LOW ENERGY NEUTRAL ATOM IMAGING IN SPACE

Space consists of plasma (i.e., a gas of ions and electrons that is approximately charge neutral) with an imbedded magnetic field. However neutral atoms permeate this plasma. These neutral atoms carry information about their sources and they have a distinct advantage over charged particles in that they are not tied to the imbedded magnetic field. Unfortunately, the neutral atom fluxes are typically quite low. The focus here is on methods for imaging low energy neutral atoms (i.e., atoms with energies between a few eV and 1 kV) in space. There are three sources of these low energy neutral atoms: Planetary magnetospheres and ionospheres, the interstellar medium, and the heliospheric termination shock. The Imager for Magnetopause to Aurora: Global Exploration (IMAGE) mission included a new type of low energy neutral atom imager. This imager produced images of charge exchanged neutrals from the Earth’s ionospheric ion outflow and investigated neutral atoms the interplanetary medium. Sample results from studies of neutral from charge exchange of ion outflow and future work on this and next generation low energy neutral atom imagers are discussed.