Observation of Low-Earth-Orbit space objects by optical sensors (telescopes) is a rather complex task that requires equipment with appropriate characteristics. Througput can be considered as one of the main characteristics of optical sensors for observing Low-Earth-Orbit space objects. An approach to the theoretical estimation of the optical telescope’s throughput when observing Low-Earth Orbit space objects is proposed in the paper. It is based on the representation of the telescope as a queuing system. The queuing system can be of various types depending on the observation methods that are used. The input flow in this queuing system is the flow of Low-Earth Orbit space objects’ passes through the viewing area of the telescope, and the output flow is the flow of observed passes. The average total time spent for observing one Low-Earth Orbit space object is taken as the average service time. Quantitative characteristics of these values can be obtained by simulating the Low-Earth Orbit space objects’ passes through the telescope's viewing area. The throughput of the queuing system was chosen as the main estimated characteristic. An example of evaluating the characteristics of such a queuing system is given. It is based on the “Sazhen-S” quantum optical station of the Centre for Special Data Reception and Processing and Navigating Field Control of the National Space Facilities Control and Test Center of State Space Agency of Ukraine. Possible ways of increasing the throughput of “Sazhen-S” quantum optical station according to the observation of Low-Earth Orbit space objects are proposed.