Magnetic Map

Extraordinary map reveals Earth's gravity field for the first time

It is one of the most fundamental and mysterious forces in the Universe.

But this is the first glimpse of what the gravity field which surrounds the Earth looks like in a unique map created be a sophisticated European satellite.

The map is known as a geoid - an imaginary global ocean dictated by gravity in the absence of tides and currents.

It was first described almost 200 years ago but this is the first time it has been mapped in real-time.

Earth's gravity field as captured by the GOCE satellite gives an unprecedented view of how the force acts on our planet. The differences in gravitational force are represented using colours that show -100 metres up to 100 metres.

Gravity does not exert an equal force everywhere on Earth. Factors such as the rotation of the planet, the effects of mountains and density variations in Earth’s interior mean that this fundamental force is not quite the same all over.

The extraordinary map will be used to measure ocean circulation, sea-level change and ice dynamics.

'GOCE is delivering where it promised: in the fine spatial scales,' GOCE Mission Manager Rune Floberghagen said.

'We have already been able to identify significant improvements in the high-resolution 'geoid', and the gravity model will improve as more data become available.'

ESA launched GOCE in March 2009 to map Earth's gravity with unprecedented accuracy and resolution.

The model, based on only two months of data, from November and December 2009, shows the excellent capability of the satellite to map tiny variations in Earth’s gravity.

GOCE’s final gravity map and geoid will be used in geophysics and surveying to oceanography and sea-level research.

Dr Floberghagen added.' Over continents, and in particular in regions poorly mapped with terrestrial or airborne techniques, we can already conclude that GOCE is changing our understanding of the gravity field.'

'Over major parts of the oceans, the situation is even clearer, as the marine gravity field at high spatial resolution is for the first time independently determined by an instrument of such quality.'

Chairman of the GOCE Mission Advisory Group, Prof. Reiner Rumme said: 'With each two-month cycle of data, the gravity model will become more detailed and accurate. I am convinced that the data will be of great interest to various disciplines of Earth sciences.'

The satellite was designed to orbit at a very low altitude because gravitational variations are stronger closer to Earth.

Since mid-September 2009, GOCE has been in its gravity-mapping orbit at a mean altitude of just 254.9 km – the lowest orbit sustained over a long period by any Earth observation satellite

Air at this low altitude causes the orbit of a standard satellite to decay very rapidly. But GOCE nullifies the drag by firing an ion thruster using xenon gas to boost its orbit.

It ensures the gravity sensors are flying as though they are in pure freefall, so they pick up only gravity readings and not the disturbing effects from other forces.

To obtain clean gravity readings, there can be no disturbances from moving parts, so the entire satellite is a single extremely sensitive measuring device.

Read more: http://www.dailymail.co.uk/sciencetech/article-1290808/Earths-gravity-field-revealed-extraordinary-map-time.html#ixzz0sjPJjJpM