elevation may move several degrees while the azimuth shows almost no motion.
Measurement delay --- During a steptrack cycle, the ACU positions the antenna to a
certain offset and then measures the level. Between the moment when the antenna reached
commanded position and the beacon level measurement the ACU waits some time to let the
beacon level settle. The optimal delay value depends on the beacon receiver's averaging /
post detector filter setting and is a quite critical for the steptrack performance.If the delay is
too short, the beacon voltage does not reach its final value, the steptrack does not properly
recognize if the signal goes better or worse after a test step. If the delay is too long, the
impact of fluctuation to the measured level grows and may cover the small level difference
caused by the test step. With the sat-nms LBRX beacon receiver, best results are achieved
if the receiver is set to 0.5 Hz post detector filter bandwidth and a measurement delay of
1500 msec.
Recovery delay --- After the ACU has done the tracking steps for the elevation axis, it waits
some time before it starts tracking the azimuth axis. This is to let the beacon level settle after
the final position has been found. A typical value for this parameter is 4000 msec.
Level averaging --- When measuring the beacon level, the ACU takes a number of
samples and averages them. The standard value of 5 samples normally should not be
changed. Larger values will slow down the ACU execution cycle.
Retry after motor fault --- When the ACU encounters a motor fault during steptrack, the
tracking cycle gets aborted and the ACU shows a fault. This parameter tells the ACU how to
proceed after this, with the next tracking cycle:
NEVER --- The ACU will not try to move the antenna again. This will stop tracking until
an operator will have checked the antenna motor and re-started the tracking.
FOREVER --- The ACU try to move the antenna again with the next tracking cycle. If the
antenna is really blocked, the ACU will try to move the antenna every tracking cycle.
This increases the probability to keep the antenna following the satellite - even if the
antenna motors show sporadic faults. But this also increases the risk to crash motors
and/or spindles of the antenna.
ONCE --- This mode offers a compromise between preserving the motors and trying to
keep the antenna following the satellite. The mode ONCE allows the ACU to do exactly
one retry after a motor fault, if this fills as well the ACU stops tracking
Smoothing interval --- This parameter controls the smoothing function. Setting it to zero
disables smoothing. Smoothing lets the ACU point the antenna to positions evaluated from a
simple model calculated from the step track peaks of the recent few hours. A detailed
description of this function you find at chapter
'8.3.3 Smoothing'
Peak jitter threshold --- If the jitter value of at least one axis exceeds this threshold, the
ACU raises an 'model fault'. If this happens three consecutive times, the ACU resets the
models of both axes. Adaptive tracking will be possible not until 6 hours after this
happens.During adaptive tracking, the ACU evaluates for each axis a figure called jitter. The
jitter value describes standard deviation of the measured peak positions with respect to the
positions calculated from the (currently selected) model. The figure is also expressed as a
percentage of the antenna's beamwidth, low values indicate, that the model ideally describes
the antenna's path. High values indicate that's something wrong. The step track results may
be to noisy at low amplitudes or the model does not fit at all. This may be the case if a
satellite gets repositioned in the orbit.A typical threshold value is 20%, this will detect very
early that a model does not fit to describe the satellite's motion. If this value causes false
alarms too often, you may want to raise the threshold to 50%. Setting it to 0 switches the
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