\chapter*{Introduction}
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\addcontentsline{toc}{chapter}{Introduction}

In these days, new challenges occur on a~daily basis. Means of the modern warfare suggest that chemical, biological, radiological and nuclear (CBRN) defense \cite{cbrn} will have increasing importance. The U. S. Department of Health and Human Services defines several types of terrorist attacks which involve sources of ionizing radiation \cite{playbook}. One of them which is discussed in world media is a~‘dirty bomb’ attack \cite{forbes}, \cite{express}. Such bomb may disperse radioactive material in urban zones. Since the radiological sources are commonly present in medical or scientific facilities, it is rather possible for an attacker to get them \cite{com-src}. If this critical situation actually happened, it would be vital to localize and dispose of the dangerous sources as quickly as possible.

Methods for localization of radiological sources described in \cite{bayes}, \cite{on-loc}, \cite{iot} and \cite{metropolis} utilize a~network of detectors and statistical models. Their disadvantage is the immobility of detectors, hence they may not be applied very fast in a~larger area. It is more convenient to mount detectors on a~mobile platform. Among other disadvantages, there is a~fact that the methods were tested only in simulations, not in real environment. Papers \cite{remote} and \cite{uav} introduce systems based on unmanned aerial vehicles (drones) carrying detectors. This approach enables swift exploration of the area of interest, disregarding terrain obstacles, but there is a~problem with limited load of the UAVs. The higher is their distance from sources located on a~terrain level, the larger volume and therefore weight of detectors is needed. Also the precision of localization is limited. There is a~possibility to use a~different type of airborne system, for example a~helicopter \cite{ares}.

Another way is to use unmanned ground vehicles, specifically reconnaissance robots. Such solution is proposed in this thesis. In comparison with a~human, the robot is less prone to radiation damage and is therefore more suitable for the described type of mission. It is likely that a~robot equipped with precise instrumentation locates radiological sources faster, more precisely and more safely in the first place. Some localization algorithms are suggested in \cite{smart} but the system is designed and tested in a~very small area (60x60 cm). System for localization in real conditions can be found in \cite{backward}. The disadvantage is its considerably limited autonomy.

The primary aim of this thesis is to develop and test algorithms for fully autonomous localization of radiological sources in defined area of interest. The first objective is a~background research of detection principles in order to choose suitable detectors. The next objective is a~development of complex system based on robotic platform that would allow to run the algorithms. It should provide directional sensitivity of the sensory system which may represent an advantage for localization. All the algorithms need to be tested in simulations first. The final objective is an evaluation of proposed algorithms in actual conditions with real radiological sources.