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'{{Infobox spaceflight | name = LAGEOS-1 | image = LAGEOS-NASA.jpg | image_caption = LAGEOS-1 ([[diameter]]=60&nbsp;cm [23.6 inches]) | mission_type = [[Geodesy]] | 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 | spacecraft_type = GEOS | 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=McDowell|work=Jonathan's Space Page|accessdate=6 May 2017}}</ref> | 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]] | 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> | 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}} }} {{Infobox spaceflight | name = LAGEOS-2 | 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 | 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 = | launch_date = {{start-date|22 October 1992, 17:09|timezone=yes}}&nbsp;UTC<ref name="launchlog">{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowell|work=Jonathan's Space Page|accessdate=6 May 2017}}</ref> | 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]] | 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;minutes | apsis = gee | instruments = {{unbulleted list|422 glass retroreflectors|4 germanium infrared retroreflectors}} }} '''LAGEOS''', '''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 == 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 giant [[golf 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 [[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. 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. 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. 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. == Mission goals == [[File:LAGEOS-FILE.jpg|thumb|The LAGEOS plaque, designed by Carl Sagan]] 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 [[Crust (geology)|crustal]] dynamics. There are two LAGEOS spacecraft, LAGEOS-1 launched in 1976, and LAGEOS-2 launched in 1992. {{As of|2011|05}}, 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> == Time capsule == 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 plaque designed by [[Carl Sagan]] 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 268435456 (in binary; 2²⁸) years in the past, indicated by a left arrow and the arrangement of the Earth's continents at that time. 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 8388608 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.<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== [[File:Sts052-80-030 lrg.jpg|thumb|Deployment of LAGEOS 2 during STS-52]] * 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://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)] * [http://www.aparchive.com/metadata/youtube/655b330326f9ab0b6d211fa7e4d6b37b LAGEOS] video (1976) at AParchive.com * [http://libarchstor.uah.edu:8081/repositories/2/resources/106 LAGEOS Collection, The University of Alabama in Huntsville Archives and Special Collections] [[Category:NASA satellites orbiting Earth]] [[Category:Time capsules]] [[Category:Laser ranging satellites]] [[Category:Italian Space Agency]] [[Category:Satellite series]]'