Focus on our magnetic planet

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Spacecraft faults: more common over the South Atlantic
Focus on our magnetic planet


24 January 2005
Mission controllers cross their fingers whenever the Sun is stormy and their spacecraft have to fly over the South Atlantic. There, even satellites in low orbits suffer many hits by atomic bullets from the Sun. Troublesome faults occur in electronic systems and astronauts see flashes in their eyes. The Earth’s magnetic field, which shields our planet against charged atomic particles coming from outer space, is curiously weak in that region.

The South Atlantic Anomaly, as the experts call it, is one pressing reason why they are intensifying their exploration of the Earth’s magnetism. Denmark’s Ørsted satellite, launched in 1999, is dedicated to magnetic research, whilst Germany’s CHAMP mission (2000) measures both magnetism and gravity. These satellites show that the danger zone for satellites over Brazil and the South Atlantic is growing wider towards the southern Indian Ocean.

The Earth’s magnetic field is becoming generally weaker at an astonishing rate. When a French-Danish team compared Ørsted’s results for 2000 with those from an American satellite, Magsat, 20 years earlier, the decline in the field’s strength suggested that it might disappear completely in a thousand years or so. The experts wonder if our planet is preparing to swap its north and south magnetic poles around, as it has often done before during the Earth’s long history.



Three satellites for Swarm

These and other mysteries about our magnetic planet will get the closer attention they deserve, in ESA’s forthcoming Swarm project. Three satellites will work together to measure the magnetic field and its variations far more accurately than ever before. The Swarm mission was proposed to ESA by Eigil Friis-Christensen (Copenhagen), Hermann Lühr (Potsdam) and Gauthier Hulot (Paris) with support from scientists in seven European countries and the USA. ESA selected the project in 2004 as an 'opportunity mission' in its Earth Explorer programme. All being well, Swarm will be operational by 2009.

http://www.esa.int/esaEO/SEMV6K71Y3E_index_0.html