Editing Satellite navigation (section)

==Global navigation satellite systems==
{{Comparison satellite navigation orbits}}
[[File:Launched GNSS 2014.jpg|thumb|Launched GNSS satellites 1978 to 2014]]

In order of first launch year:

===GPS===
{{Main|Global Positioning System}}
First launch year: 1978

The United States' Global Positioning System (GPS) consists of up to 32 [[medium Earth orbit]] satellites in six different [[orbital plane (astronomy)|orbital plane]]s. The exact number of satellites varies as older satellites are retired and replaced. Operational since 1978 and globally available since 1994, GPS is the world's most utilized satellite navigation system.

===GLONASS===
{{Main|GLONASS}}
First launch year: 1982

The formerly [[Soviet Union|Soviet]], and now [[Russia]]n, '''''Glo'''bal'naya '''Na'''vigatsionnaya '''S'''putnikovaya '''S'''istema'', (GLObal NAvigation Satellite System or GLONASS), is a space-based satellite navigation system that provides a civilian radionavigation-satellite service and is also used by the Russian Aerospace Defence Forces. GLONASS has full global coverage since 1995 and with 24 active satellites.

===BeiDou===
{{Main|BeiDou Navigation Satellite System}}
First launch year: 2000

BeiDou started as the now-decommissioned Beidou-1, an Asia-Pacific local network on the geostationary orbits. The second generation of the system BeiDou-2 became operational in China in December 2011.<ref>{{Cite news|date=2012-03-08|title=China's GPS rival is switched on|language=en-GB|work=BBC News|url=https://www.bbc.com/news/technology-16337648|access-date=2020-06-23}}</ref> The BeiDou-3 system is proposed to consist of 30 [[Medium Earth orbit|MEO]] satellites and five geostationary satellites (IGSO). A 16-satellite regional version (covering Asia and Pacific area) was completed by December 2012. Global service was completed by December 2018.<ref>{{Cite web|url=http://en.beidou.gov.cn/WHATSNEWS/201812/t20181227_16837.html|title=The BDS-3 Preliminary System Is Completed to Provide Global Services|website=news.dwnews.com|access-date=2018-12-27}}</ref> On 23 June 2020, the BDS-3 constellation deployment is fully completed after the last satellite was successfully launched at the [[Xichang Satellite Launch Center]].<ref>{{Cite web|title=APPLICATIONS-Transport|url=http://en.beidou.gov.cn/WHATSNEWS/202006/t20200623_20692.html|access-date=2020-06-23|website=en.beidou.gov.cn}}</ref>

===Galileo===
{{Main|Galileo (satellite navigation)}}
First launch year: 2011

The [[European Union]] and [[European Space Agency]] agreed in March 2002 to introduce their own alternative to GPS, called the [[Galileo positioning system]]. Galileo became operational on 15 December 2016 (global Early Operational Capability, EOC).<ref>{{cite news |publisher=europa.eu |url=http://europa.eu/rapid/press-release_IP-16-4366_en.htm |title=Galileo goes live!|date=14 December 2016}}</ref> At an estimated cost of €10 billion,<ref>{{cite news |publisher=BBC News |url=http://news.bbc.co.uk/1/hi/sci/tech/5286200.stm |title=Boost to Galileo sat-nav system |date=25 August 2006 |access-date=2008-06-10}}</ref> the system of 30 [[Medium Earth orbit|MEO]] satellites was originally scheduled to be operational in 2010. The original year to become operational was 2014.<ref>{{cite web|url= http://europa.eu/rapid/pressReleasesAction.do?reference=IP/10/7&language=en |title= Commission awards major contracts to make Galileo operational early 2014 |date=2010-01-07 |access-date=2010-04-19}}</ref> The first experimental satellite was launched on 28 December 2005.<ref>{{cite web|url=http://www.esa.int/Our_Activities/Navigation/The_future_-_Galileo/First_Galileo_Launch/GIOVE-A_launch_news|title=GIOVE-A launch News|date=2005-12-28|access-date=2015-01-16}}</ref> Galileo is expected to be compatible with the [[GPS modernization|modernized GPS]] system. The receivers will be able to combine the signals from both Galileo and GPS satellites to greatly increase the accuracy. The full Galileo constellation consists of 24 active satellites,<ref>{{cite news |title=Galileo begins serving the globe |url=https://www.internationales-verkehrswesen.de/galileo-begins-serving-the-globe/ |work=INTERNATIONALES VERKEHRSWESEN |date=23 December 2016 |language=de-DE}}</ref> the last of which was launched in December 2021.<ref>{{cite news |title=Soyuz launch from Kourou postponed until 2021, 2 others to proceed |url=https://www.spacedaily.com/reports/Soyuz_launch_from_Kourou_postponed_until_2021_2_others_to_proceed_999.html |work=Space Daily |date=19 May 2020}}</ref><ref name=autogenerated2>{{cite web|url=https://www.gsa.europa.eu/galileo/services/initial-services |title=Galileo Initial Services |website=gsa.europa.eu|date=9 December 2016 |access-date=25 September 2020}}</ref> The main modulation used in Galileo Open Service signal is the [[Composite Binary Offset Carrier]] (CBOC) modulation.