The High-Energy Particle Detector on Board the CSES-02 Satellite

The China Seismo-Electromagnetic Satellite (CSES) mission is a joint China-Italy initiative focused on investigating Earth’s geophysical environment through non-imaging remote sensing from space. Its primary objective is to establish a constellation of satellites capable of continuously monitoring global electromagnetic fields, particle fluxes, and plasma parameters within the iono-magnetospheric system. Goals of this space program are the investigation of possible lithosphere-atmosphere-ionosphere-magnetosphere coupling mechanisms and their role in inducing perturbations in the upper ionosphere and the lower boundary of the radiation belts. Additionally, CSES contributes to space weather studies, including investigations of the magnetosphere, heliosphere, and galactic cosmic rays. Each satellite in the constellation carries multiple instruments to measure charged particles, electromagnetic fields, and plasma properties. CSES-01, launched in February 2018, remains operational. The second satellite, CSES-02, was launched on June 14, 2025, marking the transition to a multi-point observation capability. Italy contributed the High-Energy Particle Detector to both missions—HEPD-01 for CSES-01 and the upgraded HEPD-02 for CSES-02. These detectors are designed for precise measurements of electrons, protons, light nuclei, and transient gamma rays in the multi-MeV range. HEPD-02 significantly enhances energy resolution and extends the detection range when combined with the lower-energy instruments aboard CSES-02, enabling continuous coverage from 100 keV to 200 MeV. This article presents the scientific goals of the CSES program, with a focus on the role of HEPD-02 in energetic particle studies, both as a standalone detector and in synergy with the mission’s multi-instrument, multi-satellite framework.