Dynamic and real-time adaptive configuration of Cyber-Physical Systems (CPSs) results in increased complexity due to a variety of heterogeneous and interdependent variables and creates unique challenges. For example, 1) Emergent Behavior: How do we ensure that system constituents dynamically and adaptively collaborate to produce a consistent repeatable functionality while supporting the capability to upgrade the individual entities through technology infusion; 2) Scale: How do we ensure scalability of these systems by managing complexity; 3) Risk Management: How do we evaluate and manage the risks associated with the connection and interdependencies of heterogenous systems.Design and development of this new generation of CPSs can be viewed through the lens of System-of-Systems (SoS) methodology which is designed to analyze and assess the evolving topologies created by interactions within a large complex system operating in dynamic and uncertain environment. In this paper, we propose the use of several SoS tools and techniques for the analysis and design of nextgeneration CPSs. Our SoS methodologies address features such as diversity of component systems, complex hierarchical structures, dynamic and emergent behavior, and interactions between components. Therefore, they are suitable to treat some of the challenging features of cyber-physical systems. However, it is necessary to modify these methodologies to address specific aspects of CPSs. Constraints and metrics from SoS methodology, applied to the design space, will support decision on component systems and the topology of their connections, and provide a set of -good designs‖, with desired characteristics.

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In this paper, we introduce the system operational dependency analysis methodology. Its purpose is to assess the effect of dependencies between components in a monolithic complex system, or between systems in a system-of-systems, and to support design decision making. We propose a parametric model of the behavior of the system. This approach results in a simple, intuitive model, whose parameters give a direct insight into the causes of observed, and possibly emergent, behavior. Using the proposed method, designers, and decision makers can quickly analyze and explore the behavior of complex systems and evaluate different architecture under various working conditions. Thus, the system operational dependency analysis method supports educated decision making both in the design and in the update process of systems architecture, without the need to execute extensive simulations. In particular, in the phase of concept generation and selection, the information given by the method can be used to identify promising architectures to be further tested and improved, while discarding architectures that do not show the required level of global features. Application of the proposed method to a small example is used to demonstrate both the validation of the parametric model, and the capabilities of the method for system analysis, design and architecture.

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This paper introduces an innovative perspective in the problem of on-orbit servicing and maintenance. A network of modular satellites and servicing satellites is modeled as a two-level System-of-Systems. At the lower level, the architecture of the modular satellites is analyzed in terms of functional interdepencies between the component modules. Analysis of the impact of such interdependencies gives insight into the operability of the satellite, and accounts for partial failures, redundancies, and criticality of the modules. At the higher level, communication, observation, and experimental satellites and constellation are constituents of a System-of-Systems functional network. The other components of this network are servicing satellites, able to perform inspection, refueling, maintenance. At this level, results from the overall functional dependency analysis are used to evaluate and compare different architectures, i.e. different number, capabilities, and location of servicing satellites. We discuss the innovation brought by the proposed approach with respect to the current practice. A hypothetical scenario is considered, featuring satellites with different architectures, whose parts are susceptible to aging and to failures over time, and on-orbit servicing satellites. Results show not only the general applicability of the method in order to perform analysis, but also possible future applications of both the proposed concepts and the analytical tool in space systems architecture and design. Nomenclature COD ij= criticality of dependency between node i and node j COD_O j = part of the operability of node j depending on the criticality of all its dependencies COD_O ji = part of the operability of node j depending on the criticality of the dependencies from node j O i = operability of node i SE i = self-effectiveness of node i SOD ij = strength of dependency between node i and node j SOD_O j = part of the operability of node j depending on the strength of all its dependencies SOD_O ji = part of the operability of node j depending on the strength of the dependencies from node j

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