Space mission: possible

Our understanding of our planet's structure, climate and the impact of climate change through global warming is to be dramatically increased by a new space mission.

The project is to set out to measure and map Earth's gravity field in far greater detail than anything achieved before. The European Space Agency's GOCE spacecraft is expected to launch later in 2007 with vital T5 ion thrusters that recently had a final test conducted by research group QinetiQ.

By using these thrusters, the spacecraft will be able to compensate for the drag experienced in orbit, thereby allowing highly accurate measurements of the planet's gravity field.

"The data collected by GOCE will be vital for the next generation of geophysical research and will contribute significantly to furthering our understanding of the impact of ocean circulation on Earth's climate. Without the precision that is provided by the spacecraft's thrusters, the mission would be impossible. Consequently, the final testing of the propulsion system is an important milestone," Alex Popescu, ESA's GOCE mission manager said.

Travelling at 8 km per second and operating at an orbital altitude of 240 km, the spacecraft will experience a small but significant disturbance in its motion from atmospheric drag.

This disturbance is constantly changing, therefore continuous and precise compensation is needed to allow the highly sensitive accelerometers on board to map the planet's gravitational field.

The GOCE mission is dedicated to measuring Earth's gravity field and modelling the planet's geoid - essentially a gravitational contour map - with extremely high accuracy and spatial resolution. It is the first Earth Explorer Core mission to be developed as part of the ESA's Living Planet Programme and should launch in late 2007.

The geoid (the surface of equal gravitational potential of a hypothetical ocean at rest) serves as the classical reference to map all topographical features on the planet. The accuracy of its determination is important for surveying and geodesy, and in studies of ocean circulation, ice motion and sea-level change - all of which are affected by climate change.

An improved knowledge of gravity anomalies will contribute to a better understanding of Earth's interior and also further knowledge of land uplift caused by post-glacial rebound.