Evaluation of Large Scale Propagation Phenomena on the Martian Surface: A 3D Ray Tracing Approach

摘要

As the attention towards the exploration of the “Red Planet”, i.e. Mars, increases, the need of models representing the Martian conditions becomes fundamental in order to support future unmanned and manned missions, that will, hopefully, take a human crew to the Martian surface. For this reasons, it is necessary to understand, among other meaningful aspects, how an electromagnetic (EM) waves propagates over the Martian environment and build a model to properly simulate communication systems under realistic channel conditions through common commercial software. This contribution aims to evaluate large scale propagation phenomena on the Martian surface in order to determine a realistic Martian channel model. First, the surface morphology is obtained through the use of a high resolution Digital Elevation Model (DEM) representing the Gale crater. Then, the DEM is converted into a tile-based structure in which the tiles are the DEM's pixel, whose dimension is set according to the DEM's resolution. Each tile vertex is interpolated with the vertex of the nearest tile, thus constructing the walls of the 3D structure. The 3D structure is characterized, from an electromagnetic viewpoint, through the estimation of the complex permittivity. By exploiting a ray tracing approach and simulating an EM signal emitted by an isotropic antenna, the line of sight (LOS) power is computed over the 3D structure. From the received power in the selected Martian location, we estimate path loss samples for different distances between transmitter (TX) and receiver (RX). The samples are averaged for each distance and the path loss exponent, which represents the roughness of the terrain, is obtained by finding the path loss curve which better fits the averaged samples. Finally, the shadow standard deviation is evaluated and analyzed with respect to the considered Martian location.