The European Space Agency will be launching three satellites next year with the objective of studying the earth’s gravity. The three identical satelittes will be launched on a Rockot launcher from Plesetsk in northern Russia and are currently undergoing testing at IABG in Ottobrunn, Germany.
Once launched, the Earth Explorer Swarm mission will be used to help understand how the Earth’s magnetic field is generated and how it changes over time. The three satellites carry magnetometers that will be used to identify and measure the magnetic signals from the various sources of the Earth’s magnetism: primarily from the magnetic field deep inside Earth that is created by an ocean of swirling iron that makes up the liquid outer core, but also from rocks in the crust and electric currents flowing in the ionosphere, magnetosphere and oceans.
More about this project at: Swarm: magnetic field satellites get their bearings