The Compact Ion Mass Spectrometer (CIMS) is a highly compact ion mass spectrometer capable of high-mass resolution for low-energy space plasma. CIMS is capable of measuring flux, energy, and mass of ions providing unique measurements of the ionospheric outflow and cold plasma in the magnetosphere. Measurements of the ionospheric outflow and cold-magnetospheric ion population will provide the necessary initial conditions of the ion populations that drive some magnetosphere-ionosphere (MI) coupling processes along with magnetospheric ion composition and dynamics. Simultaneous measurements of the cold and hot magnetospheric ion composition in the reconnection region at the magnetotail would provide clues for the outflowing ions as they journey through the plasmasphere and magnetosphere. These data are critical to advancing our current understanding of MI coupling and are required to answer the long-standing questions regarding ionospheric outflow, the source of magnetospheric mass loading, and the subsequent impact on magnetic reconnection. The CIMS utilizes a laminated collimator to define the field-of-view, a laminated electrostatic analyzer to selectively filter ions based on energy-per-charge, a magnetic sector analyzer to separate ions by mass-per-charge, and a microchannel plate with a position sensitive cross-delay anode assembly to detect the location of the ions on the detector plane. This ion mass spectrometer is a simple, compact, and robust instrument ideal for obtaining low-energy (0.1 eV to 500 eV) ion composition measurements of ionospheric and cold magnetospheric ions. The instrument design has significant mass and volume savings when compared to current state-of-the-art ion mass spectrometers and has the additional advantage of being able to simultaneously measure multiple ion species at given energy-per-charge at 100% duty cycle, thus providing a full energy spectra for individual ion species. The concept and operation are intrinsically simple, and enable ultrafast (<0.1 s) measurement of plasma ion composition to provide an improved understanding of the physical processes that drive the complex ion dynamics in the magnetosphere.

The Interstellar Boundary Explorer (IBEX) mission has shown that variations in the ENA flux from the outer heliosphere are associated with the solar cycle and longer-term variations in the solar wind. In particular, there is a good correlation between the dynamic pressure of the outbound solar wind and variations in the later-observed IBEX ENA flux. The time difference between observations of the outbound solar wind and the heliospheric ENAs with which they correlate ranges from approximately two to six years or more, depending on ENA energy and look direction. This time difference can be used as a means of “sounding” the heliosheath, that is, finding the average distance to the ENA source region in a particular direction. We apply this method to build a three-dimensional map of the heliosphere. We use IBEX ENA data collected over a complete solar cycle, from 2009 through 2019, corrected for survival probability to the inner heliosphere. We divide the data into 56 “macro-pixels” covering the entire sky, and as each point in the sky is sampled once every six months, this gives us a time series of 22 points per macro-pixel on which to time-correlate. Consistent with prior studies and heliospheric models, we find that the shortest distance to the heliopause dHP is slightly south of the nose direction (dHP ~ 110 – 120 au), with a flaring toward the flanks and poles (dHP ~ 160 – 180 au). The heliosphere extends at least ~350 au tailward, which is the distance limit of the technique.