PERFORMANCE LIMITATIONS OF FREE-SPACE OPTICAL COMMUNICATION SATELLITENETWORKS DUE TO VIBRATIONS - ANALOG CASE

Free-space optical communication between satellites networked together can make possible high-speed communication between different places o n earth. The use of optical radiation as a carrier between the satelli tes creates very narrow beam divergence angles. Due to the narrow-beam divergence angle and the large distance between the satellites, the p ointing from one satellite to another is complicated. The complication is due to vibration of the pointing system caused by two stochastic f undamental mechanisms: (1) tracking noise created by the electro-optic tracker and (2) vibrations created by internal satellite mechanical m echanisms. We derive mathematical models of signal, noise, approximate SNR, and approximate bit error rates of optical communication satelli te networks as functions of the system parameters, the number of satel lites, and the vibration amplitude. The optical intersatellite network model considered includes transmitter satellite, repeater satellites, and receiver satellite all networked together. These models are the b asis for pointing system design of appropriate complexity and performa nce to make the network as simple and inexpensive as possible. An exam ple of practical communication between Anchorage in Alaska to Johannes burg in South Africa by a free-space optical communication network com posed of nine low-earth-orbit satellites is given. From the analysis i t is clear that even low vibration amplitude of the satellite pointing systems decreases dramatically the network performance. (C) 1997 Soci ety of Photo-Optical Instrumentation Engineers.