Design and Ground Calibration of the Low-energy Ion Analyzer and Low-energy Electron Analyzer onboard the Chang'E-7 Mission

The Low-Energy Ion Analyzer (LEIA) and Low-Energy Electron Analyzer (LEEA), integral components of the Chang’e-7 (CE-7) lander’s lunar surface environment detection system, conduct in-situ measurements of low-energy charged particles (1 eV–30 keV) to elucidate solar wind-regolith interaction mechanisms, investigate microstructure evolution in the lunar near-surface plasma environment, and support space-environment assessment for future lunar research stations. Employing identical hemispherical electrostatic analyzers with asymmetric electrostatic deflectors, both analyzers achieve wide-field detection (90° × 360° FOV), broad energy coverage, and voltage-controlled variable geometric factors. Ground calibration using standard plasma beam sources confirmed compliance with mission requirements: energy resolution <15% (ΔE/E), dynamic flux range spanning seven orders of magnitude, and angular resolution <15° × 22.5°, collectively enabling comprehensive characterization of lunar surface plasma phenomena.