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The AAQ’s TLE Track software module includes a TLE propagator program that takes a user provided
TLE set and calculates the antenna Ped-AZ and Ped-EL angles versus time necessary to reliably
acquire and accurately track the target satellite. The TLE set for a particular satellite will be updated
from time to time based on NORAD tracking data and infrequent maneuvers performed by the
satellite operator to maintain the satellite’s inclined orbit. The operator of the terminal is
responsible for keeping the TLE set current. See appendix O for the TLE Tracking option.
7.4.16
Position Hold
The AAQ has a Position Hold mode that makes it tolerant of power outages. While in this mode, if
the power should fail and return without any detectable movement of the antenna system, then the
AAQ will continue to hold its position provided that the Modem reports a lock on the Target
Satellite’s signal.
7.4.17
Satellite Signal Properties
The AAQ requires a metric that it can use to discern a successful satellite acquisition and optimize
for antenna peaking purposes. That metric is some representation of the signal received by the
antenna from the target satellite. The signal itself is subject to significant perturbation by the
atmosphere through which the electromagnetic waves travel. For the AAQ, the satellite signal is
represented by the output of a device called a “Signal Source”. The AAQ is designed to work with
several types of signal sources, each with its own advantages and disadvantages that must be
accommodated by AAQ software.
7.4.18
Scintillation Effect
Scintillation is a term for rapid variation in apparent brightness or position of a distant object when
viewed through a medium such as the Earth’s atmosphere. Scintillation’s effect on a satellite signal
causes rapid changes in received signal level that can reach several decibels (dB) in magnitude. The
effect is caused by anomalous refraction of the satellite’s RF signal due to small fluctuations in air
density. The effect varies significantly in intensity with time as atmospheric conditions are
constantly changing.
In order to optimally peak the antenna system on the target satellite, the AAQ must be able to make
Fine Peaking decisions based on changes of only a fraction of a dB in received satellite signal level
from one step to the next. This becomes problematic when scintillation effects reach several dB.
Under nominal conditions, when the received satellite signal is reasonably stable, the AAQ will
