Research on the electron and proton spectra trapped with-in the Van Allen Belts has been a focal point for space research over the past decade. As understanding of the acceleration mechanisms that push particles away from the earth have been better understood, focus has turned to understanding the quantify and effects of energetic electrons and protons entering the Earth’s atmosphere. Of major interest is how these energetic particle precipitation events cause ozone depletion at the poles on the order of hours to days.

Particles that will enter Earth’s atmosphere can be identified by the angle between their velocity and the Earth’s magnetic field, called the pitch angle. By taking high angular resolution measurements of the Earth’s magnetic field and the direction electrons are traveling, the pitch angle and energy of electrons entering the atmosphere can be measured. By occupying a polar sun-synchronous orbit, the Pitch REsolving Spectrometry for Electron Transport (PRESET) mission will take high angular resolution measurements of the electron pitch-angle density near the north and south poles within the Van Allen Belts.