Medium-energy particle experiments-electron analyzer (MEP-e) for the exploration of energization and radiation in geospace (ERG) mission

The medium-energy particle experiments-electron analyzer onboard the exploration of energization and radiation in geospace spacecraft measures the energy and direction of each incoming electron in the energy range of 7-87 keV. The sensor covers a 2 pi-radian disklike field of view with 16 detectors, and the full solid angle coverage is achieved through the spacecraft's spin motion. The electron energy is independently measured by both an electrostatic analyzer and avalanche photodiodes, enabling significant background reduction. We describe the technical approach, data output, and examples of initial observations.