Editing Satellite constellation (section)

== Overview ==
[[File:Flare at Paranal.jpg|thumb|A bright artificial satellite flare is visible above the [[Very Large Telescope]]. Satellite constellations could have an impact on ground-based astronomy.<ref>{{cite web |title=On the increasing number of satellite constellations |url=https://www.eso.org/public/announcements/ann19029/ |website=www.eso.org |access-date=10 June 2019 |language=en}}</ref>]]

Satellites in [[Medium Earth orbit|medium Earth orbit (MEO)]] and [[Low Earth orbit|low Earth orbit (LEO)]] are often deployed in satellite constellations, because the coverage area provided by a single satellite only covers a small area that moves as the satellite travels at the high [[angular velocity]] needed to maintain its [[Planetary orbit|orbit]]. Many MEO or LEO satellites are needed to maintain continuous coverage over an area. This contrasts with [[geostationary]] satellites, where a single satellite, at a much higher altitude and moving at the same angular velocity as the rotation of the Earth's surface, provides permanent coverage over a large area.

For some applications, in particular digital connectivity, the lower altitude of MEO and LEO satellite constellations provide advantages over a geostationary satellite, with lower [[path loss]]es (reducing power requirements and costs) and latency.<ref>[https://www.satelliteevolutiongroup.com/articles/LEO-Constellations&Tracking.pdf ''LEO constellations and tracking challenges''] Satellite Evolution Group, September 2017, Accessed 26 March 2021</ref> The [[propagation delay]] for a round-trip [[Internet protocol suite|internet protocol]] transmission via a geostationary satellite can be over 600{{nbsp}}ms, but as low as 125{{nbsp}}ms for a MEO satellite or 30{{nbsp}}ms for a LEO system.<ref>[https://www.telesat.com/wp-content/uploads/2020/07/Real-Time-Latency-Rethinking-Remote-Networks.pdf ''Real-Time Latency: Rethinking Remote Networks''] {{Webarchive|url=https://web.archive.org/web/20210721082728/https://www.telesat.com/wp-content/uploads/2020/07/Real-Time-Latency-Rethinking-Remote-Networks.pdf |date=2021-07-21 }} Telesat, February 2020, Accessed 26 March 2021</ref>

Examples of satellite constellations include the [[Global Positioning System]] (GPS), [[Galileo positioning system|Galileo]] and [[GLONASS]] constellations for [[navigation]] and [[geodesy]] in MEO, the [[Iridium (satellite)|Iridium]] and [[Globalstar]] satellite telephony services and [[Orbcomm]] messaging service in LEO, the [[Disaster Monitoring Constellation]] and [[RapidEye]] for [[remote sensing]] in [[Sun-synchronous orbit|Sun-synchronous]] LEO, Russian [[Molniya (satellite)|Molniya]] and Tundra communications constellations in highly [[elliptic orbit]], and satellite broadband constellations, under construction from [[Starlink]] and [[OneWeb]] in LEO, and operational from [[O3b]] in MEO.