A Link Study of a Low-Earth Orbit Satellite Communications System Using Optical Intersatellite Links

Mitsuo NOHARA  Yoshinori ARIMOTO  Wataru CHUJO  Masayuki FUJISE  

IEICE TRANSACTIONS on Communications   Vol.E76-B   No.5   pp.536-543
Publication Date: 1993/05/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Satellite Communications Networking and Applications)
low-earth orbit satellite,  satellite communication,  optical intersatellite link,  ISL network,  

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Link conditions of a low-earth orbit (LEO) satellite communications system were evaluated, to provide the information necessary for designing a broadband LEO-SAT communications system. The study was made both for optical intersatellite and user/satellite links. For the optical intersatellite link (ISL), we examined several ISL configurations in a circular polar orbit, and found that when the satellites are in the same orbital plane, the link parameters are quite stable, that is, the link between adjacent satellites can be regarded as fixed and, therefore, suitable for broadband transmission via an optical link. However, the link conditions between adjacent orbits change very quickly and over a wide range. To overcome this and extend the network path between satellites in adjacent orbital planes, we proposed intermittent use of the link between satellites in co-rotating adjacent orbital planes at the low latitude region, i.e., only during the period of stable conditions. The optical intersatellite link budget also sets link parameters that are realistic, given present optoelectronic technologies. From quantitative evaluations of the user/satellite link, we believe that both the satellite altitude and minimum elevation angle are critical, both in defining the quality of the service of the LEO-SAT system and in their impact on the other transmission parameters. The link loss, the visible period and the required number of satellites vs. satellite altitude and elevation angle are also indicated. These are important considerations for future system design.