Search

The non-collimated detectors of BATSE (Burst And Transient Source Experiment) on the Compton Gamma Ray Observatory (CGRO) can be used as a high sensitivity hard X-ray and low energy gamma-ray all-sky imager in the energy range between 20 keV and 2 MeV. The fluxes from sources in the sky are modulated as the spacecraft orbits the Earth. The CGRO orbital precession further allows sampling of sky in strips corresponding to the limb of the earth at any given time. The modulation data are transformed into images by various reconstruction methods. High sensitivity images of location accuracy of about 0.1 [degree] and source separation of about 1 [degree] are obtained.

The highly transient nature of cosmic low-energy gamma-ray sources offers unique insight into the astrophysics of extreme processes. Sensitive, long-term, all-sky monitoring is required to make sense of the variable emission. Instrumentation for such observations must have the combination of large effective collection area, wide field-of-view and good angular resolution. Recent advances in position-sensitive detectors and associated electronics make it possible to consider a multi-scatter Compton telescope, combined with a coded mask, as an all-sky monitor in the energy range ~10 keV to a few MeV. We present simulations of various configurations of such an instrument and show that it can provide a substantial improvement over other sky monitor strategies in this energy regime.