🔍 Key Concepts

• Iridium system architecture – how ships, satellites, and shore stations are interconnected • Difference between ship earth station (SES), satellite, and land earth station (LES) roles • How a call or data message travels from a ship’s terminal to a shore-based phone or network

💭 Think About

• Trace the signal path: when a ship uses Iridium to call a shore telephone, what are the steps from the handset/terminal all the way to the person on land? Where does the LES fit in that chain? • Consider which option sounds like it describes the satellite’s job versus what a ground station on land would actually do. • Look for the choice that best describes a shore-based gateway function, not distress-only and not ship-to-ship-only work.

✅ Before You Answer

• Verify which entity actually connects the satellite network into terrestrial phone/data networks (PSTN, internet). • Check whether the LES’s role is limited only to distress traffic or whether it supports routine communications as well. • Confirm that Iridium does not require a separate Inmarsat LES for ship-ship calls, since Iridium is a different satellite system.