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Voyager 2
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{{short description|Space probe and the second-farthest man-made object from Earth}}{{italic title}}{{Use mdy dates|date=October 2019}}{{Use American English|date=March 2018}}







factoids
weblink}}PUBLISHER=US NATIONAL SPACE SCIENCE DATA CENTER, August 25, 2013, PUBLISHER=N2YO, August 25, 2013,
  • {{nowrap|{{time interval|20 August 1977 14:29:00|show=ymd|sep=,{edih} elapsed}}
  • Planetary mission: {{time interval|20 August 1977|2 October 1989|show=ymd|sep=,}}
  • Interstellar mission: {{time interval|2 October 1989|show=ymd|sep=,}} elapsed
}}| spacecraft_type = | manufacturer = Jet Propulsion Laboratory| dry_mass = 825.5lb}}| power = 470 watts (at launch)Titan IIIECape Canaveral Air Force Station>Cape Canaveral LC-41| launch_contractor =| last_contact = | decay_date =|interplanetary =








factoids

|arrival_date = July 9, 1979, 22:29:00 UTC
}}








factoids

|arrival_date = August 26, 1981, 03:24:05 UTC
}}








factoids

|arrival_date = January 24, 1986, 17:59:47 UTC
}}








factoids

|arrival_date = August 25, 1989, 03:56:36 UTC
}}
Flagship Program>Flagship| previous_mission = Viking 2| next_mission = Voyager 1}}Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets.Its primary mission ended with the exploration of the Neptunian system on October 2, 1989, after having visited the Uranian system in 1986, the Saturnian system in 1981, and the Jovian system in 1979. Voyager 2 is now in its extended mission to study the outer reaches of the Solar System and has been operating for {{time interval|20 August 1977 14:29:00|show=ymd}} as of {{date|2=MDY}}. It remains in contact through the NASA Deep Space Network.NASA Voyager - The Interstellar Mission Mission Overview {{webarchive|url=https://web.archive.org/web/20110502011335weblink |date=May 2, 2011 }}At a distance of {{Convert|120|AU|km|abbr=on|sigfig=3}} (about 16.4 light-hours)WEB,weblink Convert light years to astronomical unit - Conversion of Measurement Units, from the Sun as of February 25, 2019, moving at a velocity of {{convert|15.341|km/s|km/h|abbr=on}}WEB,weblink Voyager - Mission Status, relative to the Sun, Voyager 2 is the fourth of five spacecraft to achieve the escape velocity that will allow them to leave the Solar System. The probe left the heliosphere for interstellar space on November 5, 2018,NEWS, Gill, Victoria, Nasa's Voyager 2 probe 'leaves the Solar System',weblink December 10, 2018, BBC News, December 10, 2018, NEWS, Brown, Dwayne, Fox, Karen, Cofield, Calia, Potter, Sean, Release 18-115 - NASA's Voyager 2 Probe Enters Interstellar Space,weblink December 10, 2018, NASA, December 10, 2018, becoming the second artificial object to do so, and has begun to provide the first direct measurements of the density and temperature of the interstellar plasma.NEWS,weblink At last, Voyager 1 slips into interstellar space – Atom & Cosmos, Science News, September 12, 2013, September 17, 2013,weblink" title="web.archive.org/web/20130915214546weblink">weblink September 15, 2013, dead,

History

Background

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 through the entire tour. By 1972 the mission was scaled back and replaced with two Mariner-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.{{rp|263}} As the program progressed, the name was changed to Voyager.Planetary Voyage NASA Jet Propulsion Laboratory – California Institute of Technology. March 23, 2004. Retrieved April 8, 2007.The primary mission of Voyager 1 was to explore Jupiter, Saturn, and Saturn's 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.BOOK, Butrica, Andrew, From Engineering Science to Big Science, 267,weblink September 4, 2015, Despite the name change, Voyager remained in many ways the Grand Tour concept, though certainly not the Grand Tour (TOPS) spacecraft. Voyager 2 was launched on August 20, 1977, followed by Voyager 1 on September 5, 1977. The decision to reverse the order of launch had to do with keeping open the possibility of carrying out the Grand Tour mission to Uranus, Neptune, and beyond. Voyager 2, if boosted by the maximum performance from the Titan-Centaur, could just barely catch the old Grand Tour trajectory and encounter Uranus. Two weeks later, Voyager 1 would leave on an easier and much faster trajectory, visiting Jupiter and Saturn only. Voyager 1 would arrive at Jupiter four months ahead of Voyager 2, then arrive at Saturn nine months earlier. Hence, the second spacecraft launched was Voyager 1, not Voyager 2. The two Voyagers would arrive at Saturn nine months apart, so that if Voyager 1 failed to achieve its Saturn objectives, for whatever reason, Voyager 2 still could be retargeted to achieve them, though at the expense of any subsequent Uranus or Neptune encounter.,

Spacecraft design

Constructed by the Jet Propulsion Laboratory (JPL), Voyager 2 included 16 hydrazine thrusters, three-axis stabilization, gyroscopes and celestial referencing instruments (Sun sensor/Canopus Star Tracker) to maintain pointing of the high-gain antenna toward Earth. 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.WEB,weblink VOYAGER 2:Host Information, 1989, NASA, January 2, 2011,

Communications

Built with the intent for eventual interstellar travel, Voyager 2 included a large, {{convert|3.7|m|ft|abbr=on}} parabolic, high-gain antenna ((:File:Voyager Program - High-gain antenna diagram.png|see diagram)) to transceive data via the Deep Space Network on the 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 the distance increased, because of the inverse-square law. When the spacecraft is unable to communicate with Earth, the Digital Tape Recorder (DTR) can record about 64 kilobytes of data for transmission at another time.WEB, NASA News Press Kit 77-136, JPL/NASA,weblink December 15, 2014,

Power

Voyager 2 is equipped with 3 Multihundred-Watt radioisotope thermoelectric generators (MHW RTG). Each RTG includes 24 pressed plutonium oxide spheres, and provided enough heat to generate approximately 157 W of electrical power at launch. Collectively, the RTGs supplied the spacecraft with 470 watts at launch (halving every 87.7 years), and will allow operations to continue until at least 2020.WEB, Voyager 2 Craft Details,weblink NASA-NSSDC-Spacecraft-Details, NASA, March 9, 2011, JOURNAL, Furlong, Richard R., Wahlquist, Earl J., 1999, U.S. space missions using radioisotope power systems, Nuclear News, 42, 4, 26–34,weblink January 2, 2011, File:Voyager Program - RTG diagram 1.png|RTG inner heat sourceFile:Voyager Program - RTG diagram 2.png|RTG assemblyFile:Voyager Program - RTG upclose.png|RTG unit

Attitude control and propulsion

Because of the energy required to achieve a Jupiter trajectory boost with an {{convert|1819|lb|kg|round=5|adj=on}} payload, the spacecraft included a propulsion module made of a {{convert|2476|lb|kg|round=5|adj=on}} 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 MR-103 thrusters on the mission module provide attitude control.WEB, MR-103,weblink Astronautix.com, December 11, 2018, 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.WEB, Voyager Backgrounder,weblink Nasa.gov, Nasa, December 11, 2018, Thrusters are supplied by a single {{convert|28|in|cm|sigfig=1|adj=on}} diameter spherical titanium tank. It contained {{convert|230|lb|kg}} of hydrazine at launch, providing enough fuel until 2034.WEB, Koerner, Brendan, What Fuel Does Voyager 1 Use?,weblink Slate.com, December 11, 2018, November 6, 2003,

Scientific instruments

{| class="wikitable"! scope="col" style="width:135px;"| Instrument name! scope="col" style="width:50px;"| Abr.! DescriptionImaging Science System {{color{{small|(disabled)}}}}(ISS)| Utilizes a two-camera system (narrow-angle/wide-angle) to provide imagery of Jupiter, Saturn and other objects along the trajectory. More{| class="wikitable collapsible"! colspan="2" | Filters| {| style="text-align:center"! colspan="4" scope="col" style="width:320px;"| Narrow Angle Camera FiltersWEB,weblink Voyager 1 Narrow Angle Camera Description, January 17, 2011, NASA/JPL, August 26, 2003, NASA / PDS, ! scope="col" style="background:#e5e5e5; width:60px;"| Name! style="background: #e5e5e5" | Wavelength! style="background: #e5e5e5" | Spectrum! style="background: #e5e5e5" | Sensitivity| Clear| 280 nm – 640 nm50px|center)Ultraviolet>UV| 280 nm – 370 nm50px|center)| Violet| 350 nm – 450 nm50px|center)| Blue| 430 nm – 530 nm50px|center)| '| '50px|center)| '| Green| 530 nm – 640 nm50px|center)| '| '50px|center)| '| Orange| 590 nm – 640 nm50px|center)| '| '50px|center)| '| {| style="text-align:center"! colspan="4" scope="col" style="width:320px;"| Wide Angle Camera FiltersWEB,weblink Voyager 1 Wide Angle Camera Description, January 17, 2011, NASA/JPL, August 26, 2003, NASA / PDS, ! scope="col" style="background:#e5e5e5; width:60px;"| Name! style="background: #e5e5e5" | Wavelength! style="background: #e5e5e5" | Spectrum! style="background: #e5e5e5" | Sensitivity| Clear| 280 nm – 640 nm50px|center)| '| '50px|center)| '| Violet| 350 nm – 450 nm50px|center)| Blue| 430 nm – 530 nm50px|center)Methane>CH4-U| 536 nm – 546 nm50px|center)| Green| 530 nm – 640 nm50px|center)Sodium>Na-D| 588 nm – 590 nm50px|center)| Orange| 590 nm – 640 nm50px|center)Methane>CH4-JST| 614 nm – 624 nm50px|center) Radio Science System {{color{{small|(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. More Infrared Interferometer Spectrometer {{color{{small|(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. More Ultraviolet Spectrometer {{color{{small|(disabled)}}}}(UVS)| Designed to measure atmospheric properties, and to measure radiation. More Triaxial Fluxgate Magnetometer {{color{{small|(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. More Plasma (physics) Spectrometer {{color>#4CBB17(active)}}}}(PLS)| Investigates the macroscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV. More Low Energy Charged Particle Instrument {{color{{small|(active)}}}}(LECP)| Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition. More Cosmic Ray System {{color{{small|(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. More
  • {{small|Principal investigator: Edward Stone / Caltech / NASA Goddard Space Flight Center (website)}}
  • {{small|Data: NSSDC data archive}}
Planetary Radio Astronomy Investigation {{color{{small|(disabled)}}}}(PRA)| Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn. More
  • {{small|Principal investigator: James Warwick / University of Colorado}}
  • {{small|1=Data: PDS/PPI data catalog}}
Polarimeter System {{color>#E62020(disabled)}}}}(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. More Plasma Wave Subsystem {{color{{small|(partially disabled)}}}}(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. More For more details on the Voyager space probes' identical instrument packages, see the separate article on the overall Voyager Program.{{Gallery| align = centerwidth=175 |lines=2alt1=Voyager spacecraft diagram Voyager spacecraft diagram.}}alt2=Voyager in transport to a solar thermal test chamber Voyager in transport to a solar thermal test chamber.}}alt4=Voyager 2 awaiting payload entry into a Titan IIIE/Centaur rocket Voyager 2 awaiting payload entry into a Titan IIIE/Centaur rocket.}}{{commons-inlineCategory:Voyager spacecraft|the Voyager spacecraft}}}}}}

Mission profile{| class"wikitable collapsible collapsed"

!colspan=2| Images of trajectory(File:Voyager 2 skypath 1977-2030.pngVoyager 2{{'}}s trajectory from the earth, following the ecliptic through 1989 at Neptune and now heading south into the constellation Pavo (constellation)>Pavo400px)Path viewed from above the solar system480px)Path viewed from side, showing distance below ecliptic in gray{| class="wikitable collapsible collapsed"! colspan="2" | Timeline of travel! scope="col" style="width:80px;"| Date! scope="col" style="width:440px;"| Event| 1977-08-20| Spacecraft launched at 14:29:00 UTC.| 1977-12-10| Entered asteroid belt.| 1977-12-19Voyager 1 overtakes Voyager 2. ((:File:Voyager 1 - Voyager 2 - Voyager 1 overtakes Voyager 2.png>see diagram))| 1978-06| Primary radio receiver fails. Remainder of mission flown using backup.| 1978-10-21| Exited asteroid belt| 1979-04-25| Start Jupiter observation phase{| class="wikitable collapsible collapsed"! scope="col" style="width:90px;" | Time! scope="col" style="width:350px;"| Event| 1979-07-08| Encounter with Jovian system.| {{0}}{{0}}12:21Callisto (moon)>Callisto flyby at 214,930 km.| 1979-07-09| | {{0}}{{0}}07:14Ganymede (moon)>Ganymede flyby at 62,130 km.| {{0}}{{0}}17:53Europa (moon)>Europa flyby at 205,720 km.| {{0}}{{0}}20:01Amalthea (moon)>Amalthea flyby at 558,370 km.| {{0}}{{0}}22:29| Jupiter closest approach at 721,670 km from the center of mass.| {{0}}{{0}}23:17Io (moon)>Io flyby at 1,129,900 km.| 1979-08-05| Phase Stop| 1981-06-05| Start Saturn observation phase.{| class="wikitable collapsible collapsed"! scope="col" style="width:90px;"| Time! scope="col" style="width:350px;"| Event| 1981-08-22| Encounter with Saturnian system.| {{0}}{{0}}01:26:57Iapetus (moon)>Iapetus flyby at 908,680 km.| 1981-08-25|| {{0}}{{0}}01:25:26Hyperion (moon)>Hyperion flyby at 431,370 km.| {{0}}{{0}}09:37:46Titan (moon)>Titan flyby at 666,190 km.| {{0}}{{0}}22:57:33Helene (moon)>Helene flyby at 314,090 km.| 1981-08-26|| {{0}}{{0}}01:04:32Dione (moon)>Dione flyby at 502,310 km.| {{0}}{{0}}02:22:17Calypso (moon)>Calypso flyby at 151,590 km.| {{0}}{{0}}02:24:26Mimas (moon)>Mimas flyby at 309,930 km.| {{0}}{{0}}03:19:18Pandora (moon)>Pandora flyby at 107,000 km.| {{0}}{{0}}03:24:05| Saturn closest approach at 161,000 km from the center of mass.| {{0}}{{0}}03:33:02Atlas (moon)>Atlas 287,000 km.| {{0}}{{0}}03:45:16Enceladus (moon)>Enceladus flyby at 87,010 km.| {{0}}{{0}}03:50:04Janus (moon)>Janus at 223,000 km.| {{0}}{{0}}04:05:56Epimetheus (moon)>Epimetheus at 147,000 km.| {{0}}{{0}}06:02:47Telesto (moon)>Telesto at 270,000 km.| {{0}}{{0}}06:12:30Tethys (moon)>Tethys flyby at 93,010 km.| {{0}}{{0}}06:28:48Rhea (moon)>Rhea flyby at 645,260 km.| 1981-09-04| | {{0}}{{0}}01:22:34Phoebe (moon)>Phoebe flyby at 2,075,640 km.| 1981-09-25| Phase Stop| 1985-11-04| Start Uranus observation phase.{| class="wikitable collapsible collapsed"! scope="col" style="width:90px;"| Time! scope="col" style="width:350px;"| Event| 1986-01-24| Encounter with Uranian system. | {{0}}{{0}}16:50Miranda (moon)>Miranda flyby at 29,000 km.| {{0}}{{0}}17:25Ariel (moon)>Ariel flyby at 127,000 km.| {{0}}{{0}}17:25Umbriel (moon)>Umbriel flyby at 325,000 km.| {{0}}{{0}}17:25Titania (moon)>Titania flyby at 365,200 km.| {{0}}{{0}}17:25Oberon (moon)>Oberon flyby at 470,600 km.| {{0}}{{0}}17:59:47| Uranus closest approach at 107,000 km from the center of mass.| 1986-02-25| Phase Stop| 1987-08-20| 10 years of continuous flight and operation at 14:29:00 UTC.| 1989-06-05| Start Neptune observation phase.{| class="wikitable collapsible collapsed"! scope="col" style="width:90px;"| Time! scope="col" style="width:350px;"| Event| 1989-08-25| Encounter with Neptunian system.| {{0}}{{0}}03:56:36| Neptune closest approach at 4,950 km.| {{0}}{{0}}04:51Larissa (moon)>Larissa flyby at 60,180 km.| {{0}}{{0}}05:29Proteus (moon)>Proteus flyby at 97,860 km.| {{0}}{{0}}09:23Triton (moon)>Triton flyby at 39,800 km.| 1989-10-02| Phase Stop| 1989-10-02| Begin Voyager Interstellar Mission.! colspan="2" scope="col" | Interstellar phase"Voyager 2 Full Mission Timeline" {{Webarchive|url=https://web.archive.org/web/20110723095346weblink |date=July 23, 2011 }} Muller, Daniel, 2010"Voyager Mission Description" NASA, February 19, 1997"JPL Mission Information" NASA, JPL, PDS.| 1997-08-20| 20 years of continuous flight and operation at 14:29:00 UTC.| 1998-11-13| Terminate scan platform and UV observations.| 2007-08-20| 30 years of continuous flight and operation at 14:29:00 UTC.| 2007-09-06| Terminate data tape recorder operations.| 2008-02-22| Terminate planetary radio astronomy experiment operations.| 2011-11-07DATE=NOVEMBER 5, 2011 LAST=SULLIVANT PUBLISHER=JPL, | 2017-08-20| 40 years of continuous flight and operation at 14:29:00 UTC.| 2018-11-05Heliopause (astronomy)>heliopause and entered interstellar space.{{clear}}

Launch and trajectory

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.File:Titan 3E Centaur launches Voyager 2.jpg | Voyager 2 launch on August 20, 1977 with a Titan IIIE/Centaur.File:Animation of Voyager 2 trajectory.gif|thumb|Animation of Voyager 2{{'s}} trajectory from August 20, 1977 to December 30, 2000{{legend2|magenta| Voyager 2 }}{{·}}{{legend2|Royalblue|Earth}}{{·}}{{legend2|Lime|Jupiter}} {{·}}{{legend2| Cyan |Saturn}}{{·}}{{legend2| Gold |Uranus }}{{·}}{{legend2| OrangeRed |Neptune }}{{·}}{{legend2| Yellow |Sun }}File:Voyager 2 path.svg | Trajectory of Voyager 2 primary mission.File:Voyager 2 velocity vs distance from sun.svg | 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. To observe Triton, 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.WEB,weblink Basics of space flight: Interplanetary Trajectories, Voyager 1′s initial orbit had an aphelion of 8.9 AU, just a little short of Saturn's orbit of 9.5 AU. Voyager 2′s initial orbit had an aphelion of 6.2 AU, 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, a complication arose when 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.MAGAZINE, All set to encounter Uranus, 24, Henbest, Nigel, January 31, 1985, New Scientist,weblink 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.BOOK, Planets Beyond: Discovering the Outer Solar System, Littmann, Mark, 2004, Courier Corporation, 106,weblink 978-0-486-43602-9, MAGAZINE, Voyage to the tilted planet, Davies, John, January 23, 1986, 42, New Scientist,weblink For each subsequent transmission to Voyager 2, it was necessary for engineers to calculate the specific frequency for the signal so that it could be received by the spacecraft.

Encounter with Jupiter

(File:Voyager-2 Jupiter-flyby July-10-1979.png|thumb|The trajectory of Voyager 2 through the Jupiter system)Voyager 2{{'}}s closest approach to Jupiter occurred at 22:29 UT on July 9, 1979. It came within {{convert|570,000|km|mi|abbr=on}} of the planet's cloud tops.WEB,weblink History, www.jpl.nasa.gov, 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.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 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.National Aeronautics and Space Administration "Voyager 2" NASA Science: Solar System Exploration. Updated 26 January 26, 2018. Accessed December 12, 2018. 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.WEB,weblink Voyager Fact Sheet, JPL, December 11, 2018, 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 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 {{convert|30|km|mi|abbr=on}} thick) of water ice, possibly floating on a 50-kilometer-deep (30 mile) 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.{{Gallery| align = centerlines=2alt1=The Great Red Spot photographed during the Voyager 2 flyby of Jupiter The Great Red Spot photographed during the Voyager 2 flyby of Jupiter.}}alt2=A transit of Io across Jupiter, July 9, 1979 A transit of Io across Jupiter, July 9, 1979.}}alt3=Several faint volcanic eruptions on Io, photographed by Voyager 2 Several faint volcano eruptions on Io (moon)>Io, photographed by Voyager 2.}}alt4=A color mosaic of Europa A color mosaic of Europa.}}}}{{Gallery| align = center|width=175 |lines=2alt1=A color mosaic of Ganymede A color mosaic of Ganymede.}}alt2=Callisto photographed at a distance of 1 million kilometers Callisto photographed at a distance of 1 million kilometers.}}alt3=One ring of Jupiter photographed during the Voyager 2 flyby of Jupiter One faint ring of Jupiter photographed during the flyby.}}alt4=An eruptive event that occurred as Voyager 2 approached Jupiter Atmospheric eruptive event on Jupiter.}}{{commons-inlineCategory:Photos of Jupiter system by Voyager 2|the Voyager 2 Jupiter encounter}}}}}}

Encounter with Saturn

The closest approach to Saturn occurred on August 26, 1981.WEB,weblink NASA - NSSDCA - Master Catalog - Event Query, nssdc.gsfc.nasa.gov, While passing behind Saturn (as viewed from Earth), Voyager 2 probed Saturn's upper atmosphere with its radio link to gather information on atmospheric temperature and density profiles. Voyager 2 found that at the uppermost pressure levels (seven kilopascals of pressure), Saturn's temperature was 70 kelvins (−203 Â°C), while at the deepest levels measured (120 kilopascals) the temperature increased to 143 K (−130 Â°C). The north pole was found to be 10 kelvins cooler, although this may be seasonal (see also Saturn Oppositions).After the fly-by of Saturn, the camera platform of Voyager 2 locked up briefly, putting plans to officially extend the mission to Uranus and Neptune in jeopardy. The mission's engineers were able to fix the problem (caused by an overuse that temporarily depleted its lubricant), and the Voyager 2 probe was given the go-ahead to explore the Uranian system.{{Gallery| align = centerlines=2alt1=Voyager 2 Saturn approach view Voyager 2 Saturn approach view.}}alt2=North, polar region of Saturn imaged in orange and UV filters North, polar region of Saturn imaged in orange and UV filters.}}alt3=Color image of Enceladus showing terrain of widely varying ages Color image of Enceladus showing terrain of widely varying ages.}}alt4=Cratered surface of Tethys at 594,000 km Cratered surface of Tethys at 594,000 km.}}}}{{Gallery| align = center|width=175 |lines=2alt1=Atmosphere of Titan imaged from 2.3 million km Atmosphere of Titan imaged from 2.3 million km.}}alt2=Titan occultation of the Sun from 0.9 million km Titan occultation of the Sun from 0.9 million km.}}alt3=Two-toned Iapetus from Voyager 2, August 22, 1981 Two-toned Iapetus, August 22, 1981.}}alt4="Spoke" features observed in the rings of Saturn "Spoke" features observed in the rings of Saturn.}}{{commons-inlineCategory:Photos of Saturn system by Voyager 2|the Voyager 2 Saturn encounter}}}}}}

Encounter with Uranus

The closest approach to Uranus occurred on January 24, 1986, when Voyager 2 came within {{convert|81,500|km|mi|sp=us}} of the planet's cloudtops."Uranus Approach" NASA Jet Propulsion Laboratory, California Institute of Technology. Accessed December 11, 2018. Voyager 2 also discovered 11 previously unknown moons: Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalind, Belinda, Puck and Perdita.{{efn-ua|Some sources cite the discovery of only 10 Uranian moons by Voyager 2, but Perdita was discovered in Voyager 2 images more than a decade after they were taken.JOURNAL, 10.1006/icar.2001.6597, Voyager's Eleventh Discovery of a Satellite of Uranus and Photometry and the First Size Measurements of Nine Satellites, Icarus, 151, 1, 69–77, 2001, Karkoschka, E., 2001Icar..151...69K, }} The mission also studied the planet's unique atmosphere, caused by its axial tilt of 97.8°; and examined the Uranian ring system. The length of a day on Uranus as measured by Voyager 2 is 17 hours, 14 minutes. 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,JOURNAL, 10.1088/0034-4885/56/6/001, Planetary magnetospheres, Reports on Progress in Physics, 56, 6, 687–732, 1993, Russell, C. T., 1993RPPh...56..687R, and a helix-shaped magnetic tail stretching 10 million kilometers (6 million miles) away from the Sun.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 (−350°F/−213°C). Surprisingly, the illuminated and dark poles, and most of the planet, exhibit nearly the same temperatures at the cloud tops.Detailed images from Voyager 2{{'}}s 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 distinctly 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.{{Gallery| align = centerlines=1alt1=Uranus as viewed by Voyager 2 Uranus as viewed by Voyager 2}}alt2=Departing image of crescent Uranus Departing image of crescent Uranus.}}alt3=Fractured surface of Miranda Fractured surface of Miranda.}}alt4=Ariel imaged from 130,000 km Ariel as imaged from 130,000 km.}}}}{{Gallery| align = center|width=175 |lines=2alt1=Titania imaged from 500,000 km Color composite of Titania from 500,000 km.}}alt2=Umbriel imaged from 550,000 km Umbriel imaged from 550,000 km.}}alt3=Oberon imaged from 660,000 kmOberon imaged from 660,000 km.}}alt4=Voyager 2 photo of the Rings of Uranus The rings of Uranus imaged by Voyager 2.}}{{commons-inlineCategory:Photos of Uranus system by Voyager 2|the Voyager 2 Uranus encounter}}}}}}

Encounter with Neptune

Following a mid-course correction in 1987, Voyager 2{{'}}s closest approach to Neptune occurred on August 25, 1989.NEWS, Voyager Steered Toward Neptune,weblink December 6, 2017, Ukiah Daily Journal, March 15, 1987, WEB,weblink Fact Sheet, JPL, March 3, 2016, {{Harvnb|Nardo|2002|p=15|Ref=none}} 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 mid-course corrections, Voyager 2 was directed into a path about 4950 kilometers (3000 mi) above the north pole of Neptune.WEB, Neptune,weblink Jet Propulsion Laboratory, March 3, 2016, Five hours after Voyager 2 made its closest approach to Neptune, it performed a close fly-by of Triton, the larger of Neptune's two originally known moons, passing within about 40,000 kilometers (25,000 mi).National Aeronautics and Space Administration "Neptune Approach" NASA Jet Propulsion Laboratory: California Institute of Technology. Accessed December 12, 2018.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.{{efn-ua|One of these moons, Larissa, was first reported in 1981 from ground telescope observations, but not confirmed until the Voyager 2 approach.}} 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.With the decision of the International Astronomical Union to reclassify Pluto as a dwarf planet in 2006,"Pluto loses status as a planet" BBC News, August 24, 2006. Accessed December 12, 2018. the flyby of Neptune by Voyager 2 in 1989 became the point when every known planet in the Solar System had been visited at least once by a space probe.{{Gallery| align = centerlines=2alt1=Voyager 2 image of Neptune Voyager 2 image of Neptune.}}alt2=Neptune and Triton three days after Voyager's flyby Neptune and Triton three days after Voyager 2 flyby.}}alt3=Despina as imaged from Voyager 2 Despina as imaged from Voyager 2.}}alt4=Cratered surface of Larissa Cratered surface of Larissa.}}}}{{Gallery| align = center|width=175 |lines=2alt1=Dark surface of Proteus Dark surface of Proteus.}}alt2=Color mosaic of Voyager 2 Triton Color mosaic of Voyager 2 Triton.}}alt3=Cirrus clouds imaged above gaseous Neptune Cirrus clouds imaged above gaseous Neptune.}}alt4=Rings of Neptune taken in occulation from 280,000km Rings of Neptune taken in occultation from 280,000 km.}}{{commons-inlineCategory:Photos of Neptune system by Voyager 2|the Voyager 2 Neptune encounter}}}}}}

Interstellar mission

(File:PIA22924-Voyager2LeavesTheSolarSystem-20181105.jpg|thumb|right|300px|Voyager 2 left the heliosphere on November 5, 2018.)(File:Voyager speed and distance from Sun.svg|thumb|300px|right|Voyager 1 and 2 speed and distance from Sun)(File:Voyager spacecraft structurePWSred.jpg|thumb|On Voyager 2, both PWS and PRS have remained active, whereas on Voyager 1 the PRS has been off since 2007)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. Voyager 2 is currently transmitting scientific data at about 160 bits per second. Information about continuing telemetry exchanges with Voyager 2 is available from Voyager Weekly Reports.WEB,weblink Voyager Weekly Reports, Voyager.jpl.nasa.gov, September 6, 2013, September 14, 2013, File:Outersolarsystem-probes-4407b.svg|thumb|right|300px|alt=yellow spot surrounded by three concentric light-blue ellipses labeled from inside to out: Saturn, Uranus and Neptune. A grey ellipse labeled Pluto overlaps Neptune's ellipse. Four colored lines trail outwards from the central spot: a short red line labelled Voyager 2 traces to the right and up; a green and longer line labelled Pioneer 11 traces to the right; a purple line labelled Voyager 1 traces to the bottom right corner; and a dark blue line labelled Pioneer 10 traces left|Map showing location and trajectories of the Pioneer 10, Pioneer 11, Voyager 1Voyager 1In 1992, Voyager 2 observed the nova V1974 Cygni in the far-ultraviolet.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.BOOK, Ulivi, Paolo, Harland, David M, 2007, Robotic Exploration of the Solar System Part I: The Golden Age 1957-1982, Springer, 449, 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 {{convert|130|°C|°F|abbr=on}}, significantly higher than the magnetometers were designed to endure, and a sensor rotated away from the correct orientation. As of this date{{When|date=May 2019}} it had not been possible to fully diagnose and correct for the damage caused to Voyager 2's magnetometer, although efforts to do so were proceeding.Notes on Voyager 2 Quick Look Data: Data after November 29, 2006{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }}On August 30, 2007, Voyager 2 passed the termination shock and then entered into the heliosheath, approximately 1 billion miles (1.6 billion km) closer to the Sun than Voyager 1 did.WEB,weblink NASA - Voyager 2 Proves Solar System Is Squashed, www.nasa.gov, 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.NEWS,weblink NASA working on Voyager 2 data problem, John Antczak, May 6, 2010, Associated Press, On May 17, 2010, JPL engineers revealed that a flipped bit in an on-board computer had caused the issue, and scheduled a bit reset for May 19.WEB,weblink Engineers Diagnosing Voyager 2 Data System, Jet Propulsion Laboratory, May 17, 2010, On May 23, 2010, Voyager 2 resumed sending science data from deep space after engineers fixed the flipped bit.WEB,weblink NASA Fixes Bug On Voyager 2, May 25, 2010, Currently research is being made into marking the area of memory with the flipped bit off limits or disallowing its use. The Low-Energy Charged Particle Instrument is currently operational, and data from this instrument concerning charged particles is being transmitted to Earth. This data permits measurements of the heliosheath and termination shock. There has also been a modification to the on-board flight software to delay turning off the AP Branch 2 backup heater for one year. It was scheduled to go off February 2, 2011 (DOY 033, 2011–033).On July 25, 2012, Voyager 2 was traveling at 15.447 km/s relative to the Sun at about {{Convert|99.13|AU|km}} from the Sun,WEB, Staff,weblink Where are the Voyagers?, September 9, 2012, NASA, September 9, 2012, at −55.29° declination and 19.888 h right ascension, and also at an ecliptic latitude of −34.0 degrees, placing it in the constellation Telescopium as observed from Earth.WEB,weblink Spacecraft escaping the Solar System, Heavens Above, Peat, Chris, May 23, 2010, This location places it deep in the scattered disc, and traveling outward at roughly 3.264 AU per year. It is more than twice as far from the Sun as Pluto, and far beyond the perihelion of 90377 Sedna, but not yet beyond the outer limits of the orbit of the dwarf planet Eris.On September 9, 2012, Voyager 2 was {{Convert|99.077|AU|km mi|abbr=on}} from the Earth and {{Convert|99.504|AU|km mi|abbr=on}} from the Sun; and traveling at {{Convert|15.436|km/s|mph|abbr=on}} (relative to the Sun) and traveling outward at about 3.256 AU per year.WEB, Peat, Chris, Spacecraft escaping the Solar System,weblink September 9, 2012, Heavens-Above, September 9, 2012, Sunlight takes 13.73 hours to get to Voyager 2. The brightness of the Sun from the spacecraft is magnitude -16.7. Voyager 2 is heading in the direction of the constellation Telescopium. (To compare, Proxima Centauri, the closest star to the Sun, is about 4.2 light-years (or {{val|2.65|e=5|u=AU}}) distant. Voyager 2's current relative velocity to the Sun is {{convert|15.436|km/s|km/h mph|abbr=on}}. This calculates as 3.254 AU per year, about 10% slower than Voyager 1. At this velocity, 81,438 years would pass before Voyager 2 reaches the nearest star, Proxima Centauri, were the spacecraft traveling in the direction of that star. (Voyager 2 will need about 19,390 years at its current velocity to travel a complete light year)On November 7, 2012, Voyager 2 reached 100 AU from the sun, making it the third human-made object to reach 100 AU. Voyager 1 was 122 AU from the Sun, and Pioneer 10 is presumed to be at 107 AU. While Pioneer has ceased communications, both the Voyager spacecraft are performing well and are still communicating.In 2013, Voyager 1 was escaping the Solar System at a speed of about 3.6 AU per year, while Voyager 2 was only escaping at 3.3 AU per year.WEB,weblink Voyager - Fast Facts, voyager.jpl.nasa.gov, (Each year Voyager 1 increases its lead over Voyager 2)By February 25, 2019, Voyager 2 was at a distance of {{Convert|120|AU|km|abbr=on|sigfig=3}} from the Sun. There is a variation in distance from Earth caused by the Earth's revolution around the Sun relative to Voyager 2.It was originally thought that Voyager 2 would enter interstellar space in early 2016, with its plasma spectrometer providing the first direct measurements of the density and temperature of the interstellar plasma.NEWS,weblink At last, Voyager 1 slips into interstellar space – Atom & Cosmos, Science News, September 12, 2013, September 17, 2013,weblink" title="web.archive.org/web/20130915214546weblink">weblink September 15, 2013, dead, In December 2018, the Voyager project scientist, Edward C. Stone, announced that Voyager 2 reached interstellar space on November 5, 2018.(File:PIA22921-Voyager2-Position-20181210.jpg|thumb|center|600px|The current position of Voyager 2 as of December 2018. Note the vast distances condensed into an exponential scale: Earth is 1 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.)

Terminations and future of the probe

Voyager 2 is not headed toward any particular star, although in roughly 42,000 years it will pass 1.7 light-years from the star Ross 248.WEB, June 22, 2007,weblink Voyager – Mission – Interstellar Mission, NASA, August 14, 2013, JOURNAL, Future stellar flybys of the Voyager and Pioneer spacecraft, Research Notes of the AAS, 3, 4, 59, RNAAS 3, 59, April 3, 2019, 10.3847/2515-5172/ab158e, Bailer-Jones, Coryn A. L., Farnocchia, Davide, 2019RNAAS...3d..59B, And if undisturbed for 296,000 years, Voyager 2 should pass by the star Sirius at a distance of 4.3 light-years. Voyager 2 is expected to keep transmitting weak radio messages until at least the mid 2020s, more than 48 years after it was launched.WEB,weblink Voyager – Spacecraft – Spacecraft Lifetime, May 25, 2008, March 15, 2008, NASA Jet Propulsion Laboratory, As the power from the RTG slowly reduces, various items of equipment have been turned off on both spacecraft.WEB,weblink Voyager - Operations Plan to the End Mission, voyager.jpl.nasa.gov, en, September 20, 2019, The first science equipment turned off on Voyager 2, was the PPS in 1991, which saved 1.2 watts.{| class="wikitable"! Year || End of specific capabilities as a result of the available electrical power limitationsWEB,weblink Voyager - The Spacecraft, voyager.jpl.nasa.gov, | Termination of scan platform and UVS observationsDigital 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.)HTTPS://VOYAGER.JPL.NASA.GOV/SPACECRAFT/SPACECRAFTLIFE.HTML ACCESSDATE=DECEMBER 2, 2009 PUBLISHER=NASA JET PROPULSION LABORATORY, | Power off Planetary Radio Astronomy Experiment (PRA)gyroscope>gyroscopic operations?| CRS heater turned offweblink| Initiate instrument power sharing| Can no longer power any single instrument

Golden record

(File:Voyager Golden Record greeting in English.ogg|thumb|A child's greeting in English recorded on the Voyager Golden Record)(File:Voyager Golden Record fx.png|thumb|150px|left|Voyager Golden Record)Each Voyager space probe carries a gold-plated audio-visual disc in the event that either spacecraft is ever found by intelligent life-forms from other planetary systems.MAGAZINE, Ferris, Timothy, Timothy Ferris on Voyagers' Never-Ending Journey,weblink May 2012, Smithsonian (magazine), Smithsonian Magazine, June 15, 2012, The discs carry photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from the people (e.g. the Secretary-General of the United Nations and the President of the United States, and the children of the Planet Earth) 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, including works by Wolfgang Amadeus Mozart, Blind Willie Johnson, Chuck Berry's "Johnny B. Goode", Valya Balkanska and other Eastern and Western classics and ethnic performers.WEB,weblink Voyager Golden record, August 18, 2013, JPL, (see also Music in space)

See also

{{interstellar_probes_trajectory.svg}}

Notes

{{Reflist|group=upper-alpha}}

References

{{Reflist}}

Further reading

  • WEB, Saturn Science Results, Voyager Science Results at Saturn,weblink February 8, 2005,
  • WEB, Uranus Science Results, Voyager Science Results at Uranus,weblink February 8, 2005,
  • Nardo, Don (2002). Neptune. Thomson Gale. {{ISBN|0-7377-1001-2}}
  • JPL Voyager Telecom Manual

External links

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