Formal specification and analysis approaches for spacecraft attitude control requirements

The cost to develop software in aerospace systems is on an exponential curve driven by increasing system complexity, which is exacerbated by a systems engineering process that discovers the majority of design errors late in the design process. Implementing formal specification and analysis techniques starting at the requirements development phase has the potential to drastically reduce aerospace software development costs by identifying and fixing errors while the cost of fault removal is still relatively low. As an example, this paper presents an approach for formalizing common spacecraft attitude control system requirements such as actuator limits, pointing error, reachability, drift, settling time, rise time, and overshoot. The proposed formalization approach allows early analysis of requirements for consistency and can facilitate the generation of rigorous verification evidence from formal methods analysis techniques such as model checking. Limitations in analysis of nonlinear systems by model checking techniques drove use of hypothesis testing as an alternative formal approach for analysis in this research. Formal requirements may be used in hypothesis testing to provide a statistical determination of whether a simulated or tested system meets requirements. To evaluate the use of the formal requirements based hypothesis testing approach, a space filling experimental design simulation is conducted on simulated spacecraft slewing maneuvers. Finally, the results are presented and discussed.