Imaging systems using modulation and coded aperture masks

The advent of improved γ-ray telescopes which incorporate high angular resolution imaging properties and adequate sensitivity will advance this branch of astronomy from the discovery phase to the exploratory phase. As in other fields, such as radio and X-ray astronomy, which have recently undergone this change, it will prove a fascinating era. The recent development of position sensitive γ-ray detection planes operated in conjunction with a suitable coded aperture mask have made γ-ray telescopes feasible which are capable of generating γ-ray images of the sky with a precision of 1 arc minute over the photon energy range 0.1 to 10 MeV. With a sensitivity of at least 1–10 milliCrab and scintillation standard spectral resolution not only can a large number of discrete γ-ray objects be identified and studied in detail but nuclear γ-ray line images of extended objects such as the Galactic Plane, Cloud Complexes, and supernovae remnants may be generated by this class of astronomical instrument.