Earth’s magnetic field acts as a protective shield, preventing the dangerous portion of the sun’s rays from reaching the surface of our planet. Without this veritable coat of armour, there would be no life. Much of our magnetic field is generated by activity at the Earth’s core, but there are other sources too, such as the Earth’s crust, the ionosphere, the magnetosphere and even ocean circulation. The problem for scientists lies in differentiating all of these sources. Which is exactly what the European Space Agency’s Swarm mission (part of its Earth Explorers programme) has set out to do.

In 2013, three satellites were placed into different orbits at very low altitudes (530 km max.) in order to help isolate the different sources of the Earth’s magnetic field. These ‘space compasses’ are equipped with ultra-precision instruments, including an Absolute Scalar Magnetometer (ASM). Developed by CNES in partnership with CEA and IPGP, this revolutionary instrument measures both the magnitude and the direction of the magnetic field, making it the world’s first “2-in-1” instrument! Included on the Swarm satellites on an experimental basis, the instrument may one day be miniaturised and embedded on space probes, in order to measure the magnetic fields of other planets in our solar system.