The aim to practically use the results from the observations for discovery of distant objects in the visible and the infrared part of the optical specter means to seek a definite answer about a signal presence which would answer the question about the presence in the controlled space of the sought object. On research basis the signal presence probability can be defined which is described by means of a likelihood ratio. The initial value of the likelihood ratio does not contain any unknown values. It is defined on an experimental basis by using devices with concrete tactical and technical characteristics in a concrete environment by considering the fluctuations probability.