Accurate flux measurement of low energy charged particles, trapped in the magnetosphere, is necessary for Space Weather characterization and to study the coupling between the lithosphere and magnetosphere, allowing the investigation of the correlations between seismic events and particle precipitation from Van Allen Belts. In this presentation, the project of a CubeSat space spectrometer, the Low Energy Module (LEM) is shown. The detector will be able to perform an event-based measurement of energy, direction, and composition of low-energy charged particles down to 0.1 MeV. Moreover, thanks to a CdZnTe mini-calorimeter, the LEM spectrometer also allows photon detection in the sub-MeV range, joining the quest for the investigation of the nature of Gamma Ray Bursts.

The particle identification of the LEM relies on the ∆E−E technique performed by thin silicon detectors. This multipurpose spectrometer will fit within a 10x10x10 cm3 CubeSat frame and it will be constructed as a joining project between the University of Trento, FBK, and INFN-TIFPA. To fulfil the size and mass requirements an innovative approach, based on active particle collimation, was designed for the LEM, this avoids heavy/bulky passive collimators of previous space detectors. In this talk, we will present the LEM geometry, its detection concept, and the results from the developed GEANT4 simulation. Also, the results from the characterisation of LEM silicon detectors in the INFN-TIFPA laboratory will be presented.