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Medium Earth orbit

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Amedium Earth orbit(MEO) is anEarth-centered orbitwith an altitude above alow Earth orbit(LEO) and below ahigh Earth orbit(HEO) – between 2,000 and 35,786 km (1,243 and 22,236 mi) above sea level.[1]

Clickable image, highlightingmedium altitude orbits around Earth,[a]fromLow Earthto the lowestHigh Earth orbit(geostationary orbitand itsgraveyard orbit,at one ninth of theMoon's orbital distance),[b]with theVan Allen radiation beltsand theEarthto scale
To-scale diagram of low, medium, andhigh Earth orbits
Space of Medium Earth orbits (MEO) as pink area, withEarthand thedistance of the orbit of the Moonfor reference and to scale.

The boundary between MEO and LEO is an arbitrary altitude chosen by accepted convention, whereas the boundary between MEO and HEO is the particular altitude of ageosynchronous orbit,in which a satellite takes 24 hours to circle the Earth, the same period as the Earth’s own rotation. All satellites in MEO have anorbital periodof less than 24 hours, with the minimum period (for a circular orbit at the lowest MEO altitude) about 2 hours.[2]

Satellites in MEO orbits are perturbed by solar radiation pressure, which is the dominating non-gravitational perturbing force.[3]Other perturbing forces include:Earth's albedo,navigation antenna thrust, and thermal effects related to heat re-radiation.

The MEO region includes the two zones of energetic charged particles above the equator known as theVan Allen radiation belts,which can damage satellites’ electronic systems without special shielding.[4]

A medium Earth orbit is sometimes calledmid Earth orbit[1]orintermediate circular orbit(ICO).[2]

Applications

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Acameraphoto of Earth from a distance of 29,400 kilometers (18,300 miles), a distance of higher medium Earth orbits (uncropped and unrotatedThe Blue Marbleimage, fromApollo 17during lunar transfer).

Two medium Earth orbits are particularly significant. A satellite in thesemi-synchronous orbitat an altitude of approximately 20,200 kilometres (12,600 mi) has an orbital period of 12 hours and passes over the same two spots on the equator every day.[1]This reliably predictable orbit is used by theGlobal Positioning System(GPS)constellation.[2]Other navigation satellite systems use similar medium Earth orbits includingGLONASS(with an altitude of 19,100 kilometres, 11,900 mi),[5]Galileo(with an altitude of 23,222 kilometres, 14,429 mi)[6]andBeiDou(with an altitude of 21,528 kilometres, 13,377 mi).[7]

TheMolniya orbithas a highinclinationof 63.4° and higheccentricityof 0.722 with a period of 12 hours, so a satellite spends most of its orbit above the chosen area in high latitudes. This orbit was used by the (now defunct) North AmericanSirius Satellite RadioandXM Satellite Radiosatellites and the RussianMolniyamilitary communications satellites, after which it is named.[1]

Communications satellites in MEO include theO3bandO3b mPOWERconstellations for low-latencybroadbandanddata backhaulto maritime, aero and remote locations (with an altitude of 8,063 kilometres, 5,010 mi).[8]

Communications satellites to cover the North and South Pole are also put in MEO.[9]

Telstar1, an experimental communications satellite launched in 1962, orbited in MEO.[10]

In May 2022,Kazakhstanimobile network operator,Kcell,and satellite owner and operator,SESused SES'sO3bMEOsatellite constellationto demonstrate that MEO satellites could be used to provide high-speed mobile internet to remote regions of Kazakhstan for reliable video calling, conferencing and streaming, and web browsing, with alatency (delay)five times lower than on the existing platform based ongeostationary orbitsatellites.[11][12]

In September 2023, satellite operatorSESannounced the first satellite internet service to usesatellite constellationsin both MEO andLow Earth Orbit (LEO).The SES Cruise mPOWERED + Starlink service will use SES'sO3b mPOWERMEO satellites andSpaceX'sStarlinkLEO system to provide cruise ship passengers with internet, social media and video calls at up to 3 Gbps per ship anywhere in the World. Subsequently, in February 2024,SESannounced thatVirgin Voyageswill be the first cruise line to deploy the service.[13][14][15]

Space debris

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Infographic showing the space debris situation extending from low Earth orbit, across medium Earth orbits, until the lowest high Earth orbits.

Space debrisin medium Earth orbit stays practically permanently orbiting Earth. Most space debris extends to the lowest high Earth orbits just beyond the edge of medium Earth orbit, wheregeostationary satellitesare and where after their end of use they are parked in similar orbits, so-calledgraveyard orbits.

See also

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Explanatory notes

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  1. ^Orbital periods and speeds are calculated using the relations 4π2R3=T2GMandV2R=GM,whereRis the radius of orbit in metres;Tis the orbital period in seconds;Vis the orbital speed in m/s;Gis the gravitational constant, approximately6.673×10−11Nm2/kg2;Mis the mass of Earth, approximately 5.98×1024kg (1.318×1025lb).
  2. ^Approximately 8.6 times when the Moon is nearest(that is,⁠363,104 km/42,164 km⁠),to 9.6 times when the Moon is farthest(that is,⁠405,696 km/42,164 km⁠)

References

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  1. ^abcdCatalog of Earth Satellite Orbits.NASA Earth Observatory. 4 September 2009. Accessed 2 May 2021.
  2. ^abc"Definitions of geocentric orbits from the Goddard Space Flight Center".User support guide: platforms.NASA Goddard Space Flight Center. Archived fromthe originalon 27 May 2010.Retrieved8 July2012.
  3. ^Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław; Strugarek, Dariusz (February 2020)."Toward the 1-cm Galileo orbits: challenges in modeling of perturbing forces".Journal of Geodesy.94(2): 16.Bibcode:2020JGeod..94...16B.doi:10.1007/s00190-020-01342-2.
  4. ^"Popular Orbits 101".Aerospace Security. 26 October 2020. Accessed 2 May 2021.
  5. ^"The Global Navigation System GLONASS: Development and Usage in the 21st Century".34th Annual Precise Time and Time Interval (PTTI) Meeting. 2002. Archived fromthe originalon June 29, 2011.Retrieved28 February2019.
  6. ^Galileo Satellites.
  7. ^BeiDou Navigation Satellite System Signal In Space.China Satellite Navigation Office. December 2013. Access 2 May 2021.
  8. ^O3b satellites
  9. ^Satellite Basics: Solution Benefits.Archived2013-11-19 atarchive.today.
  10. ^"Medium Earth Orbit".Internet in the Sky.Archived fromthe originalon 2017-06-09.Retrieved2007-01-04.
  11. ^Kcell, SES demo O3b satellite-enabled remote mobile servicesComms Update. 26 May 2022. Accessed 30 May 2022
  12. ^"Kcell and SES Successfully Demonstrate Cellular Network connectivity in Kazakhstan"(Press release). SES. 25 May 2022.Retrieved30 May2022.
  13. ^SES Teams Up with Starlink to Package Connectivity for the Cruise SegmentVia Satellite. 13 September 2023. Accessed 27 February 2024
  14. ^"SES Introduces Cruise Industry's First Integrated MEO-LEO Service with Starlink"(Press release). SES. 13 September 2023.Retrieved27 February2024.
  15. ^Virgin Voyages Rolls Out New Improved Internet Package with SESCruise Industry News. 26 February 2024. Accessed 27 February 2024
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