Editing Geostationary orbit (section)

== 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>