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Unformatted text preview: -45-equator, the coverage near the north and south poles is inadequate. For theseregions, better communication can be achieved by LEO or HEO satellites. HEOsatellites have the additional advantage that they spend most of their time at thehigh part of their orbit so that you get the most coverage for the longest time forthis type of satellite. On the other hand, tracking and handoff is not necessary forGEO satellites because they appear stationary relative to the earth. LEO satellites,since they are so low travel very much faster, and cover less area than GEO so thattracking is more difficulty and passing off is frequent. HEOs require tracking andhandoffs, as well. However, if the HEOs have high orbits the handoff frequency canbe much less and the tracking easier than for LEOs.9.5You would use GEOs when the earth stations are not near the poles, when there is apremium on not having to steer the earth station antennas, and when broad earthcoverage is important, for television broadcasting for instance. HEOs are primarilycoverage is important, for television broadcasting for instance....
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- Fall '11