atial Redundancy 6.4.2.2 Temporal Redundancy 6.4.2.3 Combined Redundancy Implementation System Error Detection and Recovery 6.5.1 Application Oriented Fault Tolerance 6.5.1.1 Acceptance Testing 6.5.1.2 Constraint Predicates 6.5.2 Algorithm Based Fault Tolerance (ABFT) 6.5.3 Detection Through Protocol, Timing and Data Checking 6.5.4 System Recovery Provisions 6.5.4.1 Recovery Blocks 6.5.4.2 Check-Pointing and Roll-Back Recovery 6.5.4.3 Fault Containment 6.5.4.4 Reconfiguration and Recovery Development of Fault Tolerant Systems 6.6.1 Mitigation Requirements Based on Fault Criticality 6.6.2 Validation and Verification of Fault Tolerance Summary Acknowledgements References Introduction Satellite based telecommunications has progressed from the function and purpose of the earliest envisioned usage of earth orbiting systems to the primary purpose of the majority of satellites launched today. Communications satellites serve a variety of markets and function in numerous system architectures and operational concepts. Geostationary satellites have historically provided the majority of telecommunications services, but the recent deployment of low-earth orbiting constellations are supporting new market opportunities. Numerous geostationary and low-earth orbit systems are envisioned or are currently under development to support telecommunication system applications. Operating in the environment of space presents numerous requirements to the design, development, and operation of these systems. The charged particle radiation environment produces both long term and transient effects on payload systems. This environment composed of particles trapped in the geomagnetic field of the earth, particles emitted by the sun, and those traversing interstellar space. The plasma environment resulting from the presence of charged particles, operation in the vacuum environment, exposure to the flux of neutral particles, and the potential for collisions with other objects along the orbit trajectory are other factors which must be considered. D