March 31, 2011

GOCE Team Unveils Gravitational Map Of Earth

A team working with Europe's GOCE satellite has shed light on the way the Earth looks from a gravitational point of view.

Scientists use the data gathered by the space probe to show how gravity varies across the Earth.

The data has revealed how the oceans are moving and how they redistribute the heat from the Sun around the world.

GOCE has also helped scientists understand that the earthquakes that struck Japan last month and Chile last year occurred because of huge masses of rock that suddenly moved.
"Even though these quakes resulted from big movements in the Earth, at the altitude of the satellite the signals are very small. But we should still seem them in the data," Dr Johannes Bouman from the German Geodetic Research Institute (DGFI) told BBC News.

The scientists said that the data has helped shed light on how "level" the surface of the Earth is.  A boat off the coast of Europe can sit 590 feet higher than a boat in the middle of the Indian Ocean, yet they will both still be on the same level plain.

This is the trick gravity plays on Earth because the planet is not a perfect sphere and its mass is not evenly distributed.

The Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) was launched in March 2009.

The space probe flies pole to pole at an altitude of 158 miles at its lowest point in orbit.

GOCE carries three pairs of precision-built platinum blocks inside its gradiometers instrument that sense accelerations, which are as small as 1 part in 10,000,000,000,000 of the gravity experienced on Earth.

These accelerations allow GOCE to map the almost imperceptible differences in the pull exerted by the mass of the Earth from one place to the next.

"The more data we add, the more we are able to suppress the noise in the solutions, and the errors scale down," Dr Rune Floberghagen, the European Space Agency's GOCE mission manager, told BBC. "And of course the more precisely you know the geoid, the better the science you can do using the geoid.

"We are seeing completely new information in areas like the Himalayas, the Andes mountain range, and in Antarctica particularly - the whole continent is desperate for better gravity field information, which we are now providing."

The mission has funding up until the end of 2012, which is when it must seek further financial support from member states in order to continue its mission.

GOCE has delivered the data promised in its primary mission, but researchers would like to see it fly for as long as possible.

Because it flies so low in the sky, GOCE needs an angina to push it forwards through the wisps of atmosphere still present at this altitude.

The team said that GOCE probably has sufficient propellant onboard to drive its engine until 2014.


Image 1: ESA's GOCE mission has delivered the most accurate model of the 'geoid' ever produced, which will be used to further our understanding of how Earth works. A precise model of Earth's geoid is crucial for deriving accurate measurements of ocean circulation, sea-level change and terrestrial ice dynamics. The geoid is also used as a reference surface from which to map the topographical features on the planet. In addition, a better understanding of variations in the gravity field will lead to a deeper understanding of Earth's interior, such as the physics and dynamics associated with volcanic activity and earthquakes. Credits: ESA/HPF/DLR

Image 2: The sleek aerodynamic design of GOCE immediately sets it apart from most other satellites. This unique five meter-long satellite has none of the usual moving parts. The whole satellite is a single composite gravity-measuring device. Credits: ESA /AOES Medialab


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