M. Nohara et al., A LINK STUDY OF A LOW-EARTH-ORBIT SATELLITE-COMMUNICATIONS SYSTEM USING OPTICAL INTERSATELLITE LINKS, IEICE transactions on communications, E76B(5), 1993, pp. 536-543
Link conditions of a low-earth orbit (LEO) satellite communications sy
stem were evaluated, to provide the information necessary for designin
g a broadband LEO-SAT communications system. The study was made both f
or optical intersatellite and user/satellite links. For the optical in
tersatellite link (ISL), we examined several ISL configurations in a c
ircular polar orbit, and found that when the satellites are in the sam
e orbital plane, the link parameters are quite stable, that is, the li
nk between adjacent satellites can be regarded as fixed and, therefore
, suitable for broadband transmission via an optical link. However, th
e link conditions between adjacent orbits change very quickly and over
a wide range. To overcome this and extend the network path between sa
tellites in adjacent orbital planes, we proposed intermittent use of t
he link between satellites in co-rotating adjacent orbital planes at t
he low latitude region, i.e., only during the period of stable conditi
ons. The optical intersatellite link budget also sets link parameters
that are realistic, given present optoelectronic technologies. From qu
antitative evaluations of the user/satellite link, we believe that bot
h the satellite altitude and minimum elevation angle are critical, bot
h 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 alt
itude and elevation angle are also indicated. These are important cons
iderations for future system design.