The onboard low-energy particle detector (HEPP−L) can measure the electron fluxes with energy ranging from 0.1 keV to 3 MeV and the protons fluxes from 2 to 20 MeV. This range is divided into 256 energy channels with energy resolution ≤ 8.9% at 1 MeV. The maximum field of view of HEPP−L is 100◦ × 30◦ , and the silicon slice units are divided into two groups according to their field of view: 5 units with a narrow half angle of 6.5 ◦ and 4 units with a wide half angle of 15◦ . The wide and narrow field of view detection units are inter-placed and arranged in two spindles, respectively. The 9 particle detectors are mounted on the back side of the satellite (in the Y − Z plane). The measurable local pitch angles change with the real-time satellite orbits.