the original on February 29, 2020. RetrievedSeptember 4, 2015.Despite the name change, Voyager remained in many ways the Grand Tour concept, though certainly not the Grand Tour (TOPS) spacecraft.
^HORIZONSArchived October 7, 2012, at theWayback Machine, JPL Solar System Dynamics (Ephemeris Type ELEMENTS; Target Body: Voyagern (spacecraft); Center: Sun (body center); Time Span:launch + 1 month toJupiter encounter – 1 month)
^Karkoschka, E. (2001). "Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites".Icarus.151 (1):69–77.Bibcode:2001Icar..151...69K.doi:10.1006/icar.2001.6597.
^"Voyager Weekly Reports". Voyager.jpl.nasa.gov. September 6, 2013.Archived from the original on September 21, 2013. RetrievedSeptember 14, 2013.
^abcdUlivi, Paolo; Harland, David M (2007).Robotic Exploration of the Solar System Part I: The Golden Age 1957–1982. Springer. p. 449.ISBN978-0-387-49326-8.
Missions are ordered by launch date. Sign† indicates failure en route or before intended mission data returned.‡ indicates use of the planet as agravity assist en route to another destination.
Payloads are separated by bullets ( · ), launches by pipes ( | ). Crewed flights are indicated inunderline. Uncatalogued launch failures are listed initalics. Payloads deployed from other spacecraft are denoted in (brackets).
![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]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aVoyager_2_velocity_vs_distance_from_sun.svg)
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