Development of the power supply of HEPD-02 instrument on board CSES-02 satellite

The High Energy Particle Detector HEPD-02 is primarily devoted to observe fluxes of cosmic-ray electrons, protons and light nuclei, with kinetic energies in the range from less than 10 MeV to few hundreds MeV, either incoming or trapped in the terrestrial magnetosphere. HEPD-02 will be hosted on board the China Seismo-Electromagnetic Satellite CSES-02. The CSES mission, coordinated by China National Space Administration (CNSA) and Italian Space Agency (ASI), aims at developing a series of satellites for the study of the near-Earth environment, by means of electromagnetic, ionospheric, magnetospheric and cosmic-ray observations. HEPD-02 is a state-of-the-art instrument for measurement of energy and arrival direction and for identification of incoming cosmic particles; it is formed by a tower of superimposed plastic and crystal scintillator layers, read-out by photo-multiplier tubes (PMTs), with a direction detector composed of monolithic active pixel sensors. This paper describes the design, structure and operation of the power supply component of HEPD-02, which comprises a low-voltage unit for power distribution to other sub-systems and a high-voltage unit for generation of PMT bias. The HEPD-02 power supply features specific and optimized design solutions matching the demanding requirements for employment on board the CSES-02 satellite: it is conceived to guarantee at least 6 years of continuous operation, delivering stable voltages with low susceptibility to electromagnetic interference, in a harsh environment (characterized by relatively intense ionizing radiation, wide temperature excursions, absence of heat dissipation by air convection), after sustaining strong mechanical stresses at launch, at the same time complying with strict limits in mass, dimensions and available power.