Appendix C: Description Of The Iridium Network; Description Of The Iridium Network - Iridium SHOUT ns General Description Manual

APPENDIX C: DESCRIPTION OF THE IRIDIUM NETWORK

C.1 Description of the Iridium Network
The Iridium satellite network is owned and operated by Iridium Satellite LLC (ISLLC). It
is constructed as a constellation of 66 satellites in low-earth orbit (LEO), terrestrial
gateways and Iridium subscriber units (ISU). An ISU can either be an Iridium satellite phone
or various types of modems. 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 1616.0 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.
NAL Research Corporation (451-01001.B)
Constellation
Satellite
Figure C1. Iridium Network Major Components
Satellite Network
Operation Center
(SNOC)
Gateway
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