RAFTER (Ring Astrometric Field Telescope for Exo-planets and Relativity) is a TMA telescope concept aimed at astrometric missions, and providing a wide FOV and high optical response uniformity over an annular region around the optical axis. This paper describes and analyzes the process of miniaturization and implementation of this idea into a Cubesat for technology demonstration purposes, and to evaluate its feasibility by analysing the performance and challenging aspects of different designs, calculating their mechanical and thermal tolerance sensitivity. We outline the critical aspects of the payload that can be tested and optimized in the framework of a dedicated CubeSat mission, in order to demonstrate the enabling technological contributors crucial to the development of a future larger scale mission.