Formal system modeling has been a topic of interest in the research community for many years. Modeling a system helps engineers understand it better and enables them to check different aspects of it to ensure that there is no undesired or unexpected behavior and that it does what it was designed to do. This thesis takes two existing tools that were created to aid in the designing of spacecraft systems and creates a layer to connect them together and allow them to be used jointly. The first tool is a library of formal descriptions used to specify spacecraft behavior in an unambiguous manner. The second tool is a graphical modeling language that allows a designer to create a model using traditional block diagram descriptions. These block diagrams can be translated to the formal descriptions using the layer created as part of this thesis work. The software of a small satellite, and the additions made to it as part of this thesis work, is also described. Approaches to modeling this software formally are discussed, as are the problems that were encountered that led to expansions of the formal description library to allow better system description.