The goal of prospective ergonomics is to anticipate human needs and activities with the aim of creating new artefacts and services. It completes the concepts, methods and tools of corrective ergonomics and preventive ergonomics to deal with the current stakes of innovative artefacts and new uses. We investigate prospective ergonomics, initially elaborated for innovative products, in order to adapt it to long life systems. We articulate prospective ergonomics with a traditional point of view on prospective by using the methods of scenarios, watching activity and by implementing personas. We integrate them into the appropriation process in order to implement an iterative design approach that corresponds to design for and by appropriation. Design for appropriation consists in offering a set of possibilities to operators so that they adapt and adopt the technological artefacts to perform their missions and activities. It leans on the experience feedback of the routine use of technologies after adaptation and appropriation by the operators. It is completed by the results of the watch activity. This approach allows the ergonomists’ activities and methods to evolve. Ergonomists contribute to watch activity, to build scenario in a prospective approach, to identify operators’ characteristics which evolve in time. This approach has also some impacts on system architecture. Sensors are inserted to collect information on the operational environment that the system encounters. This approach has also some impacts on engineering processes because the process of operation includes the experience feedback which supports design by appropriation.