{{Short description|Artificial satellite used for military purposes}} {{distinguish|spy satellite}} [[File:SAR-Lupe.jpg|thumb|right|A model of a [[Germany|German]] [[SAR-Lupe]] reconnaissance satellite inside a Cosmos-3M rocket]] {{Spaceflight sidebar}} A '''military satellite''' is an [[artificial satellite]] used for a [[military]] purpose. The most common missions are [[intelligence (information gathering)|intelligence]] gathering, navigation and military [[communications satellite|communications]].
The first military satellites were photographic reconnaissance missions. Some attempts were made to develop [[Space weapon#Space-to-Earth weapons|satellite based weapons]] but this work was halted in 1967 following the ratification of international treaties banning the deployment of weapons of mass destruction in orbit.
As of 2013, there are 950 satellites of all types in Earth orbit. It is not possible to identify the exact number of these that are military satellites partly due to secrecy and partly due to dual purpose missions such as [[GPS]] satellites that serve both civilian and military purposes. As of December 2018 there are 320 known military or dual-use satellites in the sky, half of which are owned by the US, followed by Russia, China and India.<ref name=howmany>[https://timesofindia.indiatimes.com/india/why-isros-gsat-7a-launch-is-important-for-iaf/articleshow/67153347.cms Why Isro's Gsat-7A launch is important for the Indian Air Force], Times of India, 19 Dec 2018.</ref>
==Military reconnaissance satellites== [[File:CORONA film recovery maneuvar.jpg|thumb|left|Image showing the recovery process for a Discoverer film canister.]] The first military use of satellites was for reconnaissance.
In the United States the first formal military satellite programs, Weapon System 117L, was developed in the mid-1950s.<ref name=milsatmag>{{cite web|url=http://www.milsatmagazine.com/story.php?number=1811044549|title=Military Satellite Systems: A History — Part One|date=May 2008|accessdate=2014-01-21|publisher=MilsatMagazine}}</ref> Within this program a number of sub-programs were developed including [[Corona (satellite)|Corona]].<ref name=milsatmag/> Satellites within the Corona program carried different code names. The first launches were code named Discoverer. This mission was a series of [[reconnaissance satellite]]s, designed to enter orbit, take high-resolution photographs and then return the payload to Earth via parachute.<ref name=milsatmag/> [[Discoverer 1]], the first mission, was launched on 28 February 1959 although it didn't carry a payload being intended as a test flight to prove the technology.<ref>{{cite web|publisher=[[NASA]]|title=This Week in NASA History: Discoverer 1|url=https://appel.nasa.gov/2010/02/27/ao_2-2_sf_history-html/|date=23 February 2007|access-date=November 2, 2022}}</ref> Corona was followed by other programs including [[Canyon (satellite)|Canyon]] (seven launches between 1968 and 1977<ref>{{cite web |url=http://www.planet4589.org/space/jsr/back/news.369 |format=TXT |title=Jonathan's Space Report : No. 369 |website=Planet4589.org |accessdate=2016-02-27 |archive-url=https://web.archive.org/web/20090619224722/http://www.planet4589.org/space/jsr/back/news.369 |archive-date=2009-06-19 |url-status=dead }}</ref>), [[Aquacade (satellite)|Aquacade]]<ref>{{cite book|author=James Bamford|title=The Shadow Factory|year=2008|publisher=Doubleday|page=[https://archive.org/details/shadowfactory00bamf/page/176 176]|author-link=James Bamford|title-link=The Shadow Factory}}</ref> and [[Orion (satellite)|Orion]] (stated by US Government sources to be extremely large<ref name="afa100913">{{cite web | title=National Reconnaissance Office Update | url=http://www.afa.org/events/conference/2010/scripts/AFA-100913-Carlson.pdf | author=Bruce Carlson | publisher=Air & Space Conference and Technology Exposition 2010 | accessdate=2010-11-25 | date=2010-09-13 | archive-url=https://web.archive.org/web/20101206140015/http://www.afa.org/events/conference/2010/scripts/AFA-100913-Carlson.pdf | archive-date=2010-12-06 | url-status=dead }}</ref>). There have also been a number of subsequent programs including [[Magnum (satellite)|Magnum]] and [[Trumpet (satellite)|Trumpet]],<ref>{{cite web|url=http://www.zeit.de/1995/31/Riesige_Lauscher_am_Himmel|title=Riesige Lauscher am Himmel|publisher=Die Zeit|date=28 July 1995}}</ref> but these remain classified and therefore many details remain speculative.
The [[Soviet Union]] began the [[Almaz]] ({{langx|ru|Алмаз}}) program in the early 1960s. This program involved placing space stations in Earth orbit as an alternative to satellites. Three stations were launched between 1973 and 1976: [[Salyut 2]], [[Salyut 3]] and [[Salyut 5]]. Following Salyut 5, the [[Ministry of Defense (Soviet Union)|Soviet Ministry of Defence]] judged in 1978 that the time consumed by station maintenance outweighed the benefits relative to automatic reconnaissance satellites.{{citation needed|date=January 2014}}
In 2015, United States military space units and commercial satellite operator [[Intelsat]] became concerned about apparent reconnaissance test maneuvers by the [[Government of Russia|Russian]] satellite [[Olymp-K]], launched in September 2014, when it maneuvered between [[Intelsat 7]] and [[Intelsat 901]], which are located only half a degree from one another in [[geosynchronous orbit]].<ref name="sn20151009"> {{cite news |last=Gruss|first=Mike |url=http://spacenews.com/russian-satellite-maneuvers-silence-worry-intelsat/ |title=Russian Satellite Maneuvers, Silence Worry Intelsat |work=SpaceNews |date=2015-10-09 |accessdate=2016-01-20 }}</ref>
==Navigation satellites== [[File:ConstellationGPS.gif|thumb|right|A simulation of the original design of the GPS space segment, with 24 GPS satellites (4 satellites in each of 6 orbits)]] The first [[satellite navigation]] system, [[Transit (satellite)|Transit]], used by the [[United States Navy]], was tested in 1960.<ref>{{cite web|last=Howell|first=Elizabeth|title=Navstar: GPS Satellite Network|url=http://www.space.com/19794-navstar.html|publisher=SPACE.com|accessdate=February 14, 2013}}</ref> It used a [[satellite constellation|constellation]] of five satellites and could provide a navigational fix approximately once per hour.
During the [[Cold War]] [[arms race]], the nuclear threat was used to justify the cost of providing a more capable system. These developments led eventually to the deployment of the [[Global Positioning System]] (GPS). The US Navy required precise navigation to enable [[submarine]]s to get an accurate fix of their positions before they launched their SLBMs.<ref>{{cite web|url=http://www.trimble.com/gps/whygps.shtml#0|archiveurl=https://web.archive.org/web/20071018151253/http://www.trimble.com/gps/whygps.shtml#0|archivedate=October 18, 2007|title=Why Did the Department of Defense Develop GPS?|publisher=Trimble Navigation Ltd|accessdate=January 13, 2010}}</ref> The USAF had requirements for a more accurate and reliable navigation system, as did the [[United States Army]] for geodetic surveying <ref>{{cite web|url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660002550_1966002550.pdf |title=Release No: 65-333 : Project Geodetic Explorer-A |date=1965-10-29 |website=Ntrs.nasa.gov |accessdate=2016-02-27 |url-status=dead |archive-url=https://web.archive.org/web/20130922061006/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660002550_1966002550.pdf |archive-date=2013-09-22}}</ref> for which purpose they had developed the [[SECOR]] system. SECOR used ground-based transmitters from known locations that sent signals to satellite transponder in orbit. A fourth ground-based station, at an undetermined position, could then use those signals to fix its location precisely. The last SECOR satellite was launched in 1969.<ref>{{cite encyclopedia|url=http://www.astronautix.com/craft/secor.htm|title=SECOR Chronology|encyclopedia=Mark Wade's Encyclopedia Astronautica|accessdate=January 19, 2010|url-status=dead|archiveurl=https://web.archive.org/web/20100116213013/http://astronautix.com/craft/secor.htm|archivedate=January 16, 2010}}</ref>
In 1978, the first experimental Block-I GPS satellite was launched<ref name="ieee2008">{{cite journal | title = Evolution of the Global Navigation SatelliteSystem (GNSS) | first1 = Christopher J. | last1 = Hegarty | first2 = Eric | last2 = Chatre | journal = Proceedings of the IEEE | volume = 96 | issue = 12 | date = December 2008 | pages = 1902–1917 | doi = 10.1109/JPROC.2008.2006090 | s2cid = 838848 }}</ref> and by December 1993, GPS achieved initial operational capability (IOC), indicating a full constellation (24 satellites) was available and providing the Standard Positioning Service (SPS).<ref name="IOCFOC">{{cite web|url=http://tycho.usno.navy.mil/gpsinfo.html|title=USNO NAVSTAR Global Positioning System|publisher=U.S. Naval Observatory|accessdate=January 7, 2011|archive-url=https://web.archive.org/web/20060208110241/http://tycho.usno.navy.mil/gpsinfo.html|archive-date=February 8, 2006|url-status=dead}}</ref> Full Operational Capability (FOC) was declared by [[Air Force Space Command]] (AFSPC) in April 1995, signifying full availability of the military's secure Precise Positioning Service (PPS).<ref name="IOCFOC"/>
==Early warning systems== A number of nations have developed satellite based [[missile defense|early warning]] systems designed to detect [[intercontinental ballistic missile]] (ICBMs) during different flight phases. In the United States these satellites are operated by the [[Defense Support Program]] (DSP). The first launch of a DSP satellite was on 6 November 1970 with the 23rd and last launched 10 November 2007. This program has been superseded by the [[Space-Based Infrared System]] (SBIRS).
==Satellite weapons== In the United States, research into satellite based weapons was initiated by President [[Dwight D. Eisenhower]] in the 1950s. In 1958, the United States initiated Project Defender to develop an anti-[[ICBM]] solution launched from satellites. The satellites would have deployed a huge wire mesh to disable ICBMs during their early launch phase. The project floundered due to the lack of any mechanism to protect the satellites from attack resulting in the cancellation of Defender in 1968.<ref name=NYtimes>{{cite news|title=Star Wars Traced to Eisenhower Era|date=28 October 1986|url=https://www.nytimes.com/1986/10/28/science/star-wars-traced-to-eisenhower-era.html|newspaper=[[The New York Times]]|author=William J. Broad|accessdate=2014-02-06}}</ref>
Since October 1967, satellite based weapons systems have been limited by international treaty to conventional weapons only. [[wikisource:Outer Space Treaty of 1967#Article IV|Art.IV]] of the [[Outer Space Treaty]] specifically prohibits signatories from installing [[weapons of mass destruction]] in Earth orbit. The treaty became effective on 10 October 1967 and, as of May 2013, 102 countries are parties to the treaty with a further 27 pending full ratification.<ref name=UNtreatydatabase>{{cite web | url=http://disarmament.un.org/treaties/t/outer_space | title = Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies | accessdate = 2013-04-18 | publisher= [[United Nations Office for Disarmament Affairs]]}}</ref><ref name=az>{{cite web|url=http://en.trend.az/regions/scaucasus/azerbaijan/2149769.html|title=Azerbaijan improves legal framework for space cooperation|date=13 May 2013|accessdate=2013-05-18|archive-url=https://web.archive.org/web/20130613084435/http://en.trend.az/regions/scaucasus/azerbaijan/2149769.html|archive-date=13 June 2013|url-status=dead}}</ref>
==Military communication satellites== [[Communications satellites]] are used for [[military communications]] applications. Typically military satellites operate in the [[UHF]], [[Super high frequency|SHF]] (also known as [[X-band]]) or [[Extremely high frequency|EHF]] (also known as [[Ka band|K<sub>a</sub> band]]) frequency bands.
The US Armed Forces maintains international networks of satellites with ground stations located in various continents. [[Latency (engineering)#Satellite transmission|Signal latency]] is a major concern in satellite communications, so geographic and meteorological factors play an important role in choosing teleports. Since some of the major military activities of the U.S. army are in foreign territories, the U.S. government needs to subcontract satellite services to foreign carriers headquartered in areas with favorable climate.<ref>{{cite web|url=http://www.newsat.com/Case-Studies/proactive-communications.html/ |archive-url=https://archive.today/20120402124047/http://www.newsat.com/Case-Studies/proactive-communications.html/ |url-status=dead |archive-date=April 2, 2012 |accessdate=September 16, 2011 |title=Defence}}</ref>
Military Strategic and Tactical Relay, or [[Milstar]], is a constellation of military satellites managed by the [[United States Space Force]]. Six spacecraft were launched between 1994 and 2003, of which five are operational, with the sixth lost in a launch failure. They are deployed in [[geostationary orbit]] and provide wideband, narrowband and protected military communication systems. [[Wideband]] systems support high-bandwidth transfers. Protected systems offer more sophisticated security protection like antijam features and nuclear survivability, while [[narrowband]] systems are intended for basic communications services that do not require high bandwidth.
The [[United Kingdom]] also operates military communication satellites through its [[Skynet (satellite)|Skynet]] system. This is currently operated with support from [[Astrium Services]] and provides near worldwide coverage with both [[X band]] and [[Ultra high frequency]] services.<ref>{{cite web|title=Skynet 5 X-band |url=http://www.satcom-airbusds.com/products-solutions/government-satcom/products-systems/bandwidth/skynet-5-x-band/ |website=Airbus Defence and Space |year=2014 |url-status=dead |archive-url=https://web.archive.org/web/20140516082649/http://www.satcom-airbusds.com/products-solutions/government-satcom/products-systems/bandwidth/skynet-5-x-band/ |archive-date=16 May 2014}}</ref>
[[Skynet (satellite)|Skynet 5]] is the United Kingdom's most recent military communications satellite system. There are four Skynet satellites in orbit, with the latest launch completed in December 2012.<ref name=Skynet>{{cite web|url=https://www.bbc.co.uk/news/science-environment-20781625|publisher=BBC|accessdate=2014-04-11|title=UK's Skynet military satellite launched|author=Jonathan Amos|date=19 December 2012}}</ref> The system is provided by a private contractor, Astrium, with the UK government paying service charges based on bandwidth consumption.<ref name=Skynet/>
{{Further|X Band Satellite Communication}}
==Military satellites by country== {| class="wikitable" ! style="width:2em;" | Rank !! Country !! Military satellites !! {{abbr|Ref.|Reference}} |- |1||[[United States]]||align=right|{{nts|247}}||<ref name="src1">{{Cite web |title=Military Satellites by Country 2023 |url=https://worldpopulationreview.com/country-rankings/military-satellite-by-country |access-date=2023-12-29 |website=worldpopulationreview.com}}</ref> |- |2||[[China]]||align=right|{{nts|157}}||<ref name="src1"/> |- |3||[[Russia]]||align=right|{{nts|110}}||<ref name="src1"/> |- |4||[[France]]||align=right|{{nts|17}}||<ref name="src1"/> |- |5||[[Israel]]||align=right|{{nts|12}}||<ref name="src1"/> |- |6||[[Italy]]||align=right|{{nts|10}}||<ref name="src1"/> |- |7||[[India]]||align=right|{{nts|9}}||<ref name="src1"/> |- |8||[[Germany]]||align=right|{{nts|8}}||<ref name="src1"/> |- |9||[[United Kingdom]]||align=right|{{nts|6}}||<ref name="src1"/> |- |10||[[Poland]]||align=right|{{nts|5}}||<ref name="src1"/> |- |11||[[Spain]]||align=right|{{nts|4}}||<ref name="src1"/> |- |12 |[[Turkey]]||align=right|{{nts|3}}||<ref>{{Cite web |title=Ülkemizin Aktif Yapay Uydularını Tanıyalım {{!}} TÜBİTAK Bilim Genç |url=https://bilimgenc.tubitak.gov.tr/makale/ulkemizin-aktif-yapay-uydularini-taniyalim#:~:text=T%C3%BCrksat%203A,%20T%C3%BCrksat%204A,%20T%C3%BCrksat,s%C3%BCresi%20dolan%20uydular%C4%B1m%C4%B1z%20da%20bulunuyor. |access-date=2024-10-25 |website=Bilim Genc |language=tr}}</ref> |- |13||[[Iran]]||align=right|{{nts|2}}||<ref name="src1"/> |- |14 |[[Portugal]] | align="right" |2 |<ref>{{Cite web |date=2025-06-18 |title=Portugal acquires its first Earth observation satellite |url=https://www.janes.com/osint-insights/defence-news/air/portugal-acquires-its-first-earth-observation-satellite |access-date=2025-06-26 |website=Default |language=en}}</ref><ref>{{Cite web |title=Second Portuguese military satellite launches early this morning |url=https://www.portugalresident.com/second-portuguese-military-satellite-launches-early-this-morning/}}</ref> |}
==See also== {{Commons category|Military satellites}} *[[Missile Defense Alarm System]] *[[Space warfare]] *[[Spy satellite]] *[[Strategic Defense Initiative]]
==References== {{Reflist|30em}}
==Resources== * Squadron Leader KK Nair, "Space: The Frontiers of Modern Defence", ''Knowledge World Publishers,'' New Delhi.
==External links== * '''N-1''' For details, see [https://books.google.com/books?id=ZBXL1i-n6UAC&dq=space+frontiers+modern+defence&pg=PA4 Space: The Frontiers of Modern Defence]
{{Politics of outer space}} {{Authority control}}
[[Category:Military satellites| ]] [[Category:Military equipment]] [[Category:Satellites by type]]