A novel approach for the development of the HARMONI Integral Field Spectrograph using structured systems thinking

摘要

In this paper we will describe how the development (design, build, integration, verification and installation) of a technically compliant Integral Field Spectrograph (IFS) can be planned and executed. Firstly we will show how one would develop the product breakdown structure (PBS) making use of a structured function-based systems engineering methodology based on systems thinking. The product breakdown structure is one of the primary outputs (deliverables) of the systems architecture design process and is a hierarchy of products implementing the physical architecture of the system. The system physical architecture is developed by implementing all the functions required over the life-time of the system in hardware and software. To finalise the system architecture the control and data flow to perform the required functions in the correct sequence will also need to be considered and implemented. Once the system architecture has been developed it can be partitioned into a hierarchical product breakdown structure consisting of sub-systems, modules, assemblies, sub-assemblies, and components. Thereafter the product breakdowns structure can be partitioned into a logical work breakdown structure. By using the knowledge and understanding of the development workflows for each of the engineering disciplines required, a single product and work breakdown structure can be used to develop a robust project schedule. In addition, we will show how the processes of configuration management (CMII) are used to integrate the work elements of the various engineering disciplines into a coherent project plan to finalise the designs of parts, modules, assemblies, sub-systems or systems to a level where these parts can either be made or procured for further assembly and integration. Using project planning software such as Microsoft Project, the general shape and critical path of the project can be determined. Typically, the development of ground based and space astronomical facilities are stretched over many years, even decades. Therefore it is easy to waste a lot of time during the early development phases of the project on nugatory and non-essential tasks. We have adopted the Agile software development methodology to prepare, execute and monitor short term plans (sprints) to ensure progress is being made and that all work elements contributes to the end goal of the project. We illustrate how these novel techniques have and still are being used in the development of the HARMONI Integral Field Spectrograph. HARMONI was selected as one of the Extremely Large Telescope (ELT) first light instruments. The ELT will be the European Southern Observatory's (ESO) next generation telescope and observatory and will be built in Chile on Cerra Armazones. The instrument completed its preliminary design phase and the team is now detailing the designs as part of the detailed design phase of the project. A major objective of this paper is also to show that one single structure, namely the product breakdown structure, is all that is required to plan the development, construction, verification and validation, installation and commissioning of any scientific product. By associating the engineering artefacts required to either procure or build each of the components a robust project time-line can be develop by creating integrated work flows covering all the tasks required to progress the system from conception to a working instrument on sky.