Deployment of a communications network to explore a Lunar cave

Lunar caves are subterranean wide and long tubes that could potentially host a human base. These caves are expected to be stable, with small temperature variations and they can protect the base from micrometeorites. The entrance to these tubes, known as pit or skylight, is a small collapse with cliff-like vertical walls.  In this work, the deployment of a communication network is developed: from the pit to the unexplored zone inside the cave. An ad hoc communication network with multiple nodes is foreseen. In order to estimate the data rate of the total communication link, a propagation model has been developed, considering ground, walls and ceiling echoes. This model has been experimentally validated in Earth lava caves in Lanzarote (Spain), for different ground roughness. The measurement campaign has demonstrated that an increment of a few metres in the antenna height can increase the link distance up to 200 metres, due to the positive interference of the ground echo. Moreover, non-line of sight scenarios, like bends and small slopes have been analysed to estimate the increment of the propagation losses.  From this propagation model, the total network behaviour has been analysed.  The network shall maximize the coverage distance of the communication link, while remaining a total data rate greater than 25 Mbps. It must be taken into account that a decrease in data rate occurs with each hop between nodes. The geomorphology of the cave and the robotic capabilities have been considered to define network and operation requirements.