The Monolithic Active Pixel Sensors Tracker System of the High Energy Particle Detector aboard the Second Chinese Seismo-Electromagnetic Satellite

The High Energy Particle Detector-02 (HEPD-02), onboard the second China Seismo-Electromagnetic Satellite (CSES-02), introduces—for the first time in a space application—a tracker designed entirely using Monolithic Active Pixel Sensors (MAPS). The MAPS selected for the HEPD-02 tracker were developed as part of CERN's R&D efforts for the realization of the ALICE inner tracking system. The readout system has been optimized, significantly reducing power consumption. The performance of the MAPS has been validated for HEPD-02's scientific objectives through beam tests using particle and ion beams in the tens to hundreds of MeV energy range. This manuscript details the design principles and structure of the tracker. The integration procedure is outlined step by step, with a discussion of the challenges encountered at each stage and the strategies adopted to address them. The description concludes with an analysis of production yields and the criteria used for selecting components for the flight and qualification models. Additionally, an overview of the space qualification activities is provided. The launch of CSES-02 is scheduled for mid-2025. Following an initial in-orbit commissioning phase, the technology will achieve Technology Readiness Level (TRL) 9, making it available for future space missions.