Design of the Angle-Resolving Electron Spectrometer Aboard the PRESET Mission

Abstract

We present a design study for the Pitch REsolving Spectrometer for Electron Transport (PRESET) mission, a CubeSat that is aimed at measuring the pitch angle density spectrum in low-Earth orbit (LEO). While a few missions have measured the pitch angle density spectrum, all have provided low resolution within the loss cone. PRESET will be capable of measuring pitch angle density of electrons with a resolution of 10 degrees or better and an energy range of 0.3-7 MeV filling gaps in both energy range and angular resolution in LEO. The spectrometer is designed to fit within a 10x10x10cm3 volume (1U) including processing electronics so it can be integrated into a 3U CubeSat to be flown in a polar LEO. To achieve a 10-degree angular resolution, the detector employs a trough shaped collimator with a pin-hole type aperture followed by a single sided silicon strip detector. Aligned coaxially with the strip detector is a stack of 4 silicon detectors. To optimize the spectrometer design, extensive Monte Carlo simulations were carried out. The collimator was optimized by adjusting total length, width and height, aperture size, collimation plate spacing and material. A balance is found between increasing the instrument’s geometric factor and reducing the aperture width which directly affects the counting rate and angular resolution of the instrument, respectively. To optimize the stacking geometry of the silicon detectors, simulations were carried out by varying the number and thickness of the silicon detectors, allowing the electron energy resolution and maximum detectable electron energy to be extracted. An optimum design was deduced to accomplish an outstanding performance with a minimum of silicon detectors. Simulation results are verified using a prototype spectrometer and a commercial pulse processing system.