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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 from Earth .
The probe entered the interstellar medium on November 5, 2018, at a distance of from the Sun and moving at a velocity of 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. Voyager 2 has begun to provide the first direct measurements of the density and temperature of the interstellar plasma.
Voyager 2 is in contact with Earth through the NASA Deep Space Network.NASA Voyager – The Interstellar Mission Mission Overview Communications are the responsibility of Australia's DSS 43 communication antenna, near Canberra.
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. 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.
Sixteen hydrazine Aerojet MR-103 thrusters on the mission module provide attitude control. 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.
Thrusters are supplied by a single diameter spherical titanium tank. It contained of hydrazine at launch, providing enough fuel until 2034.
| (ISS) | Utilized a two-camera system (narrow-angle/wide-angle) to provide imagery of the outer planets and other objects along the trajectory. { | class="wikitable collapsible" | |
| { style="text-align:center" ! colspan="4" scope="col" style="width:320px;" | Narrow Angle Camera Filters | ||
| Clear | 280–640 nm; 460 nm center | ||
| Ultraviolet | 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 | ||
| ' | ' | ' |
| Clear | 280–640 nm; 460 nm center | ||
| ' | ' | ' | |
| Violet | 350–450 nm; 400 nm center | ||
| Blue | 430–530 nm; 480 nm center | ||
| Methane-U | 536–546 nm; 514 nm center | ||
| Green | 530–640 nm; 585 nm center | ||
| Sodium-D | 588–590 nm; 589 nm center | ||
| Orange | 590–640 nm; 615 nm center | ||
| Methane-JST | 614–624 nm; 619 nm center |
| | (RSS) | style="text-align:left;" | 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. |-
| | (IRIS) | style="text-align:left;" | 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. |-
| | (UVS) | style="text-align:left;" | Designed to measure atmospheric properties, and to measure radiation. |-
| | (MAG) | style="text-align:left;" | 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. |-
| | (PLS) | style="text-align:left;" | Investigates the macroscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV. |-
| | (LECP) | style="text-align:left;" | Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition. |-
| | (CRS) | style="text-align:left;" | 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. |-
| | (PRA) | style="text-align:left;" | Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. |-
| | (PPS) | style="text-align:left;" | 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. |-
| | style="text-align:center" |(PWS) | style="text-align:left;" | 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. |}
Voyager 2s trajectory from the Earth, following the ecliptic through 1989 at Neptune and now heading south into the constellation Pavo | |
Path viewed from above the Solar System | Path viewed from side, showing distance below ecliptic in gray |
| 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 { | class="wikitable collapsible collapsed" |
| 1979-07-08 | Encounter with Jovian system. | |
| 12:21 | Callisto flyby at 214,930 km. | |
| 1979-07-09 | ||
| 07:14 | Ganymede flyby at 62,130 km. | |
| 17:53 | Europa flyby at 205,720 km. | |
| 20:01 | Amalthea flyby at 558,370 km. | |
| 22:29 | Jupiter closest approach at 721,670 km from the center of mass. | |
| 23:17 | Io flyby at 1,129,900 km. | |
| 1979-08-05 | Phase Stop |
| 1981-08-22 | Encounter with Saturnian system. |
| 01:26:57 | Iapetus flyby at 908,680 km. |
| 1981-08-25 | |
| 01:25:26 | Hyperion flyby at 431,370 km. |
| 09:37:46 | Titan flyby at 666,190 km. |
| 22:57:33 | Helene flyby at 314,090 km. |
| 1981-08-26 | |
| 01:04:32 | Dione flyby at 502,310 km. |
| 02:22:17 | Calypso flyby at 151,590 km. |
| 02:24:26 | Mimas flyby at 309,930 km. |
| 03:19:18 | Pandora flyby at 107,000 km. |
| 03:24:05 | Saturn closest approach at 161,000 km from the center of mass. |
| 03:33:02 | Atlas 287,000 km. |
| 03:45:16 | Enceladus flyby at 87,010 km. |
| 03:50:04 | Janus at 223,000 km. |
| 04:05:56 | Epimetheus at 147,000 km. |
| 06:02:47 | Telesto at 270,000 km. |
| 06:12:30 | Tethys flyby at 93,010 km. |
| 06:28:48 | Rhea flyby at 645,260 km. |
| 1981-09-04 | |
| 01:22:34 | Phoebe flyby at 2,075,640 km. |
| 1981-09-25 | Phase Stop |
| 1986-01-24 | Encounter with Uranian system. |
| 16:50 | Miranda flyby at 29,000 km. |
| 17:25 | Ariel flyby at 127,000 km. |
| 17:25 | Umbriel flyby at 325,000 km. |
| 17:25 | Titania flyby at 365,200 km. |
| 17:25 | Oberon flyby at 470,600 km. |
| 17:59:47 | Uranus closest approach at 107,000 km from the center of mass. |
| 1986-02-25 | Phase Stop |
| 1989-08-25 | Encounter with Neptunian system. |
| 03:56:36 | Neptune closest approach at 4,950 km. |
| 04:41 | Galatea flyby at 18,360 km. |
| 04:51 | Larissa flyby at 60,180 km. |
| 05:29 | Proteus flyby at 97,860 km. |
| 09:23 | Triton flyby at 39,800 km. |
| 1989-10-02 | Phase Stop |
Voyager 1s initial orbit had an aphelion of , just a little short of Saturn's orbit of . Whereas, Voyager 2s initial orbit had an aphelion of , well short of Saturn's orbit. HORIZONS , JPL Solar System Dynamics (Ephemeris Type ELEMENTS; Target Body: Voyager n (spacecraft); Center: Sun (body center); Time Span: launch + 1 month to Jupiter encounter – 1 month)
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. 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.
File:Voyager 2 path.svg|Trajectory of Voyager 2 primary mission
File:Voyager 2 velocity vs distance from sun.svg|Plot of Voyager 2 heliocentric velocity against its distance from the Sun, illustrating the use of gravity assists to accelerate the spacecraft by Jupiter, Saturn and Uranus.
Voyager 2 returned images of Jupiter, as well as its moons Amalthea, Io, Callisto, Ganymede, and Europa. During a 10-hour "volcano watch", it confirmed Voyager 1s 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. 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.
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". 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 thick) of water ice, possibly floating on a -deep ocean.
Two new, small satellites, Adrastea and Metis, were found orbiting just outside the ring. A third new satellite, Thebe, was discovered between the orbits of Amalthea and Io.
After its Saturn fly-by, Voyager 2s 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, 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. 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.
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 . The illuminated and dark poles, and most of the planet, exhibit nearly the same temperatures at the cloud tops.
The Voyager 2 Planetary Radio Astronomy (PRA) experiment observed 140 lightning flashes, or Uranian electrostatic discharges with a frequency of 0.9-40 MHz. The UEDs were detected from of Uranus over 24 hours, most of which were not visible. However, microphysical modeling suggests that Uranian lightning occurs in convective storms occurring in deep troposphere water clouds. If this is the case, lightning will not be visible due to the thick cloud layers above the troposphere. 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.
Detailed images from Voyager 2s flyby of the Uranian moon Miranda showed huge canyons made from geological faults.Elizabeth Landau (2016) "Voyager Mission Celebrates 30 Years Since Uranus" National Aeronautics and Space Administration, January 22, 2016. Accessed December 11, 2018 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.
Voyager 2 discovered two previously unknown Uranian rings.Voyager 2 Mission Team (2012) "1986: Voyager at Uranus" NASA Science: Solar System Exploration, December 14, 2012. Accessed December 11, 2018. 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 Roche limit.
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.
In 1989, the Voyager 2 Planetary Radio Astronomy (PRA) experiment observed around 60 lightning flashes, or Neptunian electrostatic discharges emitting energies over 7×10 J. A plasma wave system (PWS) detected 16 electromagnetic wave events with a frequency range of 50 Hz – 12 kHz at magnetic latitudes 7˚–33˚. These plasma wave detections were possibly triggered by lightning over 20 minutes in the ammonia clouds of the magnetosphere. During Voyager 2s closest approach to Neptune, the PWS instrument provided Neptune’s first plasma wave detections at a sample rate of 28,800 samples per second. The measured plasma densities range from 10 – 10 cm.
Voyager 2 discovered previously unknown Neptunian rings,National Aeronautics and Space Administration "Neptune Moons" NASA Science: Solar System Exploration. Updated December 6, 2017. Accessed December 12, 2018. and confirmed six new moons: Despina, Galatea, Larissa, Proteus, Naiad and Thalassa.Elizabeth Howell (2016) "Neptune's Moons: 14 Discovered So Far" Space.com, June 30, 2016. Accessed December 12, 2018. 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.Phil Plait (2016) "Neptune Just Got a Little Dark" Slate, June 24, 2016. Accessed December 12, 2018. 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.National Aeronautics and Space Administration (1998) "Hubble Finds New Dark Spot on Neptune" NASA Jet Propulsion Laboratory: California Institute of Technology, August 2, 1998. Accessed December 12, 2018.
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.
In July 1994, an attempt was made to observe the impacts from fragments of the comet Comet Shoemaker–Levy 9 with Jupiter. 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. Voyager 2 failed to detect anything, with calculations showing that the fireballs were just below the craft's limit of detection. (2025). 9780387493268, Springer. ISBN 9780387493268
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 , significantly higher than the magnetometers were designed to endure, and a sensor rotated away from the correct orientation.
On August 30, 2007, Voyager 2 passed the termination shock and then entered into the heliosheath, approximately closer to the Sun than Voyager 1 did. This is due to the interstellar magnetic field of deep space. The southern hemisphere of the Solar System's heliosphere is being pushed in. Voyager 2 finds solar system's shape is 'dented' # 2007-12-10, Week Ending December 14, 2007. Retrieved December 12, 2007.
On April 22, 2010, Voyager 2 encountered scientific data format problems. 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. On May 23, 2010, Voyager 2 resumed sending science data from deep space after engineers fixed the flipped bit.
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. Finally, in December 2018, Stone announced that Voyager 2 reached interstellar space on November 5, 2018.
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. On February 12, 2021, full communications were restored after a major ground station antenna upgrade that took a year to complete.
In October 2020, astronomers reported a significant unexpected increase in density in the outer 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".
On July 18, 2023, Voyager 2 overtook Pioneer 10 as the second farthest spacecraft from the Sun.
On July 21, 2023, a programming error misaligned Voyager 2
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. 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.
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