Missions represent a key concern in the development of Systems-of-Systems (SoS) since they are related to both capabilities of constituent systems and interactions among these systems that contribute to the accomplishment of global goals of the SoS. In a mission-oriented approach to design software-intensive SoS, the activity towards the concretization of the mission model is its refinement to an architectural model. This paper addresses this synergetic relationship between mission and architectural models. As main contribution, we introduce a model-based refinement process supported by model-to-model transformations intended to apply mission models represented in mKAOS, a language to model missions, for automatically generating architecture descriptions in SosADL, a formal language to describe SoS software architectures.