To develop an Engineering Model (EM) of the mission’s instrument and to increase the Technology Readiness Level (TRL) of the critical subsystems up to 5. An EM is a light representative model in terms of form, fit and function used for the design qualification test program, it is not intended to flight. Complementary EU industrial partners develop the subsystems of the instrument (i.e. Physics Package, Laser System, Microwave Source and Ground Support Equipment) and increase its TRL by assessing the critical technologies in relevant environments. Excellent institutes bring their quantum expertise for the definition of the EM and the mastering of its performance.