Medium-Energy Electron Detector Onboard the FY-3E Satellite

The Medium-Energy Electron Detector (MEED), a space weather monitoring instrument on the Fengyun-3E (FY-3E) satellite, is introduced in this paper. The MEED utilizes pin-hole imaging technology on low-orbit satellites for medium-energy electron detection. Two orthogonal sensor heads enable the MEED to measure electrons from 18 directions simultaneously in the energy range of 30-600 keV (divided into eight exponentially distributed energy channels). The instrument has a similar to 12 degrees angular resolution and covers two 180 degrees x 30 degrees fields of view. With the magnetometer onboard the same satellite, the pitch angle distribution of medium-energy electrons can be obtained with good angular resolution. This paper presents the design principle, ground calibration results, and preliminary on-orbit test results of the FY-3E MEED. The on-orbit test results show that the medium-energy electron fluxes, geographical distribution, energy spectrum, and pitch angle observed by the MEED are in agreement with the expected results. The MEED provides a new method to observe the low-orbit energetic electron radiation environment from the FY-3E satellite. Its successful in-orbit operation will enable the theoretical study of radiation belts and improve space weather research.