Editing Geostationary orbit (section)

== 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>