IMAP-Hi consists of two identical, single-pixel high energy ENA Imagers that measure H, He, and heavier ENAs from the outer heliosphere. Each IMAP-Hi Imager is very similar in design to the IBEX-Hi ENA Imager aboard the IBEX mission, but incorporates key modifications that enable substantially improved (1) spectral, spatial, and temporal resolution, (2) spectral range, and (3) collection power. The instrument also incorporates time-of-flight (TOF) for identification of ENA species. These performance enhancements, yielding ~25 times the collection power of IBEX-Hi, enable unprecedented, detailed studies of structure and evolution of source plasmas in the heliosphere-LISM interaction region.
The two IMAP-Hi imagers are mounted 90° (Hi90 imager) and 45° (Hi45 imager) antisunward relative to the spacecraft spin axis, respectively. Each spin, the Hi90 imager views the ecliptic poles, while the combined Hi90 and Hi45 imagers sample the ecliptic plane in four different locations. The Hi90 and Hi45 imagers also enable viewing the same low-latitude regions twice within 3 months to probe rapid ENA time variability. Additionally, the Hi45 imager has increased exposure of a factor of ×3.9 at the equator and nearly ×10 at 45° latitude, a band that contains ENA emission from the heliospheric nose and tail, as well as most of the Ribbon and Belt.
All schematics and numbers are preliminary as of the beginning of Phase A. Additional information about each instrument can be found in the Open Access IMAP Paper.