Cosmic ray studies with the gamma-ray observatory

Even prior to the first undisputed observations of the diffuse galactic gamma-ray emission, it was well understood that the dominant contribution to the observed galactic gamma-ray emission above 100 MeV would be that due to the decay of neutral pi-mesons resulting from the interaction of the galactic cosmic rays with the interstellar gas. The first unambiguous detection of this radiation was made in 1968 by the OSO-3 counter telescope1, and details sufficient to allow preliminary studies of the implications of the observations were provided by the spark chamber experiments aboard NASA SAS-2 satellite2 ad by the ESA COS-B mission3. Many theoretical and observational studies have addressed this question since these initial explorations, but interpretation has been hampered by limited angular resolution in the observations, lack of broad band spectral coverage and insufficient information on the interstellar gas distribution, and contributions from discrete gamma-ray sources. This paper will give details on how the instruments aboard the Gamma-Ray Observatory will provide the details necessary to resolve these problems and aid significantly in determining the distribution of both cosmic-ray nucleons and electrons throughout the galaxy.