Computer simulations of energetic neutral atom imaging from low and high altitude spacecraft

Abstract

ENA cameras are being readied for flight on the Argentine SAC-B low-altitude mission and the NASA Cassini Saturn orbiter and an upcoming NASA MidEx mission (IMAGE) will be devoted completely to magnetospheric imaging. Computer simulation of ENA images has proved an indispensable tool for both scientific data analysis and instrument/mission design for a number of reasons. ENA emission is usually “optically thin”, so it is very difficult to imagine how magnetospheric ion distributions will image from different vantage points. ENA emission has a wide dynamic range in intensity, and contemporary cameras do not always have angular resolution sufficient to resolve the structures. Consequently, image simulation is an essential element in the extraction of the ion distributions from ENA images. Examples of simulations from past, present, and future missions that illustrate these effects are presented.