This diagram depicts the major entities which the FSW (and hence, its web pages) must track. Each box links to an index page for the entity in question; the connecting lines represent relationships (and often, links) between web pages for entities of a given type.

The top-level requirements are dictated by the goals of the scientific mission and the engineering and physical realities of spaceflight. Lower-level requirements are developed to add necessary detail. Most requirements relate to particular functions (e.g., Thermal Control) that must be performed.

The FSW group is developing tests to verify that its software meets the relevant requirements. Along with verifying the underlying hardware, these tests verify that the operational functions of the flight software are being performed correctly by the FSW tasks (roughly, processes).

Tasks are assembled, at run time, from libraries of dynamically-loadable constituents. For code-maintenance purposes, constituents are collected into packages and projects. (Actually, the situation is a bit more complicated than this; see the Expanded introduction to FSW Entities for details.)

Most FSW communication (e.g., between tasks, with the spacecraft) is performed by means of packets. The code to generate, send, accept, and process these is defined in the relevant packages.

Note: Most of these web pages (and any supporting links) are under active development.