LASP Magnetosphere Seminars

Abstract

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. Thanks to its high energy resolution, REPTile-2 revealed numerous features and dynamic variations of relativistic electrons. CIRBE was launched into a highly inclined low Earth orbit (LEO) on April 15, 2023, and re-entered on October 4, 2024. While analysis and modeling of REPTile-2 data are ongoing, the natural question arises: what comes next?

Building on the heritage of REPTile-2, the Medium Energy Electron Telescope (MEET) has been developed at the University of Colorado Boulder/LASP. MEET measures 30–800 keV electrons across 59 channels. Both REPTile-2 and MEET collect data with millisecond cadence, enabling the differentiation of various types of electron precipitation, such as strong pitch-angle diffusion precipitation versus weak pitch-angle diffusion precipitation. This capability is crucial for identifying the physical mechanisms driving the different electron precipitation processes.

By combining REPTile-2 and MEET, we can achieve high energy and time resolution measurements of energetic electrons across a broad energy range (30 keV to 6 MeV) in LEO. A constellation of such CubeSats in highly inclined LEO would provide comprehensive measurements of energetic electron precipitation, which also enables a quantitative assessment of their impact on atmospheric and ionospheric processes. Since electron penetration depth—the altitude at which electrons deposit their energy—depends strongly on energy, such measurements are essential. This need has led to the development of a new mission concept: Total Energy Spectrum measurements of Energetic Electrons (TESEE).