X-ray and γ-ray astronomy at the turning point

Since 1962, approximately 40 point x-ray sources have been isolated, only about six of which have been identified with known radio or optical objects or have been studied over the 1--300 keV energy range. Data on the x-ray fluxes, positions, sizes and spectra of these sources have provided new information of considerable astrophysical significance and indicate that the exploratory stage of x-ray astronomy is now over. At higher energies, confirmation of a diffuse flux to 6 MeV and the successful detection of 100 MeV γ-rays from the galaxy indicate the necessity of further exploratory experiments. Satellite borne instruments on a larger scale than previously implemented will be needed to take advantage of the unique opportunity now available for advancing high-energy astrophysics. (auth)