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{{Short description|Scientific research satellites}}
[[Image:LAGEOS-NASA.jpg|right|thumb|200px|The LAGEOS-1 satellite.]]
{{Infobox spaceflight
| name = LAGEOS-1
| image = LAGEOS-NASA.jpg
| image_caption = LAGEOS-1 ([[diameter]]=60 cm [23.6 inches])


| mission_type = [[Geodesy]]
'''LAGEOS''', or Laser Geodynamics Satellites, are a series of scientific research [[satellite]]s designed to provide an orbiting [[satellite laser ranging|laser ranging]] benchmark for geodynamical studies of the Earth.
| website = {{url|https://ilrs.cddis.eosdis.nasa.gov/missions/satellite_missions/current_missions/lag1_general.html|ilrs.cddis.eosdis.nasa.gov}}
| COSPAR_ID = 1976-039A
| SATCAT = 8820
| mission_duration = {{time interval|May 4, 1976, 08:00:00|show=ymd}}<br/> (in progress)


| spacecraft_type = GEOS
The spacecraft are [[aluminum]] covered [[brass]] spheres covered with [[retro-reflector]]s, giving them the appearance of giant golf balls. They have no onboard sensors or electronics, and are not attitude controlled.
| manufacturer = [[NASA]]
| launch_mass = {{convert|406.965|kg}}
| dimensions = {{convert|0.60|m}} diameter sphere
| power =


| launch_date = {{start-date|4 May 1976, 08:00|timezone=yes}}&nbsp;UTC<ref name="launchlog">{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowells|work=Jonathan's Space Page|accessdate=6 May 2017}}</ref>
Measurements are made by transmitting pulsed laser beams from Earth ground stations to the satellites. The laser beams then return to Earth after hitting the reflecting surfaces; the travel times are precisely measured, permitting ground stations in different parts of the Earth to measure their separations to better than one inch in thousands of miles.
| launch_rocket = [[Delta 2000|Delta 2913]] / [[Star (rocket stage)|Star-24]]
| launch_site = [[Vandenberg Air Force Base|Vandenberg]] [[Vandenberg AFB Space Launch Complex 2|SLC-2W]]
| launch_contractor = [[NASA]]


| disposal_type = Re-Entry
The LAGEOS satellites are able to determine positions of points on the Earth with extremely high accuracy due to the stability of their orbits.
| decay_date = in 8 Million Years


| orbit_epoch = 5 May 2017, 07:05:23&nbsp;UTC<ref name="celestrak">{{cite web|url=https://www.celestrak.com/NORAD/elements/geodetic.txt|title=Celestrak NORAD Two-Line Element Sets|date=5 May 2017|accessdate=6 May 2017}}</ref>
The high mass-to-area ratio and the precise, stable (attitude-independent) geometry of the LAGEOS spacecraft, together with their extremely regular orbits, make these satellites the most precise position references available.
| orbit_reference = [[Geocentric orbit|Geocentric]]
| orbit_regime = [[Medium Earth orbit|Medium Earth]]
| orbit_periapsis = {{convert|5838.33|km|mi|sp=us}}
| orbit_apoapsis = {{convert|5947.69|km|mi|sp=us}}
| orbit_inclination = 109.83&nbsp;degrees
| orbit_semimajor = {{convert|12271.15|km|mi|sp=us}}
| orbit_eccentricity = 0.0044560
| orbit_period = 225.70&nbsp;minutes
| apsis = gee


| instruments = {{unbulleted list|422 glass retroreflectors|4 germanium infrared retroreflectors|Time capsule plaque}}
The LAGEOS mission consists of the following key goals:
}}


{{Infobox spaceflight
* Provide an accurate measurement of the satellite's position with respect to Earth,
| name = LAGEOS-2
* Determine the planet's shape ([[geoid]]) and,
| image = STS-52 LAGEOS-II deployment.jpg
* Determine [[tectonic plate]] movements associated with [[continental drift]].
| image_caption = LAGEOS 2 during deployment on STS-52
| mission_type = [[Geodesy]]
| operator = [[NASA]]
| website = {{url|https://ilrs.cddis.eosdis.nasa.gov/missions/satellite_missions/current_missions/lag1_general.html|ilrs.cddis.eosdis.nasa.gov}}
| COSPAR_ID = 1992-070B
| SATCAT = 22195
| mission_duration = {{time interval|October 22, 1992, 17:09:00|show=ymd}}<br/> (in progress)
| spacecraft_type = LAGEOS
| manufacturer = [[Aeritalia]] for the [[Italian Space Agency|Italian Space Agency (ASI)]]
| launch_mass = {{convert|405.38|kg}}
| dimensions = {{convert|0.60|m}} diameter sphere
| power = <!-- [[watt]]s -->
| launch_date = {{start-date|22 October 1992, 17:09|timezone=yes}}&nbsp;UTC<ref name="launchlog"/>
| launch_rocket = [[STS-52|Space Shuttle STS-52 / Italian Research Interim Stage (IRIS)]]
| launch_site = [[Kennedy Space Center|Kennedy]] [[Kennedy Space Center Launch Complex 39|LC-39B]]
| disposal_type = Re-Entry
| decay_date = in 8 Million years
| orbit_epoch = 5 May 2017, 07:48:20&nbsp;UTC<ref name="celestrak">{{cite web|url=https://www.celestrak.com/NORAD/elements/geodetic.txt|title=Celestrak NORAD Two-Line Element Sets|date=5 May 2017|accessdate=6 May 2017}}</ref>
| orbit_reference = [[Geocentric orbit|Geocentric]]
| orbit_regime = [[Medium Earth orbit|Medium Earth]]
| orbit_periapsis = {{convert|5616.73|km|mi|sp=us}}
| orbit_apoapsis = {{convert|5950.68|km|mi|sp=us}}
| orbit_inclination = 52.65&nbsp;degrees
| orbit_semimajor = {{convert|12161.84|km|mi|sp=us}}
| orbit_eccentricity = 0.0137298
| orbit_period = 222.46&nbsp;minutess
| apsis = gee
| instruments = {{unbulleted list|422 glass retroreflectors|4 germanium infrared retroreflectors}}
}}
[[File:LAGEOS-FILE.jpg|thumb|upright|The LAGEOS plaque, designed by Carl Sagan|left]]
'''LAGEOS''' ({{IPAc-en|l|eɪ|ʒ|iː|oʊ|s|}}), '''Laser Geodynamics Satellite''' or '''Laser Geometric Environmental Observation Survey''', are a series of two scientific research [[satellite]]s designed to provide an orbiting [[satellite laser ranging|laser ranging]] benchmark for [[geodynamics|geodynamical]] studies of the [[Earth]]. Each satellite is a high-density passive laser reflector in a very stable [[medium Earth orbit]] (MEO).


== Function and operation ==
Ground tracking stations are located in many countries (including the US, Mexico, France, Germany, Poland, Australia, Egypt, China, Peru, Italy, and Japan) and data from these stations is available worldwide to investigators studying crustal dynamics.
The spacecraft are [[aluminum]]-covered [[brass]] spheres with diameters of {{convert|60|cm}} and masses of {{convert|400|and|411|kg|lbs|abbr=off}}, covered with 426 cube-corner [[retroreflector]]s, giving them the appearance of [[disco ball]]s.<ref>{{cite web|url=https://science.nasa.gov/missions/lageos-1-2/ |title=Missions - LAGEOS 1&2 - NASA Science |website=Science.nasa.gov |date=1976-05-04 |accessdate=2016-02-22}}</ref><ref>Kramer, Herbert J. (2013) [https://books.google.com/books?id=U3v1CAAAQBAJ&pg=PA149 ''Observation of the Earth and its Environment: Survey of Missions and Sensors''] Springer {{ISBN|9783662090381}} p149</ref><ref>[https://history.nasa.gov/SP-4012/vol3/table4.166.htm LAGEOS Characteristics] ''NASA Historical Data Book'' Volume III Table 4-166 SP-4012</ref> Of these retroreflectors, 422 are made from fused silica glass while the remaining 4 are made from germanium to obtain measurements in the infrared for experimental studies of reflectivity and satellite orientation.<ref name="ILRSLageos"/> They have no on-board sensors or electronics, and are not [[Spacecraft attitude control|attitude-controlled]].


They orbit at an altitude of {{convert|5900|km}},<ref name="LageosQL">{{cite web|url=http://space.jpl.nasa.gov/msl/QuickLooks/lageosQL.html |accessdate=March 31, 2011 |title=JPL Mission and Spacecraft Library, Lageos |website=space.jpl.nasa.gov|archiveurl=https://web.archive.org/web/20110721062751/http://space.jpl.nasa.gov/msl/QuickLooks/lageosQL.html|url-status=dead |archivedate=2011-07-21 }}</ref> well above [[low Earth orbit]] and well below [[geostationary orbit]], at orbital inclinations of 109.8 and 52.6 degrees.
There are two LAGEOS spacecraft, LAGEOS-1 launched in 1976, and LAGEOS-2 launched in 1992. As of 2004, both LAGEOS spacecraft are still in service.


Measurements are made by transmitting pulsed laser beams from Earth [[ground station]]s to the satellites. The laser beams then return to Earth after hitting the reflecting surfaces; the travel times are precisely measured, permitting ground stations in different parts of the Earth to measure their separations to better than one inch in thousands of miles.
An analysis of the laser-ranging data obtained by the two LAGEOS satellites, published in 1997, claimed to have found evidence of the [[frame-dragging]] effect predicted by Einstein's theory of [[general relativity]] with an accuracy of about 20 percent.


The LAGEOS satellites make it possible to determine positions of points on the Earth with extremely high [[Accuracy and precision|accuracy]] due to the stability of their orbits.
This effect is the same one that the [[Gravity Probe B]] satellite mission, unusual for its planned precision and its long time for planning, funding, and launching (from a suggestion by Professor [[Leonard Schiff]] in 1959, through formal planning starting in the [[1960]]s, until launch April 20, 2004), seeks to measure.
The high [[volume-to-area ratio|mass-to-area ratio]] and the precise, stable ([[attitude (geometry)|attitude]]-independent) geometry of the LAGEOS spacecraft, together with their extremely regular orbits, make these satellites the most precise position references available.


== See also ==
== Mission goals ==
The LAGEOS mission consists of the following key goals:
* [[geodesy]]
* Provide an accurate measurement of the satellite's position with respect to Earth.
* [[general relativity]]
* Determine the planet's shape ([[geoid]]).
* Determine [[tectonic plate]] movements associated with [[continental drift]].


Ground tracking stations located in many countries (including the US, Mexico, France, Germany, Poland, Australia, Egypt, China, Peru, Italy, and Japan) have ranged to the satellites and data from these stations are available worldwide to investigators studying [[Crust (geology)|crustal]] dynamics.
==References==
* {{Journal reference | Author=Neil Ashby | Title=General relativity: frame-dragging confirmed | Journal=[[Nature (journal)|Nature]]| Volume=431 | Issue=7011 | Year=2004 | Pages=918-919}} PMID 15496905
* {{Journal reference | Author=I. Ciufolini, E. C. Pavlis | Title=A confirmation of the general relativistic prediction of the Lense&#8211;Thirring effect. | Journal=[[Nature (journal)|Nature]] | Volume=431 | Issue= | Year=2004 | Pages=958-960}} PMID 15496915


There are two LAGEOS spacecraft, LAGEOS-1 launched in 1976, and LAGEOS-2 launched in 1992. {{As of|2024}}, both LAGEOS spacecraft are routinely tracked by the [[ILRS network]].<ref>{{cite web|url=http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/lag1_support.html |title=International Laser Ranging Service |website=Ilrs.gsfc.nasa.gov |date=2012-09-17 |accessdate=2016-02-22}}</ref>
== External links ==
* http://www.earth.nasa.gov/history/lageos/lageos.html


== Time capsule ==
{{NASA}}
LAGEOS-1 (which is predicted to re-enter the atmosphere in 8.4 million years<ref name="ILRSLageos">{{cite web|url=http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/lag1_general.html |title=International Laser Ranging Service |website=Ilrs.gsfc.nasa.gov |date= |accessdate=2016-02-22}}</ref>) also contains a 4&nbsp;in&nbsp;×&nbsp;7&nbsp;in plaque designed by [[Carl Sagan]]<ref>''[https://lageos.gsfc.nasa.gov/Design/Message_to_the_Future.html LAGEOS: LAser GEOdynamic Satellite : Design : Message to the Future]'', [[National Aeronautics and Space Administration]], [[Goddard Space Flight Center]]</ref> to indicate to future humanity when LAGEOS-1 was launched. The plaque includes the numbers 1 to 10 in binary. In the upper right is a diagram of the Earth orbiting the Sun, with a binary number 1 indicating one revolution, equaling one year. It then shows 268,435,456 years in the past (binary: 2<sup>28</sup>), indicated by a left arrow and the arrangement of the Earth's continents at that time (during the [[Permian]] period). The present arrangement of the Earth's continents is indicated with a 0 and both forward and backward arrows. Then the estimated arrangement of the continents in 8.4 million years with a right facing arrow and 8,388,608 in binary (2<sup>23</sup>). LAGEOS itself is shown at launch on the 0 year, and falling to the Earth in the 8.4 million year diagram.<ref>[https://historydms.hq.nasa.gov/sites/default/files/DMS/e000045273.pdf NASA Press Kit for Project Lageos] (1976) p14</ref><ref>{{Cite book|title = Science Newsfront - Message for the future|url = https://books.google.com/books?id=DgEAAAAAMBAJ|publisher = [[Bonnier Corporation]]|date = 1976-07-01|language = en|first = Popular Science|last = Magazine}}</ref>


==Launch data==
''The first version of this article was adapted from the public domain NASA website at http://www.earth.nasa.gov/history/lageos/lageos.html ''
* LAGEOS 1, launched 4 May 1976, [[National Space Science Data Center|NSSDC]] ID 1976-039A, NORAD number 8820
* LAGEOS 2, deployed 23 October 1992 from [[STS-52]], NSSDC ID 1992-070B, NORAD number 22195

==See also==
* [[GEOS-3]]
* [[PAGEOS]]
* [[Geodesy]]
* [[Post-glacial rebound]]
* [[List of laser articles]]
* [[List of laser ranging satellites]]
* [[LARES (satellite)]] a similar object made of mostly tungsten

== References ==
{{reflist}}

== Further reading ==
*{{cite book |last=Sagan |first=Carl |year=1978 |title=Murmurs of Earth: The Voyager Interstellar Record |publisher=[[Random House]] |pages=8–9|bibcode=1978mevi.book.....S }}
* The Conversation (May 3, 2017) ''Space bling: ‘jewelled’ LAGEOS satellites help us to measure the Earth'', [https://web.archive.org/web/20170514022404/http://theconversation.com/space-bling-jewelled-lageos-satellites-help-us-to-measure-the-earth-76948]

== External links ==
{{Commons category|LAGEOS}}
* {{official website|http://lageos.gsfc.nasa.gov/}}
* [http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/lag1_general.html LAGEOS-1, -2 (International Laser Ranging Service)]
* [https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1976-039A-01 LAGEOS-1 page at US National Space Science Data Center]
* [https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1992-070B LAGEOS-2 page at US National Space Science Data Center]
* [https://eoportal.org/web/eoportal/satellite-missions/l/lageos LAGEOS-1, -2 (eoPortal.org)]
* [https://www.youtube.com/watch?v=zWphd6HAaHA LAGEOS video from NASA's Marshall Space Flight Center]
* [http://www.aparchive.com/metadata/youtube/655b330326f9ab0b6d211fa7e4d6b37b LAGEOS video (1976) from AP Television]
* [http://libarchstor.uah.edu:8081/repositories/2/resources/106 LAGEOS Collection, The University of Alabama in Huntsville Archives and Special Collections]
* [http://libarchstor.uah.edu:8081/repositories/2/resources/127 Bob Spencer Collection, The University of Alabama in Huntsville Archives and Special Collections] Files of Robert Spencer, [https://lageos.gsfc.nasa.gov/docs/1973/PressRelease19731205.pdf planner] on the LAGEOS project.


[[Category:Satellites]]
[[Category:NASA satellites orbiting Earth]]
[[Category:Time capsules]]
[[de:Lageos]]
[[Category:Laser ranging satellites]]
[[Category:Italian Space Agency]]
[[Category:Satellite series]]
[[Category:Gravimetry satellites]]

Latest revision as of 03:11, 26 December 2024

LAGEOS-1
LAGEOS-1 (diameter=60 cm [23.6 inches])
Mission typeGeodesy
COSPAR ID1976-039A
SATCAT no.8820
Websiteilrs.cddis.eosdis.nasa.gov
Mission duration48 years, 7 months and 24 days
(in progress)
Spacecraft properties
Spacecraft typeGEOS
ManufacturerNASA
Launch mass406.965 kilograms (897.20 lb)
Dimensions0.60 metres (2 ft 0 in) diameter sphere
Start of mission
Launch date4 May 1976, 08:00 (1976-05-04UTC08Z) UTC[1]
RocketDelta 2913 / Star-24
Launch siteVandenberg SLC-2W
ContractorNASA
End of mission
DisposalRe-Entry
Decay datein 8 Million Years
Orbital parameters
Reference systemGeocentric
RegimeMedium Earth
Semi-major axis12,271.15 kilometers (7,624.94 mi)
Eccentricity0.0044560
Perigee altitude5,838.33 kilometers (3,627.77 mi)
Apogee altitude5,947.69 kilometers (3,695.72 mi)
Inclination109.83 degrees
Period225.70 minutes
Epoch5 May 2017, 07:05:23 UTC[2]
Instruments
  • 422 glass retroreflectors
  • 4 germanium infrared retroreflectors
  • Time capsule plaque
LAGEOS-2
LAGEOS 2 during deployment on STS-52
Mission typeGeodesy
OperatorNASA
COSPAR ID1992-070B
SATCAT no.22195
Websiteilrs.cddis.eosdis.nasa.gov
Mission duration32 years, 2 months and 5 days
(in progress)
Spacecraft properties
Spacecraft typeLAGEOS
ManufacturerAeritalia for the Italian Space Agency (ASI)
Launch mass405.38 kilograms (893.7 lb)
Dimensions0.60 metres (2 ft 0 in) diameter sphere
Start of mission
Launch date22 October 1992, 17:09 (1992-10-22UTC17:09Z) UTC[1]
RocketSpace Shuttle STS-52 / Italian Research Interim Stage (IRIS)
Launch siteKennedy LC-39B
End of mission
DisposalRe-Entry
Decay datein 8 Million years
Orbital parameters
Reference systemGeocentric
RegimeMedium Earth
Semi-major axis12,161.84 kilometers (7,557.02 mi)
Eccentricity0.0137298
Perigee altitude5,616.73 kilometers (3,490.07 mi)
Apogee altitude5,950.68 kilometers (3,697.58 mi)
Inclination52.65 degrees
Period222.46 minutess
Epoch5 May 2017, 07:48:20 UTC[2]
Instruments
  • 422 glass retroreflectors
  • 4 germanium infrared retroreflectors
The LAGEOS plaque, designed by Carl Sagan

LAGEOS (/leɪʒiːoʊs/), Laser Geodynamics Satellite or Laser Geometric Environmental Observation Survey, are a series of two scientific research satellites designed to provide an orbiting laser ranging benchmark for geodynamical studies of the Earth. Each satellite is a high-density passive laser reflector in a very stable medium Earth orbit (MEO).

Function and operation

[edit]

The spacecraft are aluminum-covered brass spheres with diameters of 60 centimetres (24 in) and masses of 400 and 411 kilograms (882 and 906 pounds), covered with 426 cube-corner retroreflectors, giving them the appearance of disco balls.[3][4][5] Of these retroreflectors, 422 are made from fused silica glass while the remaining 4 are made from germanium to obtain measurements in the infrared for experimental studies of reflectivity and satellite orientation.[6] They have no on-board sensors or electronics, and are not attitude-controlled.

They orbit at an altitude of 5,900 kilometres (3,700 mi),[7] well above low Earth orbit and well below geostationary orbit, at orbital inclinations of 109.8 and 52.6 degrees.

Measurements are made by transmitting pulsed laser beams from Earth ground stations to the satellites. The laser beams then return to Earth after hitting the reflecting surfaces; the travel times are precisely measured, permitting ground stations in different parts of the Earth to measure their separations to better than one inch in thousands of miles.

The LAGEOS satellites make it possible to determine positions of points on the Earth with extremely high accuracy due to the stability of their orbits. The high mass-to-area ratio and the precise, stable (attitude-independent) geometry of the LAGEOS spacecraft, together with their extremely regular orbits, make these satellites the most precise position references available.

Mission goals

[edit]

The LAGEOS mission consists of the following key goals:

  • Provide an accurate measurement of the satellite's position with respect to Earth.
  • Determine the planet's shape (geoid).
  • Determine tectonic plate movements associated with continental drift.

Ground tracking stations located in many countries (including the US, Mexico, France, Germany, Poland, Australia, Egypt, China, Peru, Italy, and Japan) have ranged to the satellites and data from these stations are available worldwide to investigators studying crustal dynamics.

There are two LAGEOS spacecraft, LAGEOS-1 launched in 1976, and LAGEOS-2 launched in 1992. As of 2024, both LAGEOS spacecraft are routinely tracked by the ILRS network.[8]

Time capsule

[edit]

LAGEOS-1 (which is predicted to re-enter the atmosphere in 8.4 million years[6]) also contains a 4 in × 7 in plaque designed by Carl Sagan[9] to indicate to future humanity when LAGEOS-1 was launched. The plaque includes the numbers 1 to 10 in binary. In the upper right is a diagram of the Earth orbiting the Sun, with a binary number 1 indicating one revolution, equaling one year. It then shows 268,435,456 years in the past (binary: 228), indicated by a left arrow and the arrangement of the Earth's continents at that time (during the Permian period). The present arrangement of the Earth's continents is indicated with a 0 and both forward and backward arrows. Then the estimated arrangement of the continents in 8.4 million years with a right facing arrow and 8,388,608 in binary (223). LAGEOS itself is shown at launch on the 0 year, and falling to the Earth in the 8.4 million year diagram.[10][11]

Launch data

[edit]
  • LAGEOS 1, launched 4 May 1976, NSSDC ID 1976-039A, NORAD number 8820
  • LAGEOS 2, deployed 23 October 1992 from STS-52, NSSDC ID 1992-070B, NORAD number 22195

See also

[edit]

References

[edit]
  1. ^ a b McDowells, Jonathan. "Launch Log". Jonathan's Space Page. Retrieved 6 May 2017.
  2. ^ a b "Celestrak NORAD Two-Line Element Sets". 5 May 2017. Retrieved 6 May 2017.
  3. ^ "Missions - LAGEOS 1&2 - NASA Science". Science.nasa.gov. 1976-05-04. Retrieved 2016-02-22.
  4. ^ Kramer, Herbert J. (2013) Observation of the Earth and its Environment: Survey of Missions and Sensors Springer ISBN 9783662090381 p149
  5. ^ LAGEOS Characteristics NASA Historical Data Book Volume III Table 4-166 SP-4012
  6. ^ a b "International Laser Ranging Service". Ilrs.gsfc.nasa.gov. Retrieved 2016-02-22.
  7. ^ "JPL Mission and Spacecraft Library, Lageos". space.jpl.nasa.gov. Archived from the original on 2011-07-21. Retrieved March 31, 2011.
  8. ^ "International Laser Ranging Service". Ilrs.gsfc.nasa.gov. 2012-09-17. Retrieved 2016-02-22.
  9. ^ LAGEOS: LAser GEOdynamic Satellite : Design : Message to the Future, National Aeronautics and Space Administration, Goddard Space Flight Center
  10. ^ NASA Press Kit for Project Lageos (1976) p14
  11. ^ Magazine, Popular Science (1976-07-01). Science Newsfront - Message for the future. Bonnier Corporation.

Further reading

[edit]
  • Sagan, Carl (1978). Murmurs of Earth: The Voyager Interstellar Record. Random House. pp. 8–9. Bibcode:1978mevi.book.....S.
  • The Conversation (May 3, 2017) Space bling: ‘jewelled’ LAGEOS satellites help us to measure the Earth, [1]
[edit]
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