The Ion Mass Spectrometer instrument for Plasma Observatroy – IMS

The overarching goal of the Plasma Observatory Missions is to use multiscale multi-spacecraft observations to investigate in detail plasma energization and plasma transport in the near-Earth region. Thus, the prime goals of that mission are: How are particles energized in that plasma environment? And what processes are dominant in transporting Energy in the Magnetospheric System.

The achieve these science goals electromagnetic fields and three-dimensional particle distributions will be measured in high resolution and accuracy. IMS (the Ion Mass Spectrometer) will measure the full three-dimensional distribution functions of near-Earth main ion species (H⁺, He⁺, He⁺⁺ and O⁺) at high time resolution (~150 ms for H+ , ~ 300 ms for He⁺⁺) with energy resolution down to ~10% in the range 10 eV/q to 30 keV/q and angular resolution _ ~10 .

Such high time resolution is achieved by mounting multiple sensors around the spacecraft body, in similar fashion to the MMS/FPI instrument. Each sensor combines a top-hat electrostatic analyser with deflectors at the entrance together with a time-of-flight section to perform mass selection. IMS electronics includes a fast sweeping high voltage board that is required to make measurements at high cadence. Ion detection includes Micro Channel Plates (MCP) combined with Application-Specific Integrated Circuits (ASICs) for charge amplification, discrimination and time-to-digital conversion (TDC). IMS will be designed to address directly many of the Plasma Observatory science objectives, in particular ion heating and acceleration by turbulent fluctuations in foreshock, shock and magnetosheath regions. In this presentation we will report on initial performance measurements of the IMS instrument and relate these mensurements to potential recordings at keys science areas.