High energy gamma ray observations and the coupling between galactic cosmic rays and matter

One of the primary goals of the EGRET mission on the Compton Observatory has always been the study of the diffuse gamma ray emission of both galactic and extra‐galactic origin. The first 18 months of the mission, following the initial activation period, is being devoted to the all‐sky survey with the goal of obtaining a nearly uniform exposure. In anticipation of the improved capabilities of the EGRET instrument relative to the earlier SAS‐2 and COS‐B missions, a new model of the galactic diffuse gamma ray emission was developed that incorporates recent surveys of the matter distribution and which permits a variety of assumptions regarding galactic cosmic ray distribution to be tested. This paper summarizes the model calculation and gives a preliminary comparison of the model with EGRET observations.