The imaging gamma-ray telescope COMPTEL aboard GRO

Abstract

The imaging Compton telescope COMPTEL is one of the four instruments onboard NASA's Gamma Ray Observatory GRO which is to be launched in 1991 by the Space Shuttle Atlantis. COMPTEL will explore the 1 to 30 MeV energy range with an angular resolution of a few degrees within a large field-of-view of about 1 steradian. Its medium energy resolution (8.8 % FWHM at 1.27 MeV) in addition makes it to a powerful gamma-ray line spectrometer. Within a 2-weeks observation period COMPTEL will be able to detect sources which are about 20-times weaker than the Crab. With these properties COMPTEL is well suited to perform the first complete sky survey at MeV-energies. Targets of special interest are galactic gamma ray sources (like radio pulsars, X-ray binaries, the Galactic Center, the unidentified COS-B sources, supernova remnants and molecular clouds), external galaxies (especially the nuclei of active galaxies), gamma-ray line sources (e.g. the distribution of the 1.8 MeV line emissivity throughout the Galaxy), the diffuse gamma-ray emission from interstellar space, the cosmic gamma ray background, cosmic gamma-ray bursts, and gamma-ray and neutron emission during solar flares.