A feasibility study on ground-based localization for Mars exploration

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Sähkötekniikan korkeakoulu | Master's thesis
Space Robotics and Automation
Degree programme
SST - Space Science and Technology (TS2005)
112 + 9
The goal of this work is to assert the feasibility of the use of a ground-based network, consisting of beacons, to aid in the provision of localization for mobile stations on Mars. The dayside ionosphere can be utilized to refract and reflect radio signals to some receiver beyond the horizon. The propagation of radio signals is studied with the use of a simulation, which makes use of a ray-tracing method to track radio signals in the ionosphere. Several scenarios are defined to classify the state of the ionosphere. A nominal scenario is provided, with ionospheric properties prevalent at Mars. Furthermore, scenarios are defined to include both a minimum and maximum solar activity, as well as dust storms and SEP events. The determination of the position of a mobile station can be done by exploiting the properties of the received signal. Three localization technologies are studied in detail in this work, being the time of arrival ( TOA ), received signal strength ( RSS ) and angle of arrival ( AoA ). The Cramer-Rao lower bound ( CRLB ) is used to determine the lower bound of the precision of a position estimate, produced by any of these technologies. A comparison of the obtained precisions shows that it is possible to obtain a precision of less than 13m for any scenario when using TOA technology, and 6m when using AoA technology. Furthermore, a coverage of at least 92 % is achieved in all but the most extreme scenarios. The coverage increases with decreasing frequency. The best results are obtained with a frequency of 2:5MHz. Moreover, it is shown that the best precision is obtained by placing beacons either in a rectangular or triangular grid on Mars, with beacons spaced 10_ apart. By doing so, a 4m precision can even be obtained under the nominal scenario for a frequency of 2:5MHz and 4:5MHz with any technology. Ultimately, a ground-based beacon system has proven to be a sound solution to providing positioning estimates on the Martian surface.
Kallio, Esa
Thesis advisor
Vanhamäki, Heikki
mars, ionosphere, localization, crlb
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