Browsing by Author "Bätz, Bastian"

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Open Access
Design and implementation of a framework for spacecraft flight software
(2020) Bätz, Bastian; Eickhoff, Jens (Hon.-Prof. Dr.-Ing.)
The amount of functionality provided by software in technical products is rising continuously, not only for programs in personal computers or mobile devices, but also for that embedded in other machines, such as household appliances, cars or spacecraft. However, with a rising amount of functionality comes more code, which implicates, in most cases, more complexity. This is also true for spacecraft, which makes the development of spacecraft on-board software or flight software (FSW) a challenging endeavor. This thesis sets the objective to improve design and development of FSW by applying techniques found in the discipline of software engineering. As most of these techniques do not aim at embedded software, but rather on general purpose software or Internet applications, existing techniques are surveyed for their applicability to the domain of flight software design. As a result, this survey highlights the possibility to create a component framework, which supports the development of FSW for various variants of space missions. To determine the common needs of spacecraft software, a domain analysis is performed, which identifies requirements or features not for a single, specific satellite, but spacecraft software in general. These generic features cover component management, system management, operations, and autonomy. With a set of tools at hands and the required features identified, a spacecraft software framework can be designed. This was done at the University of Stuttgart and the resulting framework is called the Flight Software Framework (FSFW). This thesis contributes to the FSFW and describes its overall design in the view of the identified software engineering techniques. The FSFW architecture defines a FSW application as a set of interacting components, which offer and invoke functionality of other components. The functionality is defined by a small number of interface definitions, e.g. for component mode handling or action invocation. Establishing communication and executing components, as well as providing access to computing resources and hardware interfaces, is the task of the FSFW-Core, which is the central element of the framework. To support the implementation of components, the FSFW offers a set of component templates, which serve as prototypes for e.g. device handling or controller components. These templates are complemented by sub-frameworks to command the spacecraft using a common space link protocol, the packet utilization standard (PUS), as well as elements to implement on-board failure detection, isolation and recovery (FDIR). To ensure the practicality of the complete component framework, the FSFW serves as basis for the software of Flying Laptop, a small satellite also developed, built, and currently operated by the University of Stuttgart. This allowed to iteratively find a good design, which proved itself useful in a real-world deployment. Also, it serves as an example to illustrate the various concepts and features of the FSFW within this thesis. A brief evaluation shows that applying selected software engineering techniques can improve flight software development. This happens by enhancing separation of concerns by encapsulation of functionality in components. Also, the FSFW enables reuse of both the unchanged FSFW-Core and entire components in various space missions.