In the context of unmanned systems autonomy means the ability of a given system to operate without the attention of a human operator. Therefore, in an oversimplified way, one might think of a total operation time, where part of the time is done without human attention while another part in an unattended way. Depending on the proportion of the unattended time operation different autonomy levels and different operation requirements might be defined. The next chapter provides a deeper insight into autonomy levels and expected performance. The following topics are discussed n details: