Van Allen Probes - Instruments: ECT
Energetic Particle, Composition, and Thermal Plasma Suite (ECT)
Principal Investigator: Harlan Spence, University of New Hampshire
Magnetic Electron Ion Spectrometer
Relativistic Electron Proton Telescope
The ECT observes the various types of particles that exist in the Van Allen radiation belts, including electrons, protons, and charged ions of oxygen and helium – all of which participate in the dynamic changes seen in the belts. The instrument records information about the particles such as their energy and direction of motion relative to the magnetic field (known as "pitch angle"), factors that can determine whether a given particle stays trapped in the radiation belts or escapes forever.
While it functions almost as a single instrument, the ECT is in fact made of three separate components:
Helium Oxygen Proton Electron (HOPE)
The HOPE instrument records helium, oxygen, protons, and electrons at lower energies and speeds. Such particles exist throughout the solar system, and play an important role in belt dynamics, since they can generate electromagnetic waves that can, in turn, affect the higher energy particles trapped in the belts.
Magnetic Electron Ion Spectrometer (MagEIS)
The MagEIS instrument observes electrons and ions in the middle energy ranges. Magnets inside the instrument deflect these particles towards the sensors, thereby differentiating them from the background radiation coming in from the belts. This will provide the cleanest measurements of radiation belt electrons so far achieved. Each RBSP spacecraft will carry four MagEIS instruments, each covering a separate part of the energy spectrum and a wide range of pitch angles.
Relativistic Electron Proton Telescope (REPT)
Stopping the highest energy particles – the ones traveling so fast they're referred to as "relativistic" – is very difficult, since they penetrate right through most materials. The REPT instrument uses a stack of solid-state detectors that can capture the energy signatures left by these electrons and protons, and so categorize and count the particles.