View source for Satellite constellation

{{short description|Group of artificial satellites working together as a system}}
[[File:GPS24goldenSML.gif|thumb|240px|The [[Global Positioning System|GPS]] constellation calls for 24 satellites to be distributed equally among six [[orbital plane (astronomy)|orbital planes]]. Notice how the number of satellites in view from a given point on the Earth's surface, in this example at 40°N, changes with time.]]

A '''satellite constellation''' is a group of [[artificial satellite]]s working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global [[pass (spaceflight)|coverage]], such that at any time everywhere on Earth at least one satellite is visible. Satellites are typically placed in sets of complementary [[orbital plane (astronomy)|orbital planes]] and connect to globally distributed [[ground station]]s. They may also use [[Inter-satellite service|inter-satellite communication]].

==Other satellite groups==
Satellite constellations should not be confused with:
* ''[[satellite cluster]]s'', which are groups of satellites moving very close together in almost identical orbits (see [[satellite formation flying]]);
* ''[[:Category:Satellite series|satellite series]]'' or ''satellite programs'' (such as [[Landsat program|Landsat]]), which are generations of satellites launched in succession;
* ''satellite fleets'', which are groups of satellites from the same manufacturer or operator that function independently from each other (not as a system).

== 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.

== Design ==

=== Walker Constellation ===
There are a large number of constellations that may satisfy a particular mission. Usually constellations are designed so that the satellites have similar orbits, eccentricity and inclination so that any perturbations affect each satellite in approximately the same way. In this way, the geometry can be preserved without excessive station-keeping thereby reducing the fuel usage and hence increasing the life of the satellites. Another consideration is that the phasing of each satellite in an orbital plane maintains sufficient separation to avoid collisions or interference at orbit plane intersections.

[[File:Walker-Delta Constellation.webp|thumb|Walker-Delta Constellation]]
A class of circular orbit geometries that has become popular is the Walker Delta Pattern constellation.
This has an associated notation to describe it which was proposed by John Walker.<ref>J. G. Walker, Satellite constellations, Journal of the British Interplanetary Society, vol. 37, pp. 559-571, 1984</ref> His notation is:

: '''i: t/p/f'''

where:
* '''i''' is the inclination;
* '''t''' is the total number of satellites;
* '''p''' is the number of equally spaced planes; and
* '''f''' is the relative spacing between satellites in adjacent planes. The change in true anomaly (in degrees) for equivalent satellites in neighbouring planes is equal to '''f''' × 360 / '''t'''.

For example, the [[Galileo (satellite navigation)|Galileo navigation system]] is a Walker Delta 56°:{{nbsp}}24/3/1 constellation. This means there are 24 satellites in 3 planes inclined at 56 degrees, spanning the 360 degrees around the [[equator]]. The "1" defines the phasing between the planes, and how they are spaced. The Walker Delta is also known as the Ballard rosette, after A. H. Ballard's similar earlier work.<ref>A. H. Ballard, Rosette Constellations of Earth Satellites, IEEE Transactions on Aerospace and Electronic Systems, Vol 16 No. 5, Sep. 1980.</ref><ref>J. G. Walker, Comments on "Rosette constellations of earth satellites", IEEE Transactions on Aerospace and Electronic Systems, vol. 18 no. 4, pp. 723-724, November 1982.</ref> Ballard's notation is (t,p,m) where m is a multiple of the fractional offset between planes.

[[File:Walker-Star Constellation.webp|thumb|Walker-Star Constellation]]
Another popular constellation type is the near-polar Walker Star, which is used by [[Iridium (satellite)|Iridium]]. Here, the satellites are in near-polar circular orbits across approximately 180 degrees, travelling north on one side of the Earth, and south on the other. The active satellites in the full Iridium constellation form a Walker Star of 86.4°:{{nbsp}}66/6/2, i.e. the phasing repeats every two planes. Walker uses similar notation for stars and deltas, which can be confusing.

These sets of circular orbits at constant altitude are sometimes referred to as orbital shells.

==Orbital shell==
In [[spaceflight]], an '''orbital shell''' is a set of [[artificial satellite]]s in [[circular orbit|circular]] [[orbit]]s at a certain fixed [[orbital altitude|altitude]].<ref name="fcc20181108b">[https://fcc.report/IBFS/SAT-MOD-20181108-00083/1569860 SPACEX NON-GEOSTATIONARY SATELLITE SYSTEM, Attachment A, TECHNICAL INFORMATION TO SUPPLEMENT SCHEDULE S], US Federal Communications Commission, 8 November 2018, accessed 19 November 2019.</ref> In the design of satellite constellations, an orbital shell usually refers to a collection of circular [[orbit]]s with the same [[orbital altitude|altitude]] and, oftentimes, [[orbital inclination]], 
distributed evenly in [[celestial longitude]] (and [[mean anomaly]]).{{citation needed|date=November 2019}} 
For a sufficiently high inclination and altitude the orbital shell [[pass (spaceflight)|covers]] the entire orbited body. In other cases the coverage extends up to a certain maximum [[latitude]].{{citation needed|date=November 2019}}

Several existing satellite constellations typically use a single orbital shell. New large [[megaconstellation]]s have been proposed that consist of multiple orbital shells.<ref name=fcc20181108b/><ref>{{Cite web|url=https://spacenews.com/amazon-lays-out-constellation-service-goals-deployment-and-deorbit-plans-to-fcc/|title=Amazon lays out constellation service goals, deployment and deorbit plans to FCC|date=2019-07-08|website=SpaceNews.com|language=en-US|access-date=2019-11-22}}</ref>

== List of satellite constellations ==
=== Navigational satellite constellations ===
{{Main article|Satellite navigation}}
{| class="wikitable sortable"
|+ Satellite constellations used for navigation
! Name
! Operator
! Satellites and orbits <br/>(latest design, excluding spares)
! Coverage
! Services
! Status
! Years in service
|-
|[[Global Positioning System]] (GPS)
|[[United States Space Force|USSF]]
|24 in 6 planes at 20,180&nbsp;km (55° [[Medium Earth orbit|MEO]]) 
|Global
|Navigation
|Operational
|1993–present
|-
|[[GLONASS]]
|[[Roscosmos]]
|24 in 3 planes at 19,130&nbsp;km (64°8' MEO)
|Global
|Navigation
|Operational
|1995–present
|-
|[[Galileo (satellite navigation)|Galileo]]
|[[European Union Agency for the Space Programme|EUSPA]], [[European Space Agency|ESA]]
|24 in 3 planes at 23,222&nbsp;km (56° MEO)
|Global
|Navigation
|Operational
|2019–present
|-
| [[BeiDou]]
| [[China National Space Administration|CNSA]]
| {{ubl
 | 3 geostationary at 35,786 km ([[Geostationary orbit|GEO]])
 | 3 in 3 planes at 35,786 km (55° [[Geosynchronous orbit|GSO]])
 | 24 in 3 planes at 21,150 km (55° MEO)
 }}
| Global
| Navigation
| Operational
| {{ubl
 | 2012–present, Asia
 | 2018–present, globally
 }}
|-
| [[NAVIC]]
| [[ISRO]]
| {{ubl
 | 3 geostationary at 35,786 km (GEO)
 | 4 in 2 planes at 250–24,000 km (29° GSO)
 }}
| Regional
| Navigation
| Operational
| 2018–present
|-
| [[QZSS]]
| [[Japan Aerospace Exploration Agency|JAXA]]
| {{ubl
 | 1 geostationary at 35,786 km (GEO)
 | 3 in 3 planes at 32,600–39,000 (43° GSO)
 }}
| Regional
| Navigation
| Operational
| 2018–present
|}

=== Communications satellite constellations ===
{{See also|Satellite communication|Category:Communications satellite constellations}}

==== Broadcasting ====

*[[Sirius Satellite Radio]] until 2013
*[[XM Satellite Radio]] until 2011
*[[SES (company)|SES]]
*[[Othernet]]
*[[Molniya (satellite)|Molniya]] (discontinued)

==== Monitoring ====

*[[Spire Global|Spire]] (AIS, ADS-B)
*[[Iridium satellite constellation|Iridium]] (AIS, ADS-B, IoT)
*[[Myriota]] (IoT)
*[[Swarm Technologies]] (IoT)
*[[Astrocast]] (IoT)
*[[TDRSS]]

==== Internet access ====
{| class="sortable wikitable"
|+ Operational communications satellite constellations
! Name
! Operator
! Constellation design
! Coverage
! Freq.
! Services
|-
|Broadband Global Area Network|Broadband Global Area Network (BGAN)
|[[Inmarsat]] 
|3 geostationary satellites
|82°S to 82°N
|
|Internet access
|-
|Global Xpress (GX)
|[[Inmarsat]] 
|5 Geostationary satellites<ref>{{cite web |url=https://www.inmarsat.com/en/solutions-services/enterprise/services/land-xpress.html |access-date=1 November 2021|title=Land Xpress }}</ref>
|
|[[Ka band|K<sub>a</sub> band]]
|Internet access
|-
|[[Globalstar]]
|[[Globalstar]]
|48 at 1400&nbsp;km, 52° (8 planes)<ref name=":0">{{Cite web|url=https://www.n2yo.com/satellites/?c=17|title=Globalstar satellites|website=www.n2yo.com|access-date=2019-11-22}}</ref>
|70°S to 70°N<ref name=":0" />
|
|Internet access, satellite telephony
|-
|[[Iridium satellite constellation|Iridium]]
|[[Iridium Communications]]
|66 at 780&nbsp;km, 86.4° (6 planes)
|Global
| {{ubl
 | [[L band]] 
 | K<sub>a</sub> band 
 }}
|Internet access, satellite telephony
|-
|[[O3b]]
|[[SES (company)|SES]]
|20 at 8,062&nbsp;km, 0° (circular equatorial orbit)
|45°S to 45°N
|K<sub>a</sub> band
|Internet access
|-
| [[O3b mPOWER]]
| [[SES (company)|SES]]
|8 at 8,062&nbsp;km, 0° (circular equatorial orbit)<br>5 more to be launched by end 2026
|45°S to 45°N
| [[Ka band|K<sub>a</sub>]] (26.5–40&nbsp;GHz)
|Internet access
|-
|[[Orbcomm (satellite)|Orbcomm]]
|[[Orbcomm|ORBCOMM]]
|17 at 750&nbsp;km, 52° (OG2)
|65°S to 65°N
|
|[[IoT]] and [[Machine to machine|M2M]], [[Automatic identification system|AIS]]
|-
|[[Defense Satellite Communications System|Defense Satellite Communications System (DSCS)]] 
|[[4th Space Operations Squadron]]
|
|
|
|Military communications
|-
|[[Wideband Global SATCOM|Wideband Global SATCOM (WGS)]]
|[[4th Space Operations Squadron]]
|10 geostationary satellites
|
|
|Military communications
|-
|[[ViaSat]]
|[[Viasat, Inc.]]
|4 geostationary satellites
|Varying
|
|Internet access
|-
|[[Eutelsat]]
|[[Eutelsat]]
|20 geostationary satellites
|
|
|Commercial
|-
|[[Thuraya]]
|[[Thuraya]]
|2 geostationary satellites
|[[Europe, the Middle East and Africa|EMEA]] and Asia
| L band
|Internet access, satellite telephony
|-
|[[Starlink]]
|[[SpaceX]]
| LEO in several orbital shells{{ubl
 | ~5000 satellites at 550 km (Oct 2023)
 | 12000 satellites at ~350–550 km (planned)
 }}
| {{ubl
 | 44°S to 52°N (Feb 2021)
 | Global
 }}
| {{ubl
 | [[Ku band|K<sub>u</sub>]] (12–18&nbsp;GHz)
 | [[Ka band|K<sub>a</sub>]] (26.5–40&nbsp;GHz)
 }}
| Internet access<ref>{{cite web|title=This is how Elon Musk plans to use SpaceX to give internet to everyone|url=https://www.cnet.com/news/how-spacex-brings-starlink-broadband-satellite-internet-to-low-earth-orbit/|website=CNET|language=en|date=21 February 2018}}</ref><ref>{{cite news |url=https://www.ispreview.co.uk/index.php/2018/02/spacex-set-launch-2-starlink-satellites-test-gigabit-broadband.html |title=SpaceX Set to Launch 2 Starlink Satellites to Test Gigabit Broadband |publisher=[[ISPreview]] |date=14 February 2018 |access-date=10 January 2019}}</ref><ref>{{Cite web|date=2020-09-09|title=SpaceX's Satellite Internet Service Latency Comes in Under 20 Milliseconds|url=https://uk.pcmag.com/switches/128545/spacexs-satellite-internet-service-latency-comes-in-under-20-milliseconds|access-date=2020-10-23|website=PCMag UK|language=en-gb}}</ref>
|-
|[[OneWeb]] constellation
|[[Eutelsat]] (completed merger in Sep 2023)
|882–1980<ref>{{cite magazine |date=2018-03-20 |title=OneWeb asks FCC to authorize 1,200 more satellites |url=https://spacenews.com/oneweb-asks-fcc-to-authorize-1200-more-satellites/ |magazine=SpaceNews |access-date=2018-03-23}}</ref>(planned)
Total number of operational satellites: 634 as of 20 May 2023
|Global
|{{ubl
 | [[Ku band|K<sub>u</sub>]] (12–18&nbsp;GHz)
 | [[Ka band|K<sub>a</sub>]] (26.5–40&nbsp;GHz)
 }}
|Internet access
|}

Other Internet access systems are proposed or currently being developed:

{| class="wikitable sortable"
|+ Proposed [[Satellite internet constellation|internet satellite constellations]]<ref name="AvWeek19dec2017">{{cite news|url=http://aviationweek.com/space/eight-satellite-constellations-promising-internet-service-space|title=Eight Satellite Constellations Promising Internet Service From Space|author=Thierry Dubois|date=Dec 19, 2017|work=Aviation Week & Space Technology}}</ref>
! Constellation
! Manufacturer
! Number
! Weight
! {{abbr|Unveil.|Unveiled}}
! {{abbr|Avail.|Available}}
! Altitude
! Offer
! Band
! Inter-sat.<br/>links
|-
|[[IRIS²]]
|[[European Space Agency]]
|TBD
|TBD
|
|
|
|
|
|

|-
| [[Telesat]] LEO
| {{ubl
 | [[Airbus]] [[Surrey Satellite Technology|SSTL]]
 | [[SS/Loral]]{{efn|first two prototypes}}
 }}
| 117–512<ref>{{cite magazine |url=https://spacenews.com/telesat-says-ideal-leo-constellation-is-292-satellites-but-could-be-512/ |title=Telesat says ideal LEO constellation is 292 satellites, but could be 512 |magazine=[[SpaceNews]] |date=11 September 2018 |access-date=10 January 2019}}</ref>
| {{N/A}}
| 2016
| 2027
| {{cvt|1,000–1,248|km|mi|disp=br}}
| [[Fiber-optic]] cable-like 
| [[Ka band|K<sub>a</sub>]] (26.5–40&nbsp;GHz)
| [[Laser communication in space|Optical]]<ref>{{Cite web|url=http://licensing.fcc.gov/myibfs/download.do?attachment_key=1190014|title=Telesat Technical Narrative|last=Telesat Canada|date=August 24, 2017|website=FCC Space Station Applications|access-date=February 23, 2018}}</ref><ref>{{Cite web|url=http://licensing.fcc.gov/cgi-bin/ws.exe/prod/ib/forms/reports/swr031b.hts?q_set=V_SITE_ANTENNA_FREQ.file_numberC/File+Number/%3D/SATPDR2017030100023&prepare=&column=V_SITE_ANTENNA_FREQ.file_numberC/File+Number|title=SAT-PDR-20170301-00023|last=Telesat Canada|date=August 24, 2017|website=FCC Space Station Applications|access-date=February 23, 2018}}</ref>
|-
| [[Hongyun (satellite)|Hongyun]]<ref>{{cite news |url=http://www.chinadaily.com.cn/a/201803/05/WS5a9c9a3ba3106e7dcc13f807.html |title=Satellite will test plan for communications network |work=[[China Daily]] |last=Zhao |first=Lei |date=5 March 2018 |access-date=20 December 2018}}</ref>
| [[China Aerospace Science and Industry Corporation|CASIC]] 
| 156
| 
| 2017
| 2022
| {{cvt|160–2,000|km|mi|disp=br}}
|
| 
| 
|-
| [[Hongyan (satellite)|Hongyan]]<ref name=hongyan>{{cite news |url=https://gbtimes.com/china-to-launch-first-hongyan-leo-communications-constellation-satellite-soon |title=China to launch first Hongyan LEO communications constellation satellite soon |work=[[GBTimes]] |first=Andrew |last=Jones |date=13 November 2018 |access-date=20 December 2018 |archive-date=20 December 2018 |archive-url=https://web.archive.org/web/20181220230438/https://gbtimes.com/china-to-launch-first-hongyan-leo-communications-constellation-satellite-soon |url-status=dead }}</ref>
| [[China Aerospace Science and Technology Corporation|CASC]]
| 320-864<ref>{{cite web |author=((EL2squirrel (cedar))) |url=https://twitter.com/EL2squirrel/status/1205338846671429632 |website=Twitter |title=Chinese version of OneWeb: The Hongyan system consists of 864 satellites, with 8&nbsp;Tbps of bandwidth, Orbital altitude 1175km |date=12 December 2019 |access-date=16 December 2019}}</ref>
| 
| 2017
| 2023
| {{cvt|1,100–1,175|km|mi|disp=br}}
|
| 
| 
|-
| [[Hanwha Systems]]<ref name=hanwha>{{cite news |url=https://www.satellitetoday.com/mobility/2021/03/31/hanwha-systems-plans-2000-satellite-leo-constellation-for-mobility-applications/ |title=Hanwha Systems Plans 2,000-Satellite LEO Constellation for Mobility Applications |work=Via Satellite |first=Rachel |last=Jewett |date=31 March 2022 |access-date=12 July 2022}}</ref>
| 
| 2000
| 
| 2022
| 2025
| 
|
| 
| 
|-
| [[Kuiper Systems|Project Kuiper]]
| [[Amazon (company)|Amazon]]
| 3236
|
| 2019
|2024
| {{cvt|590–630|km|mi|disp=br}}
| 56°S to 56°N<ref>{{Cite web|url=https://www.theverge.com/2019/4/4/18295310/amazon-project-kuiper-satellite-internet-low-earth-orbit-facebook-spacex-starlink|title=Amazon will launch thousands of satellites to provide internet around the world|last=Porter|first=Jon|date=2019-04-04|website=The Verge|language=en|access-date=2019-11-17}}</ref>
|
|
|}

Some systems were proposed but never realized:
{| class="wikitable  sortable"
|+ Abandoned communication satellite constellation designs
! Name
! Operator
! Constellation design
! Freq.
! Services
! Abandoned date
|-
|[[Celestri]]
|[[Motorola]]
|63 satellites at 1400&nbsp;km, 48° (7 planes)
|K<sub>a</sub> band (20/30&nbsp;GHz)
|Global, low-latency broadband Internet services
| 1998 May
|-
| [[Teledesic]]
| [[Teledesic]]
| {{ubl
 | 840 satellites at 700 km, 98.2° (21 planes) [1994 design]
 | 288 satellites at 1400 km, 98.2° (12 planes) [1997 design]
 }}
|K<sub>a</sub> band (20/30&nbsp;GHz)
| 100 Mbit/s up, 720&nbsp;Mbit/s down global internet access
| 2002 October
|-
|[[LeoSat]]
|[[Thales Alenia Space|Thales Alenia]]
|78–108 satellites at 1400 km
|[[Ka band|K<sub>a</sub>]] (26.5–40&nbsp;GHz)
|High-speed broadband internet
| 2019
|}


{{notelist}}

; Progress
* [[Boeing Satellite Systems|Boeing Satellite]] is transferring the application to OneWeb<ref name="boeing-to-oneweb">{{cite web|url=https://advanced-television.com/2017/12/11/boeing-wants-to-help-oneweb-satellite-plans/|title=Boeing wants to help OneWeb satellite plans|date=2017-12-17|publisher=Advanced Television|access-date=2018-10-21}}</ref>
* [[LeoSat]] shut down completely in 2019<ref>{{cite magazine |url=https://spacenews.com/leosat-absent-investors-shuts-down/ |title=LeoSat, absent investors, shuts down|magazine=Space News}}</ref>
* The [[OneWeb satellite constellation|OneWeb constellation]] had 6 pilot satellites in [[2019 in spaceflight#February|February 2019]], 74 satellites launched as of 21 March 2020<ref>{{cite news|url=https://www.bbc.com/news/science-environment-51991325|title=OneWeb increases mega-constellation to 74 satellites|date=2020-03-21|access-date=2020-04-07}}</ref> but filed for bankruptcy on 27 March 2020<ref>{{cite news|url=https://news.yahoo.com/coronavirus-oneweb-blames-coronavirus-collapse-090027262.html|title=Coronavirus: OneWeb blames pandemic for collapse|date=2020-03-30|access-date=2020-04-07}}</ref><ref>{{cite web |url=https://casedocs.omniagentsolutions.com/cmsvol2/pub_47378/808974_437-1.pdf |title=Voluntary Petition for Non-Individuals Filing for Bankruptcy |website=Omni Agent Solutions |date=2020-03-27|access-date=2020-04-07}}</ref>
* [[Starlink]]: first mission ([[List of Starlink and Starshield launches|Starlink 0]]) launched on 24 May 2019; 955 satellites launched, 51 deorbited, 904 in orbit {{as of|2020|11|25|lc=on|df=UK}}; public beta test in limited latitude range started in November 2020<ref>{{cite news|url=https://www.space.com/spacex-invites-starlink-internet-beta-testing|title=SpaceX opens Starlink satellite internet to public beta testers: report|author=Samantha Mathewson|date=6 November 2020}}</ref>
* [[O3b mPOWER]]: first 6 satellites launched December 2022-November 2023 with service start April 2024. 7 more in 2024–2026.<ref>[https://www.satellitetoday.com/connectivity/2024/04/24/ses-o3b-mpower-meo-system-is-now-operational-service-rollout-to-follow/ ''SES’ O3b mPOWER MEO System is Now Operational, Service Rollout to Follow''] Via Satellite. 24 April 2024. Accessed 29 April 2025</ref>
* [[Telesat]] LEO: two prototypes: 2018 launch 
* [[CASIC]] [[Hongyun (satellite)|Hongyun]]: prototype launched in December 2018<ref>{{cite news |url=https://www.nasaspaceflight.com/2018/12/chinese-long-march-11-launches-hongyun-satellite/ |title=Chinese Long March 11 launches with the first Hongyun satellite |work=[[NASASpaceFlight.com]] |first=Rui C. |last=Barbosa |date=21 December 2018 |access-date=24 December 2018}}</ref>
* [[China Aerospace Science and Technology Corporation|CASC]] [[Hongyan (satellite)|Hongyan]] prototype launched in December 2018,<ref>{{cite news |url=https://www.nasaspaceflight.com/2018/12/long-march-2d-20-hongyan-1-launch/ |title=Long March 2D concludes 2018 campaign with Hongyan-1 launch |work=[[NASASpaceFlight.com]] |first=Rui |last=Barbosa |date=29 December 2018 |access-date=29 December 2018}}</ref> might be merged with [[Hongyun (satellite)|Hongyun]]<ref>{{cite tweet |user=Cosmic_Penguin |number=1205840577012518913 |title=Notice that these satellites from CASC are mentioned as part of a "national satellite Internet system". There are rumors that several of the planned Chinese private LEO comsat constellations have been recently absorbed into one big nationalized one. |date=14 December 2019 |access-date=16 December 2019}}</ref>
* [[Kuiper Systems|Project Kuiper]]: FCC filing in July 2019. Prototypes launched in October 2023.

=== Earth observation satellite constellations ===
{{See also|List of Earth observation satellites}}

* [[RADARSAT Constellation]]
* [[Planet Labs]]
* [[Pleiades (satellite)|Pléiades 1A and 1B]]
* [[Satellogic]]
* [[RapidEye]]
* [[Disaster Monitoring Constellation]]
* [[A-train (satellite constellation)|A-train]]
* [[SPOT (satellite)|SPOT 6 and SPOT 7]]
* [[Spire Global|Spire]]
* [[Synspective]]

== See also ==
{{Wikisource|Category:Satellite constellations|Satellite constellations}}
* [[Satellite internet constellation]]
* [[Light pollution]]
* [[Space debris]]
* [[Geocentric orbit#Geocentric orbit types|Types of geocentric orbit]]
* [[Orbital mechanics]]

==Notes==
{{notelist}}

== References ==
{{reflist}}

== External links ==
{{Commons category}}
Satellite constellation simulation tools:

*[http://www.avmdynamics.com/index1.htm AVM Dynamics Satellite Constellation Modeler] {{Webarchive|url=https://web.archive.org/web/20230220104846/https://avmdynamics.com/index1.htm |date=2023-02-20 }}
*[https://savi.sourceforge.net/ SaVi Satellite Constellation Visualization]
*[http://www.transfinite.com/content/downloadsvisualyse.html Transfinite Visualyse Professional]

More information:

*[http://www.ee.surrey.ac.uk/Personal/L.Wood/publications/PhD-thesis/ Internetworking with satellite constellations - a PhD thesis (2001)] {{Webarchive|url=https://web.archive.org/web/20070707140928/http://www.ee.surrey.ac.uk/Personal/L.Wood/publications/PhD-thesis/ |date=2007-07-07 }}
*[http://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/ Lloyd's satellite constellations] {{Webarchive|url=https://web.archive.org/web/20070710100616/http://www.ee.surrey.ac.uk/Personal/L.Wood/constellations/ |date=2007-07-10 }} - last updated 20 July 2011
*[https://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=5371741&newsearch=true&queryText=Examination%20and%20analysis%20of%20polar%20low%20earth%20orbit%20constellation Examination and analysis of polar low Earth orbit constellation-IEEE]

{{Satellite constellations}}

[[Category:Satellite constellations| ]]
[[Category:Satellites]]
[[Category:Satellites by type]]