4 May 2011
Gravity up close
Launched in March 2009 from the Plesetsk Cosmodrome in Russia, the GOCE satellite measures Earth’s gravity field by acquiring and accumulating precise data designed to generate a reference product for use by scientists working in a range of fields.
This product takes the form of a 3D map of the geoid, the virtual surface that serves as a reference for measuring elevations.
“In March, after 12 full months of data acquisition, GOCE achieved its aims and a model of the gravity field was generated from the data,” says Steven Hosford, in charge of Solid Earth programmes at CNES. “But the satellite will continue to acquire data until end 2012. Every 61 days, GOCE completes a new cycle of measurements that allows us to refine our models a little more each time.”
From the initial mission concepts through to generation of the most accurate models obtained from the satellite’s data, CNES has fulfilled its role as an agency driving innovation.
“The space geodesy team is working in partnership with the European GOCE Gravity Consortium (EGG-C),” says Steven Hosford. “It is thus helping to process data and define reference models.”
Until now, each country had a national geoid generated from ground and aerial data using often very different references.
The high-resolution geoid produced by GOCE will serve as a global reference to make these national geoids more uniform and ease comparisons between continents.
A better understanding of planet Earth
Scientists also hope to study Earth’s internal geodynamics, in particular to improve our understanding of earthquakes.
“GOCE measures variations in mass of the planet’s crust, which provides clues about its composition,” explains Steven Hosford. “When combined with seismic data, this information will tell us more about the structure and behaviour of faults in subduction zones.”
Lastly, using the improved geoid obtained with GOCE and comparing it with precise altimetry data from other satellites, scientists can measure ocean currents and related heat transfers more accurately.
And that’s not all, as GOCE data are also useful for monitoring sea level, a crucial parameter for understanding climate change.