Editing Voyager 2 (section)

== History ==
{{further|Grand Tour program}}

=== Background ===
{{Main|Mariner Jupiter-Saturn}}
In the early space age, it was realized that a [[Syzygy (astronomy)|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 assist]]s. [[NASA]] began work on a [[Grand Tour program|Grand Tour]], which evolved into a massive project involving two groups of two probes each, with one group visiting Jupiter, Saturn, and Pluto and the other Jupiter, Uranus, and Neptune. The spacecraft would be designed with redundant systems to ensure survival throughout the entire tour. By 1972 the mission was scaled back and replaced with two [[Mariner program]]-derived spacecraft, the Mariner Jupiter-Saturn probes. To keep apparent lifetime program costs low, the mission would include only flybys of Jupiter and Saturn, but keep the Grand Tour option open.<ref name="butrica" />{{rp|263}} As the program progressed, the name was changed to Voyager.<ref>[https://voyager.jpl.nasa.gov/science/planetary.html Planetary Voyage] {{Webarchive|url=https://web.archive.org/web/20130826105129/http://voyager.jpl.nasa.gov/science/planetary.html |date=August 26, 2013 }} [[NASA]] [[Jet Propulsion Laboratory]] – California Institute of Technology. March 23, 2004. Retrieved April 8, 2007.</ref>

The primary mission of ''Voyager 1'' was to explore Jupiter, Saturn, and Saturn's largest moon, [[Titan (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''<nowiki>'</nowiki>s objectives, ''Voyager 2'' would get a mission extension to send the probe on towards Uranus and Neptune.<ref name="butrica">{{cite book |last1=Butrica |first1=Andrew |title=From Engineering Science to Big Science |page=267 |url=https://history.nasa.gov/SP-4219/Chapter11.html |access-date=September 4, 2015 |quote=Despite the name change, Voyager remained in many ways the Grand Tour concept, though certainly not the Grand Tour (TOPS) spacecraft. |archive-date=February 29, 2020 |archive-url=https://web.archive.org/web/20200229064831/https://history.nasa.gov/SP-4219/Chapter11.html |url-status=live }}</ref>
Titan was selected due to the interest developed after the images taken by ''[[Pioneer 11]]'' in 1979, which had indicated the atmosphere of the moon was substantial and complex. Hence the trajectory was designed for optimum Titan flyby.<ref>{{Cite book |last=David W. Swift |url=https://books.google.com/books?id=E-NGFqfq1LsC&pg=PA69 |title=Voyager Tales: Personal Views of the Grand Tour |date=January 1, 1997 |publisher=AIAA |isbn=978-1-56347-252-7 |page=69}}</ref><ref>{{Cite book |last=Jim Bell |url=https://books.google.com/books?id=KXPoAwAAQBAJ&pg=PT93 |title=The Interstellar Age: Inside the Forty-Year Voyager Mission |date=February 24, 2015 |publisher=Penguin Publishing Group |isbn=978-0-698-18615-6 |pages=93}}</ref>

=== 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.<ref name="nasa-1989">{{cite web |url=https://starbrite.jpl.nasa.gov/ds-view/pds/viewHostProfile.jsp?INSTRUMENT_HOST_ID=VG2 |title=Voyager 2: Host Information |date=1989 |publisher=NASA |access-date=January 2, 2011 |archive-url=https://web.archive.org/web/20170220172046/https://starbrite.jpl.nasa.gov/ds-view/pds/viewHostProfile.jsp?INSTRUMENT_HOST_ID=VG2 |archive-date=February 20, 2017}}</ref>

==== 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 Earth. Communications are conducted over the [[S-band]] (about 13&nbsp;cm wavelength) and [[X-band]] (about 3.6&nbsp;cm wavelength) providing data rates as high as 115.2 kilobits per second at the distance of Jupiter, and then ever-decreasing as distance increases, because of the [[inverse-square law]].<ref>{{Cite web |last1=Ludwig |first1=Roger |last2=Taylor |first2=Jim |date=2013 |title=Voyager Telecommunications |url=https://voyager.gsfc.nasa.gov/Library/DeepCommo_Chapter3--141029.pdf |url-status=live |access-date=August 7, 2023 |archive-date=August 8, 2023 |archive-url=https://web.archive.org/web/20230808014706/https://voyager.gsfc.nasa.gov/Library/DeepCommo_Chapter3--141029.pdf }}</ref> When the spacecraft [[Line-of-sight propagation|is unable to communicate with Earth]], the Digital Tape Recorder (DTR) can record about 64 megabytes of data for transmission at another time.<ref>{{cite web |title=NASA News Press Kit 77–136 |publisher=JPL/NASA |url=http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=9476.0;attach=591860 |access-date=December 15, 2014 |archive-date=May 29, 2019 |archive-url=https://web.archive.org/web/20190529081627/https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=9476.0;attach=591860 |url-status=live }}</ref>

==== Power ====
[[File:MHW-RTG.gif|thumb|Voyager RTG unit]]
''Voyager 2'' is equipped with three [[MHW-RTG|multihundred-watt radioisotope thermoelectric generators]] (MHW RTGs). Each RTG includes 24 pressed [[Plutonium(IV) oxide|plutonium oxide]] spheres. At launch, each RTG provided enough heat to generate approximately 157 W of electrical power. Collectively, the RTGs supplied the spacecraft with 470 watts at launch (halving every 87.7 years). They were predicted to allow operations to continue until at least 2020, and continued to provide power to five scientific instruments through the early part of 2023. In April 2023 JPL began using a reservoir of backup power intended for an onboard safety mechanism. As a result, all five instruments had been expected to continue operation through 2026.<ref name="nasa-1989" /><ref name="us national space science data center"/><ref>{{cite journal |last1=Furlong |first1=Richard R. |last2=Wahlquist |first2=Earl J. |date=1999 |title=U.S. space missions using radioisotope power systems |journal=Nuclear News |volume=42 |issue=4 |pages=26–34 |url=http://www2.ans.org/pubs/magazines/nn/pdfs/1999-4-2.pdf |access-date=January 2, 2011 |archive-date=October 16, 2018 |archive-url=https://web.archive.org/web/20181016011258/http://www3.ans.org/pubs/magazines/nn/pdfs/1999-4-2.pdf |url-status=dead }}</ref><ref name="newpower">{{cite web |title=NASA's Voyager Will Do More Science With New Power Strategy |url=https://www.jpl.nasa.gov/news/nasas-voyager-will-do-more-science-with-new-power-strategy |publisher=NASA Jet Propulsion Laboratory |access-date=April 28, 2023 |archive-date=April 27, 2023 |archive-url=https://web.archive.org/web/20230427182016/https://www.jpl.nasa.gov/news/nasas-voyager-will-do-more-science-with-new-power-strategy |url-status=live }}</ref> In October 2024 NASA announced that the plasma science instrument had been turned off, preserving power for the remaining four instruments.<ref>{{cite web |url=https://blogs.nasa.gov/voyager/2024/10/01/nasa-turns-off-science-instrument-to-save-voyager-2-power/ | title=NASA Turns Off Science Instrument to Save Voyager 2 Power |date=October 1, 2024 |publisher=NASA}}</ref>

==== Attitude control and propulsion ====
Because of the energy required to achieve a Jupiter trajectory boost with an {{convert|825|kg|lb|adj=on}} payload, the spacecraft included a propulsion module made of a {{convert|1123|kg|lb|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]] Aerojet MR-103 thrusters on the mission module provide attitude control.<ref>{{cite web |title=MR-103 |url=http://www.astronautix.com/m/mr-103.html |archive-url=https://web.archive.org/web/20161228025700/http://astronautix.com/m/mr-103.html |url-status=dead |archive-date=December 28, 2016 |website=Astronautix.com |access-date=December 11, 2018}}</ref> 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.<ref>{{cite journal |title=Voyager Backgrounder |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19810001583.pdf#page=21 |website=Nasa.gov |date=October 1980 |publisher=Nasa |access-date=December 11, 2018 |archive-date=June 9, 2019 |archive-url=https://web.archive.org/web/20190609064757/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19810001583.pdf#page=21 |url-status=live }}</ref>

Thrusters are supplied by a single {{convert|70|cm|in|adj=on|sp=us}} diameter spherical titanium tank. It contained {{convert|100|kg|lb}} of hydrazine at launch, providing enough fuel until 2034.<ref>{{cite web |last1=Koerner |first1=Brendan |title=What Fuel Does Voyager 1 Use? |url=https://slate.com/news-and-politics/2003/11/what-voyager-1-uses-for-fuel.html |website=Slate.com |access-date=December 11, 2018 |date=November 6, 2003 |archive-date=December 11, 2018 |archive-url=https://web.archive.org/web/20181211192625/https://slate.com/news-and-politics/2003/11/what-voyager-1-uses-for-fuel.html |url-status=live }}</ref>

==== Scientific instruments ====
{{Main|Voyager program}}
{| class="wikitable" style="text-align:center;"
|-
! scope="col" style="width:135px;"| Instrument name
! scope="col" style="width:50px;"| Abr.
! Description
|-
| {{partial|Imaging Science System <br />{{small|(disabled)}}}}
| (ISS)
| style="text-align:left;" | Utilized a two-camera system (narrow-angle/wide-angle) to provide imagery of the outer planets and other objects along the trajectory.
{| class="wikitable collapsible"
|-
! colspan="2" | Filters
|-
|
{| style="text-align:center"
! colspan="4" scope="col" style="width:320px;"| Narrow Angle Camera Filters<ref>{{cite web |url=https://pds-rings.seti.org/voyager/iss/inst_cat_na2.html#filters |title=Voyager 1 Narrow Angle Camera Description |access-date=January 17, 2011 |author=NASA/JPL |date=August 26, 2003 |publisher=NASA / PDS |archive-date=October 2, 2011 |archive-url=https://web.archive.org/web/20111002061657/http://pds-rings.seti.org/voyager/iss/inst_cat_na2.html#filters |url-status=live }}</ref>
|-
! scope="col" style="background:#e5e5e5; width:60px;"| Name
! style="background: #e5e5e5" | Wavelength
! style="background: #e5e5e5" | Spectrum
! style="background: #e5e5e5" | Sensitivity
|-
| Clear
| <small>280–640&nbsp;nm;</small><br /><small>460&nbsp;nm center</small>
| [[File:Voyager - Filters - Clear.png|50px|center]]
| style="background:#fff;"|
|-
| [[Ultraviolet|UV]]
| <small>280–370&nbsp;nm;</small><br /><small>325&nbsp;nm center</small>
| [[File:Voyager - Filters - UV.png|50px|center]]
| style="background: #1d0036" |
|-
| Violet
| <small>350–450&nbsp;nm;</small><br /><small>400&nbsp;nm center</small>
| [[File:Voyager - Filters - Violet.png|50px|center]]
| style="background: #8300b5" |
|-
| Blue
| <small>430–530&nbsp;nm;</small><br /><small>480&nbsp;nm center</small>
| [[File:Voyager - Filters - Blue.png|50px|center]]
| style="background: #00d5ff" |
|-
| '
| <small>'</small>
| [[File:Clear.png|50px|center]]
| '
|-
| Green
| <small>530–640&nbsp;nm;</small><br /><small>585&nbsp;nm center</small>
| [[File:Voyager - Filters - Green.png|50px|center]]
| style="background: #ffef00" |
|-
| '
| <small>'</small>
| [[File:Clear.png|50px|center]]
| '
|-
| Orange
| <small>590–640&nbsp;nm;</small><br /><small>615&nbsp;nm center</small>
| [[File:Voyager - Filters - Orange.png|50px|center]]
| style="background: #ff8900" |
|-
| '
| <small>'</small>
| [[File:Clear.png|50px|center]]
| '
|}
|
{| style="text-align:center"
! colspan="4" scope="col" style="width:320px;"| Wide Angle Camera Filters<ref>{{cite web |url=https://pds-rings.seti.org/voyager/iss/inst_cat_wa2.html#filters |title=Voyager 1 Wide Angle Camera Description |access-date=January 17, 2011 |author=NASA/JPL |date=August 26, 2003 |publisher=NASA / PDS |archive-date=August 11, 2011 |archive-url=https://web.archive.org/web/20110811232308/http://pds-rings.seti.org/voyager/iss/inst_cat_wa2.html#filters |url-status=live }}</ref>
|-
! scope="col" style="background:#e5e5e5; width:60px;"| Name
! style="background: #e5e5e5" | Wavelength
! style="background: #e5e5e5" | Spectrum
! style="background: #e5e5e5" | Sensitivity
|-
| Clear
| <small>280–640&nbsp;nm;</small><br /><small>460&nbsp;nm center</small>
| [[File:Voyager - Filters - Clear.png|50px|center]]
| style="background:#fff;"|
|-
| '
| <small>'</small>
| [[File:Clear.png|50px|center]]
| '
|-
| Violet
| <small>350–450&nbsp;nm;</small><br /><small>400&nbsp;nm center</small>
| [[File:Voyager - Filters - Violet.png|50px|center]]
| style="background: #8300b5" |
|-
| Blue
| <small>430–530&nbsp;nm;</small><br /><small>480&nbsp;nm center</small>
| [[File:Voyager - Filters - Blue.png|50px|center]]
| style="background: #00d5ff" |
|-
| [[Methane|CH<sub>4</sub>]]-U
| <small>536–546&nbsp;nm;</small><br /><small>514&nbsp;nm center</small>
| [[File:Voyager - Filters - CH4U.png|50px|center]]
| style="background: #81ff00" |
|-
| Green
| <small>530–640&nbsp;nm;</small><br /><small>585&nbsp;nm center</small>
| [[File:Voyager - Filters - Green.png|50px|center]]
| style="background: #ffef00" |
|-
| [[Sodium|Na]]-D
| <small>588–590&nbsp;nm;</small><br /><small>589&nbsp;nm center</small>
| [[File:Voyager - Filters - NaD.png|50px|center]]
| style="background: #ffe200" |
|-
| Orange
| <small>590–640&nbsp;nm;</small><br /><small>615&nbsp;nm center</small>
| [[File:Voyager - Filters - Orange.png|50px|center]]
| style="background: #ff8900" |
|-
| [[Methane|CH<sub>4</sub>]]-JST
| <small>614–624&nbsp;nm;</small><br /><small>619&nbsp;nm center</small>
| [[File:Voyager - Filters - CH4JST.png|50px|center]]
| style="background: #ff7b00" |
|}
|}
* {{small|'''Data:''' [https://web.archive.org/web/20030507144627/http://pds-imaging.jpl.nasa.gov/Admin/resources/cd_voyager.html PDS/PDI data catalog], [https://pds-rings.seti.org/voyager/iss/raw_images.html PDS/PRN data catalog]}}
|-

| {{partial|Radio Science System<br />{{small|(disabled)}}}}
| (RSS)
| style="text-align:left;" | Utilized the telecommunications system of the Voyager spacecraft to determine the physical properties of planets and satellites (ionospheres, atmospheres, masses, gravity fields, densities) and the amount and size distribution of material in Saturn's rings and the ring dimensions.
* {{small|1='''Data:''' [https://pds-ppi.igpp.ucla.edu/search/?sc=Voyager%202&i=RSS PDS/PPI data catalog], [https://pds-rings.seti.org/voyager/rss/index.html PDS/PRN data catalog] '''('''[https://pds-rings.seti.org/vol/VG_2803_peer_review/ VG_2803]''')''', [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/voyager/voyager2/radio_science_rss/ NSSDC Saturn data archive]}}
|-

| {{partial|[[Infrared interferometer spectrometer and radiometer]] <br />{{small|(disabled)}}}}
| (IRIS)
| style="text-align:left;" | Investigates both global and local energy balance and atmospheric composition. Vertical temperature profiles are also obtained from the planets and satellites as well as the composition, thermal properties, and size of particles in [[Saturn's rings]].
* {{small|'''Data:''' [https://pds-rings.seti.org/voyager/iris/original_volume.html PDS/PRN data catalog], [https://pds-rings.seti.org/voyager/iris/expanded_volumes.html PDS/PRN expanded data catalog] '''('''[https://pds-rings.seti.org/vol/VGIRIS_0001_peer_review/ VGIRIS_0001], [https://pds-rings.seti.org/vol/VGIRIS_0002_peer_review/ VGIRIS_002]''')'''}}
|-

| {{partial|Ultraviolet [[Spectrometer]] <br />{{small|(disabled)}}}}
| (UVS)
| style="text-align:left;" | Designed to measure atmospheric properties, and to measure radiation.
* {{small|'''Data:''' [https://pds-rings.seti.org/voyager/uvs/data.html PDS/PRN data catalog]}}
|-

| {{yes|Triaxial Fluxgate [[Magnetometer]] <br />{{small|(active)}}}}
| (MAG)
| style="text-align:left;" | Designed to investigate the magnetic fields of Jupiter and Saturn, the solar-wind interaction with the magnetospheres of these planets, and the interplanetary magnetic field out to the solar wind boundary with the interstellar magnetic field and beyond, if crossed.
* {{small|1='''Data:''' [https://pds-ppi.igpp.ucla.edu/search/?sc=Voyager%202&i=MAG PDS/PPI data catalog], [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/voyager/voyager2/magnetic_fields/ NSSDC data archive]}}
|-

| {{partial|[[Plasma (physics)|Plasma]] [[Spectrometer]] <br />{{small|(disabled)}}}}
| (PLS)
| style="text-align:left;" | Investigates the macroscopic properties of the plasma ions and measures electrons in the energy range from 5 eV to 1 keV.
* {{small|1='''Data:''' [https://pds-ppi.igpp.ucla.edu/search/?sc=Voyager%202&i=PLS PDS/PPI data catalog], [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/voyager/voyager2/plasma/ NSSDC data archive]}}
|-

| {{partial|Low Energy [[Charged particle|Charged Particle]] Instrument <br />{{small|(disabled)}}}}
| (LECP)
| style="text-align:left;" | Measures the differential in energy fluxes and angular distributions of ions, electrons and the differential in energy ion composition.
* {{small|1='''Data:''' [https://voyager-mac.umd.edu/ UMD data plotting], [https://pds-ppi.igpp.ucla.edu/search/?sc=Voyager%202&i=LECP PDS/PPI data catalog], [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/voyager/voyager2/particle/lecp/ NSSDC data archive]}}
|-

| {{partial|[[Cosmic Ray System]] <br />{{small|(disabled)}}}}
| (CRS)
| style="text-align:left;" | Determines the origin and acceleration process, life history, and dynamic contribution of interstellar cosmic rays, the nucleosynthesis of elements in cosmic-ray sources, the behavior of cosmic rays in the interplanetary medium, and the trapped planetary energetic-particle environment.
* {{small|1='''Data:''' [https://pds-ppi.igpp.ucla.edu/search/?sc=Voyager%202&i=CRS PDS/PPI data catalog], [ftp://nssdcftp.gsfc.nasa.gov/spacecraft_data/voyager/voyager2/particle/crs/  NSSDC data archive]}}
|-

| {{partial|Planetary [[Radio Astronomy]] Investigation <br />{{small|(disabled)}}}}
| (PRA)
| style="text-align:left;" | Utilizes a sweep-frequency radio receiver to study the radio-emission signals from Jupiter and Saturn.
* {{small|1='''Data:''' [https://pds-ppi.igpp.ucla.edu/search/?sc=Voyager%202&i=PRA PDS/PPI data catalog]}}
|-

| {{no|[[Polarimeter|Photopolarimeter]] System <br />{{small|(defective)}}}}
| (PPS)
| style="text-align:left;" | Utilized a telescope with a [[polarizer]] to gather information on surface texture and composition of Jupiter and Saturn and information on atmospheric scattering properties and density for both planets.
* {{small|'''Data:''' [https://pds-rings.seti.org/voyager/pps/data.html PDS/PRN data catalog]}}
|-

| {{yes|[[Plasma Wave Subsystem]] <br />{{small|(active)}}}}
| style="text-align:center" |(PWS)
| style="text-align:left;" | Provides continuous, sheath-independent measurements of the electron-density profiles at Jupiter and Saturn as well as basic information on local wave-particle interaction, useful in studying the magnetospheres.
* {{small|1='''Data:''' [https://pds-ppi.igpp.ucla.edu/search/?sc=Voyager%202&i=PWS PDS/PPI data catalog]}}
|}

{{Gallery| align = center
| title = Images of the spacecraft |width=175
|File:Voyager Testing 1976 PIA21732.jpg|alt2=Voyager in transport to a solar thermal test chamber | Voyager in transport to a solar thermal test chamber.
|File:Voyager 2 is encapsulated.jpg|alt4=''Voyager 2'' awaiting payload entry into a Titan IIIE/Centaur rocket | ''Voyager 2'' awaiting payload entry into a [[Titan IIIE]]/[[Centaur (rocket stage)|Centaur]] rocket.
}}