Coded Aperture Imaging for Electron Pitch Angle Observations

This study evaluates the coded aperture imaging method for pitch angle observations of magnetospheric energetic electrons in the solar, Earth, and planetary space environments. We present a review of key previous energetic electron instruments with pitch angle-resolved observations across a range of electron energies. We describe the coded aperture imaging method, typically used for high angular resolution X-ray and gamma ray observations, and evaluate design parameters in the context of energetic electron observations. We present the results of simulations of energetic electrons in Geant4 and evaluate the method's ability to resolve sources with high angular and temporal resolution. We also evaluate the impact of secondary radiation produced from electron interactions in the tungsten coded aperture, as well as the impact of artifacts from the decoding process. With these simulated results, we identify key areas in magnetospheric science that would benefit from high angular resolution observations of energetic electrons. We find that coded aperture imaging may be well-suited for high-resolution observations of intense localized structures, such as low energy (tens of eV to several keV) field-aligned electron beams or the electron strahl wind.