Developing a CubeSat Model-Based System Engineering (MBSE) Reference Model - interim status

Abstract

Model-Based Systems Engineering (MBSE) is the formalized application of modeling to support key systems engineering tasks for addressing requirements, design, analysis, validation, and verification. The International Council on Systems Engineering (INCOSE) established the MBSE Initiative to promote, advance, and institutionalize the practice of MBSE. As part of this effort, the INCOSE Space Systems Working Group (SSWG) has been investigating the applicability of MBSE for designing CubeSats. Our application of MBSE is enabled by the graphical modeling language Systems Modeling Language (SysML). SysML is used to model all aspects of a system either directly or through interfaces with other models. SysML diagrams are used to describe requirements, structures, behaviors, and parametrics from the system down to the component level. Requirements and design are contained in the model rather than in a series of independent engineering artifacts. The CubeSat Reference Model provides the logical architecture. The logical elements can be reused as a starting point for a mission-specific CubeSat logical architecture, followed by the physical architecture and the CubeSat development. Our prior work established the CubeSat Reference Model domain as consisting of the stakeholders, CubeSat enterprise, external environment, and external constraints, with the CubeSat enterprise consisting of space and ground segments. The CubeSat enterprise architecture has been refined to accommodate an external service providing CubeSat transportation to a launch site, integration into a launch vehicle, launch, and deployment. It has also been refined to accommodate a CubeSat project developing its own ground station or operating with an existing ground station that provides uplink and downlink services. Space and ground subsystems had been identified in our prior work. Use cases have now been established to further define the subsystem capabilities. It has been recognized that there are two modeling efforts. One is the SSWG developing a CubeSat Reference Model with its logical architecture. The other is a team eventually taking the CubeSat Reference Model as a basis for its mission-specific logical and physical architectures. Therefore, there are two categories of stakeholders. A stakeholder is any entity that has an interest in the system. The stakeholders for the CubeSat Reference Model include INCOSE, the Object Management Group (OMG), regulatory agencies, and the university teams that will be using the CubeSat Reference Model. We are exploring having NASA, NOAA, and FCC regulations contained within their own SysML models and connecting those models to our CubeSat Reference Model. The stakeholders for the mission-specific CubeSat model are those with an interest in the mission-specific CubeSat space and ground system. Typical stakeholders for a space and ground system include sponsor, user, operator, project manager, project engineer, developer, and tester. The list of stakeholders for a university CubeSat project is much smaller. We are collaborating with OMGs Space Domain Task Force (SDTF) to adopt the CubeSat Reference Model as an OMG specification.