Well, three to be exact – see http://phys.org/print304250622.html
The European Space Agency (EPA) are putting three satellites into orbit, each the size of a small car. They will stick fairly close to each other and beam back different kinds of data. They are concerned with improving navigation mapping techniques but they do this by studying the magnetic field of the Earth, and how the solar wind affects it. The idea is to better understand what is going on and protect communication and navigation systems on the surface.
The story can also be found in Planet Earth online – at http://planetearth.nerc.ac.uk/news/