Which Inmarsat Earth stations could a GMDSS Radio Operator select for routine Inmarsat-C traffic if the vessel is in the Sea of Japan and logged-in to the POR satellite?

The choice of Beijing (PRC), Santa Paula (USA), Auckland (New Zealand), or Sentosa (Singapore) is correct for several reasons.

When a vessel is logged into the Inmarsat-C service via the POR satellite over the Sea of Japan, it can use Earth stations that are optimally located for connectivity. The Earth stations listed in this option provide good coverage and are positioned to facilitate communication for ships in that geographic area.

Generally, for effective satellite communication, Earth stations must be within the range of the satellite’s footprint, which in the case of the POR satellite, is designed to serve the northern Pacific region, including parts of East Asia. The selected stations in this option are ideal because they are in regions that would typically have strong connectivity and support for GMDSS traffic.

The other options likely include Earth stations that are either too far away from the Sea of Japan or not positioned advantageously for reliable communication with the POR satellite. For example, stations located significantly outside of the satellite's coverage area may experience poor signal quality or higher latency, affecting the reliability of routine message traffic critical for maritime safety and operations. Thus, the selected Earth stations in the correct answer maximize the likelihood of successful communications for vessels in that specific region.