LAGEOS

LAGEOS-1

LAGEOS-1 (diameter=60 cm [23.6 inches])

Mission type| Geodesy
COSPAR ID| 1976-039A
SATCAT no.| 8820
Website| ilrs.cddis.eosdis.nasa.gov
Mission duration| 50 years and 6 days
(in progress)
Spacecraft properties
Spacecraft type| GEOS
Manufacturer| NASA
Launch mass| 406.965 kilograms (897.20 lb)
Dimensions| 0.60 metres (2 ft 0 in) diameter sphere
Start of mission
Launch date| 4 May 1976, 08:00 (1976-05-04UTC08Z) UTC[1]
Rocket| Delta 2913 / Star-24
Launch site| Vandenberg SLC-2W
Contractor| NASA
End of mission
Disposal| Re-Entry
Decay date| in 8 Million Years
Orbital parameters
Reference system| Geocentric
Regime| Medium Earth
Semi-major axis| 12,271.15 kilometers (7,624.94 mi)
Eccentricity| 0.0044560
Perigee altitude| 5,838.33 kilometers (3,627.77 mi)
Apogee altitude| 5,947.69 kilometers (3,695.72 mi)
Inclination| 109.83 degrees
Period| 225.70 minutes
Epoch| 5 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 type| Geodesy
Operator| NASA
COSPAR ID| 1992-070B
SATCAT no.| 22195
Website| ilrs.cddis.eosdis.nasa.gov
Mission duration| 33 years, 6 months and 18 days
(in progress)
Spacecraft properties
Spacecraft type| LAGEOS
Manufacturer| Aeritalia for the Italian Space Agency (ASI)
Launch mass| 405.38 kilograms (893.7 lb)
Dimensions| 0.60 metres (2 ft 0 in) diameter sphere
Start of mission
Launch date| 22 October 1992, 17:09 (1992-10-22UTC17:09Z) UTC[1]
Rocket| Space Shuttle STS-52 / Italian Research Interim Stage (IRIS)
Launch site| Kennedy LC-39B
End of mission
Disposal| Re-Entry
Decay date| in 8 Million years
Orbital parameters
Reference system| Geocentric
Regime| Medium Earth
Semi-major axis| 12,161.84 kilometers (7,557.02 mi)
Eccentricity| 0.0137298
Perigee altitude| 5,616.73 kilometers (3,490.07 mi)
Apogee altitude| 5,950.68 kilometers (3,697.58 mi)
Inclination| 52.65 degrees
Period| 222.46 minutess
Epoch| 5 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).

## Contents

* 1 Function and operation
* 2 Mission goals
* 3 Time capsule
* 4 Launch data
* 5 See also
* 6 References
* 7 Further reading
* 8 External links

## Function and operation

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

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[update], both LAGEOS spacecraft are routinely tracked by the ILRS network.[8]

## Time capsule

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

* 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

1. ↑ 1.0 1.1 McDowells, Jonathan. "Launch Log". Jonathan's Space Page. http://planet4589.org/space/log/launchlog.txt. Retrieved 6 May 2017.
2. ↑ 2.0 2.1 "Celestrak NORAD Two-Line Element Sets". 5 May 2017. https://www.celestrak.com/NORAD/elements/geodetic.txt. Retrieved 6 May 2017.
3. ↑ "Missions - LAGEOS 1&2 - NASA Science". 1976-05-04. https://science.nasa.gov/missions/lageos-1-2/. 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. ↑ 6.0 6.1 "International Laser Ranging Service". http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/lag1_general.html. Retrieved 2016-02-22.
7. ↑ "JPL Mission and Spacecraft Library, Lageos". Archived from the original on 2011-07-21. https://web.archive.org/web/20110721062751/http://space.jpl.nasa.gov/msl/QuickLooks/lageosQL.html. Retrieved March 31, 2011.
8. ↑ "International Laser Ranging Service". 2012-09-17. http://ilrs.gsfc.nasa.gov/missions/satellite_missions/current_missions/lag1_support.html. 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) (in en). Science Newsfront - Message for the future. Bonnier Corporation. https://books.google.com/books?id=DgEAAAAAMBAJ.

## Further reading

* 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]

## External links

* Official website
* 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.

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