Propagation in Lunar Caves: Terrestrial Measurement Campaign and Ray Tracing Modeling

Lunar lava tubes are seen as potential habitation sites for future long stays of humans on the Moon, although much work remains to be done to make this feasible. Previously it will be necessary to carry out the exploration of the pits that are currently identified on the lunar surface as possible entrances to these sublunarean caves and then access the cave itself. This will require the deployment of autonomous robotic systems inside the caves, which will need stable communication networks to carry out their missions. For the planning of these networks, it will be necessary to use some model of propagation losses inside the cave. This raises some issues. First, we do not have any images of these caves, so we do not know exactly what they look like. Second, any proposed model will need to be validated in analogous terrestrial lava tubes, which are smaller than those expected on the Moon. In this work, we propose a ray tracing model to analyze the behavior of radio waves in these scenarios and provide an experimental validation based on measurements performed in a terrestrial lava tube. Furthermore, using this model we analyze the effect on propagation losses of some of the parameters that define the morphology of the cave, such as its dimensions and the curvature of walls and ceiling.