MBSE APPROACH APPLIED TO LUNAR SURFACE EXPLORATION ELEMENTS

The last two decades have shown that among the new drivers of the design of space systems the level of autonomy is a key element to ensure the success of a mission. The final aim is to monitor and direct the operations or counteract unforeseen events as efficiently as possible, even without the man in the loop. To effectively accomplish these new tasks, the decision making layer of the spacecraft should be able to evaluate the available resources and the overall state of health of the system. The Model-Based System Engineering (MBSE) framework can help to understand the general behavior of a complex system as it is an autonomous space platform. The MBSE scheme exhibits the links and the interdependency between the different phases of mission analysis and between the components. The study proposed in this paper follows the MBSE methodology to design an autonomous guidance, navigation, and control (GNC) subsystem of a planetary exploration rover and its collaborative drone. The study starts from the high-level requirements of a lunar exploration mission and ends with the preliminary design of a state-machine, that describes the behavior of an autonomous GNC. To ensure a high level of autonomy, the decision-making layer of the GNC takes into account the outputs of the failure detection, identification, and recovery (FDIR) subsystem and the overall health state of the rover. The FDIR subsystem embodies the idea of a multidisciplinary design where different inputs should be managed to ensure the safety of the overall system under study. The novelty of this analysis lays in using the MBSE to define the design box of the autonomous GNC. The logic behind the MBSE enables the designer to keep track of the effects of the high-level mission-related decisions and of the FDIR on the overall behavior of an autonomous GNC subsystem. In the application presented in this paper, the preferred mean to study the mission and behavioral analysis is MBSE software Genesys 7.0 of Vitech Corporation. While the state machine and the related artificial intelligence algorithms are designed in Robot Operating System (ROS). The described approach is applied to the case study of a collaborative rover and drone on the lunar surface. The mission is designed as a "precursor mission" to assess the safety of the lunar lava tubes as possible future human settlement.