Editing Satellite (section)

== Applications ==

=== Earth observation ===
{{Main|Earth observation satellite}}
[[File:Earth Radiation Budget Satellite.jpg|thumb|Deployment of the [[Earth Radiation Budget Satellite]] on [[STS-41-G]], collecting data on Earth's weather and climate]]
Earth observation satellites are designed to monitor and survey the Earth, called [[remote sensing]]. Most Earth observation satellites are placed in low Earth orbit for a high data resolution, though some are placed in a [[geostationary orbit]] for an uninterrupted coverage. Some satellites are placed in a [[Sun-synchronous orbit]] to have consistent lighting and obtain a total view of the Earth. Depending on the satellites' functions, they might have a [[Satellite imagery|normal camera]], [[Space-based radar|radar]], [[lidar]], [[photometer]], or atmospheric instruments. Earth observation satellite's data is most used in [[archaeology]], [[cartography]], [[environmental monitoring]], [[meteorology]], and [[reconnaissance]] applications.{{Citation needed|date=July 2022}} As of 2021, there are over 950 Earth observation satellites, with the largest number of satellites operated with [[Planet Labs]].<ref>{{cite web |date=18 August 2021 |title=How many Earth observation satellites are orbiting the planet in 2021? |url=https://www.pixalytics.com/eo-sats-2021/ |last1=Andy |website=Pixalytics |url-status=live |archive-url=https://web.archive.org/web/20220721104450/https://www.pixalytics.com/eo-sats-2021/ |archive-date=21 July 2022 |access-date=25 May 2022}}</ref>

[[Weather satellite]]s monitor [[cloud]]s, [[Street light|city lights]], [[fire]]s, effects of [[pollution]], [[auroral light|aurora]]s, [[Dust storm|sand and dust storms]], [[snow]] cover, [[ice]] mapping, boundaries of [[ocean current]]s, [[energy]] flows, etc. Environmental monitoring satellites can detect changes in the Earth's [[vegetation]], atmospheric trace gas content, sea state, ocean color, and ice fields. By monitoring vegetation changes over time, droughts can be monitored by comparing the current vegetation state to its long term average.<ref>{{cite web |website=Earth Observatory |publisher=NASA |url=http://earthobservatory.nasa.gov/Drought/ |title=Drought and Vegetation Monitoring |archive-url=https://web.archive.org/web/20080819121047/http://earthobservatory.nasa.gov/Drought/ |archive-date=19 August 2008 |access-date=4 July 2008}} {{PD-notice}}</ref> Anthropogenic emissions can be monitored by evaluating data of tropospheric NO<sub>2</sub> and SO<sub>2</sub>.{{Citation needed|date=July 2022}}

=== Communication ===
{{Main|Communications satellite}}
{{Excerpt|Communications satellite|files=no|hat=no}}

===Spy satellites===
{{Main|Reconnaissance satellite}}
When an&nbsp;Earth observation satellite or&nbsp;a communications satellite is deployed for&nbsp;military&nbsp;or&nbsp;intelligence&nbsp;purposes, it is known as a spy satellite or reconnaissance satellite.

Their uses include early missile warning, nuclear explosion detection, electronic reconnaissance, and optical or radar imaging surveillance.

=== Navigation ===
{{Main|Satellite navigation}}
Navigational satellites are satellites that use radio time signals transmitted to enable mobile receivers on the ground to determine their exact location. The relatively clear line of sight between the satellites and receivers on the ground, combined with ever-improving electronics, allows satellite navigation systems to measure location to accuracies on the order of a few meters in real time.
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=== Telescope ===
{{Main|Space telescope}}

[[File:Hubble Space Telescope (27946391011).jpg|thumb|The [[Hubble Space Telescope]]]]
[[Astronomical satellite]]s are satellites used for observation of distant planets, galaxies, and other outer space objects.<ref>{{Cite web |last=Ericsson |first=Karin |date=2018-06-13 |title=8 types of satellites that make your modern world work |url=https://www.melbournespace.com.au/post/8-types-of-satellites-that-make-your-modern-world-work |url-status=live |archive-url=https://web.archive.org/web/20240330113138/https://www.melbournespace.com.au/post/8-types-of-satellites-that-make-your-modern-world-work |archive-date=2024-03-30 |access-date=2024-07-13 |website=Melbourne Space |language=en}}</ref>

=== Experimental ===
[[Tether satellite]]s are satellites that are connected to another satellite by a thin cable called a [[tether]]. [[Recovery satellite]]s are satellites that provide a recovery of reconnaissance, biological, space-production and other payloads from orbit to Earth. [[Biosatellite]]s are satellites designed to carry living organisms, generally for scientific experimentation. [[Space-based solar power]] satellites are proposed satellites that would collect energy from sunlight and transmit it for use on Earth or other places.{{citation needed|date=February 2024}}

=== Weapon ===
{{Main|Space weapon|Anti-satellite weapon|Early warning satellite}}
Since the mid-2000s, satellites have been hacked by militant organizations to broadcast propaganda and to pilfer classified information from military communication networks.<ref>{{cite web |last=Morrill |first=Dan |title=Hack a Satellite while it is in orbit |url=http://blogs.ittoolbox.com/security/dmorrill/archives/hack-a-satellite-while-it-is-in-orbit-15690 |url-status=dead |archive-url=https://web.archive.org/web/20080320084037/http://blogs.ittoolbox.com/security/dmorrill/archives/hack-a-satellite-while-it-is-in-orbit-15690 |archive-date=20 March 2008 |access-date=25 March 2008 |publisher=[[ITtoolbox]] Blogs |date=April 13, 2007}}</ref><ref>{{cite news |date=22 November 2004 |title=AsiaSat accuses Falungong of hacking satellite signals |agency=[[Press Trust of India]] |url=http://www.accessmylibrary.com/coms2/summary_0286-5205866_ITM |via=AccessMyLibrary |access-date=19 May 2008 |archive-date=19 July 2012 |archive-url=https://archive.today/20120719005250/http://www.accessmylibrary.com/coms2/summary_0286-14557996_ITM |url-status=dead}}</ref> For testing purposes, satellites in low earth orbit have been destroyed by ballistic missiles launched from the Earth. [[Russia]], [[United States]], [[China]] and [[India]] have demonstrated the ability to eliminate satellites.<ref name="asat">{{cite news |last1=Broad |first1=William J. |last2=Sanger |first2=David E. |date=18 January 2007 |title=China Tests Anti-Satellite Weapon, Unnerving U.S. |work=[[The New York Times]] |url=https://www.nytimes.com/2007/01/18/world/asia/18cnd-china.html |url-access=subscription |access-date=23 February 2017 |archive-date=17 April 2017 |archive-url=https://web.archive.org/web/20170417190320/http://www.nytimes.com/2007/01/18/world/asia/18cnd-china.html |url-status=live}}</ref> In 2007, the [[China|Chinese]] military shot down an aging weather satellite,<ref name="asat" /> followed by the [[US Navy]] shooting down a [[NRO L-21|defunct spy satellite]] in February 2008.<ref>{{cite web |date=February 21, 2008 |title=Navy Missile Successful as Spy Satellite Is Shot Down (With Video) |url=http://www.popularmechanics.com/blogs/science_news/4251430.html |access-date=25 March 2008 |work=[[Popular Mechanics]] |archive-date=1 April 2008 |archive-url=https://web.archive.org/web/20080401054054/http://www.popularmechanics.com/blogs/science_news/4251430.html |url-status=dead}}</ref> On 18 November 2015, after two failed attempts, Russia successfully carried out a flight test of an [[Anti-satellite weapon|anti-satellite]] missile known as ''[[A-235 anti-ballistic missile system|Nudol]]''.{{citation needed|date=December 2023}} On 27 March 2019, India shot down a live test satellite at 300&nbsp;km altitude in 3 minutes, becoming the fourth country to have the capability to destroy live satellites.<ref>{{Cite web |title=India successfully tests anti-satellite weapon: Modi |url=https://www.theweek.in/news/india/2019/03/27/india-test-anti-satellite-weapon-modi.html |date=March 27, 2019 |access-date=27 March 2019 |website=The Week |language=en |archive-date=12 July 2021 |archive-url=https://web.archive.org/web/20210712020749/https://www.theweek.in/news/india/2019/03/27/india-test-anti-satellite-weapon-modi.html |url-status=live}}</ref><ref>{{Cite web |last=Vasani |first=Harsh |date=June 14, 2016 |title=India's Anti-Satellite Weapons |url=https://thediplomat.com/2016/06/indias-anti-satellite-weapons/ |access-date=27 March 2019 |website=The Diplomat |language=en-US |archive-date=1 January 2018 |archive-url=https://web.archive.org/web/20180101131652/https://thediplomat.com/2016/06/indias-anti-satellite-weapons/ |url-status=live}}</ref>