The Object-oriented Analysis of the on Board Computer Software for the Brazilian Scientific Microsatellite - Saci-1

This paper presents the object-oriented analysis (OOA) of the on board software of the SACI-1, the firts Brazilian Microsatellite for Scientific Application. Emphasis is put on the object analysis using the OMT (Object Modeling Technique ) as the underlying OOA methodology and employing the best features of a set of others OOA methods. The on board computer (OBC) hardware architecture uses a fault-tolerant transputer system with dedicated I/O interfaces implementing a RS-422 protocol for bus and payload communications. The OBC software has a specific nucleous where a set of parallel and concurrent applications are run. The OBC software design is being a challenge due to its high complexity and diversity of function. Hence the adoption of a software developmemnt methodology based on the object-oriented paradigm. The application software has the following components: the gorund commmunication, housekeeping and payload data, payload communication and attitude determination and control. A responsability-driven approach is used for the classes decomposition of the OBC software and a set of guidelines presented for the functional and dynamics analysis.