Quantifying Energetic Electron Precipitations: A Combined REPTile-2 and MEET Approach to Measure 30keV – 6MeV with High Energy Resolution

Precise energy spectrum information is crucial for quantifying the impact of energetic electron precipitation into the atmosphere, as the penetration depth (the altitude at which the electrons deposit their energies) is strongly energy dependent. However, acquiring continuous spectrum data over a wide energy range (30 keV to 6 MeV) using a single instrument is challenging due to electronic saturation at lower energies and low count rates at higher energies. REPTile-2 (Relativistic Electron and Proton Telescope integrated little experiment-2), an advanced version of the REPTile instrument flown on the CSSWE CubeSat (2012-2014), measured 0.25-6 MeV electrons in 60 channels onboard the CIRBE (Colorado Inner Radiation Belt Experiment) CubeSat and revealed many features and dynamic variations of the relativistic electrons, thanks to its high energy resolution (ΔE/E <10%). CIRBE was launched into a highly inclined low Earth orbit (LEO) on April 15, 2023, and re-entered on October 4, 2024. To measure the lower energy electrons, the Medium Energy Electron Telescope (MEET) has been developed at the University of Colorado Boulder/LASP, leveraging the heritage of REPTile-2. MEET measures 30–800 keV electrons (and 1.1–60 MeV protons) in 59 channels with an energy resolution (ΔE/E) of <20% for 30–76 keV, <10% for 76–140 keV, and <5% for 140–800 keV. The combined capabilities of REPTile-2 and MEET will address the challenge of measuring energetic electrons with high energy and time resolution across a broad energy range (30 keV to 6 MeV) in LEO, which will enable the quantitative assessment of their impact to various processes in the atmosphere and ionosphere.