Fast Plasma Investigation for Magnetospheric Multiscale

TLDR

The Fast Plasma Investigation (FPI) was developed for the Magnetospheric Multiscale mission to measure differential directional fluxes of electrons and ions at unprecedented time resolution, enabling study of kinetic‑scale plasma dynamics. This paper presents the design, ground and in‑flight calibration, operational concept, and data products of the FPI. FPI achieves high‑resolution measurements by deploying four dual 180‑degree top‑hat spectrometers per spacecraft, providing 4π‑sr field of view with ≤11.25° angular sampling and 10–30,000 eV/q energy/charge resolution, all controlled by a single redundant instrument data processing unit.

Abstract

The Fast Plasma Investigation (FPI) was developed for flight on the Magnetospheric Multiscale (MMS) mission to measure the differential directional flux of magnetospheric electrons and ions with unprecedented time resolution to resolve kinetic-scale plasma dynamics. This increased resolution has been accomplished by placing four dual 180-degree top hat spectrometers for electrons and four dual 180-degree top hat spectrometers for ions around the periphery of each of four MMS spacecraft. Using electrostatic field-of-view deflection, the eight spectrometers for each species together provide 4pi-sr field-of-view with, at worst, 11.25-degree sample spacing. Energy/charge sampling is provided by swept electrostatic energy/charge selection over the range from 10 eV/q to 30000 eV/q. The eight dual spectrometers on each spacecraft are controlled and interrogated by a single block redundant Instrument Data Processing Unit, which in turn interfaces to the observatory's Instrument Suite Central Instrument Data Processor. This paper describes the design of FPI, its ground and in-flight calibration, its operational concept, and its data products.