Observations and results from the High-Energy Particle Detector (HEPD) on-board CSES-01 satellite

The China Seismo-Electromagnetic Satellite (CSES-01) is a mission developed by

the Chinese National Space Administration (CNSA) together with the Italian Space Agency (ASI), to investigate the near-Earth electromagnetic, plasma and particle environment. In addition, it has been designed to detect a wide number of disturbances of the ionosphere/magnetosphere transition region.

One of the main instruments on-board CSES-01 is the High Energy Particle Detector (HEPD); it is an advanced detector, completely designed and built in Italy, based on a tower of 16 scintillators and a silicon tracker that provides good energy resolution and a wide angular acceptance for electrons/positrons (3–100 MeV), protons (30–200 MeV) and light nuclei up to Oxygen.

The very good capabilities in particle detection and separation make the detector extremely well suited for Space Weather purposes;  being also able to continuously monitor the magnetospheric environment with high stability in time, HEPD can detect small variations related to transient phenomena taking place on the Sun and propagating through the solar wind.
After two years of data-taking, HEPD showed impressive capabilities in measuring the various particle distributions along its orbit, starting from sub-cutoff protons/electrons, up to galactic cosmic ray particles at higher latitudes. The former class includes both stably-trapped particles in the Radiation Belts and particles bounced back from the top of the atmosphere without being able to escape the magnetic trap (re-entrant albedo). For cosmic ray particles, precise measurements of their spectra are needed to understand the acceleration and subsequent propagation of low-energy particles in the inner sector of the heliosphere and, more general, in our Galaxy.

We report precision measurements of the protons in the >30 MeV energy region and electrons in the >5 MeV energy range, performed by HEPD in a un-disturbed heliosphere during a low solar activity period (2018/2020).