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{{Short description|Scientific research satellites}}

factoids

| COSPAR_ID = 1976-039A| SATCAT = 8820May 4, 1976, 08:00:00|show=ymd}} (in progress)| spacecraft_type = GEOS| manufacturer = NASA406.965|kg}}0.60|m}} diameter sphere| power =FIRST=JONATHANWORK=JONATHAN'S SPACE PAGE, 6 May 2017, Delta 2000>Delta 2913 / Star-24Vandenberg Air Force Base>Vandenberg SLC-2W| launch_contractor = NASA| disposal_type = Re-Entry| decay_date = in 8 Million YearsDATE=5 MAY 2017, 6 May 2017, Geocentric orbit>GeocentricMedium Earth orbit>Medium Earth5838.33mi|sp=us}}5947.69mi|sp=us}}| orbit_inclination = 109.83 degrees12271.15mi|sp=us}}| orbit_eccentricity = 0.0044560| orbit_period = 225.70 minutes| apsis = gee422 glass retroreflectorsTime capsule plaque}}}}

factoids

| COSPAR_ID = 1992-070B| SATCAT = 22195October 22, 1992, 17:09:00|show=ymd}} (in progress)| spacecraft_type = LAGEOSAeritalia for the Italian Space Agency>Italian Space Agency (ASI)405.38|kg}}0.60|m}} diameter sphere| power =STS-52>Space Shuttle STS-52 / Italian Research Interim Stage (IRIS)Kennedy Space Center>Kennedy LC-39B| disposal_type = Re-Entry | decay_date = in 8 Million yearsDATE=5 MAY 2017, 6 May 2017, Geocentric orbit>GeocentricMedium Earth orbit>Medium Earth5616.73mi|sp=us}}5950.68mi|sp=us}}| orbit_inclination = 52.65 degrees12161.84mi|sp=us}}| orbit_eccentricity = 0.0137298| orbit_period = 222.46 minutess| apsis = gee422 glass retroreflectors|4 germanium infrared retroreflectors}}}}LAGEOS, 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

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 retroreflectors, giving them the appearance of disco balls.WEB,weblink Missions - LAGEOS 1&2 - NASA Science, Science.nasa.gov, 1976-05-04, 2016-02-22, Kramer, Herbert J. (2013) Observation of the Earth and its Environment: Survey of Missions and Sensors Springer {{ISBN|9783662090381}} p149LAGEOS Characteristics NASA Historical Data Book Volume III Table 4-166 SP-4012 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. They have no on-board sensors or electronics, and are not attitude-controlled.They orbit at an altitude of {{convert|5900|km}},WEB,weblink March 31, 2011, JPL Mission and Spacecraft Library, Lageos, space.jpl.nasa.gov,weblink" title="web.archive.org/web/20110721062751weblink">weblink dead, 2011-07-21, 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

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|2023}}, both LAGEOS spacecraft are routinely tracked by the ILRS network.WEB,weblink International Laser Ranging Service, Ilrs.gsfc.nasa.gov, 2012-09-17, 2016-02-22,

Time capsule

(File:LAGEOS-FILE.jpg|thumb|upright|The LAGEOS plaque, designed by Carl Sagan)LAGEOS-1 (which is predicted to re-enter the atmosphere in 8.4 million yearsWEB,weblink International Laser Ranging Service, Ilrs.gsfc.nasa.gov, 2016-02-22, ) also contains a 4 in Ã— 7 in plaque designed by Carl SaganLAGEOS: LAser GEOdynamic Satellite : Design : Message to the Future, National Aeronautics and Space Administration, Goddard Space Flight Center 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.NASA Press Kit for Project Lageos (1976) p14BOOK, Science Newsfront - Message for the future,weblink Bonnier Corporation, 1976-07-01, en, Popular Science, Magazine,

Launch data

(File:Sts052-80-030 lrg.jpg|thumb|Deployment of LAGEOS 2 during STS-52)

• 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

• 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

• BOOK, Sagan, Carl, 1978, Murmurs of Earth: The Voyager Interstellar Record, Random House, 8–9, 1978mevi.book.....S,
• The Conversation (May 3, 2017) Space bling: ‘jewelled’ LAGEOS satellites help us to measure the Earth, weblink" title="https:/-/web.archive.org/web/20170514022404weblink">weblink

External links

{{Commons category|LAGEOS}}

• {{official websiteweblink}}
• LAGEOS-1, -2 (International Laser Ranging Service)
• LAGEOS-1 page at US National Space Science Data Center
• LAGEOS-2 page at US National Space Science Data Center
• LAGEOS-1, -2 (eoPortal.org)
• LAGEOS video from NASA's Marshall Space Flight Center
• LAGEOS video (1976) from AP Television
• LAGEOS Collection, The University of Alabama in Huntsville Archives and Special Collections
• Bob Spencer Collection, The University of Alabama in Huntsville Archives and Special Collections Files of Robert Spencer, planner on the LAGEOS project.