China Seismo-Electromagnetic Satellites are the most advanced initiative for the study of the
ionosphere-lithosphere coupling from space. They are sensitive to any type of short- to long-lasting
perturbations in the ionosphere, thanks to the variety of instruments that they host on board.
Among them, the High-Energy Particle Detector is devoted to the observation of electrons and
protons with energy thresholds of 3 MeV and 30 MeV respectively. The Limadou collaboration has
designed an improved version of the HEPD for the second satellite of the CSES constellation,
whose launch is scheduled for the end of 2022. The main upgrade pertains to the tracker, which will be
made of Monolithic Active Pixel Sensors, never used so far in space. With respect to the standard
hybrid silicon microstrip technology, MAPS are more precise, more robust, easier to control and
readout, cheaper and less invasive. On the other hand, they are still relatively small-sized and
power-demanding. 
We report on the process of spatialisation carried out by the HEPD-02 tracker team, which has
adapted the operation mode of the ALPIDE sensor to realize a modular and compact particle
detector, made of 5 turrets, each one containing 3 stacked sensitive planes. All of 150 ALPIDE
sensors are controlled and readout with a Hybrid Integrated Circuit and supported by Carbon Fiber
Reinforced Plastics staves, housed in an aluminium case. We describe in detail the HEPD-02
tracker project, demonstrating the advantages of using MAPS in space and manifesting the
pioneering nature of the project for next-future larger size space missions.