RC3000 Antenna Controller | Chapter 3 | Detailed Operation |
3.2.2.3 Locate
The LOCATE mode performs a calculation of the pointing angle (1.3.4) to a selected satellite based on the RC3000’s estimate of where the antenna is positioned (lat/lon) and oriented (true heading). After the calculation is performed the user may initiate an automatic antenna movement to locate the selected satellite.
When the mode is first entered the following screen appears.
POS: | 38°56N | 94°44W | 180.0 | LOCATE |
SAT:GALAXY 6 | 74.0W |
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| EL: 40.0 |
<1>SELECT NEW SAT | READY TO LOCATE | |||
POS: 38°56N 94°44W 180.0
The POS: field shows the RC3000’s current estimate of antenna position. If no estimate of antenna position is available, the RC3000 will automatically attempt to obtain position information from the navigation sensors (GPS receiver and fluxgate compass) if present.
Mount Position Initialization. In order to calculate a pointing solution, the RC3000 requires knowledge of the mount’s “position”. The three components of mount position are latitude, longitude and true heading.
The current latitude, longitude and true heading where the RC3000 believes the antenna is positioned is displayed on the top line. The position data obviously affects the pointing angle that the RC3000 calculates and is displayed as a crosscheck for the user in case the vehicle has been moved and the RC3000’s position has not been updated. If the lat/lon or heading data is not considered valid by the RC3000, asterisks will be displayed in the appropriate field and the “parameter needed” message will be triggered in the location readiness field.
The RC3000 polls the GPS receiver first to get latitude and longitude information. If no communication with the GPS is received, the error message “GPS OFFLINE” will be displayed. In this case the interface between the RC3000 and the GPS receiver would need to be checked. If the RC3000 is communicating with the GPS receiver but the GPS indicates it has not yet been able to generate a valid lat/lon, then the message “NAV NOT READY” will be displayed. The “NAV NOT READY” situation should not last for more than a minute. If it does, then investigate whether or not the GPS receiver’s view of the sky is blocked by buildings, etc.
If a valid lat/lon is received from the GPS then the lat/lon information will be displayed. Next the RC3000 will flash “MAGVAR” while it calculates the local magnetic deviation as a function of latitude, longitude and time. After calculating the local magnetic variation, the RC3000 will poll the fluxgate compass for magnetic heading information. The magnetic variation will be applied to the magnetic heading to form the estimated true heading of the mount.
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