Iridium Satellite System

Iridium is the world’s largest commercial satellite constellation providing global mobile satellite communications, including voice and data solutions. This global mobile satellite communications system is owned by the Iridium Communications, Inc. Company based in McLean, VA, United States. The Iridium System is a satellite-based wireless communications network providing a robust suite of data services to virtually any destination anywhere on Earth. Its three principal components are : the satellite network, the ground network and the Iridium subscriber products including ocean platforms fitted with Iridium modems.  

Iridium's 66 low-Earth orbiting (LEO) cross-linked satellites - the world's largest commercial constellation - operate as a fully meshed network that is supported by multiple in-orbit spares. The satellites are placed in an approximate polar orbit at an altitude of 780 km. There are 6 polar planes populated with 11 satellites per orbit constituting the 66 satellite constellation. The near polar orbits of the Iridium constellation provide truly real-time and global coverage from pole-to-pole. The Iridium is designed to operate in the band of 1616 to 1626.5 MHz although the exact frequencies used depend on the local regulating authorities and issued licenses in any particular region. Each satellite projects 48 beams on the surface of earth, which may be viewed as providing coverage cells on the ground similar to terrestrial systems. Each beam is approximately 600 km in diameter. The 66-satellite constellation has the potential to support a total of 3,168 spot beams; however, as the satellite orbits converge at the poles, overlapping beams are shut down. The satellite footprint is ~4,700 km in diameter. Under each footprint, a satellite is power limited to ~1,100 simultaneous circuits.