Helium, Oxygen, Proton, and Electron (HOPE) Mass Spectrometer for the Radiation Belt Storm Probes Mission

Abstract

The HOPE mass spectrometer of the Radiation Belt Storm Probes (RBSP) mission (renamed the Van Allen Probes) is designed to measure the in situ plasma ion and electron fluxes over 4π sr at each RBSP spacecraft within the terrestrial radiation belts. The scientific goal is to understand the underlying physical processes that govern the radiation belt structure and dynamics. Spectral measurements for both ions and electrons are acquired over 1 eV to 50 keV in 36 log-spaced steps at an energy resolution E FWHM /E ≈ 15 %. The dominant ion species (H + , He + , and O + ) of the magnetosphere are identified using foil-based time-of-flight (TOF) mass spectrometry with channel electron multiplier (CEM) detectors. Angular measurements are derived using five polar pixels coplanar with the spacecraft spin axis, and up to 16 azimuthal bins are acquired for each polar pixel over time as the spacecraft spins. Ion and electron measurements are acquired on alternate spacecraft spins. HOPE incorporates several new methods to minimize and monitor the background induced by penetrating particles in the harsh environment of the radiation belts. The absolute efficiencies of detection are continuously monitored, enabling precise, quantitative measurements of electron and ion fluxes and ion species abundances throughout the mission. We describe the engineering approaches for plasma measurements in the radiation belts and present summaries of HOPE measurement strategy and performance.

Storm time response of the midlatitude thermosphere: Observations from a network of Fabry‐Perot interferometers

“…Indication of an injection of low‐energy O + ions into the inner magnetosphere and ring current during the 2 October 2013 storm period considered here is provided by the Energetic Particle, Composition, and Thermal Plasma Suite's (ECT) Helium, Oxygen, Proton, and Electron (HOPE) mass spectrometer instruments on the twin Van Allen Probes spacecraft [ Funsten et al , ]. Results from these instruments are shown in Figure , indicating that O + , as well as other ionic species, is readily available in the inner magnetosphere.…”

Ion nose spectral structures observed by the Van Allen Probes

“…The HOPE mass spectrometer [Funsten et al, 2013], part of the RBSP-ECT suite , measures both ions and electrons over the~1eV to~50keV energy range in five angular directions coplanar with the spacecraft spin axis and 72 energy channels with energy resolution ΔE/E≈15%. The most abundant magnetospheric ion species (H + , He + , and O + ) are distinguished by using a spherical electrostatic analyzer and a time-of-flight mass spectrometer with channel electron multiplier detectors.…”

Whistler anisotropy instabilities as the source of banded chorus: Van Allen Probes observations and particle‐in‐cell simulations

“…The Van Allen Probes mission was designed, in part, to make the measurements required to quantitatively test theories of wave generation. The Helium, Oxygen, Proton, and Electron (HOPE) mass spectrometer of the Van Allen Probes mission measures the ion and electron fluxes at each of the two spacecraft within the terrestrial radiation belts over the energy range from 10 eV to 50 keV [ Funsten et al , 2013; Spence et al , 2013]. This energy range encompasses the electrons which are the likely drivers of large-amplitude magnetospheric chorus, which has its source in the whistler anisotropy instability [e.g., MacDonald et al , 2008, and references therein] driven by the electron T ⊥ / T ∥ >1.…”