DART: A Dual Aperture Relativistic Electron Telescope for Smallsats

Abstract The precipitation of particles into the Earth's atmosphere is a primary loss mechanism of the radiation belt for which many unknowns remain. With the growing number of space mission concepts to solve them, less expensive alternatives such as CubeSats are being used. Here we present the Double Aperture Relativistic Telescope (DART), a miniaturized solid‐state charged particle telescope whose objective is to measure differential energy particles at 180° separation. Designed for low altitude orbit, this instrument will provide measurements of energetic electrons streaming in opposite directions along Earth's magnetic field, enabling determination of precipitating particles as well as those backscattered and returning up the magnetic field line. This paper presents a description of the DART design, including a Geant4‐based analysis to characterize the instrument response and test results from a radioactive Sr‐90/Y‐90 source and atmospheric muons. Our Geant4 analysis shows that DART can measure electrons from – and the results from the radioactive source and muon tests have verified the performance of the instrument. These measurements will allow a new scientific understanding of energy deposition by radiation belt particle precipitation to the atmosphere, which is crucial to better understanding this particle loss mechanism.