Magnetosphere Seminars

May 07, 2013 – “The Relativistic Electron-Proton Telescope (REPT) Instruments On Board the Van Allen Probes Mission: Characterization of Earth’s Radiation Belt High-Energy Particle Populations”

Speaker:Dan Baker (LASP)
Date:Tuesday, May 07, 2013
Time:4:00 PM
Location:Note: different room: LASP Space Science Building, room W120. Map

Seminar Abstract:

Particle acceleration and loss in the megaelectron Volt (MeV) energy range (and above) is the least understood aspect of radiation belt science. In order to measure cleanly both the energetic electron and energetic proton components, there has long been a need for a carefully designed detector system. The Relativistic Electron-Proton Telescope (REPT) on board the Radiation Belt Storm Probes (Van Allen Probes) pair of spacecraft consists of high-performance silicon solid-state detectors in a telescope configuration, a collimation aperture, and a thick case surrounding the detector stack to shield the sensors from penetrating radiation and bremsstrahlung. The instrument points perpendicular to the spin axis of the spacecraft and measures high-energy electrons (up to ~20 MeV) with excellent sensitivity and also measures magnetospheric and solar protons to energies well above E = 100 MeV. The instrument has a large geometric factor (g=0.2 cm^2-sr) to get reasonable count rates (above background) at the higher energies and yet will not saturate at the lower energy ranges. There is fast enough electronics to avert undue dead-time limitations and chance coincidence effects. The key goal for the REPT design is to measure the directional electron intensities (in the range 10^-2 – 10^6 particles/cm^2-s-sr-MeV) and energy spectra (ΔE/E~25%) throughout the spacecraft orbits. Precise simulations, detailed laboratory calibrations, and early orbit observations show that an excellent design has been attained for the REPT instrument. This talk presents the exciting new observations from the REPT instruments. These results have already been rewriting the textbooks about the structure, dynamics, and energetics of the Van Allen Belts.