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11-APR-06 Rev E OMACS3000
35 of 51
System Screens
Figure 26 shows the base satellite as 26498 / GALAXY 4R. If the operator wishes to track a different
satellite, he must select that satellite in the satellite table screen.
The tracking mode parameters that are modifiable from this screen are the scan cycle time, the scan cycle
level, the low signal level, the beacon offset value, and the downlink frequency. The scan cycle time is the
maximum time in minutes between step tracking cycles when either Step Track mode is selected or
SmarTrack® mode is selected and is in the process of building a model using step tracking. For highly
inclined satellites the scan cycle time value may need to be less than 15 minutes. A value of 15 minutes is
sufficient for most satellites. The scan cycle level is the maximum drop allowed in beacon level prior to
mandating a new step track cycle. The low signal level is the beacon level at which step tracking is
terminated because of loss of beacon. The beacon offset is the data value added to the computed beacon
level. The offset is most often used to normalize the beacon level to zero for a peaked beacon. The
downlink frequency is the frequency to which the beacon receiver is tuned to receive the satellite signal. The
downlink frequency and the antenna size are used to compute the antenna beamwidth. The antenna
beamwidth is then used to compute the step size used in peaking. The step size is computed as 15% of the
beamwidth.
Step Track will revert to Standby if there is no beacon level data or if the beacon level falls too low.
SmarTrack® will not be able to build a model if there is no beacon or if the beacon level falls too low. If
SmarTrack® has already built a model, it will continue to use the model when the beacon goes away or the
level falls too low. The SmarTrack® model stays valid for two days.
NORAD Track does not need beacon level data to track the selected satellite. However, it does need a
current NORAD two-line element data set in the satellite table. If no NORAD data has been entered into the
satellite table for the selected satellite or if the data in the satellite table is invalid, the system will revert to
Standby mode. INTELSAT Track needs current INTELSAT data in the satellite table for the selected satellite,
but it does not need valid beacon levels. The INTELSAT data will be validated before the system will switch
to INTELSAT Track mode. If valid INTELSAT data is not available the system will revert to Standby mode.
Tracking Summary
After the base satellite has been selected, the operator may select one of the following track modes:
Step Track
SmarTrack®
NORAD Track
INTELSAT Track
If Step Track mode is to be selected, the operator must place the antenna within 3 dB of the peak position
before activating Step Track. After Step Track has peaked the antenna, it is recommended the signal be
normalized to 0 dB. For example, if the signal indicates +10 dB, an offset of -10 dB should be entered into
the beacon offset parameter. The signal should normalize to 0 dB regardless of the tracking mode selected.
The Scan Cycle time sets the minimum time between Step Track movements. The Scan Cycle Level sets
the amount the signal can fall from the previous peaked level. When this level is reached Step Track
movements will start and the antenna is repeaked. The Low Signal Level set the threshold at which Step
Track is suspended. The Low Signal Level is used to keep the system from tracking on side lobes or on a
corrupted signal.
If SmarTrack® is selected the same procedure is followed as is used for Step Track. When starting
SmarTrack® for the first time the antenna will track the target the first six hours using Step Track. After six
hours the model of the satellite movement is complete and the antenna will follow the model generated by
the SmarTrack® algorithm. The model ready message will appear in the status box. Once a model is valid,
SmarTrack® will initiate a Step Track movement every 30 minutes to add a new point into the model. The
new points continually update and refine the model. After the model is valid and the signal is lost, the
ACS3000 will move the antenna along the calculated path, thus keeping the antenna pointed at the target. A