RUBIKS (Reconstruction of Undercrust Behaviour with Interconnected (K)cube Satellites): a nanosatellite mission dedicated to analysing the mantle. With 8 CubeSats (6U) on two Cartwheel-helix orbits, it is proposed to take magnetic and gravity measurements of the Earth’s interior, in order to gain information on the electrical conductivity and density of the mantle, especially the lower mantle.