Model-Based Systems Engineering (MBSE) is a key practice to advance the systems engineering discipline, and the International Council on Systems Engineering (INCOSE) has 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) Challenge Team has been investigating the applicability of MBSE for designing CubeSats since 2011. At the core of MBSE is the development of the system model that helps integrate other discipline-specific engineering models and simulations. The team has been working to create this system model by capturing all aspects of a CubeSat project using the Systems Modeling Language (SysML), which is a graphical modeling language for systems engineering. In the past phases of the project, the team has created the initial iteration of the reference model, applied it to the Radio Aurora Explorer (RAX) mission, executed simulations of system behaviors, interfaced with commercial simulation tools, and demonstrated how behaviors and constraint equations can be executed to perform operational trade studies. The CubeSat Reference Model starts with an identification of potential stakeholders. A stakeholder is any entity that has an interest in the system including sponsor, end-user, procurer, supplier, and regulatory agencies. Each stakeholder’s needs, objectives, constraints, and measures of effectiveness are incorporated into the model. The CubeSat Reference Model decomposes the system into logical elements which are abstractions of elements that comprise the system.  The model has a library of logical elements of stereotypes that can be used to create mission-specific logical elements.  The logical elements can then be allocated to physical elements that can be implemented as hardware, software, data, procedures, and operator actions. This paper reports on the status of developing the CubeSat Reference Model including incorporating the Cal Poly CubeSat Design Specification into its own SysML model.