We propose a set of integrated Activities in the High Energy Astrophysics Domain (AHEAD) in response to the INFRAIA-2014-2015 call Research Infrastructures for High EnergyAstrophysics.The overall objective of AHEAD is to integrate national efforts in high-energy Astrophysics and to promote the domain at the European level, to keep its community at the cutting edge of science and technology in this competitive research area and ensure that space observatories for high-energy astrophysics are at the state of the art. AHEAD will integrate key research infrastructures for on-ground test and calibration of space-based sensors and electronics and promote their coordinated use. In parallel, the best facilities for data analysis of high-energy astrophysical observatories will be made available to the European community. The technological development will focus on the improvement of selected critical technologies, background modeling, cross calibration, and feasibility studies of space-based instrumentation for the benefit of future X-ray and gamma-ray missions, and the best exploitation of existing observatories. AHEAD will support the community via grants for collaborative studies, dissemination of results, and promotion of workshops. A strong public outreach package will ensure that the domain is well publicized at national, European and International level. The virtual circle infrastructure - networking - joint research activities, as devised in AHEAD, serves to establish strong connections between institutes and industry to create the basis for a more rapid advancement of high-energy astrophysical science, space-oriented instrumentation and cutting-edge sensor technology in Europe. This enables the development of new technologies and the associated growth of the European technology market, - with a dedicated technology innovation package - as well as the creation of a new generation of researchers.