The IMAP-Lo Instrument

The IMAP-Lo instrument is a large geometric factor, single pixel camera that measures energetic neutral atoms (ENAs) and interstellar neutral atoms (ISNs) over the low-energy portions of the ENA spectrum from 0.01 to 1 keV. It derives heritage from IBEX-Lo and shares a design philosophy with IBEX-Hi and IMAP-Hi. IMAP-Lo eliminates ion, electron, and ultraviolet photon background sources, and greatly reduces internal backgrounds compared to the heritage IBEX-Lo sensor. IMAP-Lo is mounted on a pivot platform for boresight articulation over a range of elongations (∼ 60^∘ – 180^∘) from the spin-axis to enable tracking the interstellar flow. The instrument is divided into seven subsystems: the pivot platform articulates the instrument; the entry subsystem eliminates charged particles and determines the field-of-view; the star sensor provides pointing determination; the conversion subsystem converts neutrals to ions; the electrostatic analyzer determines the energy passband; the time-of-flight subsystem provides species separation (H, D, He, O, and Ne); and the electronics provides data and command interfaces, and supplies instrument high voltages. Measurements substantially reduce the ISN flow parameter uncertainties, mitigate systematic uncertainties, and provide accurate interstellar Ne/O and D/H ratios. The increased geometric factor and lower internal backgrounds of IMAP-Lo, coupled with the ability to pivot the boresight open an enormous array of new scientific opportunities that contribute to IMAP’s quantum leap in understanding the composition and properties of the local interstellar medium, the evolution of the heliospheric boundaries, and the physics of interstellar-heliospheric interactions.