IMAP-Lo cutaway drawing (right side), overlaid with SIMION ray-tracing (left side) of ENAs (blue), negative ions after conversion (green), neutrals and ions after passing the C foil(s) in the TOF section (blue), and secondary electrons emitted at the foils (red).

IMAP-Lo is a single-pixel neutral atom imager mounted on a pivot platform. It delivers (1) energy and angle-resolved measurements of Interstellar Neutral (ISN) atoms (H, He, O, Ne, and D) tracked over >180˚ in ecliptic longitude and (2) energy resolved global maps of ENA H and O. IMAP-Lo tracks the interstellar flow to precisely determine the species-dependent flow speed, temperature, and direction of the Local Interstellar Medium (LISM) that surrounds, interacts with, and determines the outer boundaries of the global heliosphere. It returns detailed abundance information defining composition of the LISM. The ecliptic longitude, arrival direction relative to the Sun, and hyperbolic trajectory of the ISN bulk flow determine a characteristic relation between inflow longitude and speed at infinity. IMAP-Lo uses the pivoting FOV (pivot angle, PA, with FOV = 90◦ + PA to spin-axis) to pinpoint the intersection in the relation between the ISN inflow speed and longitude to uniquely determine the LISM flow vector.

Building on heritage from the IBEX-Lo instrument aboard IBEX, IMAP-Lo provides much larger collection power due to its position at L1 (average increased viewing time 4× due to low backgrounds) and increases in geometric factor (3.2×), duty cycle, and efficiency of IBEX-Lo. This maximizes the weak heliospheric neutral signal, while eliminating ion, electron, and UV background sources. Combined with the pivoting FOV, IMAP-Lo improves the angular resolution of ISN flow parameters and can track the ISN flow over almost the entire year, overcoming the serious limitations facing body-fixed sensors.

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.

IMAP Lo Instrument Table

IMAP-Lo Instrument Performance.