This paper presents the development, testing, and early operation of a space-borne instrument that can measure and identify chargedparticles and neutrals in the energy range of 20？400 keV with a 6.25 keV energy resolution. The instrument generates electric fields per-pendicular to its entrance aperture, which allows it to identify electrons, ions, and neutrals by deflecting the trajectories of charged par-ticles along the direction of the electric fields. Four identical detector pixels with thin windows, relatively positioned along the direction ofthe electric fields, independently measure each energy distribution of particles with a total geometric factor of approximately 0.01 cm2sr.In addition, to measure higher particle fluxes, up to 109/(cm2？sr？s), a reduction in particle fluxes by a factor of100 is possible with amechanical attenuator. Two identical telescopes, each with a field-of-view of 15°70°, are orthogonally placed to measure particles withdifferent pitch angles relative to local magnetic fields. The test results of the flight model instrument against laboratory radioisotopes,241Am,133Ba, and14C, are provided, together with results from a numerical simulation to estimate the instrument’s performance.The instrument capabilities are successfully demonstrated with energy spectra of particle distributions acquired from in-orbit operations.