International Telemetering Conference Proceedings / October 22-25, 1984 / Riviera Hotel, Las Vegas, Nevada / Software for real-time (time critical) control applications has been shown in military and industry studies to be a very expensive type of software effort. This type of software is not typically addressed in discussions of software architecture design methods and techniques, therefore the software engineer is usually left with a sparse design “tool kit” when confronted with overall system design involving time critical and/or control problems. This paper outlines the successful application of data flow and transaction analysis design methods to achieve a structured yet flexible software architecture for a fairly complex antenna controller used in automatic tracking antenna systems. Interesting adaptations of, and variations on, techniques described in the literature are discussed; as are issues of modularity, coupling, morphology, global data handling, and evolution (maintenance). Both positive and negative aspects of this choice of design method are outlined, and the importance of a capable real-time executive and conditional compilation and assembly is stressed.