16,952
edits
m
clean up
>Heythereimaguy m (→Tundra orbit: Added "the") |
CleanupBot (talk | contribs) m (clean up) |
||
| Line 22: | Line 22: | ||
The first geosynchronous satellite was designed by [[Harold Rosen (electrical engineer)|Harold Rosen]] while he was working at [[Hughes Aircraft]] in 1959. Inspired by [[Sputnik 1]], he wanted to use a geostationary (geosynchronous equatorial) satellite to globalise communications. Telecommunications between the US and Europe was then possible between just 136 people at a time, and reliant on [[high frequency]] radios and an [[Submarine communications cable|undersea cable]].<ref name=dm>{{Cite magazine|first=Jack|last=McClintock|date=November 9, 2003|url=http://discovermagazine.com/2003/nov/communications|title=Communications: Harold Rosen – The Seer of Geostationary Satellites|website=Discover Magazine |access-date=August 25, 2019}}</ref> | The first geosynchronous satellite was designed by [[Harold Rosen (electrical engineer)|Harold Rosen]] while he was working at [[Hughes Aircraft]] in 1959. Inspired by [[Sputnik 1]], he wanted to use a geostationary (geosynchronous equatorial) satellite to globalise communications. Telecommunications between the US and Europe was then possible between just 136 people at a time, and reliant on [[high frequency]] radios and an [[Submarine communications cable|undersea cable]].<ref name=dm>{{Cite magazine|first=Jack|last=McClintock|date=November 9, 2003|url=http://discovermagazine.com/2003/nov/communications|title=Communications: Harold Rosen – The Seer of Geostationary Satellites|website=Discover Magazine |access-date=August 25, 2019}}</ref> | ||
Conventional wisdom at the time was that it would require too much [[rocket]] power to place a satellite in a geosynchronous orbit and it would not survive long enough to justify the expense,<ref>{{Cite book|url=https://www.caltech.edu/about/news/harold-rosen-1926-2017-53790|title=Harold Rosen, 1926–2017|publisher=Caltech|last=Perkins|first=Robert|date=January 31, 2017 |access-date=August 25, 2019}}</ref> so early efforts were put towards constellations of satellites in [[low Earth orbit|low]] or [[Medium Earth Orbit|medium]] Earth orbit.<ref name="lat"/> The first of these were the passive [[Project Echo|Echo balloon satellites]] in 1960, followed by [[Telstar 1]] in 1962.<ref>{{cite book|title=Beyond The Ionosphere: Fifty Years of Satellite Communication|year=1997|chapter-url=https://history.nasa.gov/SP-4217/ch6.htm |first=Daniel R.|last=Glover |editor=Andrew J Butrica|publisher=NASA |chapter=Chapter 6: NASA Experimental Communications Satellites, 1958-1995|bibcode=1997bify.book.....B}}</ref> Although these projects had difficulties with signal strength and tracking that could be solved through geosynchronous satellites, the concept was seen as impractical, so Hughes often withheld funds and support.<ref name="lat">{{Cite news|url=https://www.latimes.com/nation/la-na-syncom-satellite-20130726-dto-htmlstory.html|title=How a satellite called Syncom changed the world|first=Ralph|last=Vartabedian|newspaper=[[Los Angeles Times]] |date=July 26, 2013 |access-date=August 25, 2019}}</ref | Conventional wisdom at the time was that it would require too much [[rocket]] power to place a satellite in a geosynchronous orbit and it would not survive long enough to justify the expense,<ref>{{Cite book|url=https://www.caltech.edu/about/news/harold-rosen-1926-2017-53790|title=Harold Rosen, 1926–2017|publisher=Caltech|last=Perkins|first=Robert|date=January 31, 2017 |access-date=August 25, 2019}}</ref> so early efforts were put towards constellations of satellites in [[low Earth orbit|low]] or [[Medium Earth Orbit|medium]] Earth orbit.<ref name="lat"/> The first of these were the passive [[Project Echo|Echo balloon satellites]] in 1960, followed by [[Telstar 1]] in 1962.<ref>{{cite book|title=Beyond The Ionosphere: Fifty Years of Satellite Communication|year=1997|chapter-url=https://history.nasa.gov/SP-4217/ch6.htm |first=Daniel R.|last=Glover |editor=Andrew J Butrica|publisher=NASA |chapter=Chapter 6: NASA Experimental Communications Satellites, 1958-1995|bibcode=1997bify.book.....B}}</ref> Although these projects had difficulties with signal strength and tracking that could be solved through geosynchronous satellites, the concept was seen as impractical, so Hughes often withheld funds and support.<ref name=dm/><ref name="lat">{{Cite news|url=https://www.latimes.com/nation/la-na-syncom-satellite-20130726-dto-htmlstory.html|title=How a satellite called Syncom changed the world|first=Ralph|last=Vartabedian|newspaper=[[Los Angeles Times]] |date=July 26, 2013 |access-date=August 25, 2019}}</ref> | ||
By 1961, Rosen and his team had produced a cylindrical prototype with a diameter of {{convert|76|cm|in}}, height of {{convert|38|cm|in}}, weighing {{convert|11.3|kg|lb}}; it was light, and small, enough to be placed into orbit by then-available rocketry, was [[Spin-stabilisation|spin stabilised]] and used dipole antennas<!-- As a physicist/engineer, I boldly changed the grammatical number of “antenna”, in the belief that a single antenna could not have been economically/logistically efficient. A reliable source should be sought, however. --> producing a pancake-shaped waveform. <!-- “pancake-shaped waveform” is plainly nonsense: Most likely what was intended is to insinuate that dispersion out of a preferred plane was limited; it‘s plausible that it reflects nothing more than our colleague misconstruing a graphic that was intended to convey something entirely different. --><ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-031A|publisher=NASA|title=Syncom 2|editor=David R. Williams |access-date=September 29, 2019}}</ref> In August 1961, they were contracted to begin building the working satellite.<ref name=dm/> They lost [[Syncom#Syncom 1|Syncom 1]] to electronics failure, but Syncom 2 was successfully placed into a geosynchronous orbit in 1963. Although its [[inclined orbit]] still required moving antennas, it was able to relay TV transmissions, and allowed for US President [[John F. Kennedy]] to phone Nigerian prime minister [[Abubakar Tafawa Balewa]] from a ship on August 23, 1963.<ref name="lat"/><ref>{{Cite web|url=https://www.historychannel.com.au/this-day-in-history/worlds-first-geosynchronous-satellite-launched/|title=World's First Geosynchronous Satellite Launched |publisher=Foxtel|date=June 19, 2016|website=History Channel |access-date=August 25, 2019}}</ref> | By 1961, Rosen and his team had produced a cylindrical prototype with a diameter of {{convert|76|cm|in}}, height of {{convert|38|cm|in}}, weighing {{convert|11.3|kg|lb}}; it was light, and small, enough to be placed into orbit by then-available rocketry, was [[Spin-stabilisation|spin stabilised]] and used dipole antennas<!-- As a physicist/engineer, I boldly changed the grammatical number of “antenna”, in the belief that a single antenna could not have been economically/logistically efficient. A reliable source should be sought, however. --> producing a pancake-shaped waveform. <!-- “pancake-shaped waveform” is plainly nonsense: Most likely what was intended is to insinuate that dispersion out of a preferred plane was limited; it‘s plausible that it reflects nothing more than our colleague misconstruing a graphic that was intended to convey something entirely different. --><ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-031A|publisher=NASA|title=Syncom 2|editor=David R. Williams |access-date=September 29, 2019}}</ref> In August 1961, they were contracted to begin building the working satellite.<ref name=dm/> They lost [[Syncom#Syncom 1|Syncom 1]] to electronics failure, but Syncom 2 was successfully placed into a geosynchronous orbit in 1963. Although its [[inclined orbit]] still required moving antennas, it was able to relay TV transmissions, and allowed for US President [[John F. Kennedy]] to phone Nigerian prime minister [[Abubakar Tafawa Balewa]] from a ship on August 23, 1963.<ref name="lat"/><ref>{{Cite web|url=https://www.historychannel.com.au/this-day-in-history/worlds-first-geosynchronous-satellite-launched/|title=World's First Geosynchronous Satellite Launched |publisher=Foxtel|date=June 19, 2016|website=History Channel |access-date=August 25, 2019}}</ref> | ||
| Line 108: | Line 108: | ||
Debris less than 10 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 |first=Caleb |last=Henry}}</ref> | Debris less than 10 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 |first=Caleb |last=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>{{cite web|url=http://www.spaceref.com/news/viewsr.html?pid=20320|title=Notification for Express-AM11 satellite users in connection with the spacecraft failure|publisher=Russian Satellite Communications Company|date=April 19, 2006|via=Spaceref}}</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 | 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>{{cite web|url=http://www.spaceref.com/news/viewsr.html?pid=20320|title=Notification for Express-AM11 satellite users in connection with the spacecraft failure|publisher=Russian Satellite Communications Company|date=April 19, 2006|via=Spaceref}}</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 name="telk1"/><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>{{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> | ||
==Properties== | ==Properties== | ||
| Line 119: | Line 119: | ||
===Period=== | ===Period=== | ||
All geosynchronous orbits have an orbital period equal to exactly one sidereal day.<ref>{{cite book |editor-first1=Vladimir|editor-last1=Chobotov |year=1996 |title=Orbital Mechanics |publisher=AIAA Education Series |page=304|edition=2nd|location=Washington, DC|isbn=9781563471797|oclc=807084516}}</ref> This means that the satellite will return to the same point above the Earth's surface every (sidereal) day, regardless of other orbital properties.<ref> | All geosynchronous orbits have an orbital period equal to exactly one sidereal day.<ref>{{cite book |editor-first1=Vladimir|editor-last1=Chobotov |year=1996 |title=Orbital Mechanics |publisher=AIAA Education Series |page=304|edition=2nd|location=Washington, DC|isbn=9781563471797|oclc=807084516}}</ref> This means that the satellite will return to the same point above the Earth's surface every (sidereal) day, regardless of other orbital properties.<ref name="smad"/>{{rp|121}}<ref> | ||
{{cite book |title=Fundamentals of Astrodynamics and Applications |last=Vallado |first=David A. |year=2007 |publisher=Microcosm Press |location=Hawthorne, CA |pages=31|oclc=263448232}} | {{cite book |title=Fundamentals of Astrodynamics and Applications |last=Vallado |first=David A. |year=2007 |publisher=Microcosm Press |location=Hawthorne, CA |pages=31|oclc=263448232}} | ||
</ref> | </ref> This orbital period, T, is directly related to the semi-major axis of the orbit through the formula: | ||
: <math>T = 2\pi\sqrt{a^3 \over \mu}</math> | : <math>T = 2\pi\sqrt{a^3 \over \mu}</math> | ||