Electrical power outages, loss of radio signals, and errors in navigation systems are all examples of phenomena that the Sun can cause, through the interaction of the solar wind - a stream of gas and particles flowing outward from the Sun - with the Earth's magnetic field.

The close relationship between the Earth and the Sun sometimes results in conflict. But the magnetic field of the Earth forms an efficient shield protecting it from the bombardment of the Sun's particles.

Since August 2000, the simultaneous observations of the Cluster programme's 4 satellites have helped scientists make 3-dimensional studies of the frontier zones between the solar wind and Earth's magnetosphere . The mission has a pioneering aspect, because for the first time, 4 identical spacecraft are exploring the same phenomena from different angles.

The Cluster mission, in association with the SOHO programme, is supplying comprehensive information on Sun/Earth interactions.

This enables scientists to better understand the physical phenomena occurring in interplanetary space, and to determine their influence on the Earth's environment.

At the moment, the Cluster mission is foreseen to be ended in 2014.

^{Last updated: August 2010}