Resilience in Space — An Applied Systems Thinking Approach

In the context of distributed computing systems, resilience refers to the ability of the system to support the services and functions essential to mission success with (i) high probability, and (ii) shorter durations of reduced capability across a wide range of operational scenarios, failure conditions, and attack vectors [1]. Traditional systems engineering analysis views a system as a collection of functionally decomposed, independent parts, allowing analysts to reason about the system but providing limited understanding of emergent system behaviors. Conversely, systems thinking views the system as a whole, allowing the analyst to reason from the system, enabling a better understanding of functional interdependencies and emergent system behaviors. This paper introduces a hybrid methodology, referred to as Applied Systems Thinking, that embraces both the analytical methods of traditional systems engineering complemented by the established systems thinking toolkit, allowing the system engineer to both reason about the system and from the system at the same time. The objectives of this paper are to (a) address the concept of system resilience using techniques from the Applied Systems Thinking toolkit, (b) to discuss system resilience as it applies to system of systems, using Non-Terrestrial Networks (NTN) as a reference framework, and (c) to provide an initial foray into more in-depth research that intends to develop a principled framework for Service Availability that incorporates its constituent components, such as system availability, reliability, resilience, survivability, and verification of the contractual parameters found in an associated Service Level Agreement, or SLA.