High Reliability System Design Experience with the Gamma Ray Large Area Space Telescope

The Large Area Telescope (LAT) is the primary instrument on the Gamma Ray Large Area Space Telescope (GLAST), a space based observatory which is scheduled to launch late this year. The LAT traces its heritage from the particle physics community and represents a large departure in design and capability from previous space based experiments. Similarly, power, communication, and physical access limitations of a space based platform place strict requirements on the design and reliability of both the LAT and its Trigger and Dataflow (T&DF) system. The resulting T&DF system consists of a hierarchical trigger with both Level 0 and Level 3 components, distributed event processing, and slow control. We describe our experiences developing and testing the T&DF system in the context of a space mission, and we report the performance and status of the system as GLAST approaches launch.