WAAS Geostationary Communication Segment (GCS) requirements analysis

The Federal Administration System´s (FAA) Wide Area Augmentation System (WAAS) is a critical component for modernization of air traffic management and control in the National Airspace System (NAS). WAAS augments the Global Positioning System (GPS) to enhance navigation performance for air flight. The FAA has developed very stringent performance requirements for WAAS to ensure safe air flight en-route, and for non-precision and precision approaches. The requirements are grouped into the four general categories of availability, accuracy, integrity, and continuity. Critical to meeting these requirements is the provision of a robust WAAS signal-in-space (SIS) capability. The SIS provides two services: (1) correction and integrity data on the WAAS and GPS signals, and (2) GPS-like ranging signals to augment GPS signals. The SIS requirements apply to the satellite signals and the WAAS ground segment, and thus flow down to the Geostationary Communication Segment (GCS) and the WAAS ground network. The GCS requirements then flow down to the two main components of the GCS (the GEO satellite(s), and the Ground Uplink Subsystems (GUSs) that support the GEO(s)). This paper only addresses the analysis and flow down of the GCS requirements.