Real-time systems are commonplace in satellites. In this system type, software has become a crucial factor to satellite's success projects because its complexity quickly increases, along with cost. Some factors that contribute to increase complexity of software are: it interacts with different kind of hardware, it has several states and for each state commonly a different control law, it has hard-deadlines, and it must have a high level of reliability. Attitude and Orbit Control System (AOCS) is a good example for this type of system. With the necessity to launch more satellites, Brazilian National Institute for Space Research (INPE) has been carrying out research on modeling and verifying real-time software, like a lot of other space agencies and research institutes. The main focus is to obtain a better balance between dependability, schedule, and cost. However, instead of creating one more brand-new, one-of-a-kind approach, method or process, we are trying to use Object Management Group (OMG) specifications, which have been proposed and adopted by community in some degree. Another concern from this INPE research is to be independent from commercial tools establishing itself on open source software. This paper presents a detailed approach to implement Model-Driven Architecture (MDA) in real-time space software based strongly in OMG specifications. It shows how models are defined, linked, verified and transformed, as well as a set of tools for this. We place special emphasis on fUML (Semantics of a Foundational Subset for Executable UML Models) and MARTE (UML Profile for Modeling and Analysis of Real-Time Embedded Systems) that allow us to define a completely executable Platform Independent Model (PIM). At the end, a case study is presented, along with an assessment of the proposed approach. This assessment allowed us to conclude that MDA, following the proposal presented, has advantages versus the current approaches applied to real-time space software development.
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