Research On Deep-space Channel Modeling For Mars Exploration

A reliable communication system is the key to support the deep-space exploration.In this graduation thesis,the electromagnetic propagation process of Mars-to-Earth communication link was studied based on the Mars exploration communication scenario.The channel model of the Mars-to-Earth communication link was analyzed,and a deep-space channel simulator was built by java software combined with STK and Matlab.The research results could help the design of future Mars exploration communication link.This graduation thesis could be divided into the following three parts:First of all,due to the great differences of physical environment between Earth and Mars,the Earth-to-Mars communication link could be divided into three parts: the Earth proximity space channel,the Mars proximity space channel,and the free-space channel of Earth-to-Mars.Because the electromagnetic propagation characteristics of these links was different: 1)In the Earth proximity space channel,the main affecting factors were: atmospheric absorption,rain attenuation,fog attenuation and ionosphere influence;2)In the Mars proximity space channel,the main affecting factors were: Martian atmosphere absorption and dust storms attenuation on the surface of Mars;3)When passing through the free-space channel of Earth-to-Mars,the main influence factor was path loss,and it also would be affected by solar scintillation and other cosmic rays.Therefore,first of all,combined with the mature research results and models of the Earth proximity space channel,the channel propagation characteristics were analyzed and modeled.Then,combined with related reports of NASA,the Mars proximity space channel was modeled.Then,in the free-space channel of Earth-to-Mars,besides the path loss,the signal was also affected by the scintillation of solar radiation particles,resulted in: intensity scintillation,spectrum broadening and phase fluctuation.Because this solar scintillation showed cyclical changes with the revolution of Earth and Mars,the paper calculated and modeled the solar scintillation intensity with the change of the angle between Earth-Sun-Mars in the Mars-to-Earth superior conjunction cycle.The research proved,the solar scintillation intensity varied periodically with the change of the angle between Earth-Sun-Mars,and had a certain random fluctuation.In order to estimate the solar scintillation intensity more accurately,Autoregressive(AR)model was used to predict the solar scintillation intensity.So this paper modeled channel propagation characteristics of Mars-to-Earth link in the deep-space.Finally,based on the above three different channel model,combined with the preliminary results of solar scintillation,through Java,Satellite Tool Kit and Matlab,the visual simulation function platform was set up.The main functions were: 1)The location of the Earth stations,relay satellites,Mars probes,and the data with link connectivity,propagation delay could be obtained from the platform through a visual software interface that could show the process of Mars exploration;2)By fitting with the data from the platform,a statistical model of solar scintillation in the superior conjunction cycle was calculated,it could analyze the influence that Mars-to-Earth communication links affected by intensity scintillation,spectrum broadening and phase fluctuations.Channel modeling analysis of Mars-to-Earth link and visual simulation could provide reference for link budget of future Mars exploration.