Imaging principles and techniques in space-borne gamma-ray astronomy

Gamma-ray astronomy in the photon energy band from several 100 keV up to say 10 GeV can only be performed from space. Tremendous progress has been made in this young research field during the last 40 years. All-Sky maps exist now in continuum and line emission and short gamma-ray bursts—lasting only seconds—can be located to better than 1 arcmin. The imaging principles used in gamma-ray astronomy are different at low energies (<30 MeV) and at high energies (>30 MeV). Low-energy telescopes are based on the photo- or Compton-effect, whereas high-energy telescopes use the pair-production effect. The angular resolutions achieved by modern telescopes are in the range of 0.1 to 1°. A review of previous, current, and future telescopes is given for gamma-ray astronomy in general, and for burst astronomy in particular.