When sailing offshore, the ship relies on a satellite communication system called Inmarsat-C to communicate with the world. Inmarsat stands for INternational MARitime SATellite.
The system makes use of four satellites, each in a geo-stationary orbit around the earth. That means that they orbit at the same speed that the earth spins. Thus, above a certain "geographic" location, the satellites appear "stationary."
Each satellite covers a different region of the world's oceans: the Atlantic Ocean Region - East (AOR-E), the Atlantic Ocean Region - West (AOR-W), the Indian Ocean Region (IOR), and the Pacific Ocean Region (POR). Their "footprint" is the area on earth which can "see" the satellite. Concordia can send and receive to and from these regions.
Aboard Concordia is a special transceiver (transmitter/receiver). Called SEASAT (and built by SEA in Seattle), this device is used specifically to send and receive signals that are received and re-transmitted by the Inmarsat-C satellites.