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4.2 A Software Architecture Example - Satellite Commanding

An example of the software architecture and describe the elements involved is presented next. In particular, the software architecture for the Commanding application will be used to illustrate the various elements. Appendices A through E contain detailed software architectures for Mission Planning, Telemetry, Commanding, Orbit Analysis, and Attitude Analysis, respectively.

The first element of the software architecture is the information base structure, indicating the types of information needed by a particular application. Here, the data type is described and the various layers of information are depicted. This is used as a top-level introductory perspective enabling the reader to see the relationship between the application and the data it uses.

Figure 6. Information base concept for the Commanding example.

Figure 6 illustrates the information base relationship for Commanding. The information base for Commanding includes a database of command formats, command constraints, command plans, and display formats. The knowledge base assists in constraint checking, command evaluation, and resolution of commanding anomalies. There may also be some mission-unique code needed to convert (or map) command mnemonics from one convention to another. As with all TT&C applications described in this document, Commanding requires data that can be classified into levels ranging from mission-area-unique to satellite-unique. This information-driven architecture allows a common application to support multiple satellite programs.

The remainder of this example includes:

* a top-level Commanding DFD indicating the data that is passed between the high-level functions of commanding and the external segments, mission-unique applications, and other SSCS applications,

* a CFD that indicates the order in which processes occur, and

* a brief excerpt of the functional API definition between Commanding and Telemetry.