Gravity Recovery And Climate Experiment

Information about Gravity Recovery And Climate Experiment

The goal of the Gravity Recovery And Climate Experiment (GRACE) space mission is to obtain accurate global and high-resolution determination of both the static and the time-variable components of the Earth's gravity field. GRACE is intended to enable precise measurement of Earth's shifting water masses by detecting their effects on our planet's gravity field, allowing the study of global climatic issues by enabling a better understanding of ocean surface currents and heat transport, measuring changes in sea-floor pressure, watching the mass of the oceans change, and by monitoring changes in the storage of water and snow on the continents. Also data on ocean and deep sea currents as well on tectonics are derived from the data.

Gravity anomaly map from GRACE

Explanation

GRACE maps variations in the Earth's gravity field over its five-year spacetime (extended to eight years in 2005) with its two identical spacecraft flying about 220 kilometers apart in a polar orbit 500 kilometers above the Earth. The twin GRACE satellites were launched from Plesetsk Cosmodrome, Russia on a Rockot (SS-19 + Breeze upper stage) launch vehicle, on March 17, 2002.

Operation

The two satellites constantly maintain a two-way microwave-ranging link between them, as well as measuring their own movements using accelerometers and star cameras and by listening to GPS satellite broadcasts. All of this information is then downloaded to ground stations. The GRACE vehicles also have optical corner reflectors to enable laser ranging from ground stations.

Spacecraft manufacture

The spacecraft were manufactured by Astrium of Germany. The microwave RF systems, and attitude determination and control system algorithms were provided by Space Systems/Loral. The star cameras used to measure the spacecraft attitude were provided by Technical University of Denmark. The instrument computer along with a highly precise GPS and digital signal processing system has been provided by JPL in Pasadena. The highly precise accelerometer that is needed to separate atmospheric and solar wind effects from the gravitation data has been manufactured by ONERA. JPL is responsible for the overall mission management under the NASA ESSP program.

Discoveries

The data so far obtained by GRACE is the most precise gravimetric data yet recorded: it has been used to re-analyse data obtained from the LAGEOS experiment to try to measure the relativistic frame-dragging effect.

In 2006 a team of researchers led by Ralph von Frese and Laramie Potts used GRACE data to discover the 480 km (300 miles) wide Wilkes Land crater in Antarctica, which probably formed about 250 million years ago.^[1]

Other deployment

GRACE data has also been used to analyze the shifts in the Earth's crust caused by the earthquake that created the 2004 Indian Ocean tsunami. ^[2]

References

1. ^ Gorder, Pam Frost (June 1, 2006). Big Bang in Antarctica -- Killer Crater Found Under Ice. Research News.
2. ^ Chang, Kenneth (August 8, 2006). Before the ’04 Tsunami, an Earthquake So Violent It Even Shook Gravity. New York Times.

External links

GRACE mission home page (Primary Investigator)
GRACE mission home page (co Primary Investigator) (language: German)
GRACE Mission Profile by NASA's Solar System Exploration
Science@NASA article about GRACE
Weighing Earth's Water from Space Estimating ground water using GRACE (written for non-scientists)
Report by BBC showing early results
GPS World Discussion of instrumentation

An early version of this article was adapted from public domain text at [1]

• • [ e] Meteorological, EOS, and GIS Remote Sensing Observation Systems (Earth orbit)
Current	Aqua
Historical and defunct systems	ERS

EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001. Their greatest hit, their debut single "time after time", peaked at #13 in the Oricon singles chart.
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Gravitation is a natural phenomenon by which all objects with mass attract each other. In everyday life, gravitation is most familiar as the agency that endows objects with weight.
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A polar orbit is an orbit in which a satellite passes above or nearly above both poles of the planet (or other celestial body) it is orbiting on each revolution. It therefore has an inclination of (or very close to) 90 degrees to the equator.
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Plesetsk Cosmodrome is a Russian spaceport, located in Arkhangelsk Oblast, about 800 km north of Moscow and south of Arkhangelsk.

It was originally developed by the Soviet Union as a launch site for intercontinental ballistic missiles.
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Anthem
Hymn of the Russian Federation

Capital
(and largest city) Moscow

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The Rockot (also Rokot) (Russian: Ро́кот) is a Russian space launch vehicle that can launch a payload of 1,950 kilogrammes into a 200 kilometre high Earth orbit with 63° inclination.
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March 17 is the 1st day of the year (2nd in leap years) in the Gregorian calendar. There are 0 days remaining.

Events

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20th century - 21st century - 22nd century
1970s 1980s 1990s - 2000s - 2010s 2020s 2030s
1999 2000 2001 - 2002 - 2003 2004 2005

2002 by topic:
News by month
Jan - Feb - Mar - Apr - May - Jun
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accelerometer is a measuring device for specific external force. Specific external force is the sum total of external forces acting on an object divided by the mass. Accelerometers do not measure internal forces such as gravity.
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Attitude control is control of the orientation of a spacecraft, or other flight vehicle, either relative to the celestial sphere or to a gravitating body influencing its flight path.
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Global Positioning System (GPS) is the only fully functional Global Navigation Satellite System (GNSS). Utilizing a constellation of at least 24 medium Earth orbit satellites that transmit precise microwave signals, the system enables a GPS receiver to determine its
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A corner reflector is a retroreflector consisting of three mutually perpendicular, intersecting flat surfaces, which reflects electromagnetic waves back towards the source. The three intersecting surfaces often have square shapes. This is also known as a corner cube.
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In satellite laser ranging (SLR) a global network of observation stations measure the round trip time of flight of ultrashort pulses of light to satellites equipped with retroreflectors.
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EADS Astrium is an aerospace subsidiary of the European Aeronautic Defence and Space Company (EADS).

Corporate history

In June 2006, EADS Astrium, EADS Space Transportation and EADS Space Services were merged into a single company; EADS SPACE.
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Anthem
"Das Lied der Deutschen" (third stanza)
also called "Einigkeit und Recht und Freiheit"
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Radio frequency, or RF, is a frequency or rate of oscillation within the range of about 3 Hz and 300 GHz. This range corresponds to frequency of alternating current electrical signals used to produce and detect radio waves.
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Space Systems/Loral (SS/L), of Palo Alto, California, is the wholly owned manufacturing subsidiary of Loral Space & Communications. It was acquired in 1990 for $715 million by Loral Corp. from Ford Motor Company as the Space Systems Division of Ford Aerospace.
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Technical University of Denmark (Danish: Danmarks Tekniske Universitet, DTU) was founded in 1829 as the 'College of Advanced Technology' (Danish: Den Polytekniske Læreanstalt).
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National Aeronautics and Space Administration

NASA logo
Motto: For the Benefit of All^[1]

NASA seal
Agency overview
Formed 29 July 1958

Headquarters Washington D.C.

Annual Budget $16.
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Gravimetry is the measurement of a gravitational field. Gravimetry may be used when either the magnitude of gravitational field or the properties of matter responsible for its creation are of interest.
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LAGEOS, or Laser Geodynamics Satellites, are a series of scientific research satellites designed to provide an orbiting laser ranging benchmark for geodynamical studies of the Earth.
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frame-dragging. The rotational frame-dragging effect was first derived from the theory of general relativity in 1918 by the Austrian physicists Joseph Lense and Hans Thirring, and is also known as the Lense-Thirring effect.
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Ralph R. B. von Frese is an American geologist at the Ohio State University who identified the Wilkes Land crater with Laramie Potts.

In 1969, von Frese obtained a B.A. cum laude from Park College in physics, mathematics and German. He earned M.
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Laramie Potts is an American scientist at the Ohio State University who identified the Wilkes Land crater with Ralph von Frese.

Potts is a Post Doctoral Researcher in Civil and Environmental Engineering and Geodetic Science.
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Wilkes Land crater is an informal term that may apply to two separate cases of conjectured giant impact craters hidden beneath the ice cap of Wilkes Land, Antarctica. These are separated below under the heading Wilkes Land anomaly and
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2004 Indian Ocean earthquake, known by the scientific community as the great Sumatra-Andaman earthquake,^[1] was an undersea earthquake that occurred at 00:58:53 UTC (07:58:53 local time) December 26, 2004, with an epicentre off the west coast of Sumatra, Indonesia.
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Aqua (EOS PM-1) is a multi-national NASA scientific research satellite in orbit around the Earth, studying the precipitation, evaporation, and cycling of water. It is the second major component of the Earth Observing System (EOS) following on Terra (launched 1999) and
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European Remote-Sensing satellite (ERS) was the European Space Agency's first Earth-observing satellite. It was launched on July 17, 1991 into a Sun synchronous polar orbit at a height of 782–785 km.
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