Because of the Earth's atmosphere shield, gamma-ray astronomy could not develop until it was possible to get detectors on spacecrafts, and to build large and sensitive ground-based detectors. The first gamma-ray telescope carried into orbit, on the Explorer XI satellite in 1961, picked up less than 100 cosmic gamma photons. Additional gamma-ray experiments flew on the OGO, OSO, Vela, and Cosmos series of satellites, and in the 80's we had the first missions completely dedicated to the exploration of the gamma universe. New unexpected phenomena were discovered by satellite observations, as for example gamma-ray bursts and gamma-ray emission from blazars.
The expectations from the next generation of ground-based and space-borne high energy gamma-ray projects are very exciting both for quantity and quality of data that will be produced. The great vitality of this field in the current ``post-EGRET era'' is witnessed by the large number of ongoing and forthcoming gamma-ray experiments, complementary to various cosmic- ray, neutrino and astroparticle projects, and to X-ray missions. The scientific community interested in gamma-ray astrophysics and astroparticle physics is rapidly growing, and this workshop series aims at exchanging periodically ideas and results, and optimizing the analysis of data.
The workshop is organized by the Physics Department of the Udine University and by I.N.F.N.