View source for Astronomy:Voyager program

{{Short description|Ongoing NASA interstellar program}}

[[File:Voyager probes with the outer worlds.jpg|thumb|250px|A poster of the planets and moons visited during the Voyager program.]]

The '''Voyager program''' is an American scientific program that employs two [[Astronomy:Interstellar probe|interstellar probe]]s, ''[[Astronomy:Voyager 1|Voyager 1]]'' and ''[[Astronomy:Voyager 2|Voyager 2]]''. They were launched in 1977 to take advantage of a favorable planetary alignment to explore the two gas giants [[Astronomy:Jupiter|Jupiter]] and [[Astronomy:Saturn|Saturn]] and potentially also the ice giants, Uranus and Neptune—to [[Engineering:Flyby (spaceflight)|fly near them]] while collecting data for transmission back to Earth. After ''Voyager 1'' successfully completed its flyby of Saturn and its moon [[Astronomy:Titan (moon)|Titan]], it was decided to send ''Voyager 2'' on flybys of [[Astronomy:Uranus|Uranus]] and [[Astronomy:Neptune|Neptune]].<ref name="The Fantastic Voyage of Voyager">{{cite web|title=The Fantastic Voyage of Voyager|url=https://www.theattic.space/home-page-blogs/2020/1/9/the-astonishing-voyage-of-voyager|website=The Attic|date=9 January 2020|access-date=3 March 2020|archive-date=13 April 2020|archive-url=https://web.archive.org/web/20200413080737/https://www.theattic.space/home-page-blogs/2020/1/9/the-astonishing-voyage-of-voyager|url-status=live}}</ref> 

After the planetary flybys were complete, decisions were made to keep the probes in operation to explore [[Astronomy:Outer space|interstellar space]] and the outer regions of the Solar System. On 25 August 2012, data from ''Voyager 1'' indicated that it had entered interstellar space.<ref name="JPL.NASA" /> On 5 November 2019, data from ''Voyager 2'' indicated that it also had entered interstellar space.<ref name="NASA-20181210" /> On 4 November 2019, scientists reported that on 5 November 2018, the ''Voyager 2'' probe had officially reached the [[Astronomy:Interstellar medium|interstellar medium]] (ISM), a region of [[Astronomy:Outer space|outer space]] beyond the influence of the [[Astronomy:Solar wind|solar wind]], as did ''Voyager 1'' in 2012.<ref name="EA-20191104">{{cite news |author=University of Iowa |title=Voyager 2 reaches interstellar space – Iowa-led instrument detects plasma density jump, confirming spacecraft has entered the realm of the stars |url=https://www.eurekalert.org/pub_releases/2019-11/uoi-v2r103119.php |date=4 November 2019 |work=EurekAlert! |access-date=4 November 2019 |archive-date=13 April 2020 |archive-url=https://web.archive.org/web/20200413080722/https://www.eurekalert.org/pub_releases/2019-11/uoi-v2r103119.php |url-status=live }}</ref><ref name="NYT-20191104">{{cite news |last=Chang |first=Kenneth |title=Voyager 2's Discoveries From Interstellar Space – In its journey beyond the boundary of the solar wind's bubble, the probe observed some notable differences from its twin, Voyager 1. |url=https://www.nytimes.com/2019/11/04/science/voyager-2-interstellar-solar-wind.html |date=4 November 2019 |work=The New York Times |access-date=5 November 2019 |archive-date=13 April 2020 |archive-url=https://web.archive.org/web/20200413080724/https://www.nytimes.com/2019/11/04/science/voyager-2-interstellar-solar-wind.html |url-status=live }}</ref><ref name="NASA-Solar-System">{{cite web |url=https://solarsystem.nasa.gov/missions/voyager-1/in-depth/ |title=Solar System Exploration |date=6 December 2017 |publisher=JPL-NASA |access-date=19 February 2021 |archive-date=18 April 2019 |archive-url=https://web.archive.org/web/20190418200450/https://solarsystem.nasa.gov/missions/voyager-1/in-depth/ |url-status=live }}</ref> In August 2018, NASA confirmed, based on results by the ''[[Astronomy:New Horizons|New Horizons]]'' spacecraft, the existence of a "[[Astronomy:Heliosphere#Hydrogen wall|hydrogen wall]]" at the outer edges of the Solar System that was first detected in 1992 by the two Voyager spacecraft.<ref name="GRL-20180807">{{cite journal |author=Gladstone, G. Randall|display-authors=0 |title=The Lyman-α Sky Background as Observed by New Horizons
|date=7 August 2018 |journal=[[Earth:Geophysical Research Letters|Geophysical Research Letters]] |volume=45 |issue=16 |pages=8022–8028 |doi=10.1029/2018GL078808 |arxiv=1808.00400 |bibcode=2018GeoRL..45.8022G |s2cid=119395450 }}</ref><ref name="LS-20180809">{{cite web |last=Letzter |first=Rafi |title=NASA Spotted a Vast, Glowing 'Hydrogen Wall' at the Edge of Our Solar System |url=https://www.livescience.com/63297-hydrogen-wall-glowing-interstellar-space.html |date=9 August 2018 |work=Live Science |access-date=10 August 2018 |archive-date=13 April 2020 |archive-url=https://web.archive.org/web/20200413080736/https://www.livescience.com/63297-hydrogen-wall-glowing-interstellar-space.html |url-status=live }}</ref><ref>{{Cite web|url=https://voyager.jpl.nasa.gov/frequently-asked-questions/fact-sheet/|title=Voyager – Fact Sheet|website=voyager.jpl.nasa.gov|access-date=17 May 2018|archive-date=13 April 2020|archive-url=https://web.archive.org/web/20200413080739/https://voyager.jpl.nasa.gov/frequently-asked-questions/fact-sheet/|url-status=live}}</ref>

{{As of|2024|post=,}} the Voyagers are still in operation beyond the outer boundary of the [[Astronomy:Heliosphere|heliosphere]] in interstellar space. ''Voyager 1'' is moving with a velocity of {{convert|61,198|km/h|sp=us}}, or 17&nbsp;km/s, (10.5 miles/second) relative to the Sun, and is {{convert|24,475,900,000|km|sp=us}} from the Sun<ref name="JPL.Voyager1">{{cite web |url=https://voyager.jpl.nasa.gov/mission/status/#where_are_they_now |title=Voyager Mission Status |publisher=JPL |access-date=10 February 2022 |archive-date=1 January 2018 |archive-url=https://web.archive.org/web/20180101025244/https://voyager.jpl.nasa.gov/mission/status/#where_are_they_now |url-status=live }}</ref> reaching a distance of {{Convert|162|AU|e9km e9mi|sigfig=3|abbr=unit|lk=on}} from Earth as of May 25, 2024.<ref name="voyager">{{cite web |url=https://voyager.jpl.nasa.gov/mission/status/ |title=Voyager – Mission Status |work=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]] |publisher=[[Organization:National Aeronautics and Space Administration|National Aeronautics and Space Administration]] |access-date=April 24, 2021 |archive-date=1 January 2018 |archive-url=https://web.archive.org/web/20180101025244/https://voyager.jpl.nasa.gov/mission/status/ |url-status=live }}</ref> {{as of|2024}}, ''Voyager 2'' is moving with a velocity of {{convert|55,347|km/h|sp=us}}, or 15&nbsp;km/s, relative to the Sun, and is {{convert|20,439,100,000|km|sp=us}} from the Sun<ref name="JPL.Voyager2">{{cite web|url=https://solarsystem.nasa.gov/missions/voyager-2/in-depth/|title=In Depth – Voyager 2|publisher=JPL|access-date=10 February 2022|archive-date=20 April 2017|archive-url=https://web.archive.org/web/20170420085656/https://solarsystem.nasa.gov/missions/voyager2/indepth|url-status=live}}</ref> reaching a distance of {{Convert|136.627|AU|e9km e9mi|sigfig=3|abbr=unit|lk=on}} from Earth as of May 25, 2024.<ref name="voyager" /> 

The two Voyagers are the only human-made objects to date that have passed into interstellar space — a record they will hold until at least the 2040s — and ''Voyager 1'' is the farthest human-made object from Earth.<ref name=":0" />

==History==
 
=== Mariner Jupiter-Saturn ===
{{also|Grand Tour program#Mariner Jupiter-Saturn}}
[[File:Voyager Path.svg|right|thumb|The trajectories that enabled the Voyager spacecraft to visit the outer planets and achieve velocity to escape the Solar System]]
[[File:Voyager 2 velocity vs distance from sun.svg|thumb|Plot of ''Voyager 2''{{'}}s heliocentric velocity against its distance from the Sun, illustrating the use of gravity assist to accelerate the spacecraft by Jupiter, Saturn and Uranus. To observe [[Triton (moon)|Triton]], ''Voyager 2'' passed over Neptune's north pole, resulting in an acceleration out of the plane of the ecliptic and reduced its velocity away from the Sun.<ref>{{cite web |author=Dave Doody |url=http://www2.jpl.nasa.gov/basics/bsf4-1.php |title=Basics of Space Flight Section I. The Environment of Space |publisher=.jpl.nasa.gov |date=15 September 2004 |access-date=29 December 2017 |archive-date=17 August 2015 |archive-url=https://web.archive.org/web/20150817051745/http://www2.jpl.nasa.gov/basics/bsf4-1.php |url-status=live }}</ref>]]

{{Blockquote
|text=Voyager did things no one predicted, found scenes no one expected, and promises to outlive its inventors. Like a great painting or an abiding institution, it has acquired an existence of its own, a destiny beyond the grasp of its handlers.
|author=Stephen J. Pyne<ref name="The Fantastic Voyage of Voyager"/>
}}
The two Voyager space probes were originally conceived as part of the Planetary Grand Tour planned during the late 1960s and early 70s that aimed to explore  [[Astronomy:Jupiter|Jupiter]], [[Astronomy:Saturn|Saturn]], Saturn's moon [[Astronomy:Titan (moon)|Titan]], [[Astronomy:Uranus|Uranus]], [[Astronomy:Neptune|Neptune]], and [[Astronomy:Pluto|Pluto]]. The mission originated from the [[Astronomy:Grand Tour program|Grand Tour program]], conceptualized by [[Biography:Gary Flandro|Gary Flandro]], an aerospace engineer at the Jet Propulsion Laboratory, in 1964, which leveraged a rare [[Syzygy|planetary alignment]] occurring once every 175 years.<ref>{{cite journal |last=Flandro |first=Gary |title=Fast Reconnaissance Missions to the Outer Solar System Using Energy Derived from the Gravitational Field of Jupiter |journal=Astronautica Acta |volume=12 |pages=329–337 |date=1966 |url=http://www.gravityassist.com/IAF3-2/Ref.%203-143.pdf |access-date=1 June 2024 |archive-date=30 March 2019 |archive-url=https://web.archive.org/web/20190330015134/http://www.gravityassist.com/IAF3-2/Ref.%203-143.pdf |url-status=live }}</ref><ref>{{cite web|url=http://voyager.jpl.nasa.gov/science/planetary.html|archive-url=https://web.archive.org/web/20131127192310/http://voyager.jpl.nasa.gov/science/planetary.html|archive-date=27 November 2013|url-status=dead|title=Planetary Voyage|date=30 October 2013|publisher=USA.gov|access-date=15 October 2013}}</ref> This alignment allowed a craft to reach all [[Astronomy:Outer planets|outer planets]] using gravitational assists. The mission was to send several pairs of probes and gained momentum in 1966 when it was endorsed by [[Organization:NASA|NASA]]'s [[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]]. However, in December 1971, the Grand Tour mission was canceled when funding was redirected to the [[Engineering:Space Shuttle program|Space Shuttle program]].<ref name="GTN">{{cite book
 |last          = Butrica
 |first         = Andrew J.
 |title         = From Engineering Science to Big Science: The NACA and NASA Collier Trophy Research Project Winners
 |chapter       = Voyager: The Grand Tour of Big Science
 |editor1-last  = Mack
 |editor1-first = Pamela E.
 |url           = https://history.nasa.gov/SP-4219/Chapter11.html
 |access-date   = August 25, 2014
 |location      = Washington, D.C.
 |publisher     = NASA
 |date          = 1998
 |archive-url   = https://web.archive.org/web/20140823084758/http://history.nasa.gov/SP-4219/Chapter11.html
 |archive-date  = August 23, 2014
 |url-status    = live
 |isbn          = 978-1-4102-2531-3
}}</ref>

In 1972, a scaled-down (four planets, two identical spacecraft) mission was proposed, utilizing a spacecraft derived from the [[Astronomy:Mariner program|Mariner]] series, initially intended to be [[Astronomy:Mariner 11|Mariner 11]] and [[Astronomy:Mariner 12|Mariner 12]]. The gravity-assist technique, successfully demonstrated by [[Astronomy:Mariner 10|Mariner 10]], would be used to achieve significant velocity changes by maneuvering through an intermediate planet's [[Physics:Gravitational field|gravitational field]] to minimize time towards Saturn.<ref name="HMSmurmeier1974">{{cite web |last1=Smurmeier |first1=H. M. |title=The Mariner Jupiter/Saturn 1977 Mission" (1974) |url=https://commons.erau.edu/cgi/viewcontent.cgi?article=2830&context=space-congress-proceedings |website=[[Organization:Embry–Riddle Aeronautical University|Embry–Riddle Aeronautical University]] |access-date=May 16, 2024 |date=April 1, 1974 |archive-date=20 April 2023 |archive-url=https://web.archive.org/web/20230420101913/https://commons.erau.edu/cgi/viewcontent.cgi?article=2830&context=space-congress-proceedings |url-status=live }}</ref> The spacecrafts were then moved into a separate program named '''Mariner Jupiter-Saturn''' (also '''Mariner Jupiter-Saturn-Uranus''',<ref>{{cite web |title=The Voyagers: An unprecedented on-going mission of exploration |url=https://www.nasaspaceflight.com/2011/08/voyagers-unprecedented-on-going-mission-exploration/ |website=NASASpaceFlight.com |publisher=Jeff Goldader, Chris Gebhardt |access-date=May 17, 2024 |date=August 7, 2011 |archive-date=17 May 2024 |archive-url=https://web.archive.org/web/20240517013934/https://www.nasaspaceflight.com/2011/08/voyagers-unprecedented-on-going-mission-exploration/ |url-status=live }}</ref> '''MJS''', or '''MJSU'''), part of the [[Astronomy:Mariner program|Mariner program]], later renamed because it was thought that the design of the two space probes had progressed sufficiently beyond that of the Mariner family to merit a separate name.<ref>[https://history.nasa.gov/SP-4219/Chapter11.html '' Chapter 11 "Voyager: The Grand Tour of Big Science"''] {{Webarchive|url=https://web.archive.org/web/20200229064831/https://history.nasa.gov/SP-4219/Chapter11.html |date=29 February 2020 }} (sec. 268.), by Andrew,J. Butrica, found in ''From Engineering Science To Big Science'' {{ISBN|978-0-16-049640-0}} edited by Pamela E. Mack, NASA, 1998</ref>

=== Voyager probes ===
[[File:Voyager Probe.stl|thumb|left|304x304px|Interactive 3D model of the Voyager spacecraft .]]

On March 4, 1977, [[Organization:NASA|NASA]] announced a competition to rename the mission, believing the existing name was not appropriate as the mission had differed significantly from previous [[Astronomy:Mariner program|Mariner]] missions. ''Voyager'' was chosen as the new name, referencing an earlier suggestion by William Pickering, who had proposed the name ''Navigator''. Due to the name change occurring close to launch, the probes were still occasionally referred to as Mariner 11 and Mariner 12, or even Voyager 11 and Voyager 12.<ref name="GTN" /><!-- cf page 269 of source -->

Two mission trajectories were established: JST aimed at Jupiter, Saturn, and enhancing a [[Astronomy:Titan (moon)|Titan]] flyby, while JSX served as a contingency plan. JST focused on a Titan flyby, while JSX provided a flexible mission plan. If JST succeeded, JSX could proceed with the Grand Tour, but in case of failure, JSX could be redirected for a separate Titan flyby, forfeiting the Grand Tour opportunity.<ref name="HMSmurmeier1974" /> The second probe, now [[Astronomy:Voyager 2|Voyager 2]], followed the JSX trajectory, granting it the option to continue on to Uranus and Neptune. Upon [[Astronomy:Voyager 1|Voyager 1]] completing its main objectives at Saturn, Voyager 2 received a mission extension, enabling it to proceed to Uranus and Neptune. This allowed Voyager 2 to diverge from the originally planned JST trajectory.<ref name="GTN" />

The probes would be launched in August or September 1977, with their main objective being to compare the characteristics of Jupiter and Saturn, such as their atmospheres, [[Magnetic field|magnetic field]]s, particle environments, [[Astronomy:Ring system|ring system]]s, and moons. They would fly by planets and moons in either a JST or JSX trajectory. After completing their flybys, the probes would communicate with Earth, relaying vital data using their [[Physics:Magnetometer|magnetometer]]s, [[Physics:Spectrometer|spectrometer]]s, and other instruments to detect [[Astronomy:Interstellar medium|interstellar]], [[Physics:Solar radiation|solar]], and cosmic radiation. Their radioisotope thermoelectric generators (RTGs) would limit the maximum communication time with the probes to roughly a [[Physics:Decade|decade]]. Following their primary missions, the probes would continue to drift into interstellar space.<ref name="HMSmurmeier1974" />

''[[Astronomy:Voyager 2|Voyager 2]]'' was the first to be launched. Its trajectory was designed to allow flybys of Jupiter, Saturn, Uranus, and Neptune. ''Voyager 1'' was launched after ''Voyager 2'', but along a shorter and faster trajectory that was designed to provide an optimal flyby of Saturn's moon [[Astronomy:Titan (moon)|Titan]],<ref name="Swift1997">{{cite book|author=David W. Swift|title=Voyager Tales: Personal Views of the Grand Tour|url=https://books.google.com/books?id=E-NGFqfq1LsC&pg=PA69|date=1 January 1997|publisher=AIAA|isbn=978-1-56347-252-7|page=69}}</ref> which was known to be quite large and to possess a dense atmosphere. This encounter sent ''Voyager 1'' out of the plane of the ecliptic, ending its planetary science mission.<ref>{{cite web|title=Voyager FAQ|url=http://voyager.jpl.nasa.gov/faq.html|website=Jet Propulsion Laboratory|access-date=1 January 2015|url-status=dead|archive-url=https://web.archive.org/web/20110721050617/http://voyager.jpl.nasa.gov/faq.html|archive-date=21 July 2011}}</ref> Had ''Voyager 1'' been unable to perform the Titan flyby, the trajectory of ''Voyager 2'' could have been altered to explore Titan, forgoing any visit to Uranus and Neptune.<ref name="Bell2015">{{cite book|author=Jim Bell|title=The Interstellar Age: Inside the Forty-Year Voyager Mission|url=https://books.google.com/books?id=KXPoAwAAQBAJ&pg=PT94|date=24 February 2015|publisher=Penguin Publishing Group|isbn=978-0-698-18615-6|page=94|access-date=9 February 2016|archive-date=24 July 2024|archive-url=https://web.archive.org/web/20240724092318/https://books.google.com/books?id=KXPoAwAAQBAJ&pg=PT94#v=onepage&q&f=false|url-status=live}}</ref> ''Voyager 1'' was not launched on a trajectory that would have allowed it to continue to Uranus and Neptune, but could have continued from Saturn to Pluto without exploring Titan.<ref name="Stern">{{cite web <!-- |  alternate url=http://www.spacedaily.com/reports/What_If_Voyager_Had_Explored_Pluto_999.html --> |url=http://pluto.jhuapl.edu/News-Center/PI-Perspectives.php?page=piPerspective_06_23_2014  | title=The PI's Perspective: What If Voyager Had Explored Pluto? | access-date=29 August 2020 |date=23 June 2014 |author=[[Biography:Alan Stern|Alan Stern]] |website=New Horizons: NASA's Mission to Pluto and the Kuiper Belt }}</ref>

During the 1990s, ''Voyager 1'' overtook the slower deep-space probes [[Astronomy:Pioneer 10|Pioneer 10]] and [[Astronomy:Pioneer 11|Pioneer 11]] to become the most distant human-made object from Earth, a record that it will keep for the foreseeable future. The ''[[Astronomy:New Horizons|New Horizons]]'' probe, which had a higher launch velocity than ''Voyager 1'', is travelling more slowly due to the extra speed ''Voyager 1'' gained from its flybys of Jupiter and Saturn. ''Voyager 1'' and Pioneer 10 are the most widely separated human-made objects anywhere since they are travelling in roughly opposite directions from the [[Astronomy:Solar System|Solar System]].

In December 2004, ''Voyager 1'' crossed the termination shock, where the solar wind is slowed to subsonic speed, and entered the heliosheath, where the solar wind is compressed and made turbulent due to interactions with the [[Astronomy:Interstellar medium|interstellar medium]]. On 10 December 2007, ''Voyager 2'' also reached the termination shock, about {{convert|1|e9mi|e9km|abbr=off|order=flip}} closer to the Sun than from where ''Voyager 1'' first crossed it, indicating that the Solar System is [[Asymmetry|asymmetrical]].<ref>{{Cite web|url=https://www.nasa.gov/mission_pages/voyager/voyager-20071210.html|title=NASA - Voyager 2 Proves Solar System Is Squashed|website=www.nasa.gov|access-date=6 February 2020|archive-date=13 April 2020|archive-url=https://web.archive.org/web/20200413080741/https://www.nasa.gov/mission_pages/voyager/voyager-20071210.html|url-status=dead}}</ref>

In 2010 ''Voyager 1'' reported that the outward velocity of the solar wind had dropped to zero, and scientists predicted it was nearing interstellar space.<ref>{{cite news
 |author = Brown, Dwayne
 |author2 = Cook, Jia-Rui
 |author3 = Buckley, M.
 |title = Nearing Interstellar Space, NASA Probe Sees Solar Wind Decline
 |publisher = Applied Physics Lab, Johns Hopkins University
 |date = 14 December 2010
 |url = http://www.jhuapl.edu/newscenter/pressreleases/2010/101214.asp
 |archive-url = https://web.archive.org/web/20101215061146/http://www.jhuapl.edu/newscenter/pressreleases/2010/101214.asp
 |archive-date = 15 December 2010
 |url-status = dead
 |df = dmy-all
}}</ref> In 2011, data from the Voyagers determined that the heliosheath was not smooth, but filled with giant [[Physics:Magnetic|magnetic]] bubbles. It was theorized that they formed when the [[Magnetic field|magnetic field]] of the Sun became warped at the edge of the Solar System.<ref>{{cite news | url=http://www.huffingtonpost.com/2011/06/10/nasa-voyager-bubbles-solar-system-heliosphere_n_874733.html?icid=maing-grid7%7Cmain5%7Cdl1%7Csec3_lnk3%7C69958 | work=Huffington Post | first=Catharine | last=Smith | title=WATCH: NASA Discovers 'Bubbles' At Solar System's Edge | date=10 June 2011 | access-date=11 June 2011 | archive-date=13 April 2020 | archive-url=https://web.archive.org/web/20200413080729/https://www.huffpost.com/entry/nasa-voyager-bubbles-solar-system-heliosphere_n_874733?icid=maing-grid7%7Cmain5%7Cdl1%7Csec3_lnk3%7C69958 | url-status=live }}</ref>

In June 2012, scientists at NASA reported that ''[[Astronomy:Voyager 1|Voyager 1]]'' was very close to entering interstellar space, which was indicated by a sharp rise in [[Astronomy:Cosmic ray|high-energy particles]] from outside the Solar System.<ref name="BBC-20120615">{{cite news |last=Amos |first=Jonathan |title=Particles point way for Nasa's Voyager |url=https://www.bbc.co.uk/news/science-environment-18458478 |date=15 June 2012 |work=BBC News |access-date=15 June 2012 |archive-date=15 June 2012 |archive-url=https://web.archive.org/web/20120615183422/http://www.bbc.co.uk/news/science-environment-18458478 |url-status=live }}</ref><ref name="Ferris-201205">{{cite magazine |last=Ferris |first=Timothy |title=Timothy Ferris on Voyagers' Never-Ending Journey |url=http://www.smithsonianmag.com/science-nature/Timothy-Ferris-on-Voyagers-Never-Ending-Journey.html |date=May 2012 |magazine=Smithsonian Magazine |access-date=15 June 2012 |archive-date=4 November 2013 |archive-url=https://web.archive.org/web/20131104221550/http://www.smithsonianmag.com/science-nature/Timothy-Ferris-on-Voyagers-Never-Ending-Journey.html |url-status=dead }}</ref> In September 2013, NASA announced that ''Voyager 1'' had crossed the heliopause on 25 August 2012, making it the first spacecraft to enter interstellar space.<ref name="NASA-20130912">{{cite web |last1=Cook |first1=Jia-Rui C. |last2=Agle |first2=D. C. |last3=Brown |first3=Dwayne |title=NASA Spacecraft Embarks on Historic Journey into Interstellar Space |url=http://www.nasa.gov/mission_pages/voyager/voyager20130912.html |work=[[Organization:NASA|NASA]] |date=12 September 2013 |access-date=12 September 2013 |archive-date=11 June 2020 |archive-url=https://web.archive.org/web/20200611233345/https://www.nasa.gov/mission_pages/voyager/voyager20130912.html |url-status=dead }}</ref><ref name="agu">{{cite web|title=Voyager 1 has entered a new region of space, sudden changes in cosmic rays indicate|url=http://www.agu.org/news/press/pr_archives/2013/2013-11.shtml|access-date=20 March 2013|archive-url=https://web.archive.org/web/20130322025117/http://www.agu.org/news/press/pr_archives/2013/2013-11.shtml|archive-date=22 March 2013|url-status=dead}}</ref><ref name="NASA">{{cite web|title=Report: NASA Voyager Status Update on Voyager 1 Location|url=http://www.jpl.nasa.gov/news/news.php?release=2013-117&cid=release_2013-107&msource=2013107|publisher=NASA|access-date=20 March 2013|archive-date=13 April 2020|archive-url=https://web.archive.org/web/20200413080743/http://www.jpl.nasa.gov/news/news.php?release=2013-117&cid=release_2013-107&msource=2013107|url-status=dead}}</ref>

In December 2018, NASA announced that ''Voyager 2'' had crossed the heliopause on 5 November 2018, making it the second spacecraft to enter interstellar space.<ref name="NASA-20181210"/>

{{As of|2017}} ''Voyager 1'' and ''Voyager 2'' continued to monitor conditions in the outer expanses of the Solar System.<ref name="NYT-20170905">{{cite news |last=Krauss |first=Lawrence M. |title=Pondering Voyagers' Interstellar Journeys, and Our Own |url=https://www.nytimes.com/2017/09/05/opinion/pondering-voyagers-interstellar-journeys-and-our-own.html |date=5 September 2017 |work=The New York Times |access-date=5 September 2017 |archive-date=13 April 2020 |archive-url=https://web.archive.org/web/20200413080730/https://www.nytimes.com/2017/09/05/opinion/pondering-voyagers-interstellar-journeys-and-our-own.html |url-status=live }}</ref> The Voyager spacecraft were expected to be able to operate science instruments through 2020, when limited power would require instruments to be deactivated one by one. It was expected that circa 2025 there would no longer be sufficient power to operate any scientific instruments.

In July 2019, a revised power management plan was implemented for the two probes' dwindling power supplies.<ref name="NASA-20190712">{{cite news |last=Cofield |first=Calla |title=A New Plan for Keeping NASA's Oldest Explorers Going |url=https://www.jpl.nasa.gov/news/news.php?feature=7446 |date=8 July 2019 |work=[[Organization:NASA|NASA]] |access-date=12 July 2019 |archive-date=13 April 2020 |archive-url=https://web.archive.org/web/20200413080726/https://www.jpl.nasa.gov/news/news.php?feature=7446 |url-status=live }}</ref>

==Spacecraft design==
[[File:Voyager Program - spacecraft diagram.png|thumb|upright=1.3|alt=A space probe with squat cylindrical body topped by a large parabolic radio antenna dish pointing left, a three-element radioisotope thermoelectric generator on a boom extending down, and scientific instruments on a boom extending up. A disk is fixed to the body facing front left. A long triaxial boom extends down left and two radio antennas extend down left and down right.|Voyager spacecraft diagram]]

The Voyager spacecraft each weighed {{convert|815|kg|lb|abbr=off}} at launch, but after fuel usage are now about {{convert|733|kg|lb|abbr=off}}.<ref name="FAQ"/>  Of this weight, each spacecraft carries {{convert|105|kg|lb|abbr=off}} of scientific instruments.<ref>{{cite journal|last=Haynes|first=Robert|title=How We Get Pictures from Space, Revised Edition|url=https://ntrs.nasa.gov/search.jsp?R=19880001821|journal=NASA Facts|date=January 1987|publisher=NTRS|access-date=7 July 2017|archive-date=30 July 2023|archive-url=https://web.archive.org/web/20230730174044/https://ntrs.nasa.gov/search.jsp?R=19880001821|url-status=live}}</ref> The identical Voyager spacecraft use three-axis-stabilized [[Engineering:Guidance system|guidance system]]s that use gyroscopic and [[Physics:Accelerometer|accelerometer]] inputs to their [[Astronomy:Spacecraft attitude control|attitude control]] computers to point their high-gain antennas towards the Earth and their scientific instruments towards their targets, sometimes with the help of a movable instrument platform for the smaller instruments and the [[Engineering:Video camera tube|electronic photography]] system.

The diagram shows the high-gain antenna (HGA) with a {{convert|3.7|m|ft|abbr=on}} diameter dish attached to the hollow [[Decagon|decagon]]al [[Engineering:Electronics|electronics]] container. There is also a spherical tank that contains the [[Chemistry:Hydrazine|hydrazine]] [[Chemistry:Monopropellant|monopropellant]] fuel.

The [[Astronomy:Voyager Golden Record|Voyager Golden Record]] is attached to one of the bus sides. The angled square panel to the right is the optical calibration target and excess heat radiator. The three radioisotope thermoelectric generators (RTGs) are mounted end-to-end on the lower boom.

The scan platform comprises: the Infrared Interferometer Spectrometer (IRIS) (largest camera at top right); the Ultraviolet Spectrometer (UVS) just above the IRIS; the two Imaging Science Subsystem (ISS) vidicon cameras to the left of the UVS; and the Photopolarimeter System (PPS) under the ISS.

Only five investigation teams are still supported, though data is collected for two additional instruments.<ref>[http://voyager.jpl.nasa.gov/spacecraft/index.html ''Voyager - Spacecraft''] {{Webarchive|url=https://web.archive.org/web/20070324035810/http://voyager.jpl.nasa.gov/spacecraft/index.html |date=24 March 2007 }} Nasa website</ref>
The Flight Data Subsystem (FDS) and a single eight-track [[Physics:Magnetic tape|digital tape recorder]] (DTR) provide the data handling functions.

The FDS configures each instrument and controls instrument operations. It also collects engineering and science data and formats the data for [[Data transmission|transmission]]. The DTR is used to record high-rate [[Software:Plasma|Plasma]] Wave Subsystem (PWS) data, which is played back every six months.

The Imaging Science Subsystem made up of a wide-angle and a narrow-angle camera is a modified version of the slow scan vidicon camera designs that were used in the earlier Mariner flights. The Imaging Science Subsystem consists of two television-type cameras, each with eight filters in a commandable filter wheel mounted in front of the vidicons. One has a low resolution {{convert|200|mm|in|abbr=on}} [[Focal length|focal length]] wide-angle lens with an [[Astronomy:Aperture|aperture]] of f/3 (the wide-angle camera), while the other uses a higher resolution {{cvt|1500|mm}} narrow-angle f/8.5 lens (the narrow-angle camera).

Three spacecraft were built, ''Voyager 1'' (VGR 77-1), ''Voyager 2'' (VGR 77-3), and test spare model (VGR 77-2).{{sfn|Pyne|2010|p=39}}<ref name=":0">{{cite journal | last = Folger | first = Tim | url = https://www.scientificamerican.com/article/record-breaking-voyager-spacecraft-begin-to-power-down/ | title = Record-Breaking Voyager Spacecraft Begin to Power Down | journal = Scientific American | date = July 2022 | access-date = 12 April 2024 | archive-date = 23 June 2022 | archive-url = https://web.archive.org/web/20220623222423/https://www.scientificamerican.com/article/record-breaking-voyager-spacecraft-begin-to-power-down/ | url-status = live }}</ref>

=== Scientific instruments ===
{| class="wikitable mw-collapsible mw" <!-- or mw-collapsed-->
|+ {{nowrap|List of scientific instruments}}
|-
! scope="col" style="width:135px;"| Instrument name
! scope="col" style="width:50px;"| Abbreviation
<!--! scope="col" width="50" | Image-->
! Description
|-
| {{center|Imaging Science System }}
| {{center|ISS}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
<!--Diagram image-->
<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
| Used a two-camera system (narrow-angle/wide-angle) to provide imagery of Jupiter, Saturn and other objects along the trajectory.
{| class="wikitable collapsible"
|-
! colspan="2" | Filters
|-
|
{| style="text-align:center; width:320px;"
! colspan="4" scope="col" |Narrow-angle camera<ref name="NACam3">{{cite web |title=Voyager 1 Narrow Angle Camera Description |url=https://pds-rings.seti.org/voyager/iss/inst_cat_na1.html#filters |access-date=January 17, 2011 |publisher=NASA |archive-date=11 August 2011 |archive-url=https://web.archive.org/web/20110811232250/http://pds-rings.seti.org/voyager/iss/inst_cat_na1.html#filters |url-status=live }}</ref>
|-
! scope="col" style="background:#e5e5e5; width:60px;" |Name
! scope="col" style="background:#e5e5e5;" |Wavelength
! scope="col" style="background:#e5e5e5;" |Spectrum
! scope="col" style="background:#e5e5e5;" |Sensitivity
|-
|<small>0 – Clear</small>
|<small>280–640&nbsp;nm</small>
|[[File:Voyager - Filters - Clear.png|center|50x50px]]
| style="background:#fff;" |
|-
| style="text-align:center; height:25px;" |<small>4 – Clear</small>
|<small>280–640&nbsp;nm</small>
|[[File:Voyager - Filters - Clear.png|center|50x50px]]
| style="background:#fff;" |
|-
|<small>7 – [[Physics:Ultraviolet|UV]]</small>
|<small>280–370&nbsp;nm</small>
|[[File:Voyager - Filters - UV.png|center|50x50px]]
| style="background:#1d0036;" |
|-
|<small>1 – Violet</small>
|<small>350–450&nbsp;nm</small>
|[[File:Voyager - Filters - Violet.png|center|50x50px]]
| style="background:#8300b5;" |
|-
|<small>2 – Blue</small>
|<small>430–530&nbsp;nm</small>
|[[File:Voyager - Filters - Blue.png|center|50x50px]]
| style="background:#00d5ff;" |
|-
|<small>5 – Green</small>
|<small>530–640&nbsp;nm</small>
|[[File:Voyager - Filters - Green.png|center|50x50px]]
| style="background:#ffef00;" |
|-
| style="text-align:center; height:25px;" |<small>6 – Green</small>
|<small>530–640&nbsp;nm</small>
|[[File:Voyager - Filters - Green.png|center|50x50px]]
| style="background:#ffef00;" |
|-
|<small>3 – Orange</small>
|<small>590–640&nbsp;nm</small>
|[[File:Voyager - Filters - Orange.png|center|50x50px]]
| style="background:#ff8900;" |
|}
|
{| style="text-align:center; width:320px;"
! colspan="4" scope="col" |Wide-angle camera<ref name="WACam3">{{cite web |title=Voyager 1 Wide Angle Camera Description |url=https://pds-rings.seti.org/voyager/iss/inst_cat_wa1.html#filters |access-date=January 17, 2011 |publisher=NASA |archive-date=7 November 2021 |archive-url=https://web.archive.org/web/20211107025433/https://pds-rings.seti.org/voyager/iss/inst_cat_wa1.html#filters |url-status=live }}</ref>
|-
! scope="col" style="background:#e5e5e5; width:60px;" |Name
! scope="col" style="background:#e5e5e5;" |Wavelength
! scope="col" style="background:#e5e5e5;" |Spectrum
! scope="col" style="background:#e5e5e5;" |Sensitivity
|-
|<small>2 – Clear</small>
|<small>280–640&nbsp;nm</small>
|[[File:Voyager - Filters - Clear.png|center|50x50px]]
| style="background:#fff;" |
|-
|<small>3 – Violet</small>
|<small>350–450&nbsp;nm</small>
|[[File:Voyager - Filters - Violet.png|center|50x50px]]
| style="background:#8300b5;" |
|-
|<small>1 – Blue</small>
|<small>430–530&nbsp;nm</small>
|[[File:Voyager - Filters - Blue.png|center|50x50px]]
| style="background:#00d5ff;" |
|-
|<small>6 – [[Chemistry:Methane|CH<sub>4</sub>]]-U</small>
|<small>536–546&nbsp;nm</small>
|[[File:Voyager - Filters - CH4U.png|center|50x50px]]
| style="background:#81ff00;" |
|-
|<small>5 – Green</small>
|<small>530–640&nbsp;nm</small>
|[[File:Voyager - Filters - Green.png|center|50x50px]]
| style="background:#ffef00;" |
|-
|<small>4 – [[Chemistry:Sodium|Na]]-D</small>
|<small>588–590&nbsp;nm</small>
|[[File:Voyager - Filters - NaD.png|center|50x50px]]
| style="background:#ffe200;" |
|-
|<small>7 – Orange</small>
|<small>590–640&nbsp;nm</small>
|[[File:Voyager - Filters - Orange.png|center|50x50px]]
| style="background:#ff8900;" |
|-
|<small>0 – [[Chemistry:Methane|CH<sub>4</sub>]]-JST</small>
|<small>614–624&nbsp;nm</small>
|[[File:Voyager - Filters - CH4JST.png|center|50x50px]]
| style="background:#ff7b00;" |
|}
|}
* <small>'''Principal investigator:''' Bradford A. Smith / University of Arizona</small>
* <small>'''Data:''' PDS/PDI data catalog, PDS/PRN data catalog</small>
|-
| {{center|Radio Science System }}
| {{center|RSS}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
| Used 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 the Saturn rings and the ring dimensions.
* <small>'''Principal investigator:''' [[Biography:Von R. Eshleman|Von R. Eshleman]]</small>
* <small>'''Data:''' PDS/PPI data catalog, PDS/PRN data catalog '''('''VG_2803''')''', NSSDC data archive</small>
|-
| {{center|[[Engineering:Infrared interferometer spectrometer and radiometer|Infrared interferometer spectrometer and radiometer]] }}
| {{center|IRIS}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
| Investigated both global and local energy balance and atmospheric composition. Vertical temperature profiles were also obtained from the planets and satellites, as well as the composition, thermal properties, and size of particles in Saturn's rings.
* <small>'''Principal investigator:''' Rudolf Hanel / NASA Goddard Space Flight Center</small>
* <small>'''Data:''' PDS/PRN data catalog, PDS/PRN expanded data catalog '''('''VGIRIS_0001, VGIRIS_002''')''', NSSDC Jupiter data archive</small>
|-
| {{center|Ultraviolet [[Physics:Spectrometer|Spectrometer]] }}
| {{center|UVS}}
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| Designed to measure atmospheric properties, and to measure radiation.
* <small>'''Principal investigator:''' A. Lyle Broadfoot / University of Southern California</small>
* <small>'''Data:''' PDS/PRN data catalog</small>
|-
| {{center|Triaxial Fluxgate [[Physics:Magnetometer|Magnetometer]] }} [[File:Deployed magnetometer boom of one of NASA's Voyager PIA21738.jpg|center|140px]]
| {{center|MAG}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
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| 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.
* <small>'''Principal investigator:''' Norman F. Ness / NASA Goddard Space Flight Center</small>
* <small>'''Data:''' PDS/PPI data catalog, NSSDC data archive</small>
|-
| {{center|[[Software:Plasma|Plasma]] [[Physics:Spectrometer|Spectrometer]] }} [[File:PIA22922~orig.jpg|center|140px]]
| {{center|PLS}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
| Investigated the macroscopic properties of the [[Software:Plasma|plasma]] ions and measures electrons in the energy range from 5 eV to 1 keV.
* <small>'''Principal investigator:''' Herbert S. Bridge / MIT</small>
* <small>'''Data:''' PDS/PPI data catalog, NSSDC data archive</small>
|-
| {{center|Low Energy Charged Particle Instrument }} [[File:Voyager Low Energy Charged Particle Instrument.jpg|center|140px]]
| {{center|LECP}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
| Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition.
* <small>'''Principal investigator:''' [[Biography:Stamatios Krimigis|Stamatios Krimigis]] / JHU/APL / University of Maryland</small>
* <small>'''Data:''' UMD data plotting, PDS/PPI data catalog, NSSDC data archive</small>
|-
| {{center|Cosmic Ray System }}
| {{center|CRS}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
| 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.
* <small>'''Principal investigator:''' [[Biography:Rochus Eugen Vogt|Rochus Eugen Vogt]], [[Biography:Edward C. Stone|Edward C. Stone]], [[Biography:Alan C. Cummings|Alan C. Cummings]] / Caltech / NASA Goddard Space Flight Center</small>
* <small>'''Data:''' PDS/PPI data catalog, NSSDC data archive</small>
|-
| {{center|Planetary Radio Astronomy Investigation }}
| {{center|PRA}}
<!--| --> <!--If single image in use, change to cHeight= 160-->
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<!--{{Css Image Crop |Image= |bSize= 160px |cWidth= 50 |cHeight= 80 |oTop= 0 |oLeft= 0 |Location= Center}}-->
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| Used a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn.
* <small>'''Principal investigator:''' [[Biography:James W. Warwick|James W. Warwick]] / University of Colorado</small>
* <small>'''Data:''' PDS/PPI data catalog, NSSDC data archive</small>
|-
| {{center|[[Physics:Polarimeter|Photopolarimeter]] System }}
| {{center|PPS}}
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<!--| Used a 6-inch f/1.4 Dahl-Kirkham-type Cassegrain telescope with an analyzer wheel containing five analyzers of {{formatnum:060120}},45 and 135 degrees and filter wheel with eight spectral bands covering 2350 to 7500A to gather information on surface texture and composition of Jupiter, Saturn, Uranus and Neptune and information on atmospheric scattering properties and density for these planets. [https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1977-084A-11 '''More''']-->
| Used a 6-inch f/1.4 Dahl-Kirkham-type Cassegrain telescope with an analyzer wheel containing five analyzers of 0,60,120,45 and 135 degrees and filter wheel with eight spectral bands covering 2350 to 7500A to gather information on surface texture and composition of Jupiter, Saturn, Uranus and Neptune and information on atmospheric scattering properties and density for these planets.
* <small>'''Principal investigator:''' Charles F. Lillie, Charles W. Hord </small>
* <small>'''Data:''' PDS/PRN data catalog and PDS Atmospheric Node</small>
|-
| {{center|[[Astronomy:Plasma Wave Subsystem|Plasma Wave Subsystem]] }}
| {{center|PWS}}
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| 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.
* <small>'''Principal investigator:''' [[Biography:Frederick L. Scarf|Frederick L. Scarf]] / [[Company:TRW Inc.|TRW]], [[Biography:Donald Gurnett|Donald Gurnett]] / University of Iowa</small>
* <small>'''Data:''' PDS/PPI data catalog</small>
|}

<gallery mode=packed heights=200>
File:Voyager instruments boom.jpg|A view of some of Voyager's instruments from below. Left: the cameras, ultraviolet and infrared spectrometers (far left), plasma detector (black box lower right), particle and radiation detectors (far right). On the boom, center and right, are plasma, particle, and cosmic ray detectors.
File:Voyager’s 13-meter-long magnetometer boom.jpg|Voyager's fully extended 13-meter-long magnetometer boom
</gallery>

=== Computers and data processing ===
There are three different computer types on the Voyager spacecraft, two of each kind, sometimes used for redundancy. They are proprietary, custom-built computers built from [[Engineering:CMOS|CMOS]] and [[Transistor–transistor logic|TTL]] medium-scale CMOS integrated circuits and discrete components, mostly from the [[Engineering:7400-series integrated circuits|7400 series]] of [[Company:Texas Instruments|Texas Instruments]].<ref>{{cite web |url=https://www.eejournal.com/article/voyagers-1-and-2-take-embedded-computers-into-interstellar-space/ |title=Voyagers 1 and 2 Take Embedded Computers into Interstellar Space |date=25 July 2022 |access-date=5 August 2023 |archive-date=5 August 2023 |archive-url=https://web.archive.org/web/20230805033258/https://www.eejournal.com/article/voyagers-1-and-2-take-embedded-computers-into-interstellar-space/ |url-status=live}}</ref> Total number of [[Word (computer architecture)|words]] among the six computers is about 32K. Voyager&nbsp;1 and Voyager&nbsp;2 have identical computer systems.<ref name="FAQ">{{cite web |url=http://voyager.jpl.nasa.gov/faq.html |title=Voyager Frequently Asked Questions |url-status=dead |archive-url=https://web.archive.org/web/20110721050617/http://voyager.jpl.nasa.gov/faq.html |archive-date=21 July 2011}}</ref><ref>{{cite web |url=https://pds-rings.seti.org/voyager/spacecraft/vg1host.html |title=Voyager 1 Instrument Host Information |publisher=seti.org |access-date=10 August 2019 |archive-date=24 July 2024 |archive-url=https://web.archive.org/web/20240724092319/https://pds-rings.seti.org/voyager/spacecraft/vg1host.html |url-status=live }}</ref>

The Computer Command System (CCS), the central controller of the spacecraft, has two 18-bit word, interrupt-type processors with 4096 words each of non-volatile [[Plated-wire memory|plated-wire memory]]. During most of the Voyager mission the two CCS computers on each spacecraft were used non-redundantly to increase the command and processing capability of the spacecraft. The CCS is nearly identical to the system flown on the Viking spacecraft.<ref name="Tomayko">{{cite book
 |first         = James E.
 |last          = Tomayko
 |editor-last1  = Kent
 |editor-first1 = Allen
 |editor-last2  = Williams
 |editor-first2 = James G.
 |chapter       = Distributed Computing On Board Voyager and Galileo (chapter 6)
 |url           = https://ntrs.nasa.gov/citations/19880069935
 |title         = Computers in Spaceflight: The NASA Experience
 |series        = Encyclopedia of Computer Science and Technology
 |chapter-url   = https://history.nasa.gov/computers/Ch6-2.html
 |publisher     = NASA
 |date          = 1987-08-03
 |isbn          = 978-0-8247-2268-5
 |volume        = 18. Supplement&nbsp;3
 |via           = NASA History
 |access-date   = 26 July 2022
 |archive-date  = 18 October 2023
 |archive-url   = https://web.archive.org/web/20231018062947/https://ntrs.nasa.gov/citations/19880069935
 |url-status    = live
}}</ref>

The Flight Data System (FDS) is two 16-bit word machines with modular memories and 8198 words each.

The Attitude and Articulation Control System (AACS) is two 18-bit word machines with 4096 words each.

Unlike the other on-board instruments, the operation of the cameras for [[Physics:Visible light|visible light]] is not autonomous, but rather it is controlled by an imaging parameter table contained in one of the on-board digital computers, the Flight Data Subsystem (FDS). More recent space probes, since about 1990, usually have completely [[Automaton|autonomous]] cameras.

The computer command subsystem (CCS) controls the cameras. The CCS contains fixed [[Computer program|computer program]]s such as command decoding, fault detection, and correction routines, antenna-pointing routines, and spacecraft sequencing routines. This computer is an improved version of the one that was used in the [[Engineering:Viking program|''Viking'' orbiter]].<ref name="Tomayko"/> The hardware in both custom-built CCS subsystems in the Voyagers is identical. There is only a minor software modification for one of them that has a scientific subsystem that the other lacks.

According to Guinness Book of Records, CCS holds record of "longest period of continual operation for a computer". It has been running continuously since 20 August 1977.<ref>{{Cite web |title=Longest period of continual operation for a computer |url=https://www.guinnessworldrecords.com/world-records/635980-longest-period-of-continual-operation-for-a-computer |access-date=2023-04-28 |website=Guinness World Records |date=1977-08-20 |language=en-gb |archive-date=2023-04-28 |archive-url=https://web.archive.org/web/20230428123751/https://www.guinnessworldrecords.com/world-records/635980-longest-period-of-continual-operation-for-a-computer |url-status=live }}</ref>

The Attitude and Articulation Control Subsystem (AACS) controls the spacecraft orientation (its attitude). It keeps the high-gain antenna pointing towards the Earth, controls attitude changes, and points the scan platform. The custom-built AACS systems on both craft are identical.

It has been erroneously reported<ref>{{cite web |last=Johnson |first=Herb |date=November 2014 |url=http://www.retrotechnology.com/memship/1802_spacecraft.html |access-date=27 July 2015 |title=COSMAC 1802 History in Space |archive-date=15 July 2015 |archive-url=https://web.archive.org/web/20150715200158/http://www.retrotechnology.com/memship/1802_spacecraft.html |url-status=live }}</ref> on the [[Internet]] that the Voyager space probes were controlled by a version of the RCA&nbsp;1802 (RCA CDP1802 "COSMAC" [[Engineering:Microprocessor|microprocessor]]), but such claims are not supported by the primary design documents. The CDP1802 microprocessor was used later in the [[Engineering:Galileo (spacecraft)|''Galileo'' space probe]], which was designed and built years later. The digital control electronics of the Voyagers were not based on a microprocessor integrated-circuit chip.

===Communications===
The [[Astronomy:Uplink|uplink]] communications are executed via S-band microwave communications. The [[Astronomy:Downlink|downlink]] communications are carried out by an [[Astronomy:X-band|X-band]] [[Physics:Microwave|microwave]] transmitter on board the spacecraft, with an S-band transmitter as a back-up. All long-range communications to and from the two Voyagers have been carried out using their {{convert|3.7|m|ft|adj=on|sp=us}} high-gain antennas. The high-gain antenna has a beamwidth of 0.5° for X-band, and 2.3° for S-band.<ref name=Ludwig2002/>{{rp|17}} (The low-gain antenna has a 7&nbsp;dB gain and 60° beamwidth.)<ref name=Ludwig2002/>{{rp|17}}

Because of the [[Inverse-square law|inverse-square law]] in radio communications, the digital data rates used in the downlinks from the Voyagers have been continually decreasing the farther that they get from the Earth. For example, the data rate used from Jupiter was about 115,000 bits per second. That was halved at the distance of Saturn, and it has gone down continually since then.<ref name=Ludwig2002>{{cite web|last1=Ludwig|first1=Roger|last2=Taylor|first2=Jim|publisher=NASA|date=March 2002|url=http://descanso.jpl.nasa.gov/DPSummary/Descanso4--Voyager_new.pdf|access-date=26 March 2016|title=Voyager Telecommunications|archive-date=18 March 2021|archive-url=https://web.archive.org/web/20210318092548/http://descanso.jpl.nasa.gov/DPSummary/Descanso4--Voyager_new.pdf|url-status=live}}</ref> Some measures were taken on the ground along the way to reduce the effects of the inverse-square law. In between 1982 and 1985, the diameters of the three main parabolic dish antennas of the Deep Space Network were increased from {{convert|64|to|70|m|abbr=on}}<ref name=Ludwig2002/>{{rp|34}} dramatically increasing their areas for gathering weak microwave signals.

Whilst the craft were between Saturn and Uranus the onboard software was upgraded to do a degree of image compression and to use a more efficient [[Reed–Solomon error correction#Space transmission|Reed-Solomon error-correcting encoding]].<ref name=Ludwig2002/>{{rp|33}}

Then between 1986 and 1989, new techniques were brought into play to combine the signals from multiple antennas on the ground into one, more powerful signal, in a kind of an antenna array.<ref name=Ludwig2002/>{{rp|34}} This was done at Goldstone, California, [[Engineering:Canberra Deep Space Communication Complex|Canberra (Australia)]], and Madrid (Spain) using the additional dish antennas available there. Also, in Australia, the Parkes Radio Telescope was brought into the array in time for the fly-by of Neptune in 1989. In the United States, the [[Astronomy:Very Large Array|Very Large Array]] in New Mexico was brought into temporary use along with the antennas of the Deep Space Network at Goldstone.<ref name=Ludwig2002/>{{rp|34}} Using this new technology of antenna arrays helped to compensate for the immense radio distance from Neptune to the Earth.

===Power===
[[File:MHW-RTGs.gif|right|thumb|[[Radioisotope thermoelectric generator|RTGs]] for the Voyager program|238x238px]]
[[Physics:Electric power|Electrical power]] is supplied by three [[Astronomy:MHW-RTG|MHW-RTG]] [[Physics:Radioisotope thermoelectric generator|radioisotope thermoelectric generator]]s (RTGs). They are powered by [[Physics:Plutonium-238|plutonium-238]] (distinct from the [[Physics:Plutonium-239|Pu-239]] isotope used in nuclear weapons) and provided approximately 470 [[Watt|W]] at 30 [[Volt|volt]]s [[Physics:Direct current|DC]] when the spacecraft was launched. Plutonium-238 decays with a [[Physics:Half-life|half-life]] of 87.74 years,<ref>{{Cite web|url=https://lanl.gov/source/orgs/nmt/nmtdo/AQarchive/97summer/Pu_238.html|title=The Actinide Research Quarterly: Summer 1997|website=lanl.gov|access-date=6 February 2020|archive-date=8 March 2022|archive-url=https://web.archive.org/web/20220308131514/https://lanl.gov/source/orgs/nmt/nmtdo/AQarchive/97summer/Pu_238.html|url-status=live}}</ref> so RTGs using Pu-238 will lose a factor of 1−0.5<sup>(1/87.74)</sup> = 0.79% of their power output per year.

In 2011, 34 years after launch, the thermal power generated by such an RTG would be reduced to (1/2)<sup>(34/87.74)</sup> ≈ 76% of its initial power. The RTG [[Physics:Thermocouple|thermocouple]]s, which convert thermal power into electricity, also degrade over time reducing available electric power below this calculated level.

By 7 October 2011 the power generated by ''Voyager 1'' and ''Voyager 2'' had dropped to 267.9 W and 269.2 W respectively, about 57% of the power at launch. The level of power output was better than pre-launch predictions based on a conservative thermocouple degradation model. As the electrical power decreases, spacecraft loads must be turned off, eliminating some capabilities. There may be insufficient power for communications by 2032.<ref>{{cite news|last1=Segal|first1=Michael|title=Beyond Voyager|url=http://nautil.us/issue/51/limits/beyond-voyager|access-date=2 September 2017|work=Nautilus|date=1 September 2017|archive-date=2 September 2017|archive-url=https://web.archive.org/web/20170902052932/http://nautil.us/issue/51/limits/beyond-voyager|url-status=dead}}</ref>
{{Clear}}

== Voyager Interstellar Mission ==
[[File:PIA22835-VoyagerProgram&Heliosphere-Chart-20181210.png|thumb|center|600px|<div class="center">''[[Astronomy:Voyager 1|Voyager 1]]'' crossed the heliopause, or the edge of the [[Astronomy:Heliosphere|heliosphere]], in August 2012.<br />''[[Astronomy:Voyager 2|Voyager 2]]'' crossed the heliosheath in November 2018.<ref name="NASA-20181210">{{cite news |last1=Brown |first1=Dwayne |last2=Fox |first2=Karen |last3=Cofield |first3=Calia |last4=Potter |first4=Sean |title=Release 18-115 – NASA's Voyager 2 Probe Enters Interstellar Space |url=https://www.nasa.gov/press-release/nasa-s-voyager-2-probe-enters-interstellar-space |date=10 December 2018 |work=[[Organization:NASA|NASA]] |access-date=10 December 2018 |archive-date=27 June 2023 |archive-url=https://web.archive.org/web/20230627023807/https://www.nasa.gov/press-release/nasa-s-voyager-2-probe-enters-interstellar-space/ |url-status=live }}</ref><ref name="NASA-20181005">{{cite news |last1=Cofield |first1=Calia |last2=Cook |first2=Jia-Rui |last3=Fox |first3=Karen |title=NASA Voyager 2 Could Be Nearing Interstellar Space |url=https://www.jpl.nasa.gov/news/news.php?feature=7252 |date=5 October 2018 |work=[[Organization:NASA|NASA]] |access-date=6 October 2018 |archive-date=5 October 2018 |archive-url=https://web.archive.org/web/20181005173131/https://www.jpl.nasa.gov/news/news.php?feature=7252 |url-status=live }}</ref></div>]]
The Voyager primary mission was completed in 1989, with the close flyby of Neptune by ''Voyager 2''. The Voyager Interstellar Mission (VIM) is a mission extension, which began when the two spacecraft had already been in flight for over 12 years.<ref>{{cite web |url=http://voyager.jpl.nasa.gov/mission/interstellar.html |title=Interstellar Mission |publisher=NASA |access-date=30 May 2008 |archive-date=15 October 2009 |archive-url=https://web.archive.org/web/20091015172229/http://voyager.jpl.nasa.gov/mission/interstellar.html |url-status=live }}</ref> The Heliophysics Division of the NASA Science Mission Directorate conducted a Heliophysics Senior Review in 2008. The panel found that the VIM "is a mission that is absolutely imperative to continue" and that VIM "funding near the optimal level and increased DSN ([[Astronomy:NASA Deep Space Network|Deep Space Network]]) support is warranted."<ref>{{cite web |url=http://www.igpp.ucla.edu/public/THEMIS/SCI/Pubs/Proposals%20and%20Reports/Senior%20Review%202008%20Report%20Final.pdf |title=Senior Review 2008 of the Mission Operations and Data Analysis Program for the Heliophysics Operating Missions |page=7 |publisher=NASA |access-date=30 May 2008 |archive-url=https://web.archive.org/web/20080626213548/http://www.igpp.ucla.edu/public/THEMIS/SCI/Pubs/Proposals%20and%20Reports/Senior%20Review%202008%20Report%20Final.pdf |archive-date=26 June 2008 |url-status=dead  }}</ref>

The main objective of the VIM was to extend the exploration of the Solar System beyond the outer planets to the [[Astronomy:Heliosphere|heliopause]] (the farthest extent at which the Sun's radiation predominates over interstellar winds) and if possible even beyond. Voyager 1 crossed the heliopause boundary in 2012, followed by Voyager 2 in 2018. Passing through the heliopause boundary has allowed both spacecraft to make measurements of the interstellar fields, particles and waves unaffected by the [[Astronomy:Solar wind|solar wind]]. Two significant findings so far have been the discovery of a region of magnetic bubbles<ref>{{cite web | url=https://svs.gsfc.nasa.gov/10790 | title=GMS: Voyager Satellites Find Magnetic Bubbles at Edge of Solar System | date=9 June 2011 | access-date=11 August 2022 | archive-date=5 December 2022 | archive-url=https://web.archive.org/web/20221205112656/https://svs.gsfc.nasa.gov/10790 | url-status=live }}</ref> and no indication of an expected shift in the Solar magnetic field.<ref>{{cite journal | url=https://physicstoday.scitation.org/do/10.1063/pt.6.3.20190215a/full/ | doi=10.1063/pt.6.3.20190215a | title=The confounding magnetic readings of Voyager 1 | journal=Physics Today | year=2019 | last1=Grant | first1=Andrew | issue=2 | page=30645 | bibcode=2019PhT..2019b0645G | s2cid=242207067 | access-date=11 August 2022 | archive-date=15 August 2022 | archive-url=https://web.archive.org/web/20220815164724/https://physicstoday.scitation.org/do/10.1063/PT.6.3.20190215a/full/ | url-status=live | url-access=subscription }}</ref>

The entire ''Voyager 2'' scan platform, including all of the platform instruments, was switched off in 1998. All platform instruments on ''Voyager 1'', except for the ultraviolet spectrometer (UVS)<ref>{{cite web | title=Ultraviolet Spectrometer | work=Voyager: The Interstellar Mission | publisher=NASA JPL | url=http://voyager.jpl.nasa.gov/spacecraft/instruments_uvs.html | access-date=11 June 2006 | archive-date=5 March 2006 | archive-url=https://web.archive.org/web/20060305105235/http://voyager.jpl.nasa.gov/spacecraft/instruments_uvs.html | url-status=live }}</ref> have also been switched off.

The ''Voyager 1'' scan platform was scheduled to go off-line in late 2000 but has been left on to investigate UV emission from the upwind direction.
UVS data are still captured but scans are no longer possible.<ref>{{cite web|url=http://voyager.jpl.nasa.gov/Proposal-2010/VGRSR.pdf|title=The Voyager Interstellar Mission Proposal to Senior Review 2010 of the Mission Operations and Data Analysis Program for the Heliophysics Operating Missions|page=24 |author=E. C. Stone |author2=J. D. Richardson |author3=E. B. Massey |publisher=NASA |access-date=20 November 2016|archive-url=https://web.archive.org/web/20161223041419/http://voyager.jpl.nasa.gov/Proposal-2010/VGRSR.pdf|archive-date=23 December 2016|url-status=dead}}</ref>

Gyro operations ended in 2016 for ''Voyager 2'' and in 2017 for ''Voyager 1''. Gyro operations are used to rotate the probe 360 degrees six times per year to measure the magnetic field of the spacecraft, which is then subtracted from the magnetometer science data.<!-- [[File:Voyager 1 entering heliosheath region.jpg|thumb|right|300px|Voyagers as of March 2013]] -->

On 14 November 2023, Voyager 1 stopped sending all telemetry and data, though the signal was still present.  After months of experiments, made considerably more difficult by the 45 hour round trip time, the cause was traced to a bad memory chip.  New software was written to avoid the bad memory block, and engineering data resumed on 20 April 2024.<ref>{{cite web |url=https://www.jpl.nasa.gov/news/nasas-voyager-1-resumes-sending-engineering-updates-to-earth/ |title=NASA's Voyager 1 Resumes Sending Engineering Updates to Earth|website=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]] }}</ref>  Science data from two instruments resumed in May 2024,<ref>{{cite web |url=https://science.nasa.gov/blogs/voyager/2024/05/22/voyager-1-resumes-sending-science-data-from-two-instruments/ |title=Voyager 1 Resumes Sending Science Data from Two Instruments|date=22 May 2024 }}</ref> and full recovery (of all science instruments that were still powered up) was in June 2024.<ref>{{cite web |url=https://www.jpl.nasa.gov/news/voyager-1-returning-science-data-from-all-four-instruments/ |title=Voyager 1 Returning Science Data From All Four Instruments|website=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]] }}</ref>  For more details of this intricate operation, see [[Astronomy:Voyager 1|Voyager 1]].

The two spacecraft continue to operate, with some loss in subsystem redundancy but retain the capability to return scientific data from a full complement of Voyager Interstellar Mission (VIM) science instruments.

Both spacecraft also have adequate electrical power and attitude control propellant to continue operating and collecting science data through at least 2026.<ref>{{cite web |url=https://www.jpl.nasa.gov/news/nasas-voyager-will-do-more-science-with-new-power-strategy/ |title=NASA's Voyager Will Do More Science With New Power Strategy|website=[[Organization:Jet Propulsion Laboratory|Jet Propulsion Laboratory]] }}</ref>  Though additional science instruments may need to be turned off, the spacecraft are expected to be able to communicate until 2036, in the absence of additional failures.<ref>{{cite web |url=https://science.nasa.gov/mission/voyager/frequently-asked-questions/ |title=Frequently Asked Questions|date=12 March 2024 }}</ref>

=== Mission details ===
[[File:Transitional regions.jpg|thumb|right|350x350px|This diagram about the heliosphere was released on 28 June 2013 and incorporates results from the Voyager spacecraft.<ref>{{Cite web|url=http://voyager.jpl.nasa.gov/news/transitional_regions.html|archive-url=https://web.archive.org/web/20130708092850/http://voyager.jpl.nasa.gov/news/transitional_regions.html|url-status=dead|title=NASA – Transitional Regions at the Heliosphere's Outer Limits|archive-date=8 July 2013}}</ref>]]
By the start of VIM, ''Voyager 1'' was at a distance of 40 [[Astronomical unit|AU]] from the Earth, while ''Voyager 2'' was at 31 AU. VIM is in three phases: termination shock, heliosheath exploration, and interstellar exploration phase. The spacecraft began VIM in an environment controlled by the Sun's magnetic field, with the plasma particles being dominated by those contained in the expanding supersonic solar wind. This is the characteristic environment of the termination shock phase. At some distance from the Sun, the supersonic solar wind will be held back from further expansion by the interstellar wind. The first feature encountered by a spacecraft as a result of this interaction – between interstellar wind and solar wind – was the termination shock, where the solar wind slows to subsonic speed, and large changes in plasma flow direction and magnetic field orientation occur. ''Voyager 1'' completed the phase of termination shock in December 2004 at a distance of 94 AU, while ''Voyager 2'' completed it in August 2007 at a distance of 84 AU. After entering into the heliosheath, the spacecraft were in an area that is dominated by the Sun's magnetic field and solar wind particles. After passing through the heliosheath, the two Voyagers began the phase of interstellar exploration. The outer boundary of the heliosheath is called the heliopause. This is the region where the Sun's influence begins to decrease and interstellar space can be detected.<ref>{{cite web|url=http://voyager.jpl.nasa.gov/mission/interstellar.html|title=Voyager – The Interstellar Mission|last=JPL.NASA.GOV|website=voyager.jpl.nasa.gov|access-date=2016-05-27|archive-date=15 October 2009|archive-url=https://web.archive.org/web/20091015172229/http://voyager.jpl.nasa.gov/mission/interstellar.html|url-status=live}}</ref> 

''Voyager 1'' is escaping the Solar System at the speed of 3.6 AU per year 35° north of the [[Astronomy:Ecliptic|ecliptic]] in the general direction of the [[Astronomy:Solar apex|solar apex]] in [[Astronomy:Hercules (constellation)|Hercules]], while ''Voyager 2''{{'}}s speed is about 3.3 AU per year, heading 48° south of the ecliptic. The Voyager spacecraft will eventually go on to the stars. In about [[Unsolved:Timeline of the far future#Spacecraft and space exploration|40,000 years]], ''Voyager 1'' will be within 1.6 [[Light-year|light years]] (ly) of AC+79 3888, also known as [[Astronomy:Gliese 445|Gliese 445]], which is approaching the Sun. In 40,000 years ''Voyager 2'' will be within 1.7 ly of [[Astronomy:Ross 248|Ross 248]] (another star which is approaching the Sun), and in [[Unsolved:Timeline of the far future#Spacecreaft and space exploration|296,000 years]] it will pass within 4.6 ly of [[Astronomy:Sirius|Sirius]], which is the brightest star in the night-sky.<ref name="JPL.NASA">{{cite web |author=Jpl.Nasa.Gov |url=http://www.jpl.nasa.gov/interstellarvoyager/ |title=Voyager Enters Interstellar Space – NASA Jet Propulsion Laboratory |publisher=Jpl.nasa.gov |access-date=14 September 2013 |archive-date=13 April 2020 |archive-url=https://web.archive.org/web/20200413080732/https://voyager.jpl.nasa.gov/mission/interstellar-mission// |url-status=live }}</ref> The spacecraft are not expected to collide with a star for 1 sextillion (10<sup>20</sup>) years.<ref name=lavender>{{Cite journal|title = Future stellar flybys of the Voyager and Pioneer spacecraft|journal = Research Notes of the American Astronomical Society|volume= 3|pages = 59|number=4|doi=10.3847/2515-5172/ab158e|date = 3 April 2019|author = Coryn A.L. Bailer-Jones, Davide Farnocchia|arxiv = 1912.03503|bibcode = 2019RNAAS...3...59B|s2cid = 134524048 | doi-access=free }}</ref>

In October 2020, astronomers reported a significant unexpected increase in density in the [[Astronomy:Outer space|space]] beyond the [[Astronomy:Solar System|Solar System]], as detected by the Voyager [[Engineering:Space probe|space probe]]s. According to the researchers, this implies that "the density gradient is a large-scale feature of the [[Astronomy:Interstellar medium#Structures|VLISM]] (very local [[Astronomy:Interstellar medium|interstellar medium]]) in the general direction of the [[Astronomy:Heliosphere#Edge structure|heliospheric nose]]".<ref name="SA-20201019">{{cite news |last=Starr |first=Michelle |title=Voyager Spacecraft Detect an Increase in The Density of Space Outside The Solar System |url=https://www.sciencealert.com/for-some-reason-the-density-of-space-is-higher-just-outside-the-solar-system |date=19 October 2020 |work=ScienceAlert |access-date=19 October 2020 |archive-date=19 October 2020 |archive-url=https://web.archive.org/web/20201019133221/https://www.sciencealert.com/for-some-reason-the-density-of-space-is-higher-just-outside-the-solar-system |url-status=live }}</ref><ref name="AJL-20200825">{{cite journal |last1=Kurth |first1=W.S. |last2=Gurnett |first2=D.A. |title=Observations of a Radial Density Gradient in the Very Local Interstellar Medium by Voyager 2 |date=25 August 2020 |journal=The Astrophysical Journal Letters |volume=900 |number=1 |pages=L1 |doi=10.3847/2041-8213/abae58 |bibcode=2020ApJ...900L...1K |s2cid=225312823 |doi-access=free }}</ref>

==Voyager Golden Record==
{{Main|Astronomy:Voyager Golden Record}}
[[File:Voyager Golden Record fx.png|thumb|116x116px|The cover of the [[Astronomy:Voyager Golden Record|Voyager Golden Record]]]]
Both spacecraft carry a {{convert|12|in|cm|adj=on}} golden phonograph record that contains pictures and sounds of Earth, symbolic directions on the cover for playing the record, and data detailing the location of Earth.<ref name="NYT-20170905" /><ref name="Ferris-201205" /> The record is intended as a combination [[Astronomy:Time capsule|time capsule]] and an interstellar message to any civilization, alien or far-future human, that may recover either of the Voyagers. The contents of this record were selected by a committee that included [[Biography:Timothy Ferris|Timothy Ferris]] and was chaired by [[Biography:Carl Sagan|Carl Sagan]].<ref name="Ferris-201205" />

== ''Pale Blue Dot'' ==
{{Main|Astronomy:Pale Blue Dot}}
[[File:Pale Blue Dot.png|thumb|upright=1.1|right|Seen from {{convert|6|e9km|e9mi|abbr=off|sp=us}}, Earth appears as a "[[pale blue dot]]" (the blueish-white speck approximately halfway down the light band to the right).]]
''Pale Blue Dot'' is a photograph of [[Astronomy:Earth|Earth]] taken on February 14, 1990, by the ''[[Astronomy:Voyager 1|Voyager 1]]'' [[Engineering:Space probe|space probe]] from a distance of approximately {{Nowrap|6 billion}} kilometers ({{nowrap|3.7 billion}} miles, 40.5 [[Astronomical unit|AU]]), as part of that day's [[Astronomy:Family Portrait (Voyager)|''Family Portrait'']] series of images of the [[Astronomy:Solar System|Solar System]].<ref name="NASA-20200212">{{cite news |author=Staff |title=Pale Blue Dot Revisited |url=https://photojournal.jpl.nasa.gov/catalog/PIA23645 |date=12 February 2020 |work=[[Organization:NASA|NASA]] |access-date=12 February 2020 |archive-date=12 February 2020 |archive-url=https://web.archive.org/web/20200212230826/https://photojournal.jpl.nasa.gov/catalog/PIA23645 |url-status=live }}</ref>
The Voyager program's discoveries during the primary phase of its mission, including new close-up color photos of the major planets, were regularly documented by print and electronic media outlets. Among the best-known of these is an image of the Earth as a ''[[Astronomy:Pale Blue Dot|Pale Blue Dot]]'', taken in 1990 by ''Voyager 1'', and popularized by Carl Sagan,<ref>{{Cite book|title=Pale Blue Dot|last=Sagan|first=Carl|publisher=Random House USA Inc|year=1997|isbn=978-0-345-37659-6|location=United States|url-access=registration|url=https://archive.org/details/palebluedot00carl|page=[https://archive.org/details/palebluedot00carl/page/6 6]-[https://archive.org/details/palebluedot00carl/page/7 7]}}</ref>

{{Blockquote|Consider again that dot. That's here. That's home. That's us....The Earth is a very small stage in a vast cosmic arena.... To my mind, there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly and compassionately with one another and to preserve and cherish that pale blue dot, the only home we've ever known.}}

==See also==
{{Div col}}
* ''[[Astronomy:Family Portrait (Voyager)|Family Portrait]]''
* ''[[Astronomy:The Farthest|The Farthest]]'', a 2017 documentary on the program.
* ''[[Astronomy:Interstellar Express|Interstellar Express]]'', a pair of [[Organization:China National Space Administration|Chinese]] probes inspired in part by the Voyagers.
* [[Astronomy:Interstellar probe|Interstellar probe]]
* [[Astronomy:Pioneer program|Pioneer program]]
* Planetary Grand Tour
* [[Astronomy:Timeline of Solar System exploration|Timeline of Solar System exploration]]
{{Div col end}}

==References==
{{Reflist}}

== Further reading ==
* {{cite book | last=Swift | first=David W. | title=Voyager Tales | publisher=American Institute of Aeronautics and Astronautics | publication-place=Reston, Va | date=1997 | isbn=978-1-56347-252-7}}
* {{cite book | last=Gallentine | first=Jay | title=Ambassadors from Earth: Pioneering Explorations with Unmanned Spacecraft | publisher=U of Nebraska Press | publication-place=Lincoln | date=2009 | isbn=978-0-8032-2220-5}}
* {{cite book | last=Pyne | first=Stephen J. | title=Voyager: Exploration, Space, and the Third Great Age of Discovery | publisher=Penguin Books | date=2010 | isbn=978-0-14-311959-3}}
* {{cite book|first=Jim |last=Bell |title=The Interstellar Age: Inside the Forty-Year Voyager Mission |date=2015|publisher=Penguin Publishing Group|isbn=978-0-698-18615-6}}

==External links==
{{commons}}
'''NASA sites'''
* [http://voyager.jpl.nasa.gov NASA Voyager website]
* [http://voyager.jpl.nasa.gov/mission/status/ Voyager Mission status (updated in real time)]
* [https://web.archive.org/web/20170301102317/http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html Voyager Spacecraft Lifetime]
* [https://web.archive.org/web/20090328090432/http://www.jpl.nasa.gov/news/fact_sheets/voyager.pdf NASA Facts – Voyager Mission to the Outer Planets]
* [https://web.archive.org/web/20070703065122/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19840027171_1984027171.pdf Voyager 1 and 2 atlas of six Saturnian satellites, 1984]
* [http://descanso.jpl.nasa.gov/DPSummary/Descanso4--Voyager_new.pdf JPL Voyager Telecom Manual]
'''NASA instrument information pages:'''
* {{cite web |title=Voyager instrument overview |url=http://starbrite.jpl.nasa.gov/pds/viewHostProfile.jsp?INSTRUMENT_HOST_ID=VG2 |url-status=dead |archive-url=https://web.archive.org/web/20110721050912/http://starbrite.jpl.nasa.gov/pds/viewHostProfile.jsp?INSTRUMENT_HOST_ID=VG2 |archive-date=21 July 2011  }}
* {{cite web |title=CRS – COSMIC RAY SUBSYSTEM |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=CRS&amp;INSTRUMENT_HOST_ID=VG1 |access-date=11 November 2017 |archive-url=https://web.archive.org/web/20140803100339/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=CRS&INSTRUMENT_HOST_ID=VG1 |archive-date=3 August 2014 |url-status=dead  }}
* {{cite web|title=ISS NA – IMAGING SCIENCE SUBSYSTEM – NARROW ANGLE|url=https://pds.nasa.gov/ds-view/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=ISSN&INSTRUMENT_HOST_ID=VG2|access-date=April 2, 2023|publisher=NASA}}
* {{cite web|title=ISS WA – IMAGING SCIENCE SUBSYSTEM – WIDE ANGLE|url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=ISSW&INSTRUMENT_HOST_ID=VG2|access-date=29 October 2009|archive-url=https://web.archive.org/web/20090718164117/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=ISSW&INSTRUMENT_HOST_ID=VG2|archive-date=18 July 2009|url-status=dead}}
* {{cite web |title=IRIS – INFRARED INTERFEROMETER SPECTROMETER AND RADIOMETER |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=IRIS&INSTRUMENT_HOST_ID=VG2 |access-date=29 October 2009 |archive-url=https://web.archive.org/web/20090718171718/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=IRIS&INSTRUMENT_HOST_ID=VG2 |archive-date=18 July 2009 |url-status=dead  }}
* {{cite web |title=LECP – LOW ENERGY CHARGED PARTICLE |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=LECP&INSTRUMENT_HOST_ID=VG2 |access-date=29 October 2009 |archive-url=https://web.archive.org/web/20090718171216/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=LECP&INSTRUMENT_HOST_ID=VG2 |archive-date=18 July 2009 |url-status=dead  }}
* {{cite web |title=MAG – TRIAXIAL FLUXGATE MAGNETOMETER |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=MAG&INSTRUMENT_HOST_ID=VG2 |access-date=29 October 2009 |archive-url=https://web.archive.org/web/20090718165706/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=MAG&INSTRUMENT_HOST_ID=VG2 |archive-date=18 July 2009 |url-status=dead  }}
* {{cite web |title=PLS – PLASMA SCIENCE EXPERIMENT |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PLS&INSTRUMENT_HOST_ID=VG2 |access-date=29 October 2009 |archive-url=https://web.archive.org/web/20090718171426/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PLS&INSTRUMENT_HOST_ID=VG2 |archive-date=18 July 2009 |url-status=dead  }}
* {{cite web |title=PPS – PHOTOPOLARIMETER SUBSYSTEM |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PPS&INSTRUMENT_HOST_ID=VG2 |access-date=29 October 2009 |archive-url=https://web.archive.org/web/20090825210557/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PPS&INSTRUMENT_HOST_ID=VG2 |archive-date=25 August 2009 |url-status=dead  }}
* {{cite web |title=PRA – PLANETARY RADIO ASTRONOMY RECEIVER |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PRA&INSTRUMENT_HOST_ID=VG2 |access-date=29 October 2009 |archive-url=https://web.archive.org/web/20090718171504/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PRA&INSTRUMENT_HOST_ID=VG2 |archive-date=18 July 2009 |url-status=dead  }}
* {{cite web |title=PWS – PLASMA WAVE RECEIVER |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PWS&INSTRUMENT_HOST_ID=VG2 |access-date=29 October 2009 |archive-url=https://web.archive.org/web/20090718171350/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=PWS&INSTRUMENT_HOST_ID=VG2 |archive-date=18 July 2009 |url-status=dead  }}
* {{cite web |title=RSS – RADIO SCIENCE SUBSYSTEM |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=RSS-VG1S&amp;INSTRUMENT_HOST_ID=VG1 |access-date=11 November 2017 |archive-url=https://web.archive.org/web/20140803084200/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=RSS-VG1S&INSTRUMENT_HOST_ID=VG1 |archive-date=3 August 2014 |url-status=dead  }}
* {{cite web |title=UVS – ULTRAVIOLET SPECTROMETER |url=http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=UVS&amp;INSTRUMENT_HOST_ID=VG1 |access-date=11 November 2017 |archive-url=https://web.archive.org/web/20140803093912/http://starbrite.jpl.nasa.gov/pds/viewInstrumentProfile.jsp?INSTRUMENT_ID=UVS&INSTRUMENT_HOST_ID=VG1 |archive-date=3 August 2014 |url-status=dead  }}
'''Non-NASA sites'''
* [http://www.heavens-above.com/SolarEscape.aspx Spacecraft Escaping the Solar System] – current positions and diagrams
* [https://web.archive.org/web/20070930185312/http://www.sciencefriday.com/pages/2007/Aug/hour1_082407.html NPR: Science Friday 8/24/07 Interviews for 30th anniversary of Voyager spacecraft]
* [https://web.archive.org/web/20140331162615/http://www.stickings90.webspace.virginmedia.com/voyager.htm Illustrated technical paper] by [[Biography:Raymond Heacock|RL Heacock]], the project engineer
* {{cite web|last=Gray|first=Meghan|title=Voyager and Interstellar Space|url=http://www.deepskyvideos.com/videos/other/voyager.html|work=Deep Space Videos|publisher=[[Biography:Brady Haran|Brady Haran]]}}
* [https://web.archive.org/web/20170521202818/http://www.pbs.org/the-farthest/home/ PBS featured documentary ''The Farthest-Voyager in Space'']
* [https://www.flickr.com/photos/kevinmgill/albums/72157651267194998 Voyager image album] by Kevin M. Gill

{{Voyager program}}
{{NASA space program}}
{{NASA planetary exploration programs}}
{{Flagship Program}}
{{Jet Propulsion Laboratory}}

[[Category:Voyager program| ]]
[[Category:Missions to Jupiter]]
[[Category:Missions to Saturn]]
[[Category:Missions to Uranus]]
[[Category:Missions to Neptune]]
[[Category:NASA programs]]

{{Sourceattribution|Voyager program}}