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E-ELT phase-A instrument studies: a system engineering view

During the last two and half years ten phase-A instrument studies for the E-ELT have been launched by ESO and carried out by consortia of institutes in the ESO member states and Chile. These studies have been undertaken in parallel with the phase B of the E-ELT telescope. This effort has pursued two main goals: to prove the feasibility and performance of a set of instruments to meet the project science goals and to identify and incorporate in the telescope design those features that satisfy best the needs of the future hosts, i.e., the science instruments. To succeed on this goal it is crucial to identify such needs as early as possible in the design process. This concurrent approach definitively benefits both the instruments concept design and the telescope development, but implies as well a number of difficult tasks. This paper compiles, from a system-engineering point of view, the benefits and difficulties as well as the lesson learned during this concurrent process. In addition, the main outcomes of the process, in terms of telescope-instruments interfaces definition and requirements from the instruments to the telescope and vice-versa, are reported.