A vessel loses Inmarsat-B SES operation after a large course change. Which of the following could most likely cause this?

The correct choice revolves around the importance of accurate heading data for the functioning of Inmarsat-B SES (Ship Earth Station) communication systems. Inmarsat-B SES systems rely on the alignment of their antenna with the satellite, which requires precise knowledge of the vessel's heading and movement.

When a vessel makes a large course change, the antenna must adjust its orientation to maintain a solid connection with the satellite. If the system loses gyro follow-up, it means that it cannot track the heading of the vessel accurately, which can lead to a misalignment of the antenna. This misalignment results in the loss of signal or connectivity with the Inmarsat satellite, causing communication interruptions.

Understanding this operation highlights the critical role of the gyro system in maritime satellite communications. If the gyro system malfunctions or cannot follow the vessel's heading change, the antenna will not align correctly with the satellite, leading to the loss of SES operation.