Maximum-entropy image processing in gamma-ray astronomy

Imaging γ-ray astronomy is a slowly evolving field because experiments are expensive, few and far between. For energies above 100 MeV the only satellite experiments to date with real imaging capabilities have been NASA’s SAS-2 and ESA’s COS-B. At lower energies (1-30 MeV) only balloon experiments have so far had imaging capabilities (e.g. the MPE Compton Telescope). Much of the scientific analysis of such data can be done without actually generating images at all -for example source searches can be done by cross-correlation or similar methods, and quantitative studies of the diffuse Galactic emission are best done by model fitting using radio surveys of Galactic gas as a basis. However visual presentation is also essential as a means for understanding the data, comparing it with other wavelengths, and looking for the unexpected. Because of the particular problems associated with γ-ray observations, it is logical that considerable investment be made at this time in studying methods to obtain the best possible images for scientific analysis, especially since the forthcoming launch of NASA’s Gamma-Ray Observatory will increase the amount of 7-ray data by two orders of magnitude.