Satellite Laser Ranging
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In satellite laser ranging (SLR) a global network of observation stations measures the round trip time of flight of ultrashort pulses of
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
to
satellite A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...
s equipped with
retroreflector A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects radiation (usually light) back to its source with minimum scattering. This works at a wide range of angle of incidence, unlike a planar mirror, ...
s. This provides instantaneous range measurements of millimeter level precision which can be accumulated to provide accurate measurement of orbits and a host of important scientific data. The laser pulse can also be reflected by the surface of a satellite without a
retroreflector A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects radiation (usually light) back to its source with minimum scattering. This works at a wide range of angle of incidence, unlike a planar mirror, ...
, which is used for tracking space debris. Satellite laser ranging is a proven geodetic technique with significant potential for important contributions to scientific studies of the earth/atmosphere/ocean system. It is the most accurate technique currently available to determine the geocentric position of an Earth satellite, allowing for the precise calibration of radar altimeters and separation of long-term instrumentation drift from secular changes in ocean topography. Its ability to measure the variations over time in Earth's
gravity field In physics, a gravitational field is a model used to explain the influences that a massive body extends into the space around itself, producing a force on another massive body. Thus, a gravitational field is used to explain gravitational phenome ...
and to monitor motion of the station network with respect to the geocenter, together with the capability to monitor vertical motion in an absolute system, makes it unique for modeling and evaluating long-term climate change by: * providing a reference system for
post-glacial rebound Post-glacial rebound (also called isostatic rebound or crustal rebound) is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound ...
,
plate tectonics Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large t ...
, sea level and ice volume change * determining the temporal mass redistribution of the solid earth, ocean, and atmosphere system * determining
Earth orientation parameters In geodesy and astrometry, earth orientation parameters (EOP) describe irregularities in the rotation of planet Earth. EOP provide the rotational transform from the International Terrestrial Reference System (ITRS) to the International Celestia ...
, such as Earth pole coordinates and length-of-day variations * determining of precise satellite orbits for artificial satellites with and without active devices onboard * monitoring the response of the atmosphere to seasonal variations in solar heating. SLR provides a unique capability for verification of the predictions of the theory of
general relativity General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. ...
, such as the
frame-dragging Frame-dragging is an effect on spacetime, predicted by Albert Einstein's general theory of relativity, that is due to non-static stationary distributions of mass–energy. A stationary field is one that is in a steady state, but the masses c ...
effect. SLR stations form an important part of the international network of space geodetic observatories, which include
VLBI Very-long-baseline interferometry (VLBI) is a type of astronomical interferometry used in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth or in space. T ...
,
GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
, DORIS and PRARE systems. On several critical missions, SLR has provided failsafe redundancy when other radiometric tracking systems have failed.


History

Laser ranging A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The firs ...
to a near-Earth satellite was first carried out by NASA in 1964 with the launch of the Beacon-B satellite. Since that time, ranging precision, spurred by scientific requirements, has improved by a factor of a thousand from a few metres to a few millimetres, and more satellites equipped with retroreflectors have been launched. Several sets of retroreflectors were installed on Earth's
Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width ...
as part of the American
Apollo Apollo, grc, Ἀπόλλωνος, Apóllōnos, label=genitive , ; , grc-dor, Ἀπέλλων, Apéllōn, ; grc, Ἀπείλων, Apeílōn, label=Arcadocypriot Greek, ; grc-aeo, Ἄπλουν, Áploun, la, Apollō, la, Apollinis, label= ...
and Soviet Lunokhod space programs. These retroreflectors are also ranged on a regular basis ( lunar laser ranging), providing a highly accurate measurement of the dynamics of the Earth/Moon system. During the subsequent decades, the global satellite laser ranging network has evolved into a powerful source of data for studies of the solid Earth and its ocean and atmospheric systems. In addition, SLR provides
precise orbit determination Orbit determination is the estimation of orbits of objects such as moons, planets, and spacecraft. One major application is to allow tracking newly observed asteroids and verify that they have not been previously discovered. The basic methods wer ...
for spaceborne radar altimeter missions mapping the ocean surface (which are used to model global ocean circulation), for mapping volumetric changes in continental ice masses, and for land topography. It provides a means for subnanosecond global time transfer, and a basis for special tests of the Theory of General Relativity. The International Laser Ranging Service was formed in 1998 by the global SLR community to enhance geophysical and geodetic research activities, replacing the previous CSTG Satellite and Laser Ranging Subcommission.


Applications

SLR data has provided the standard, highly accurate, long wavelength gravity field reference model which supports all precision orbit determination and provides the basis for studying temporal gravitational variations due to mass redistribution. The height of the
geoid The geoid () is the shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth's rotation, if other influences such as winds and tides were absent. This surface is exten ...
has been determined to less than ten centimeters at long wavelengths less than 1,500 km. SLR provides mm/year accurate determinations of tectonic drift station motion on a global scale in a geocentric reference frame. Combined with gravity models and decadal changes in Earth rotation, these results contribute to modeling of convection in the Earth's mantle by providing constraints on related Earth interior processes. The velocity of the fiducial station in Hawaii is 70 mm/year and closely matches the rate of the background geophysical model.


List of satellites


List of passive satellites

Several dedicated laser ranging satellites were put in orbit: * Ajisai (Experimental Geodetic Payload) * BLITS *Calsphere satellites * EGP (Ajisai) * Etalon **Kosmos 1989 **Kosmos 2024 * LAGEOS **LAGEOS 1 **LAGEOS 2, see
STS-52 STS-52 was a ''Space Transportation System'' ( NASA Space Shuttle) mission using Space Shuttle ''Columbia'', and was launched on October 22, 1992. Crew Backup crew Mission highlights Primary mission objectives were deployment of t ...
*
LARES Lares ( , ; archaic , singular ''Lar'') were guardian deities in ancient Roman religion. Their origin is uncertain; they may have been hero-ancestors, guardians of the hearth, fields, boundaries, or fruitfulness, or an amalgam of these. Lares ...
* Larets * STARSHINE **Starshine 1, see
STS-96 STS-96 was a Space Shuttle mission to the International Space Station (ISS) flown by Space Shuttle '' Discovery'', and the first shuttle flight to dock at the International Space Station. The shuttle carried the Spacehab module in the payload, f ...
**Starshine 2, see
STS-108 STS-108 was a Space Shuttle mission to the International Space Station (ISS) flown by Space Shuttle '' Endeavour''. Its primary objective was to deliver supplies to and help maintain the ISS. STS-108 was the 12th shuttle flight to visit the ...
* Starlette and Stella


List of shared satellites

Several satellites carried laser retroreflectors, sharing the
bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...
with other instruments: *
Beacon Explorers The Explorers program is a NASA exploration program that provides flight opportunities for physics, geophysics, heliophysics, and astrophysics investigations from space. Launched in 1958, Explorer 1 was the first spacecraft of the United Sta ...
(
Beacon Explorer-B Explorer 27 (or BE-C or Beacon Explorer-C, Beacon-C or S-66C) was a small NASA satellite, launched in 1965, designed to conduct scientific research in the ionosphere. It was powered by 4 solar panels. One goal of the mission was to study in de ...
and
Beacon Explorer-C Explorer 27 (or BE-C or Beacon Explorer-C, Beacon-C or S-66C) was a small NASA satellite, launched in 1965, designed to conduct scientific research in the ionosphere. It was powered by 4 solar panels. One goal of the mission was to study in de ...
) *
GEOS #REDIRECT GEOS {{redirect category shell, {{R from other capitalisation{{R from ambiguous page ...
(
GEOS-1 Explorer 29, also called GEOS 1 or GEOS A, acronym to Geodetic Earth Orbiting Satellite, was a NASA satellite launched as part of the Explorer program, being the first of the two satellites GEOS. Explorer 29 was launched on 6 November 1965 from ...
,
GEOS-2 Explorer 36 (also called GEOS 2 or GEOS B, acronym for Geodetic Earth Orbiting Satellite) was a NASA satellite launched as part of the Explorer program, being the second of the two satellites GEOS. Explorer 36 was launched on 11 January 1968 fr ...
,
GEOS-3 GEOS-3, or Geodynamics Experimental Ocean Satellite 3, or GEOS-C, was the third and final satellite as part of NASA's Geodetic Earth Orbiting Satellite/Geodynamics Experimental Ocean Satellite program (NGSP)Henriksen, S. W. (ed) (1977National Geo ...
) * * *
CHAMP Champ is the short form of champion. It may also refer to: People * Champ (nickname) * Champ (surname) * Champ Butler (1926–1992), American singer * Champ Lyons (born 1940), justice of the Supreme Court of Alabama from 1998 to 2011 * Champ Se ...
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GRACE Grace may refer to: Places United States * Grace, Idaho, a city * Grace (CTA station), Chicago Transit Authority's Howard Line, Illinois * Little Goose Creek (Kentucky), location of Grace post office * Grace, Carroll County, Missouri, an uninc ...
*
GOCE ''Goce'' is an opera composed by Kiril Makedonski (1925–1984), written by Venko Markovski and dedicated to Gotse Delchev. The work was commissioned to be the very first opera performed by the Macedonian National Opera Company. It premiered on ...
* Navigation satellites **
GLONASS GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная навигационная спутниковая система, r=Global'naya Navigatsionnaya Sputnikovaya Sistema, t=Global Navigation Satellite System) is ...
**
GPS The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
(two experimental satellites) ** Galileo **
BeiDou The BeiDou Navigation Satellite System (BDS; ) is a Chinese satellite navigation system. It consists of two separate satellite constellations. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System and ...
**
NavIC The Indian Regional Navigation Satellite System (IRNSS), with an operational name of NavIC (acronym for 'Navigation with Indian Constellation; also, 'sailor' or 'navigator' in Indian languages), is an autonomous regional satellite navigation s ...
** QZSS *
Altimeter satellite Satellite geodesy is geodesy by means of artificial satellites—the measurement of the form and dimensions of Earth, the location of objects on its surface and the figure of the Earth's gravity field by means of artificial satellite techniques. ...
s **
GEOS-3 GEOS-3, or Geodynamics Experimental Ocean Satellite 3, or GEOS-C, was the third and final satellite as part of NASA's Geodetic Earth Orbiting Satellite/Geodynamics Experimental Ocean Satellite program (NGSP)Henriksen, S. W. (ed) (1977National Geo ...
**
TOPEX/Poseidon TOPEX/Poseidon was a joint satellite altimeter mission between NASA, the U.S. space agency; and CNES, the French space agency, to map ocean surface topography. Launched on August 10, 1992, it was the first major oceanographic research satelli ...
**
Sentinel-3 Sentinel-3 is an Earth observation satellite series developed by the European Space Agency as part of the Copernicus Programme. It currently (as of 2020) consists of 2 satellites: Sentinel-3A and Sentinel-3B. After initial commissioning, ea ...
**
SARAL SARAL (''S''atellite with ''AR''gos and ''AL''tiKa) is a cooperative altimetry technology mission of Indian Space Research Organisation (ISRO) and Centre National d'Études Spatiales (CNES). SARAL performs altimetric measurements designed to st ...


See also

*
Lidar Lidar (, also LIDAR, or LiDAR; sometimes LADAR) is a method for determining ranges (variable distance) by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. It can also be ...
* Lunar laser ranging * Retroreflector#In satellites *
Laser communication in space Laser communication in space is the use of free-space optical communication in outer space. Communication may be fully in space (an inter-satellite laser link) or in a ground-to-satellite or satellite-to-ground application. The main advantage ...


References


Further reading

* (
public domain The public domain (PD) consists of all the creative work to which no exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly waived, or may be inapplicable. Because those rights have expired, ...
)'' * Seeber, Günter (2003
''Satellite Geodesy''
Walter de Gruyter pg 404 * Kramer, Herbert J. (2002
''Observation of the Earth and Its Environment: Survey of Missions and Sensors''
Springer {{ISBN, 9783540423881 pg 131-132 * Turcotte, Donald L. (ed) (1993) ''Contributions of Space Geodesy to Geodynamics'' Washington, DC: American Geophysical Union Geodynamics Series, ISSN 0277-6669 * U.S. National Research Council (1985
''Geodesy: a look to the future''
NAP pg 80-84


External links


International Laser Ranging Service
website
McDonald Laser Ranging Station

NERC Space Geodesy Facility



Fixed Shutter Dome (FSD) for SLR