An Instrument Concept for High-Resolution Observations of the Solar Wind Electron Strahl Using Coded Aperture Imaging

Abstract

In this concept study, we explore coded aperture imaging as a high-angular resolution imaging technique for suprathermal electron strahl observations in the solar wind. In particular, studying the relative contribution of pitch-angle scattering to solar wind strahl broadening near 1 AU requires very high-resolution observations of electron pitch angle. Coded aperture imaging is advantageous because it is a high-signal method that can provide high-angular resolution observations from a simple, and compact platform. In this study, we present an initial design concept to achieve a 40$°$ field-of-view with 3.1$°$ angular resolution from a CubeSat-sized platform. We include an “egg-crate” collimator design to mitigate the impact of the partially coded field-of-view as well as block solar photons. We also describe an estimate of the instrument data production and a possible CMOS candidate for low energy energetic particle detection. Finally, we present initial results of simulated strahl in Geant4 and the instrument response to these distributions. We find that reconstructed distributions can have accurate estimates of the strahl width. However, we find that especially for more broad strahl observations, coded aperture artifacts diminish the reconstruction quality and result in large deviations between input and output distributions. Possible options to improve accuracy include increasing integration time or reducing energy resolution.