The satellites are in a near-polar orbit at an altitude of 485 miles (780 km). They fly in formation in six orbital planes, each comprising 11 satellites, evenly spaced around the planet. They circle the earth once every 100 minutes traveling at a rate of 16,832 miles per hour. Each satellite is cross-linked to four other satellites; two satellites in the same orbital plane and two in an adjacent plane.When you place a call or send data from a handset or terminal, that device connects to the Iridium satellite that happens to be overhead. The traffic is routed among Iridium satellites around the globe to reach the satellite above the Earth gateway, which downlinks the call and transfers it to the global public voice network or the Internet so that it reaches the recipient.
Because the Iridium constellation comprises Low Earth Orbit (LEO) satellites, voice delays are typically so minimal they are virtually unnoticeable. Iridium is the only connection available to many parts of the world. Even in urban and suburban environments, Iridium data solutions increasingly provide reliable backup for business communications transmissions.
The ground network is comprised of the System Control Segment and telephony gateways used to connect into the terrestrial telephone system.
- The System Control Segment is the central management component for the Iridium system. It provides global operational support and control services for the satellite constellation, delivers satellite tracking data to the gateways, and performs the termination control function of messaging services.
- Gateways are the terrestrial infrastructure that provides telephony services, messaging, and support to the network operations. The key features of gateways are their support and management of mobile subscribers and the interconnection of the Iridium network to the terrestrial phone system. Gateways also provide network management functions for their own network elements and links.
- System improvements in the satellite and handset have been introduced, providing improved voice quality and subscriber equipment performance. The healthy satellite constellation is demonstrating outstanding longevity.