ESA to probe Earth's magnetic field

Satellites to launch in 2009

The European Space Agency has announced a satellite mission to study the Earth's magnetic field.

Dubbed Swarm, the mission comprises three satellites which will blast off in a single launcher in 2009. The Swarm constellation will be arranged with two of the satellites flying in a side-by-side pair at an initial altitude of 450km and a single, higher, satellite at 530km.

Swarm will conduct the most detailed survey yet of the planet's protective geomagnetic field, and in particular, how it changes with time. This should provide new insight into the workings of the Earth's interior and climate.

The Earth Science Advisory Committee said that Swarm was chosen from the range of candidate Earth Explorer missions for its scientific excellence.

The satellites' data will provide a unique view 'inside' the Earth. They will take precise and high-resolution measurements of the strength, direction and variation of the magnetic field, which, along with navigation, accelerometer and electric field measurements, will be used to untangle and model the various sources of the geomagnetic field.

The geomagnetic field is what protects us from the bulk of the Sun's harmful radiation. Its effects can be seen at high latitudes as the Aurora Polaris, or the Northern/Southern Lights. The particles in the solar wind carry a charge, so they move along the field lines. When these particles hit gases in Earth's atmosphere, the result is a spectacular light show.

The exact nature of the field is still something of a mystery, however. For instance, we know that the polarity of the field flips every million years or so. Some researchers think we may be seeing the beginning of a flip right now, but the debate is far from settled.

A better understanding of the field will allow for analysis of the Sun's influence in the solar system, and will provide insight into space weather and navigation. ®

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