The High-energy Ion Telescope (HIT) measures the elemental composition, energy spectra, angle distributions, and arrival times of high-energy ions. HIT delivers full-sky coverage from a wide instrument field-of-view (FOV) to enable a high resolution of ion measurements, such as observing shock-accelerated ions, determining the origin of the solar energetic particles (SEPs) spectra, and resolving particle transport in the heliosphere.
 
The instrument consists of a sensor head and electronics box, separated by a mechanical bracket. The sensor head is equipped with several silicon solid-state detectors (SSDs) oriented with varying fields-of-view (FOV) angles in relationship to IMAP’s spin axis. As ions enter the instrument from multiple angles, HIT is able to sort the energetic ions, which range from hydrogen (H) to nickel (Ni), by intensity, species, mass, and direction of origin.
 
Two of HIT's SSD FOVs are sensitive to high-energy electrons and report data used for the I-ALiRT space weather data stream, allowing space weather metrics to be provided in near-real-time. In-situ electrons can be used as a predictor of solar radiation and other drivers of space weather that may arrive at Earth later in a solar event.

HIT design and assembly is led by Goddard Space Flight Center (GSFC).