Feasibility studies of coded masks for high-energy gamma-ray telescopes in space

It is a well-known fact that the high-energy gamma-ray telescopes in conventional designs are inherently limited in their spatial resolving powers. EGRET can locate a point source to 5 to 10 arcmin accuracy, while GLAST can achieve source location capabilities to better than 0.5 arcmin. Although there is still room for improvement in the angular resolution of the conventional high-energy gamma-ray telescopes, other means can also be explored at this time. Coded masks have been successfully used for X-ray and low-energy gamma-ray telescopes. Such devices have also been considered for high-energy gamma-ray telescopes from time to time. In this paper we investigate the feasibility of using coded masks to achieve much higher source location capabilities for a high-energy gamma-ray space telescope. We discuss the merits and the difficulties of using coded masks to achieve this goal. In particular, we look into the issues of size, weight, field of view, and the trade-off between the angular resolution and the field of view for such coded masks.