The availability of structures that can autonomously assemble in orbit could have a key role in future space explorations and research. Thanks to the last 20 years of miniaturization in space technologies, CubeSats have emerged as the perfect tool for in-orbit demonstration missions. However, a successful docking mission between two CubeSats still represents an unmet challenge because of the high accuracy required in the last meters of this operation. In fact, during the final approach phase, the relative position and attitude of the two spacecrafts are coupled and all the 6 degrees of freedom of the chasing CubeSat must be estimated and controlled simultaneously.