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Encyclopedia > 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. Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Gravity is a force of attraction that acts between bodies that have mass. ...


GRACE maps variations in the Earth's gravity field over its five-year lifetime (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. A satellite in a polar orbit passes above or nearly above both poles of the planet (or other celestial body) on each revolution. ... Cyclone-3 rocket launching Meteor-3 satellite (Plesetsk, August 15, 1991) Plesetsk Cosmodrome is a Russian spaceport, located about 800 km north of Moscow and south of Arkhangelsk (coordinates vary in different sources, but 62°08′ N 41°01′ E seems plausible). ... Rockot The Rockot is a Russian space launch vehicle. ... March 17 is the 76th day of the year in the Gregorian Calendar (77th in leap years). ... For album titles with the same name, see 2002 (album). ...


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. A depiction of an accelerometer designed at Sandia National Laboratories. ... Over fifty GPS satellites such as this NAVSTAR have been launched since 1978. ... Buoy in San Diego Harbor. ... 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. ...


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.


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 instrument computer along with a highly precise GPS 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. ... Rough plot of Earths atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation, including radio waves. ... Space Systems/Loral (SS/L), of Palo Alto, California, is the wholly owned manufacturing subsidiary of Loral Space & Communications. ... The JPL complex in Pasadena, Ca. ... The Office National dÉtudes et de Recherches Aerospatiales (National Office of Aerospatial Studies and Research, ONERA) is a French national research institution dedicated to the study of aerospace problems (flow mechanics, materials and structures, information processing, physics). ...


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. Gravimetry is the measurement of a gravitational field. ... The LAGEOS-1 satellite. ... According to Albert Einsteins theory of general relativity, space and time get pulled out of shape near a rotating body in a phenomenon referred to as frame-dragging. ...


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] Ralph R. B. von Frese is an American geologist at the Ohio State University who identified the Wilkes Land crater with Laramie Potts. ... Laramie Potts is an American scientist at the Ohio State University who identified the Wilkes Land crater with Ralph von Frese. ... Map of Antarctica, with Wilkes Land slightly to the right The Wilkes Land crater is a proposed name for a 300 mile (500 km) -wide geological feature, located in Wilkes Land, Antarctica, and centered at , that has been explained as an impact crater. ...


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] Animation of the tsunami caused by the earthquake (see also the full-length version) The 2004 Indian Ocean earthquake was an undersea earthquake that occurred at 00:58:53 UTC (07:58:53 local time) on December 26, 2004. ...


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

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


  Results from FactBites:
 
TACC > Gravity Recovery and Climate Experiment (GRACE) (530 words)
Determining the gravity field of the Earth from the perturbations of the inter-satellite distance is a complex, non-linear estimation problem involving up to 40,000 gravity coefficients and hundreds of thousands of associated parameters.
The twin GRACE satellites are the instruments that measure the nonuniformities in the Earth's gravity field.
GRACE measurements will enable scientists to measure changes in the Greenland or portions of Antarctic ice sheets, measure changes in large aquifers, estimate deep ocean currents, and isolate geoid changes due to changes in global mean sea level to better than 0.1 mm/yr.
  More results at FactBites »

 
 

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