Azimuth Elevation Calculator
Sat Long
Ship Lat
Ship Long

Automatic Beam Switching

Is ABS ready for the real world? | How ABS works. | OpenAMIP |
Automatic Beam Switching is a really cool concept that allows the antenna to be automatically commanded by the modem to switch to a different satellite, as needed, when it reaches the edge of the footprint or when it is blocked for any reason, without any intervention by the ship personnel.

This allows the patchwork of regional satellite beams around the globe to be stitched together to form a continuous band of almost-global coverage.

It is set up by the Network Operations Center to do this automatically, without any intervention by the teleport or the shipboard personnel.

In a perfect world, this would be a very valuable feature, that allows the system to take care of itself.

If it is set up correctly, and if you have the patience, it will finally settle down on a valid satellite beam and continue working as before. In the real world it can be quite cumbersome while the modem commands the antenna to search satellite beam after satellite beam before finding a working beam.

From my recent experience on a vessel with ABS, if the VSAT link was interrupted for any reason, it would take about 15 minutes for the antenna to settle down on a working beam. This would probably be fine, as the link was finally restored, without me doing anything, but in situations where there could be frequent interruptions due to power or blockage, this could cause unecessarily long outages.
Since it is quite new, I am sure that the process will be refined and later versions of this technology will work as they intended.
The modem has the satellite parameters loaded in the option file for a primary satellite and several alternate satellites. When the modem has lost lock for a specified period (perhaps 5 minutes) , the modem then resets itself, and reboots in one of the alternate modes. During this process, it sends commands via serial or ethernet to the antenna controller to change tracking frequencies, polarizations, and satellite longitude and commands the antenna to target the new satellite.

If it the modem still does not achieve modem lock for some reason (like if the new satellite is blocked by the stack), it resets itself again and goes through the same routine and sets up the antenna to target  the next satellite in the list. This can take several minutes for each satellite, which can cause some delay. The modem does not "remember" which satellites work best, so it needs to go through the routine each time.

All this is fine, but the biggest problem is that there is no quick and easy way to override the ABS and force the satellite to the required beam. One usually needs to log into a command line interface and type in complicated beamselector commands.
The ABS switching was originally developed by iDirect to communicate with SeaTel antennas. In 2006 iDirect developed this into an industry wide open architecture called OpenAMIP that allows iDirect modems, and several other modems, like Hughes, Gilat, Comtech and STM to communicate, not only with SeaTel antennas, but several other stabilised platform manufacturers like Intellian, Jotron, KNS, Navisystems and Mitsubishisi(Furuno).