The Energetic Particle Experiment on the Plasma Observatory Daughter Spacecraft

Plasma Observatory is a candidate mission of the European Space Agency (ESA) with a possible mission selection foreseen in 2026 and possible mission adoption in 2029. The mission aims to investigate cross-scale coupling and plasma energization across key regions of the magnetosphere, including: the bow shock, magnetopause, magnetotail and transition regions. To achieve this aim, Plasma Observatory will investigate the rich range of interesting plasma phenomena in these regions in the Earth’s magnetosphere, using a constellation of a mother and six daughter spacecraft. This allows configuration of the spacecraft in two nested tetrahedra to probe coupling on both ion and fluid scales. Since energetic particles are sensitive tracers of energization processes, altering the energy (or velocity) of both ions and electrons, measuring these effects in situ and at high cadence is of high importance for the mission. Energetic electrons and ions will be measured by the Energetic Particle Experiments (EPE) on the main (-M) and six daughter (-D) spacecraft. Here we present the EPE-D instrument, which is a compact, dual-particle telescope, solid state detector design based on ELFIN’s EPD instruments. Using three telescopes, it achieves near 3-D distributions for ions and electrons (135 x 360 deg). The development consists of deflecting magnets on the ion side (to screen out electrons) and a Lexan foil cover on electron side (to screen out low energy ions). The energy range (30-600 keV) for both species is targeted on low-end, suprathermal energies (minimising the effective gyro-scales for the computation of moments, PAD (e) and FDF determination), and so allowing spatial differences to be resolved. Detector layering is based on expected dynamic energy range and allows anti-coincident logic to be applied to separate out the higher energy species.