Extraction of ion distributions from magnetospheric ENA and EUV images E. C. Roelof and A. J. Skinner To be published in the IMAGE Mission Handbook, 1998 A variety of energetic neutral atom (ENA) and extreme ultra-violet photon (EUV) imagers will soon be probing magnetospheric ion distributions from the NASA space missions IMAGE and TWINS. The Swedish `Munin' nanosatellite will carry an ENA imager into low altitude orbit in May, 1999. Although the images will differ greatly, the same basic mathematical approach can be applied to deducing the ion distributions: extracting the parameters of a model ion distribution in a model magnetic field (and, in the case of ENA, interacting with a model cold neutral population). The extraction is accomplished by a robust hierarchy of computer algorithms that minimizes the differences between a simulated (instrument-specific) image and an observed image (or set of images). The interplay of the diverse imaging requirements for the variety of upcoming missions should cross-fertilize the development of the ion distribution extraction techniques.