9602-LP User Guide Version A
Document Number: 451-92750-001A
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PPENDIX
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I
RIDIUM
N
ETWORK
The Iridium satellite network is owned and operated by Iridium Communications Inc. It was
constructed as a constellation of 66 satellites in low-earth orbit, terrestrial gateways, and
Iridium Subscriber Units (ISUs). An ISU can either be an Iridium satellite phone or any of
the modems. The satellites are placed in an approximate polar orbit at an altitude of 780
km. There are six (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.
Figure 37: Iridium Network
The Iridium network 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 approximately 4,700 km
in diameter. Under each footprint, a satellite is power limited to approximately 1,100
simultaneous circuits.
