A Model-Based Systems Engineering (MBSE) approach for defining the behaviors of CubeSats

This paper describes an eight-step approach for defining the behaviors of CubeSats that begins with mission requirements and ends with a functional architecture modeled as an activity hierarchy using the Object Management Group's (OMG) Systems Modeling Language (SysML). This approach could be applied to other satellite development efforts but the emphasis here is on CubeSats because of their historically high mission failure rate and the rapid growth in the number of these missions over the last few years. In addition, this approach complements the International Council on Systems Engineering's (INCOSE) Space Systems Working Group's (SSWG) efforts to develop a CubeSat Reference Model. This approach provides a repeatable, generalized method for CubeSat development teams to follow that incorporates standard systems engineering practices such as: a top-down approach, requirements analysis, use case development, and functional analysis. This effort uses a Model-Based Systems Engineering (MBSE) approach. Some of the benefits of using an MBSE approach over a traditional document-based approach are: enhanced communications, reduced development risk, improved quality, and enhanced knowledge transfer 1. Systems engineering artifacts produced using this approach, such as definitions of the mission domain elements, requirements, use cases, and activities, are captured in a system model which serves as a single-source-of-truth for members of the CubeSat development team. Examples are provided throughout the paper which illustrates the application of this approach to a CubeSat development effort. Since most space missions are concerned with the generation or flow of information, the examples focus on requirements to collect and distribute mission data ending with a definition of the required system functionality to satisfy those requirements.