Guaranteeing Timing Requirements in the IXV On-Board Software

Ensuring the correct timing behavior of the control software of a spacecraft is a complex endeavor. This paper describes the real-time aspects of the Intermediate eXperimental Vehicle’s (IXV) On-Board Software (OBSW), including the schedulability analysis performed for the validation of this safety-critical, hard real-time system of the European Space Agency (ESA). We then give details of how the Ravenscar profile has been used to obtain predictability over RTEMS, and quantify the overhead of different mechanisms for measuring computation times. We provide the timing measurements of each task during the different modes of the mission, including the Guidance, Navigation, and Control (GNC) tasks, to aid in the development of future OBSW projects.