Ranging and processing satellite (RAPSAT)

The following features of RAPSAT are described: performance requirements, operations, onboard processor architecture, and power and spectrum requirements. The proposed RAPSAT would provide surveillance and data link services for aviation. A feasibility study conducted over the past year shows the system can serve 50000 peak instantaneous users with a total aircraft-to-satellite bandwidth of 4.5 MHz. The results reflect realistic message sizes and frequencies, plus the projected geographic distribution of air traffic in the year 2010. The system offers both automatic dependent surveillance and cooperative independent surveillance services. It uses two or more geostationary satellites, a cross link for coordination between the satellites, and an onboard processor for each satellite. By carefully scheduling discrete polls to aircraft, the system prevents garbling of aircraft replies at the satellite receive antenna and thus achieves higher spectral efficiency than previously proposed satellite-based surveillance systems