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Figure 7.4.7a – Wide Az. Line Scan Example
When the difference between the longitude of the target satellite and the terminal is small, the
target satellite will appear near the top of the geosynchronous satellite arc when viewed from the
terminal’s location (Satellite B in Figure 7.4.7a). As shown in the figure, the AZ line scan for Satellite
B passes very close to several other GSO satellites. If the EL angle is off by even a small amount
and/or any of those other satellites is transmitting higher broadband power than the target satellite,
then the AAQ could easily select and peak on the wrong satellite’s signal. In order to minimize the
probability of making the wrong choice under these circumstances, a SATTANT is automatically
performed by the AAQ before target satellite acquisition (peaking only) is attempted. This process is
illustrated in Figure 7.4.7b. The longitude difference between satellite and terminal that triggers the
automatic SATTANT is user configurable and typically set to a value of 20 degrees.
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