Oct 29, 2013

Spirit Of GOCE Lives On In Modeling Ocean Currents

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(28, October) Although the European Space Agency’s (ESA) Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite has completed its mission and is heading back to burn up in Earth’s atmosphere, it will be living on in spirit through another mission.

The primary objective of the GOCE mission was to map Earth’s gravity with great precision. GOCE has been orbiting Earth since March 2009, and ESA said a few weeks ago that the satellite has completed its mission and is heading back down to Earth. However, mission data from GOCE will allow it to live on in another research project aimed at understanding ocean currents.

Ocean currents are caused by wind, solar heating, rain and tides caused by the gravitational pull of the Sun and Moon. Gravity affects the shape of the ocean by creating large “bumps” in places where it is high and pulling more water closer. These variations do have a large influence on the ocean surface height, although they do not influence ocean currents.

Earth-observing satellites have been mapping out the ocean shape using radar altimeters. These measurements are made by a combination of ocean shape from currents and ocean shape from gravity. In order to derive ocean currents alone, the shape from gravity needs to be removed from the altimetric measurements.

Scientists at the French company CLS have begun using the GOCE geoid model to help improve their measurements of ocean surface currents from altimetry measurements. By taking GOCE’s measurements of the gravitational ‘bumps’ and then subtracting them from the altimetry measurements they are able to obtain a clearer view of an ocean shaped only by currents.

“The first geoids based on only two months of GOCE data were already providing estimates of Earth’s gravity with an unprecedented accuracy, and this accuracy has continuously improved, subsequently improving our ocean topography solution,” Dr Marie-Hélène Rio from CLS said in a press release.

GOCE’s gravity measurements are what scientists call their “fourth generation.” Over the past year the satellite has been lowered to help further improve its measurements and the gravity model.

“The data GOCE acquired during these last months when the satellite was put in a lower orbit will give us more exciting details about ocean circulation, which we plan to release in mid-2014,” Rio said in a statement.