The dark energy responsible of the apparent acceleration of the universe is one of the most challenging questions of our time. On both side of the Atlantic a great deal of effort has been spent to design and optimize space missions able to determine the nature of this dark energy. These missions will use at least three different probes: Baryonic Acoustic Oscillation (BAO), Weak Lensing (WL) and Type Ia Supernovae (SNe). Most of the proposed missions rely on the concept of having