So how do you engineer a behemoth like the SKA?
The SKA is not only vast in scale, covering huge tracts of the desert regions in Africa and Australia, but is also one of the most complex science projects ever conceived. With the SKA, a global effort involving thousands of engineers, scientists, astronomers and construction specialists will work together to deliver a truly remarkable telescope.
This is where System Engineering comes in – it is a formal way to ensure that the hardware and software is not only of the highest quality standards but that it also delivers real value for money.
Whilst working towards building the SKA, we ‘build’ many SKAs. These are ‘paper’ SKAs, essentially computer models whose behaviour as a system can be analysed, and changes to the designs made at very low cost. These models, sometimes will then be developed in to real phyiscal prototypes, which can be used for many purposes such as performance assessment, maintenance needs analysis and most importantly, cost assessment.
Trade-off studies are carried out using multiple models so that we can see what drives the cost and whether we must make compromises in performance. The SKA is so large and complex, with every telescope in each array needing to perform to the same high standards, and importantly in an identical manner, that engineers working on it must study detailed choices because small cost/performance differences in millions of parts have a large effect on the behaviour of the system as a whole.
During the initial stages of the SKA project, scientists will be modeling these engineering requirements, and talking to leaders in industry and engineering around the world, to make sure that the SKA system delivers all of its scientific promises. As there are millions of parts, many of them replicated thousands of times in the telescopes, making sure the most cost effective, yet efficient and durable components are used is a priority.
The scientists and engineers working with the project managers and the wider astronomical community who will be using these models to ensure that the SKA meets and even exceeds the science requirements. Once the modeling is completed, all of the engineering requirements will be understood. Scientists will also factor in existing large scale scientific instruments and look at the performance, and success of the pathfinder and precursor telescopes as a guide to future development.
How do we approach SKA System Engineering?
First we consider the scientific objectives of the SKA. These are of paramount importance as they drive what the SKA must do and how it will perform. These are called the science requirements.
Next we take into account the fact that the SKA must be built in the real world, be operated by humans, use existing or projected technology, exist within a legal framework and respect the environment.
These considerations give rise to further requirements and constraints which are taken into account when designing the SKA. We also use experience gained from existing large science facilities to provide additional operational requirements.
The topmost system design architecture is then proposed and alternatives are analysed. The best architecture is broken down and the various elements go through the same outline design and analysis process. This is repeated down to the point where simple parts can be made or procured.
Components from the smallest screws to the fully deployed high frequency dishes will be manufactured and/or purchased, then assembled over the various phases that will culminate in the scientific operations starting in the early 2020s.
At each level of assembly, testing is carried out so that problems are found as early as possible. For the SKA, this is an enormous process which takes several years but leaves nothing to chance. Time and time again, it has been demonstrated that this disciplined approach gets the best final performance for the budget.