Design of Particle Instrument for the Energization and Radiation in Geospace (ERG) Spacecraft

Geospace is the region of outer space near Earth, which includes the magnetosphere and the upper region of the atmosphere. It is a hazardous environment that contains high energy particles and is strongly dependant on the space weather. Studies show a high correlation between satellite operational anomalies, such as deep dielectric charging, and large flux enhancement of relativistic electrons in the outer radiation belt. An astronaut is exposed to radiation through high energy protons and relativistic electrons during extravehicular activities since these kinds of particles can penetrate a space suit. Furthermore, high energy particles can penetrate and transmit through instrument walls and thereby contaminate measurements through secondary electrons detected as noise. In order to prevent these radiation-induced effects it is crucial to explore and study how the space weather affects the radiation environment in geospace. The Energization and Radiation in Geospace (ERG) project is currently under development in the Institute of Space and Astronautical Science (ISAS)/ Japan Aerospace Exploration Agency (JAXA) for the declining phase of solar cycle 24. The main objective of this mission is to understand the dynamics of the Earth’s radiation belts. The satellite will be launched into the inner magnetosphere in December 2015. A set of instruments to cover a wide energy range and measure both ions and electrons will be onboard. One of those instruments is the Low Energy Particle instrument for ions (LEP-i). It is very difficult to measure low energy particles (