NAL A3LA-RM, Руководство пользователя

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AL3A-RM User Guide Version B
Document Number: 451-93156-002B 160 of 172
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PPENDIX
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HE
I
RIDIUM
N
ETWORK
The Iridium satellite network is owned and operated by Iridium Communications Inc. It is
constructed as a constellation of 66 satellites in low-earth orbit (LEO), terrestrial gateways, and
Iridium subscriber units (ISUs). 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.
Figure 18: Iridium Network Major Components
The Iridium network 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