Future large space structures, such as the Space Station (figure 1), will have high power dissipation and long life requirements which dictate the need for steerable radiators. With the advent of a rotary coupling that enables radiators to be positioned toward a desired environment, this need can be met. In order to perform this task, the coupling must have a control system. Several different concepts have been evaluated for this application. Hardware concepts involved sensors located on the solar arrays, or rotating sensors located on the radiators to measure solar radiation. Software control options involved comparisons of instantaneous radiator position with a minimum environment radiator position obtained from a data base and software control using Space Station guidance, navigation and control (GN&C) computer inputs. The most effective system is one that uses information from the GN&C computer to determine the current and required radiator position. Once operational, updates to the program are not required for growth. Fault detection, replacement, and repair operations are less complex than for the sensor systems. This software control system was selected for the flight design.