Editing Geostationary orbit

{{Short description|Circular orbit above Earth's Equator and following the direction of Earth's rotation}}
{{Broader|Geosynchronous orbit}}
{{Use mdy dates|date=October 2019}}
{{Good article}}
[[File:Geostationaryjava3D.gif|thumb|right|Two geostationary satellites in the same orbit]]
[[File: Geosats compilation.jpg|thumb|right|A 5° × 6° view of a part of the geostationary belt, showing several geostationary satellites. Those with inclination 0° form a diagonal belt across the image; a few objects with small [[orbital inclination|inclinations]] to the [[Equator]] are visible above this line. The satellites are pinpoint, while stars have created [[star trail]]s due to [[Earth's rotation]].]]

A '''geostationary orbit''', also referred to as a '''geosynchronous equatorial orbit'''<ref group=lower-alpha>''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources.</ref> ('''GEO'''), is a [[circular orbit|circular]] [[geosynchronous orbit]] {{cvt|35,786|km|mi}} in altitude above Earth's [[equator]], {{cvt|42,164|km|mi}} in radius from Earth's center, and following the [[retrograde and prograde motion|direction]] of [[Earth's rotation]].

An object in such an orbit has an [[orbital period]] equal to Earth's rotational period, one [[sidereal time|sidereal day]], and so to ground observers it appears motionless, in a fixed position in the sky. The concept of a geostationary orbit was popularised by the science fiction writer [[Arthur C. Clarke]] in the 1940s as a way to revolutionise telecommunications, and the first [[satellite]] to be placed in this kind of orbit was launched in 1963.

[[Communications satellite]]s are often placed in a geostationary orbit so that Earth-based [[satellite dish|satellite antennas]] do not have to rotate to track them but can be pointed permanently at the position in the sky where the satellites are located. [[Weather satellite]]s are also placed in this orbit for real-time monitoring and data collection, as are [[navigation satellites]] in order to provide a known calibration point and enhance GPS accuracy.

Geostationary satellites are launched via a [[parking orbit|temporary orbit]], and then placed in a "slot" above a particular point on the Earth's surface. The satellite requires periodic station-keeping to maintain its position. Modern retired geostationary satellites are placed in a higher [[graveyard orbit]] to avoid collisions.

== History ==

[[File:Syncom 2 side.jpg|thumb|upright|Syncom 2, the first geosynchronous satellite]]

In 1929, [[Herman Potočnik]] described both geosynchronous orbits in general and the special case of the geostationary Earth orbit in particular as useful orbits for [[space station]]s.<ref>{{Cite book|last=Noordung|first=Hermann|url=https://commons.wikimedia.org/w/index.php?title=File%3AHerman_Poto%C4%8Dnik_Noordung_-_Das_Problem_der_Befahrung_des_Weltraums.pdf&page=102|title=Das Problem der Befahrung des Weltraums: Der Raketen-Motor|publisher=Richard Carl Schmidt & Co.|year=1929|location=Berlin|pages=98–100|format=PDF}}</ref> The first appearance of a geostationary [[orbit]] in popular literature was in October 1942, in the first [[Venus Equilateral]] story by [[George O. Smith]],<ref name="VE">"(Korvus's message is sent) to a small, squat building at the outskirts of Northern Landing. It was hurled at the sky. ... It ... arrived at the relay station tired and worn, ... when it reached a space station only five hundred miles above the city of North Landing." {{cite book|last=Smith|first=George O.|author-link=George O. Smith |title=The Complete Venus Equilateral|date=1976|publisher=[[Ballantine Books]]|location=New York|isbn=978-0-345-28953-7|pages=3–4 |url=https://books.google.com/books?id=lj8H3R4J5GUC&q=squat}}</ref> but Smith did not go into details. British [[science fiction]] author [[Arthur C. Clarke]] popularised and expanded the concept in a 1945 paper entitled ''Extra-Terrestrial Relays – Can Rocket Stations Give Worldwide Radio Coverage?'', published in ''[[Wireless World]]'' magazine. Clarke acknowledged the connection in his introduction to ''The Complete Venus Equilateral''.<ref name="VEintro">"It is therefore quite possible that these stories influenced me subconsciously when ... I worked out the principles of synchronous communications satellites ...", {{cite book|url=https://archive.org/details/arthurcclarkeaut00mcal/page/54 |page=54 |title=Arthur C. Clarke |first=Neil |last=McAleer|year=1992 |isbn=978-0-809-24324-2|publisher=Contemporary Books}}</ref><ref name="clarke"/> The orbit, which Clarke first described as useful for broadcast and relay communications satellites,<ref name="clarke">{{cite web| url=http://clarkeinstitute.org/wp-content/uploads/2010/04/ClarkeWirelessWorldArticle.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://clarkeinstitute.org/wp-content/uploads/2010/04/ClarkeWirelessWorldArticle.pdf |archive-date=2022-10-09 |url-status=live |author=Arthur C. Clarke|title= Extraterrestrial Relays: Can Rocket Stations Give World-wide Radio Coverage?|publisher=Arthur C. Clarke Institute for Space Education|date=October 1945|access-date=1 January 2021}}</ref> is sometimes called the Clarke orbit.<ref>{{cite web | publisher = [[NASA]] | url = http://www2.jpl.nasa.gov/basics/bsf5-1.php | title = Basics of Space Flight Section 1 Part 5, Geostationary Orbits | access-date = August 25, 2019 |editor=Phillips Davis | archive-url = https://archive.today/20121212130943/http://www2.jpl.nasa.gov/basics/bsf5-1.php | archive-date = 12 December 2012 }}</ref> Similarly, the collection of artificial satellites in this orbit is known as the Clarke Belt.<ref>{{Cite magazine|url=http://web.mit.edu/m-i-t/science_fiction/jenkins/jenkins_4.html|title=Orbit Wars: Arthur C. Clarke and the Global Communications Satellite|last= Mills|first=Mike|magazine=The Washington Post Magazine |date=August 3, 1997|pages= 12–13 |access-date=August 25, 2019}}</ref>

In technical terminology the orbit is referred to as either a geostationary or geosynchronous equatorial orbit, with the terms used somewhat interchangeably.<ref>{{cite book|chapter=Satellites and satellite remote senssing: Orbits |title=Encyclopedia of Atmospheric Sciences |edition=2 |year=2015 |pages=95–106 |last=Kidder |first=S.Q. |editor-first=Gerald |editor-last=North |editor-first2=John |editor-last2=Pyla |editor-first3=Fuqing |editor-last3=Zhang |doi=10.1016/B978-0-12-382225-3.00362-5 |publisher=Elsiver|isbn=9780123822253 }}</ref>

The first geostationary satellite was designed by [[Harold Rosen (electrical engineer)|Harold Rosen]] while he was working at [[Hughes Aircraft]] in 1959. Inspired by [[Sputnik 1]], he wanted to use a geostationary satellite to globalise communications. Telecommunications between the US and Europe was then possible between just 136 people at a time, and reliant on [[high frequency]] radios and an [[Submarine communications cable|undersea cable]].<ref name=dm>{{Cite magazine|first=Jack|last=McClintock|date=November 9, 2003|url=http://discovermagazine.com/2003/nov/communications|title=Communications: Harold Rosen – The Seer of Geostationary Satellites|website=Discover Magazine |access-date=August 25, 2019}}</ref>

Conventional wisdom at the time was that it would require too much [[rocket]] power to place a satellite in a geostationary orbit and it would not survive long enough to justify the expense,<ref>{{Cite book|url=https://www.caltech.edu/about/news/harold-rosen-1926-2017-53790|title=Harold Rosen, 1926–2017|publisher=Caltech|last=Perkins|first=Robert|date=January 31, 2017 |access-date=August 25, 2019}}</ref> so early efforts were put towards constellations of satellites in [[low Earth orbit|low]] or [[Medium Earth Orbit|medium]] Earth orbit.<ref name="lat"/> The first of these were the passive [[Project Echo|Echo balloon satellites]] in 1960, followed by [[Telstar 1]] in 1962.<ref>{{cite book|title=Beyond The Ionosphere: Fifty Years of Satellite Communication|year=1997|chapter-url=https://history.nasa.gov/SP-4217/ch6.htm |author=Daniel R. Glover |editor=Andrew J Butrica|publisher=NASA |chapter=Chapter 6: NASA Experimental Communications Satellites, 1958-1995|bibcode=1997bify.book.....B}}</ref> Although these projects had difficulties with signal strength and tracking, issues that could be solved using geostationary orbits, the concept was seen as impractical, so Hughes often withheld funds and support.<ref name="lat">{{Cite news|url=https://www.latimes.com/nation/la-na-syncom-satellite-20130726-dto-htmlstory.html|title=How a satellite called Syncom changed the world|first=Ralph|last=Vartabedian|newspaper=Los Angeles Times |date=July 26, 2013 |access-date=August 25, 2019}}</ref><ref name=dm/>

By 1961, Rosen and his team had produced a cylindrical prototype with a diameter of {{convert|76|cm|in}}, height of {{convert|38|cm|in}}, weighing {{convert|11.3|kg|lb}}, light and small enough to be placed into orbit. It was [[Spin-stabilisation|spin stabilised]] with a dipole antenna producing a pancake shaped beam.<ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-031A|publisher=NASA|title=Syncom 2|editor=David R. Williams |access-date=September 29, 2019}}</ref> In August 1961, they were contracted to begin building the real satellite.<ref name=dm/> They lost [[Syncom#Syncom 1|Syncom 1]] to electronics failure, but [[Syncom#Syncom 2|Syncom 2]] was successfully placed into a geosynchronous orbit in 1963. Although its [[inclined orbit]] still required moving antennas, it was able to relay TV transmissions, and allowed for US President [[John F. Kennedy]] in Washington D.C., to phone Nigerian prime minister [[Abubakar Tafawa Balewa]] aboard the [[USNS Kingsport]] docked in [[Lagos]] on August 23, 1963.<ref name="lat"/><ref>{{Cite web|url=https://www.historychannel.com.au/this-day-in-history/worlds-first-geosynchronous-satellite-launched/|title=World's First Geosynchronous Satellite Launched|publisher=Foxtel|date=June 19, 2016|website=History Channel|access-date=August 25, 2019|archive-date=December 7, 2019|archive-url=https://web.archive.org/web/20191207144926/https://www.historychannel.com.au/this-day-in-history/worlds-first-geosynchronous-satellite-launched/|url-status=dead}}</ref>

The first satellite placed in a geostationary orbit was [[Syncom#Syncom 3|Syncom 3]], which was launched by a [[Delta (rocket family)#Delta D|Delta D rocket]] in 1964.<ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1964-047A |title=Syncom 3|publisher=NASA |editor=David R. Williams |access-date=September 29, 2019}}</ref> With its increased bandwidth, this satellite was able to transmit live coverage of the Summer Olympics from Japan to America. Geostationary orbits have been in common use ever since, in particular for satellite television.<ref name="lat"/>

Today there are hundreds of geostationary satellites providing [[remote sensing]] and communications.<ref name=dm/><ref>{{Cite web|url=https://www.space.com/29222-geosynchronous-orbit.html|title=What Is a Geosynchronous Orbit?|website=Space.com|first=Elizabeth|last= Howell|date=April 24, 2015 |access-date=August 25, 2019}}</ref>

Although most populated land locations on the planet now have terrestrial communications facilities ([[microwave]], [[fiber-optic]]), with telephone access covering 96% of the population and internet access 90%,<ref>{{cite web|url=https://www.itu.int/en/mediacentre/Pages/2018-PR40.aspx |title=ITU releases 2018 global and regional ICT estimates |publisher=[[International Telecommunication Union]] |access-date=August 25, 2019 |date= December 7, 2018}}</ref> some rural and remote areas in developed countries are still reliant on satellite communications.<ref>{{cite news|publisher=[[Australian Broadcasting Corporation|ABC]] |access-date=August 25, 2019 |title=Australia was promised superfast broadband with the NBN. This is what we got |first=Geoff |last=Thompson |date=April 24, 2019 |url=https://www.abc.net.au/news/2019-04-23/what-happened-to-superfast-nbn/11037620}}</ref><ref>{{cite news|publisher=[[CNET]] |url=https://www.cnet.com/news/in-rural-farm-country-forget-broadband-you-might-not-have-internet-at-all/ |title=In farm country, forget broadband. You might not have internet at all. 5G is around the corner, yet pockets of America still can't get basic internet access. |first=Shara |last=Tibken |date=October 22, 2018 |access-date=August 25, 2019}}</ref>

== Uses ==
{{See also| Geosynchronous satellite}}

Most commercial [[communications satellite]]s, [[broadcast satellite]]s and [[SBAS]] satellites operate in geostationary orbits.<ref>{{cite web|url=https://www.esa.int/Our_Activities/Telecommunications_Integrated_Applications/Orbits |title=Orbits |publisher=[[ESA]] |access-date=October 1, 2019 |date=October 4, 2018}}</ref><ref name="gmv"/><ref>{{cite web|url=https://www.sws.bom.gov.au/Educational/5/4/3 |title=Satellites, Geo-stationary orbits and Solar Eclipses |access-date=October 1, 2019 |publisher=[[Bureau of Meteorology|BOM]]|author=Richard Thompson}}</ref>

=== Communications ===
Geostationary communication satellites are useful because they are visible from a large area of the earth's surface, extending 81° away in latitude and 77° in longitude.<ref name="eisemann"/> They appear stationary in the sky, which eliminates the need for ground stations to have movable antennas. This means that Earth-based observers can erect small, cheap and stationary antennas that are always directed at the desired satellite.<ref name="smad"/>{{rp|537}} However, [[Latency (engineering)|latency]] becomes significant as it takes about 240&nbsp;ms for a signal to pass from a ground based transmitter on the equator to the satellite and back again.<ref name="smad"/>{{rp|538}} This delay presents problems for latency-sensitive applications such as voice communication,<ref>{{cite web|url=http://www.isoc.org/inet96/proceedings/g1/g1_3.htm |title=The Teledesic Network: Using Low-Earth-Orbit Satellites to Provide Broadband, Wireless, Real-Time Internet Access Worldwide |first=Daniel |last=Kohn |publisher=Teledesic Corporation, USA |date=March 6, 2016}}</ref> so geostationary communication satellites are primarily used for unidirectional entertainment and applications where low latency alternatives are not available.<ref name="wiley">{{cite book|chapter=Satellite Communications|first=Roger L.|last=Freeman|date=July 22, 2002|publisher=American Cancer Society|doi=10.1002/0471208051.fre018|title = Reference Manual for Telecommunications Engineering|isbn = 0471208051}}</ref>

Geostationary satellites are directly overhead at the equator and appear lower in the sky to an observer nearer the poles. As the observer's latitude increases, communication becomes more difficult due to factors such as [[atmospheric refraction]], Earth's [[thermal radiation|thermal emission]], line-of-sight obstructions, and signal reflections from the ground or nearby structures. At latitudes above about 81°, geostationary satellites are below the horizon and cannot be seen at all.<ref name="eisemann">{{cite journal|url=http://www.ngs.noaa.gov/CORS/Articles/SolerEisemannJSE.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.ngs.noaa.gov/CORS/Articles/SolerEisemannJSE.pdf |archive-date=2022-10-09 |url-status=live|page=123|title=Determination of Look Angles To Geostationary Communication Satellites|first1=Tomás |last1=Soler|first2= David W. |last2=Eisemann|journal=Journal of Surveying Engineering |volume=120|issue=3|date=August 1994|issn=0733-9453|access-date=April 16, 2019|doi=10.1061/(ASCE)0733-9453(1994)120:3(115)}}</ref> Because of this, some [[Russia]]n communication satellites have used [[elliptic orbit|elliptical]] [[Molniya orbit|Molniya]] and [[Tundra orbit|Tundra]] orbits, which have excellent visibility at high latitudes.<ref name=seh>{{cite book|page=416|url=https://books.google.com/books?id=2ZNxDwAAQBAJ&q=molniya+orbit+OKB-1+history&pg=PA416|isbn=978-1-85109-514-8|title = Space Exploration and Humanity: A Historical Encyclopedia|volume=1|author=History Committee of the American Astronautical Society |editor-first=Stephen B. |editor-last=Johnson|publisher = Greenwood Publishing Group|date = August 23, 2010|access-date=April 17, 2019}}</ref>

=== Meteorology ===
{{see also|Weather satellite}}

A worldwide network of operational [[geostationary meteorological satellite]]s is used to provide visible and [[Thermographic camera|infrared images]] of Earth's surface and atmosphere for weather observation, [[oceanography]], and atmospheric tracking. As of 2019 there are 19 satellites in either operation or stand-by.<ref>{{cite web|url=http://www.wmo.int/pages/prog/sat/satellitestatus.php|title=Satellite Status|publisher=World Meteorological Organization|access-date=July 6, 2019}}</ref> These satellite systems include:
* the United States' [[Geostationary Operational Environmental Satellite|GOES]] series, operated by [[National Oceanic and Atmospheric Administration|NOAA]]<ref>{{Cite web|url=https://www.nesdis.noaa.gov/content/our-satellites|title=Our Satellites|work=[[NOAA]] [[National Environmental Satellite, Data, and Information Service]] (NESDIS)}}</ref>
* the [[Meteosat]] series, launched by the [[European Space Agency]] and operated by the European Weather Satellite Organization, [[EUMETSAT]]<ref name="auto">{{Cite web|url=https://www.eumetsat.int/website/home/Satellites/CurrentSatellites/Meteosat/index.html|title=Meteosat|website=EUMETSAT.int|access-date=July 1, 2019|archive-date=January 14, 2020|archive-url=https://web.archive.org/web/20200114164122/https://www.eumetsat.int/website/home/Satellites/CurrentSatellites/Meteosat/index.html|url-status=dead}}</ref>
* the Republic of Korea [[Chollian|COMS-1]] and<ref name="LK">{{cite web|url=http://www.arianespace.com/images/launch-kits/launch-kit-pdf-eng/GB-ARABSAT-5A-COMS.pdf|title=Satellite Launches for the Middle East and South Korea|publisher=Arianespace|access-date=June 26, 2010|url-status=dead|archive-url=https://web.archive.org/web/20100704234145/http://www.arianespace.com/images/launch-kits/launch-kit-pdf-eng/GB-ARABSAT-5A-COMS.pdf|archive-date=July 4, 2010}}</ref> [[GEO-KOMPSAT 2A|GK-2A]] multi mission satellites.<ref>{{Cite web|url=https://www.airbus.com/newsroom/press-releases/en/2014/09/airbus-defence-and-space-supports-south-korean-weather-satellite-programme.html|title=Airbus Defence and Space supports South Korean weather satellite programme|website=Airbus|date=September 9, 2014|first=Ralph|last=Heinrich|access-date=July 2, 2019|archive-date=December 26, 2019|archive-url=https://web.archive.org/web/20191226065525/https://www.airbus.com/newsroom/press-releases/en/2014/09/airbus-defence-and-space-supports-south-korean-weather-satellite-programme.html|url-status=dead}}</ref>
* the Russian [[Elektro-L]] satellites
* the Japanese [[Himawari (satellite)|Himawari]] series<ref>{{Cite web|url=https://www.nasaspaceflight.com/2014/10/japan-loft-himawari-8-satellite-h-iia/|title=Japan lofts Himawari 8 weather satellite via H-IIA rocket |publisher=NASASpaceFlight.com|first=William |last=Graham|date=October 6, 2014}}</ref>
* Chinese [[Fengyun]] series<ref>{{cite news |title=China plans to launch additional nine Fengyun meteorological satellites by 2025 |date=November 15, 2018 |url=https://gbtimes.com/china-plans-to-launch-additional-nine-fengyun-meteorological-satellites-by-2025 |newspaper=GBTimes |access-date=July 2, 2019 |archive-date=July 2, 2019 |archive-url=https://web.archive.org/web/20190702115542/https://gbtimes.com/china-plans-to-launch-additional-nine-fengyun-meteorological-satellites-by-2025 |url-status=dead }}</ref>
* India's [[Indian National Satellite System|INSAT]] series<ref name=isro>{{cite web|url=https://www.isro.gov.in/rapid-gateway-to-indian-weather-satellite-data|publisher=Indian Space Research Organisation|title=RAPID: Gateway to Indian Weather Satellite Data|date=July 2, 2019|access-date=July 2, 2019|archive-date=December 25, 2019|archive-url=https://web.archive.org/web/20191225031828/https://www.isro.gov.in/rapid-gateway-to-indian-weather-satellite-data|url-status=dead}}</ref>

These satellites typically capture images in the visual and infrared spectrum with a spatial resolution between 0.5 and 4 square kilometres.<ref name="bomm"/> The coverage is typically 70°,<ref name="bomm">{{cite web|publisher=[[Bureau of Meteorology|BOM]]|url=http://www.bom.gov.au/australia/satellite/about_satellites.shtml |title=About environmental satellites
|access-date=July 6, 2019}}</ref> and in some cases less.<ref>{{Cite web|url=http://www.planetary.org/multimedia/space-images/charts/coverage-of-a-geostationary.html|title=Coverage of a geostationary satellite at Earth|publisher=The Planetary Society}}</ref>

Geostationary satellite imagery has been used for tracking [[volcanic ash]],<ref>{{Cite web|url=http://www.spaceref.com/news/viewpr.html?pid=15216|title=NOAA Satellites, Scientists Monitor Mt. St. Helens for Possible Eruption|website=SpaceRef|date=October 6, 2004|access-date=July 1, 2019|archive-date=September 10, 2012|archive-url=https://archive.today/20120910225555/http://www.spaceref.com/news/viewpr.html?pid=15216|url-status=dead}}</ref> measuring cloud top temperatures and water vapour, [[Geostationary Ocean Color Imager|oceanography]],<ref>{{cite web |publisher=NASA |title=GOCI |url=https://oceancolor.gsfc.nasa.gov/data/goci/ |access-date=August 25, 2019 |archive-date=June 24, 2021 |archive-url=https://web.archive.org/web/20210624041150/https://oceancolor.gsfc.nasa.gov/data/goci/ |url-status=dead }}</ref> measuring land temperature and vegetation coverage,<ref>{{Cite journal|last1=Miura|first1=Tomoaki|last2=Nagai|first2=Shin|last3=Takeuchi|first3=Mika|last4=Ichii|first4=Kazuhito|last5=Yoshioka|first5=Hiroki|date=2019-10-30|title=Improved Characterisation of Vegetation and Land Surface Seasonal Dynamics in Central Japan with Himawari-8 Hypertemporal Data|journal=Scientific Reports|language=en|volume=9|issue=1|page=15692|doi=10.1038/s41598-019-52076-x|issn=2045-2322|pmc=6821777|pmid=31666582|bibcode=2019NatSR...915692M}}</ref><ref name="noaa"/> facilitating [[cyclone]] path prediction,<ref name=isro/> and providing real time cloud coverage and other tracking data.<ref>{{Cite web|url=https://sos.noaa.gov/datasets/goes-r-todays-satellite-for-tomorrows-forecast/|title=GOES-R: Today's Satellite for Tomorrow's Forecast Dataset|work=Science On a Sphere|date=November 14, 2016 |publisher=[[National Oceanic and Atmospheric Administration|NOAA]]}}</ref> Some information has been incorporated into [[Numerical weather prediction|meteorological prediction models]], but due to their wide field of view, full-time monitoring and lower resolution, geostationary weather satellite images are primarily used for short-term and real-time forecasting.<ref>{{Cite journal|title=Latest US weather satellite highlights forecasting challenges|first=Jeff|last=Tollefson|date=March 2, 2018|journal=Nature|volume=555|issue=7695|pages=154|doi=10.1038/d41586-018-02630-w|pmid=29517031|bibcode=2018Natur.555..154T|doi-access=free}}</ref><ref name="noaa">{{Cite web|url=https://public-old.wmo.int/en/resources/bulletin/noaa%E2%80%99s-eyes-sky-after-five-decades-of-weather-forecasting-environmental|archive-url=https://web.archive.org/web/20231218171711/https://public-old.wmo.int/en/resources/bulletin/noaa%E2%80%99s-eyes-sky-after-five-decades-of-weather-forecasting-environmental|url-status=dead|archive-date=December 18, 2023|title=NOAA's Eyes in the Sky – After Five Decades of Weather Forecasting with Environmental Satellites, What Do Future Satellites Promise for Meteorologists and Society?|date=November 12, 2015|website=World Meteorological Organization|first1=Derek|last1=Hanson|first2=James|last2=Peronto|first3=Douglas|last3=Hilderbrand|access-date=July 2, 2019}}</ref>

===Navigation===
{{further|GNSS augmentation}}

[[Image:SBAS Service Areas.png|thumb|upright=1.35|Service areas of satellite-based augmentation systems (SBAS).<ref name="gmv">{{cite web|url=https://www.gmv.com/en/Company/Communication/News/2016/06/SBASAfrica.html| publisher=[[GMV (company)|GMV]] |title= Deployment of an SBAS system demonstration in Southern Africa |date=August 6, 2016|access-date=October 1, 2019}}</ref>]]

Geostationary satellites can be used to augment [[GNSS]] systems by relaying [[Error analysis for the Global Positioning System#Ephemeris and clock errors|clock]], [[Error analysis for the Global Positioning System#Ephemeris and clock errors|ephemeris]] and [[Error analysis for the Global Positioning System#Atmospheric effects|ionospheric]] error corrections (calculated from ground stations of a known position) and providing an additional reference signal.<ref>{{Cite web|url=https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/waas/howitworks/|title=Satellite Navigation – WAAS – How It Works|publisher=[[Federal Aviation Administration|FAA]]|date=June 12, 2019}}</ref> This improves position accuracy from approximately 5m to 1m or less.<ref>{{cite web|url=https://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-for-the-future/satellite-based-augmentation-system |archive-url=https://web.archive.org/web/20190707040109/https://www.ga.gov.au/scientific-topics/positioning-navigation/positioning-for-the-future/satellite-based-augmentation-system |archive-date=July 7, 2019|publisher=Geoscience Australia|title=Satellite Based Augmentation System test-bed project}}</ref>

Past and current navigation systems that use geostationary satellites include:
* The [[Wide Area Augmentation System]] (WAAS), operated by the [[United States]] [[Federal Aviation Administration]] (FAA);
* The [[European Geostationary Navigation Overlay Service]] (EGNOS), operated by the [[European Satellite Services Provider|ESSP]] (on behalf of [[EU]]'s [[European GNSS Agency|GSA]]);
* The [[Multi-functional Satellite Augmentation System]] (MSAS), operated by [[Japan]]'s [[Ministry of Land, Infrastructure, Transport and Tourism|Ministry of Land, Infrastructure and Transport]] [[Japan Civil Aviation Bureau]] (JCAB);
* The [[GPS Aided Geo Augmented Navigation]] (GAGAN) system being operated by [[India]].<ref>{{cite press release|url=http://isro.gov.in/pressrelease/scripts/pressreleasein.aspx?Jan03_2014|date=January 3, 2014|title=GAGAN System Certified for RNP0.1 Operations|archive-url=https://web.archive.org/web/20140103233538/http://isro.gov.in/pressrelease/scripts/pressreleasein.aspx?Jan03_2014|archive-date=January 3, 2014|publisher=[[Indian Space Research Organisation]]}}</ref><ref>{{Cite news|url=https://www.thehindu.com/news/national/kerala/gagan-system-ready-for-operations/article5565700.ece|title=GAGAN system ready for operations|first=S. Anil|last=Radhakrishnan|date=January 11, 2014|work=The Hindu}}</ref>
* The commercial [[StarFire (navigation system)|StarFire navigation system]], operated by [[Deere & Company|John Deere]] and [[C-Nav]] Positioning Solutions ([[Oceaneering]]);
* The commercial [[Starfix DGPS System]] and [[OmniSTAR]] system, operated by [[Fugro]].<ref>{{Cite conference|title=Ten Years of Experience with A Commercial Satellite Navigation System|last= Ott |first= L. E. |conference=International Cooperation in Satellite Communications, Proceedings of the AIAA/ESA Workshop |place= ESTEC, Noordwijk, the Netherlands. |editor-first=C. |editor-last=Mattok |page=101 |bibcode=1995ESASP.372..101O}}</ref>

==Implementation==

===Launch===
{{See also|Geostationary transfer orbit}}
{{multiple image|perrow = 1|total_width=
| image1 = Animation of EchoStar XVII trajectory.gif
| image2 = Animation of EchoStar XVII trajectory Equatorial view.gif
| footer = An example of a transition from temporary [[Geostationary transfer orbit|GTO]] to GSO.<br />{{legend2|magenta|[[EchoStar XVII]]}}{{·}}{{legend2|RoyalBlue|[[Earth]]}}.
}}

Geostationary satellites are launched to the east into a prograde orbit that matches the rotation rate of the equator. The smallest inclination that a satellite can be launched into is that of the launch site's latitude, so launching the satellite from close to the equator limits the amount of [[Orbital inclination change|inclination change]] needed later.<ref name="conf"/> Additionally, launching from close to the equator allows the speed of the Earth's rotation to give the satellite a boost. A launch site should have water or deserts to the east, so any failed rockets do not fall on a populated area.<ref>{{Cite web|url=https://www.eumetsat.int/website/home/Satellites/LaunchesandOrbits/LaunchingSatellites/index.html|title=Launching Satellites|website=Eumetsat|access-date=July 22, 2019|archive-date=December 21, 2019|archive-url=https://web.archive.org/web/20191221164243/https://www.eumetsat.int/website/home/Satellites/LaunchesandOrbits/LaunchingSatellites/index.html|url-status=dead}}</ref>

Most [[launch vehicle]]s place geostationary satellites directly into a [[geostationary transfer orbit]] (GTO), an elliptical orbit with an [[apsis|apogee]] at GEO height and a low [[apsis|perigee]]. On-board satellite propulsion is then used to raise the perigee, circularise and reach GEO.<ref name="conf">{{cite conference|url=https://www.researchgate.net/publication/282014319 |conference=20th International Symposium on Space Flight Dynamics|first1=Nicholas |last1=Farber |first2=Andrea |last2=Aresini |first3=Pascal |last3=Wauthier |first4=Philippe |last4=Francken|date=September 2007 |title=A general approach to the geostationary transfer orbit mission recovery |page=2}}</ref><ref>{{cite web|url=http://www.planetary.org/blogs/jason-davis/20140116-how-to-get-a-satellite-to-gto.html |title=How to get a satellite to geostationary orbit |author=Jason Davis|date=January 17, 2014|access-date=October 2, 2019 |publisher=The Planetary Society}}</ref>

=== Orbit allocation ===
{{see also|Bogota Declaration}}
Satellites in geostationary orbit must all occupy a single ring above the [[equator]]. The requirement to space these satellites apart, to avoid harmful radio-frequency interference during operations, means that there are a limited number of orbital slots available, and thus only a limited number of satellites can be operated in geostationary orbit. This has led to conflict between different countries wishing access to the same orbital slots (countries near the same [[longitude]] but differing [[latitudes]]) and [[radio frequencies]]. These disputes are addressed through the [[International Telecommunication Union]]'s allocation mechanism under the [[ITU Radio Regulations|Radio Regulations]].<ref>{{cite web|url=http://www.itu.int/ITU-R/conferences/seminars/mexico-2001/docs/06-procedure-mechanism.doc |archive-url=https://web.archive.org/web/20090327092830/http://www.itu.int/ITU-R/conferences/seminars/mexico-2001/docs/06-procedure-mechanism.doc|archive-date=March 27, 2009 |title=Orbit/Spectrum Allocation Procedures Registration Mechanism under the Radio Regulations |last=Henri |first=Yvon |publisher=Space Services Department}}</ref><ref>{{cite web|url=http://www.itu.int/ITU-R/go/space/en |access-date=July 26, 2019 |publisher=ITU |title=Space Services Division}}</ref> In the 1976 [[Bogota Declaration]], eight countries located on the Earth's equator claimed sovereignty over the geostationary orbits above their territory, but the claims gained no international recognition.<ref>{{cite journal|last=Oduntan|first= Gbenga|s2cid= 10047170| title = The Never Ending Dispute: Legal Theories on the Spatial Demarcation Boundary Plane between Airspace and Outer Space|journal= Hertfordshire Law Journal|volume=1|issue= 2|page=75}}</ref>

===Statite proposal===
A [[statite]] is a hypothetical satellite that uses [[Radiation pressure#Solar radiation pressure|radiation pressure]] from the sun against a [[solar sail]] to modify its orbit.

It would hold its location over the dark side of the Earth at a latitude of approximately 30 degrees. A statite is stationary relative to the Earth and Sun system rather than compared to surface of the Earth, and could ease congestion in the geostationary ring.<ref>{{cite patent |country = US |number = 5183225 |status = patent |title = STATITE: SPACECRAFT THAT UTILIZES SIGHT PRESSURE AND METHOD OF USE |pubdate = February 2, 1993 |pridate = 1989-01-09 |inventor-surname = Forward |inventor-given = Robert}}</ref><ref>{{cite magazine|magazine=New Scientist |date=March 9, 1991 |title=Science: Polar 'satellite' could revolutionise communications|issue=1759|url=https://www.newscientist.com/article/mg12917594-000-science-polar-satellite-could-revolutionisecommunications/ |access-date=October 2, 2019}}</ref>

== Retired satellites ==

[[Geostationary satellite]]s require some [[Orbital station-keeping|station keeping]] to keep their position, and once they run out of thruster fuel they are generally retired. The [[Transponder (satellite communications)|transponders]] and other onboard systems often outlive the thruster fuel and by allowing the satellite to move naturally into an inclined geosynchronous orbit some satellites can remain in use,<ref>{{cite web | url=http://www.satsig.net/satellite/inclined-orbit-operation.htm | title = Inclined orbit operation | work=SatSig.net}}</ref> or else be elevated to a [[graveyard orbit]]. This process is becoming increasingly regulated and satellites must have a 90% chance of moving over 200&nbsp;km above the geostationary belt at end of life.<ref>{{Cite web|url=https://phys.org/news/2017-04-satellites-die.html|title=Where old satellites go to die|website=phys.org|date=April 3, 2017|author=EUMETSAT}}</ref>

=== Space debris ===
{{main|Space debris#Characterization}}

[[File:Debris-GEO1280.jpg|thumb|alt=Earth from space, surrounded by small white dots|A computer-generated image from 2005 showing the distribution of mostly space debris in [[geocentric orbit]] with two areas of concentration: geostationary orbit and low Earth orbit.]]

Space debris at geostationary orbits typically has a lower collision speed than at [[low Earth orbit|low Earth orbit (LEO)]] since all GEO satellites orbit in the same plane, altitude and speed; however, the presence of satellites in [[Orbital eccentricity|eccentric orbits]] allows for collisions at up to {{cvt|4|km/s|km/h mph|-2}}. Although a collision is comparatively unlikely, GEO satellites have a limited ability to avoid any debris.<ref>{{Cite web|url=https://physicsworld.com/a/space-debris-threat-to-geosynchronous-satellites-has-been-drastically-underestimated/|title=Space debris threat to geosynchronous satellites has been drastically underestimated|date=December 12, 2017|website=Physics World |author=Marric Stephens}}</ref>

At geosynchronous altitude, objects less than 10&nbsp;cm in diameter cannot be seen from the Earth, making it difficult to assess their prevalence.<ref name="telk1">{{Cite web|url=https://spacenews.com/exoanalytic-video-shows-telkom-1-satellite-erupting-debris/|title=ExoAnalytic video shows Telkom-1 satellite erupting debris|date=August 30, 2017|website=SpaceNews.com |author=Caleb Henry}}</ref>

Despite efforts to reduce risk, spacecraft collisions have occurred. The [[European Space Agency]] telecom satellite [[Olympus-1]] was struck by a [[meteoroid]] on August 11, 1993, and eventually moved to a [[graveyard orbit]],<ref name="The Olympus failure">[http://www.selkirkshire.demon.co.uk/analoguesat/olympuspr.html "The Olympus failure"] ''ESA press release'', August 26, 1993.  {{webarchive |url=https://web.archive.org/web/20070911181644/http://www.selkirkshire.demon.co.uk/analoguesat/olympuspr.html |date=September 11, 2007 }}</ref> and in 2006 the Russian [[Express (satellite)|Express-AM11]] communications satellite was struck by an unknown object and rendered inoperable,<ref name=srdc20060419>[https://archive.today/20130104185122/http://www.spaceref.com/news/viewsr.html?pid=20320 "Notification for Express-AM11 satellite users in connection with the spacecraft failure"] ''Russian Satellite Communications Company'', April 19, 2006.</ref> although its engineers had enough contact time with the satellite to send it into a graveyard orbit. In 2017, both [[AMC-9]] and [[Telkom-1]] broke apart from an unknown cause.<ref>{{Cite web|url=https://spacenews.com/op-ed-do-we-care-about-orbital-debris-at-all/|title=Do we care about orbital debris at all?|first=James E.|last=Dunstan|date=January 30, 2018|website=SpaceNews.com}}</ref><ref name="telk1"/><ref>{{Cite web|url=http://spaceflight101.com/amc-9-satellite-anomaly-orbit-change/|title=AMC 9 Satellite Anomaly associated with Energetic Event & sudden Orbit Change – Spaceflight101|date=June 20, 2017|website=spaceflight101.com}}</ref>

==Properties==

A typical geostationary orbit has the following properties:
* Inclination: 0°
* Period: 1436 minutes (one [[sidereal day]])<ref name="smad">{{cite book|title=Space Mission Analysis and Design|publisher=Microcosm Press and Kluwer Academic Publishers |editor1-first=Wiley J. |editor1-last=Larson |editor2-first=James R. |editor2-last=Wertz |bibcode=1999smad.book.....W |last1=Wertz |first1=James Richard |last2=Larson |first2=Wiley J. |year=1999|isbn=1-881883-10-8}}</ref>{{rp|121}}
* Eccentricity: 0
* Argument of perigee: undefined
* [[Semi-major and semi-minor axes#Astronomy|Semi-major axis]]: 42,164&nbsp;km

===Inclination===
An inclination of zero ensures that the orbit remains over the equator at all times, making it stationary with respect to latitude from the point of view of a ground observer (and in the [[ECEF|Earth-centered Earth-fixed]] reference frame).<ref name="smad"/>{{rp|122}}

===Period===
The orbital period is equal to exactly one sidereal day. This means that the satellite will return to the same point above the Earth's surface every (sidereal) day, regardless of other orbital properties. For a geostationary orbit in particular, it ensures that it holds the same longitude over time.<ref name="smad"/>{{rp|121}} This orbital period, ''T'', is directly related to the semi-major axis of the orbit through [[Kepler's laws|Kepler's Third Law]]:

: <math>T = 2\pi\sqrt{a^3 \over \mu}</math>

where:
* {{mvar|a}} is the length of the orbit's semi-major axis
* {{mvar|μ}} is the [[standard gravitational parameter]] of the central body<ref name="smad"/>{{rp|137}}

===Eccentricity===
The [[Orbital eccentricity|eccentricity]] is zero, which produces a [[circular orbit]]. This ensures that the satellite does not move closer or further away from the Earth, which would cause it to track backwards and forwards across the sky.<ref name="smad"/>{{rp|122}}

== Stability ==
A geostationary orbit can be achieved only at an altitude very close to {{convert|35786|km|mi|0|abbr=off}} and directly above the equator. This equates to an orbital speed of {{convert|3.07|km/s|mi/s|2| abbr=off}} and an orbital period of 1,436 minutes, one [[sidereal day]]. This ensures that the satellite will match the Earth's rotational period and has a stationary [[Footprint (satellite)|footprint]] on the ground. All geostationary satellites have to be located on this ring.

A combination of [[Moon|lunar]] gravity, [[Sun|solar]] gravity, and the [[Equatorial bulge#On Earth|flattening of the Earth]] at its poles causes a [[precession]] motion of the orbital plane of any geostationary object, with an [[orbital period]] of about 53 years and an initial inclination gradient of about 0.85° per year, achieving a maximal inclination of 15° after 26.5 years.<ref name=Anderson2015>{{Cite conference|url=http://hanspeterschaub.info/Papers/Anderson2015c.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://hanspeterschaub.info/Papers/Anderson2015c.pdf |archive-date=2022-10-09 |url-status=live|title=Operational Considerations of GEO Debris Synchronization Dynamics|first1=Paul|last1=Anderson|display-authors=etal|conference=66th [[International Astronautical Congress]]|location=Jerusalem, Israel|date=2015|id=IAC-15,A6,7,3,x27478}}</ref><ref name="smad"/>{{rp|156}} To correct for this [[perturbation (astronomy)|perturbation]], regular [[orbital stationkeeping]] maneuvers are necessary, amounting to a [[delta-v]] of approximately 50&nbsp;m/s per year.<ref name="iop">{{cite conference|doi-access=free|title=Plasma propulsion for geostationary satellites fortelecommunication and interplanetary missions |conference=IOP Conference Series: Materials Science and Engineering |first1=M |last1=Dundeck |first2 = F |last2=Doveil |first3=N |last3=Arcis |first4=S |last4=Zurbach |year=2012 |number=29 |doi=10.1088/1757-899X/29/1/012010}}</ref>

A second effect to be taken into account is the longitudinal drift, caused by the asymmetry of the Earth – the equator is slightly elliptical ([[Figure of the Earth#Triaxiality (equatorial eccentricity)|equatorial eccentricity]]).<ref name="smad"/>{{rp|156}} There are two stable equilibrium points sometimes called "gravitational wells"<ref>{{cite book |last1=Jefferson Barker |title=U.S. Military Space Reference Text |date=Mar 2006 |publisher=National Security Space Institute |page=56 |url=https://edocs.nps.edu/2012/December/U.S.%20Military%20Space%20Reference%20Text%20-%202006.pdf}}</ref> (at 75.3°E and 108°W) and two corresponding unstable points (at 165.3°E and 14.7°W). Any geostationary object placed between the equilibrium points would (without any action) be slowly accelerated towards the stable equilibrium position, causing a periodic longitude variation.<ref name=Anderson2015/> The correction of this effect requires [[Orbital station-keeping#Station-keeping in geostationary orbit|station-keeping maneuvers]] with a maximal delta-v of about 2&nbsp;m/s per year, depending on the desired longitude.<ref name="iop"/>

[[Solar wind]] and [[radiation pressure]] also exert small forces on satellites: over time, these cause them to slowly drift away from their prescribed orbits.<ref>{{cite conference|url=http://www.riccardobevilacqua.com/SOLAR%20RADIATION%20PRESSURE%20APPLICATIONS%20ON%20GEOSTATIONARY%20SATELLITES_SUBMISSION.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.riccardobevilacqua.com/SOLAR%20RADIATION%20PRESSURE%20APPLICATIONS%20ON%20GEOSTATIONARY%20SATELLITES_SUBMISSION.pdf |archive-date=2022-10-09 |url-status=live |first1=Patrick |last1=Kelly |first2=Richard S.|last2= Erwin|first3=Riccardo |last3=Bevilacqua|first4=Leonel |last4=Mazal |title=Solar radiation pressure applications on geostationary satellites |conference=Proceedings of the 2016 AAS GP & C Conference |publisher=[[American Astronautical Society]] |year=2016}}</ref>

In the absence of servicing missions from the Earth or a renewable propulsion method, the consumption of thruster propellant for station-keeping places a limitation on the lifetime of the satellite. [[Hall-effect thruster]]s, which are currently in use, have the potential to prolong the service life of a satellite by providing high-efficiency [[Electrically powered spacecraft propulsion|electric propulsion]].<ref name="iop"/>

== Derivation ==
[[Image:Comparison satellite navigation orbits.svg|thumb|upright=1.4|Comparison of geostationary Earth orbit with [[GPS]], [[GLONASS]], [[Galileo (satellite navigation)|Galileo]] and [[Compass navigation system|Compass (medium Earth orbit)]] [[satellite navigation system]] orbits with the [[International Space Station]], [[Hubble Space Telescope]] and [[Iridium constellation]] orbits, and the nominal size of the [[Earth]].<ref group=lower-alpha>Orbital periods and speeds are calculated using the relations 4π<sup>2</sup>''R''<sup>3</sup>&nbsp;=&nbsp;''T''<sup>2</sup>''GM'' and ''V''<sup>2</sup>''R''&nbsp;=&nbsp;''GM'', where ''R'' is the radius of orbit in metres; ''T'', the orbital period in seconds; ''V'', the orbital speed in m/s; ''G'', the gravitational constant ≈ {{val|6.673e-11|u=Nm<sup>2</sup>/kg<sup>2</sup>}}; ''M'', the mass of Earth ≈ {{val|5.98e24|u=kg}}.</ref> The [[Moon]]'s orbit is around 9 times larger (in radius and length) than geostationary orbit.<ref group=lower-alpha>The Moon's orbit is not perfectly circular, and is approximately 8.6 times further away from the Earth than the geostationary ring when the Moon is at perigee (363&thinsp;104 km ÷ 42&thinsp;164 km) and 9.6 times further away when the Moon is at apogee (405,696 km ÷ 42,164 km).</ref>]]

For circular orbits around a body, the [[centripetal force]] required to maintain the orbit (''F''<sub>c</sub>) is equal to the gravitational force acting on the satellite (''F''<sub>g</sub>):<ref name="Pople" />

: <math>F_\text{c} = F_\text{g}</math>

From [[Isaac Newton]]'s [[Newton's law of universal gravitation|universal law of gravitation]],

:<math>F_\text{g} = G \frac{M_\text{E} m_\text{s}}{r^2}</math>,

where ''F''<sub>g</sub> is the gravitational force acting between two objects, ''M''<sub>E</sub> is the mass of the Earth, {{val|5.9736e24|u=kg}}, ''m''<sub>s</sub> is the mass of the satellite, ''r'' is the distance between the [[Center of mass|centers of their masses]], and ''G'' is the [[gravitational constant]], {{val|6.67428e−11|0.00067|u=m<sup>3</sup> kg<sup>−1</sup> s<sup>−2</sup>}}.<ref name=Pople>{{cite book |last=Pople |first=Stephen |date=2001 |title=Advanced Physics Through Diagrams |url=https://books.google.com/books?id=pjIW6QRlugsC&q=physics+of+geostationary+orbits&pg=PA72 |publisher=Oxford University Press |page=72 |isbn= 0-19-914199-1}}</ref>

The magnitude of the acceleration, ''a'', of a body moving in a circle is given by:

:<math>a = \frac{v^2}{r}</math>

where ''v'' is the magnitude of the [[velocity]] (i.e. the speed) of the satellite. From [[Newton's laws of motion#Newton's second law|Newton's second law of motion]], the centripetal force ''F''<sub>c</sub> is given by:

:<math>F_\text{c} = m_\text{s}\frac{v^2}{r}</math>.<ref name="Pople" />

As ''F''<sub>c</sub> = ''F''<sub>g</sub>,

:<math>m_\text{s}\frac{v^2}{r} = G \frac{M_\text{E} m_\text{s}}{r^2}</math>,

so that

:<math>v^2 = G \frac{M_\text{E}}{r}</math>

Replacing ''v'' with the equation for the [[Circular motion#Uniform circular motion|speed of an object moving around a circle]] produces:

:<math>\left(\frac{2\pi r}{T}\right)^2  = G \frac{M_\text{E}}{r}</math>

where ''T'' is the orbital period (i.e. one sidereal day), and is equal to {{val|86164.09054|u=seconds}}.<ref>Edited by P. Kenneth Seidelmann, "Explanatory Supplement to the Astronomical Almanac", University Science Books,1992, p. 700.</ref> This gives an equation for ''r'':<ref>{{cite book |last= Mohindroo|first= K. K.|title=Basic Principles of Physics |volume=1|url= https://books.google.com/books?id=xsffXbNqpOsC&q=physics+of+geostationary+orbits&pg=RA6-PA19 |location= New Delhi|publisher= Pitambar Publishing Company|pages=6–8.19 |isbn= 81-209-0199-1|year= 1997}}
</ref>

:<math>r = \sqrt[3]{\frac{GM_\text{E} T^2}{4\pi^2}}</math>

The product ''GM''<sub>E</sub> is known with much greater precision than either factor alone; it is known as the [[geocentric gravitational constant]] ''μ'' = {{val|398,600.4418|0.0008|u=km<sup>3</sup> s<sup>−2</sup>}}. Hence

:<math> r = \sqrt[3]{\frac{\mu T^2}{4\pi^2}}</math>

The resulting orbital radius is {{convert|42164|km|mi|abbr=off}}. Subtracting the [[Earth radius|Earth's equatorial radius]], {{convert|6378|km|mi|abbr=off}}, gives the altitude of {{convert|35786|km|mi|abbr=off}}.<ref>{{cite web |url= https://physics.info/orbital-mechanics-1/practice.shtml|title= Orbital Mechanics I |last= Elert |first= Glenn |date= 2019|website=The Physics Hypertextbook |access-date= September 30, 2019 }}</ref>

The orbital speed is calculated by multiplying the angular speed by the orbital radius:

: <math>v = \omega r  \quad  \approx 3074.6~\text{m/s}</math>

==In other planets==
By the same method, we can determine the orbital altitude for any similar pair of bodies, including the [[areostationary orbit]] of an object in relation to [[Mars]], if it is assumed that it is spherical (which it is not entirely).<ref>{{cite web |url= http://www.planetary.org/blogs/emily-lakdawalla/2013/stationkeeping-in-mars-orbit.html|title= Stationkeeping in Mars orbit
|last= Lakdawalla|first= Emily |date= 2013|website= The Planetary Society|access-date=September 30, 2019 }}</ref> The [[geocentric gravitational constant|gravitational constant]] ''GM'' (''μ'') for Mars has the value of {{val|42830|u=km<sup>3</sup> s<sup>−2</sup>}}, its equatorial radius is {{val|3389.50|u=km}} and the known [[rotational period]] (''T'') of the planet is {{val|1.02595676|u=Earth days}} ({{val|88642.66|u=seconds}}). Using these values, Mars' orbital altitude is equal to {{val|17039|u=km}}.<ref>{{cite web |url= https://ssd.jpl.nasa.gov/?planet_phys_par|title=Solar System Dynamics |date=2017 |publisher=NASA |access-date= September 30, 2019 }}</ref>

== See also ==
{{Portal|Spaceflight}}
* [[List of orbits]]
* [[List of satellites in geosynchronous orbit]]
* [[Orbital station-keeping]]
* [[Space elevator]], which ultimately reaches to and beyond a geostationary orbit

== Explanatory notes ==
{{notelist}}

== References ==
{{reflist|35em}}
{{FS1037C MS188}}

==External links==
* [http://www.planetary.org/blogs/jason-davis/20140116-how-to-get-a-satellite-to-gto.html How to get a satellite to geostationary orbit]
* [https://web.archive.org/web/20120204054322/http://www.braeunig.us/space/orbmech.htm Orbital Mechanics] (Rocket and Space Technology)
* [http://www.satsig.net/sslist.htm List of satellites in geostationary orbit]
* [https://web.archive.org/web/20060626002953/http://www.golombek.com/sat/ Clarke Belt Snapshot Calculator]
* [https://web.archive.org/web/20130904234835/http://science1.nasa.gov/realtime/jtrack/3d/JTrack3D.html/ 3D Real Time Satellite Tracking]
* [https://web.archive.org/web/20140404194939/http://www.radio-electronics.com/info/satellite/satellite-orbits/geostationary-earth-orbit.php Geostationary satellite orbit overview]
* [https://web.archive.org/web/20141218004537/http://p-l-a.net/ Daily animation of the Earth, made by geostationary satellite 'Electro L' photos] Satellite shoots 48 images of the planet every day.
* [https://books.google.com/books?id=rzw4wOHDpjQC&q=physics+of+geostationary+orbits Orbital Mechanics for Engineering Students]

{{Orbits}}

{{DEFAULTSORT:Geostationary Orbit}}
[[Category:Astrodynamics]]
[[Category:Earth orbits]]
[[Category:Satellites in geostationary orbit|*]]