GAMMA-RAY ASTRONOMY - FUTURE-PROSPECTS

With the advent of Sigma/Granat and of the Compton Gamma Ray Observatory, the gamma-ray band has at last been opened up for astronomy. It is starting to be possible to realize some of the potential that observations in this band have for contributing to our understanding of high energy astrophysics. What, though, of prospects beyond the current generation of gamma-ray instruments? It is ironical that in the part of the spectrum where the diffraction limit is in the micro-arcsecond range, angular resolutions available are still comparable with the angular diameter of the moon. Similarly, none of the current generation of space instruments has energy resolution better than about E/Delta E similar to 10. Yet this is a regime where resolutions of similar to 1000 are easily achieved in the laboratory and where the theoretical limits are many orders of magnitude better than this. A major problem is sensitivity. The large detector masses necessary to stop high energy gamma-rays attract both high backgrounds from particle interactions and worried looks from spacecraft engineers. Ingenuity, large lift-off masses and long observations are all needed. The prospects for INTEGRAL and beyond are discussed in the context of developments over the last 20 years and the present status.