The Energetic Particles and Ion Composition (EPIC) instrument is actually composed of two separate sensor and processing assemblies.
* The STICS assembly (Supra-Thermal Ion Composition Spectrometer) uses a quadrispherical electrostatic analyzer followed by a foil/solid state detector time-of-flight (TOF) telecope to measure charge state, mass and energy of ions with energies of 30 - 230 keV/charge. It uses an electrostatic analyzer with a geometry factor of 0.05 cm^2 sr, time of flight and energy analysis. STICS includes 6 heads and provides 3D distribution functions.
* The ICS assembly (Ion Composition Subsystem) measures mass and energy properties of energetic ions with energies of less than 50 keV to 3 MeV. It uses a pair of collimators (heads) pointng +/- 23 deg apart the GSE equatorial, followed by TOF and energy analysis, with a geometry factor of 0.2 cm^2 sr. A thin foil/solid state detector electron telescope measures electrons higher than 30 keV.