System simulation: risk reduction for the new millennium

Full System Simulations of spacecraft have been used for over twenty years (principally in Europe) to support operations preparation and operations activities for Scientific, Earth Observation, Military and Communications spacecraft. Traditionally, software simulation has also been used extensively in the design and development but usually focuses on one subsystem or aspect of the spacecraft or mission design, and is often run off-line or in non-real-time. New simulation tools and technologies allow system simulators to be developed much more easily, cheaply and quickly, and therefore make it possible to extend the benefits of system simulation to much earlier in the development of a space system. In this paper, we first describe what we mean by a "System Simulation". We then look how this approach can be extended to help reduce the risk throughout the spacecraft's lifecycle-during specification, design, development, test and operations - and how it can help to reduce development costs and even insurance costs. We also look at the technologies that enable this approach, and the processes that need to be applied in order for this to be effective. Finally, we look at the processes and issues that need to be considered when using system simulations and how these might be addressed.