Editing Ganymede (moon) (section)

===Completed flybys===
[[File:Ganymede from Pioneer 10 19.jpg|thumb|Ganymede from ''[[Pioneer 10]]'' (1973)]]
The first spacecraft to approach close to Ganymede was ''[[Pioneer 10]]'', which performed a flyby in 1973 as it passed through the Jupiter system at high speed. ''[[Pioneer 11]]'' made a similar flyby in 1974.<ref name="Pioneer 11">{{cite web|url=http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Advanced&MCode=Pioneer_11 |title=Pioneer 11 |work=Solar System Exploration |access-date=January 6, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20110902202131/http://sse.jpl.nasa.gov/missions/profile.cfm?Sort=Advanced&MCode=Pioneer_11 |archive-date=September 2, 2011 }}</ref> Data sent back by the two spacecraft was used to determine the moon's physical characteristics<ref name="Terraformers">{{cite web |url=http://society.terraformers.ca/content/view/63/112/ |archive-url=https://web.archive.org/web/20070319083334/http://society.terraformers.ca/content/view/63/112/ |archive-date=March 19, 2007 |title=Exploration of Ganymede |work=Terraformers Society of Canada |access-date=January 6, 2008 }}</ref> and provided images of the surface with up to {{convert|400|km|mi|abbr=on}} resolution.<ref name="chap6">{{cite web |url=https://history.nasa.gov/SP-349/ch6.htm |work=SP-349/396 Pioneer Odyssey |title=Chapter 6: Results at the New Frontiers |publisher=NASA |date=August 1974 |access-date=July 12, 2017 |archive-date=July 14, 2019 |archive-url=https://web.archive.org/web/20190714121940/https://history.nasa.gov/SP-349/ch6.htm |url-status=live }}</ref> Pioneer 10's closest approach was 446,250&nbsp;km, about 85 times Ganymede's diameter.<ref name="dmu.p10">{{cite web |url=http://www.dmuller.net/spaceflight/mission.php?mission=pioneer10&appear=black&showimg=yes |title=Pioneer 10 Full Mission Timeline |publisher=D Muller |access-date=May 25, 2011 |archive-url=https://web.archive.org/web/20110723095322/http://www.dmuller.net/spaceflight/mission.php?mission=pioneer10&appear=black&showimg=yes |archive-date=July 23, 2011 |url-status=dead }}</ref>

''[[Voyager 1]]'' and ''[[Voyager 2]]'' both studied Ganymede when passing through the Jupiter system in 1979. Data from those flybys were used to refine the size of Ganymede, revealing it was larger than [[Saturn]]'s moon Titan, which was previously thought to have been bigger.<ref name="Voyager">{{cite web|url=http://library.thinkquest.org/J0112188/voyager_1_and_2.htm |title=Voyager 1 and 2 |work=ThinkQuest |access-date=January 6, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20071226052127/http://library.thinkquest.org/J0112188/voyager_1_and_2.htm |archive-date=December 26, 2007 }}</ref> Images from the ''Voyagers'' provided the first views of the moon's grooved surface terrain.<ref name="Voyager Mission">{{cite web |url=http://www.solarviews.com/eng/vgrfs.htm |title=The Voyager Planetary Mission |work=Views of the Solar System |access-date=January 6, 2008 |archive-url=https://web.archive.org/web/20080203032714/http://www.solarviews.com/eng/vgrfs.htm |archive-date=February 3, 2008 |url-status=dead }}</ref>

The ''Pioneer'' and ''Voyager'' flybys were all at large distances and high speeds, as they flew on [[hyperbolic orbit|unbound trajectories]] through the Jupiter system. Better data can be obtained from a spacecraft which is orbiting Jupiter, as it can encounter Ganymede at a lower speed and adjust the orbit for a closer approach. In 1995, the ''[[Galileo (spacecraft)|Galileo]]'' spacecraft entered orbit around Jupiter and between 1996 and 2000 made six close flybys of Ganymede.<ref name="The Grand Tour" /> These flybys were denoted G1, G2, G7, G8, G28 and G29.<ref name="Kivelson2002" /> During the closest flyby (G2), ''Galileo'' passed just 264&nbsp;km from the surface of Ganymede (five percent of the moon's diameter),<ref name="Kivelson2002" /> which remains the closest approach by any spacecraft. During the G1 flyby in 1996, ''Galileo'' instruments detected Ganymede's magnetic field.<ref name="Magnetic Field Discovery">{{cite web |url=http://www2.jpl.nasa.gov/galileo/status961212.html |archive-url=https://web.archive.org/web/19970105134408/http://www.jpl.nasa.gov/galileo/status961212.html |url-status=dead |archive-date=January 5, 1997 |title=New Discoveries From Galileo |work=Jet Propulsion Laboratory |access-date=January 6, 2008 }}</ref> Data from the ''Galileo'' flybys was used to discover the sub-surface ocean, which was announced in 2001.<ref name="Kivelson2002" /><ref name="The Grand Tour" /> High spatial resolution spectra of Ganymede taken by ''Galileo'' were used to identify several non-ice compounds on the surface.<ref name="McCord1998" />

The ''[[New Horizons]]'' spacecraft also observed Ganymede, but from a much larger distance as it passed through the Jupiter system in 2007 (en route to [[Pluto]]). The data were used to perform topographic and compositional mapping of Ganymede.<ref name="New Horizons">{{cite web |url=http://www.spacedaily.com/reports/Pluto_Bound_New_Horizons_Spacecraft_Gets_A_Boost_From_Jupiter_999.html |title=Pluto-Bound New Horizons Spacecraft Gets A Boost From Jupiter |work=Space Daily |access-date=January 6, 2008 |archive-date=March 23, 2019 |archive-url=https://web.archive.org/web/20190323054132/http://www.spacedaily.com/reports/Pluto_Bound_New_Horizons_Spacecraft_Gets_A_Boost_From_Jupiter_999.html |url-status=live }}</ref><ref name="Grundy2007">{{cite journal |last1=Grundy |first1=W.M. |last2=Buratti |first2=B.J. |last3=Cheng |first3=A.F. |last4=Emery |first4=J. P. |last5=Lunsford |first5=A. |last6=McKinnon |first6=W. B. |last7=Moore |first7=J. M. |last8=Newman |first8=S. F. |last9=Olkin |first9=C. B. |display-authors=2 |title=New Horizons Mapping of Europa and Ganymede |journal=Science |date=2007 |volume=318 |pages=234–237 |doi=10.1126/science.1147623 |bibcode=2007Sci...318..234G |pmid=17932288 |issue=5848 |s2cid=21071030 }}</ref>

Like ''Galileo'', the ''[[Juno (spacecraft)|Juno]]'' spacecraft orbited Jupiter. On 2019 December 25, ''Juno'' performed a distant flyby of Ganymede during its 24th orbit of Jupiter, at a range of {{convert|97680|to|109439|km|mi|sp=us}}. This flyby provided images of the moon's polar regions.<ref name="Juno">{{cite web |url=https://www.missionjuno.swri.edu/news/Ganymede |publisher=Southwest Research Institute |title=Ganymede |date=January 9, 2020 |access-date=January 10, 2020 |archive-date=February 15, 2020 |archive-url=https://web.archive.org/web/20200215020827/https://www.missionjuno.swri.edu/news/Ganymede |url-status=live }}</ref><ref name="Inaf">{{Cite web|last=Inaf|first=Ufficio stampa|date=August 6, 2021|title=Gli occhi di Jiram sull'equatore di Ganimede|url=https://www.media.inaf.it/2021/08/06/jiram-equatore-ganimede/|access-date=December 8, 2021|website=MEDIA INAF|language=it-IT|archive-date=December 8, 2021|archive-url=https://web.archive.org/web/20211208140147/https://www.media.inaf.it/2021/08/06/jiram-equatore-ganimede/|url-status=live}}</ref> In June 2021, ''Juno'' performed a second flyby, at a closer distance of {{convert|1038|km|mi|sp=us}}.<ref name="NYT-20210608" /><ref>{{cite news |title=Nasa spacecraft captures first closeups of Jupiter's largest moon in decades |url=https://www.theguardian.com/science/2021/jun/08/juno-nasa-jupiter-moon-ganymede |access-date=June 9, 2021 |work=The Guardian |agency=Associated Press |date=June 8, 2021 |language=en |archive-date=June 9, 2021 |archive-url=https://archive.today/20210609043534/https://www.theguardian.com/science/2021/jun/08/juno-nasa-jupiter-moon-ganymede |url-status=live }}</ref> This encounter was designed to provide a [[gravity assist]] to reduce ''Juno'''s orbital period from 53 days to 43 days. Additional images of the surface were collected.<ref name="NYT-20210608" />