This paper discusses how Software Architectural design patterns could be used to build the architecture of a system. The application of design patterns helps to improve the quality of software architecture and to reduce the flaws in the architecture. Generic architectural design patterns for real-time software components are customized to suit the functionality of system. This is illustrated using the Solar TErrestrial RElations Observatory (STEREO) a case study based on NASA?s STEREO mission. The customized design patterns are validated using IBM Rational Rhapsody. These validated design patterns form templates for further use in building the architecture of flight software