We are all familiar with AIS signals being picked up by shore based stations and the positions being communicated to Marine Traffic. As ship based AIS transmissions are on VHF a digital frequency, range is limited depending on heights of antennas to around 30 Nm. This is fine for collision avoidance purposes but of limited value for open sea tracking. There is a procedure whereby vessels can make a manual position report to Marine Traffic by email but this is tedious on a daily basis and not often utilised.

Large merchant vessels with Class A transponders now have an option of position tracking by satellite which obviously removes the limitation of being within range of a shore station and Marine Traffic is now showing deep sea positions of such vessels.
 Does anyone know:
(a) if this is a subscription service or is it automatically provided by Marine Traffic, IMO or some other body?
(b) is it available for Class B transmitters?
(c) is there a mechanism whereby merchant vessels can re-transmit AIS positions received from other (Class B) vessels by satellite?