One of the critical activities in the systems engineering scope of work is managing requirements. In line with this, E-ELT devotes a significant effort to this activity, which follows a well-established process. This involves optimally deriving requirements from the user (Top-Level Requirements) through the system Level 1 Requirements and from here down to subsystems procurement specifications.<p> </p> This paper describes the process, which is illustrated with some practical examples, including in particular the role of technical budgets to derive requirements on subsystems. Also, the provisions taken for the requirements verification are discussed.
After having completed the phase B (front-end design) of the several subsystems, the E-ELT project is entering into the
construction phase. The subsystems specifications, interface control documents and accompanying technical
documentation resulting from the said design activities are being drafted along with the statements of work needed for
the tendering processes.
This paper presents an overview of the Systems Engineering Plan for the construction phase focusing on the specific
systems engineering processes. The goal is to ensure that this phase is developed following an efficient systems
engineering approach based on the lessons learned during phase B. The ultimate objective is that the E-ELT meets the
science requirements defined by the users while the risk of overruns in cost or schedule, which might otherwise originate
from the lack of a system perspective, is minimized.
The E-ELT has completed its design phase and is now entering construction. ESO is acting as prime contractor and
usually procures subsystems, including their design, from industry. This, in turn, leads to a large number of
requirements, whose validity, consistency and conformity with user needs requires extensive management.
Therefore E-ELT Systems Engineering has chosen to follow a systematic approach, based on a reasoned requirement
architecture that follows the product breakdown structure of the observatory. The challenge ahead is the controlled flow-down
of science user needs into engineering requirements, requirement specifications and system design documents.
This paper shows how the E-ELT project manages this. The project has adopted IBM DOOR<sup>TM</sup> as a supporting
requirements management tool. This paper deals with emerging problems and pictures potential solutions. It shows
trade-offs made to reach a proper balance between the effort put in this activity and potential overheads, and the benefit
for the project.