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QMultiFlex-400™ Installation and Operating Handbook
2. The satellite orbit inclination is too great. Most geostationary satellites are positioned and
maintained at 0° latitude to within a few tenths of a degree. Towards the end of a satellite's
operational life, the ability to maintain its position diminishes as its propellant resources
decrease. Consequently, the requirements on maintaining the satellite's orbit might be
allowed to relax. As a result, it might be allowed to operate on a slightly inclined orbit as a
way of extending its lifetime. A consequence of operating the satellite on an inclined orbit
is the increase in the maximum rate of change in the carrier RTD and frequency offset
Doppler. If the satellite orbit inclination becomes too great, the canceller might not be able
to track these maximum rates of change. The maximum rate of change of RTD occurs twice
a day, as does the maximum rate of change of frequency Doppler, but they are not in phase
with one another. An example of this is shown below in Figure 8-22 and 8-23. These graphs
show the simulated RTD and frequency offset Doppler profiles of Intelsat-12 observed from
London.
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Figure 8-22
Round Trip Delay of Intelsat-12 as seen from London
8-22
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