Practical Applications of a Space Station (1984) / Chapter Skim
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SATELLITE COMMUNICATIONS
SATELLITE COMMUNICATIONS
Pages 60-71
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MAJOR DOMESTIC SATELLITE COMMUNICATIONS SERVICES Today communications satellites are in wide use for commercial and military purposes. The growth of the domestic satellite (domsat)
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From page 61... ...
This results in multiple reuse of the allocated spectrum. Frequency reuse at C-band is limited, however, because of adjacent beam side lobe interference and geographically skewed traffic distribution in the most developed portions of the country.
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service. Fixed Satellite Service Included in the fixed-service category are point-to-point voice, video, and data services delivered either through commercial trunking networks or private networks, as well as distribution (point-to-multipoint)
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Similar polarization reuse can be achieved on Ky-band satellites, and an additional frequency reuse can be achieved using a spot beam antenna. Current methods should enable the formation of l° to l.5° spot beams (probably aimed toward the east and west coasts of the continental United States)
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However, a comprehensive forecast was presented by the Federal Communications Commission's Regional Administrative Radio Conference Advisory Committee (RARC, l983) in its final report.
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To achieve MSAT system capacities approaching the potential user needs, frequency reuse must be employed. This is possible with spot beams, but because of the low *
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Developments that would assist growth of direct broadcast services are high-power broadcast satellites (in the range of one-half to one million effective radiated watts) , and high-efficiency shaped-beam satellite antennas that confine the broadcast signal to the desired region and permit low-cost receiving earth stations.
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From page 67... ...
; air and ship traffic control and safety services; vehicle emergency alerting and location; disaster warning to individual homes; and multimode land and maritime remote-area service. Personal and Business Paging Service Today mobile radio is used mainly for telephone extension service and dispatching (police, fire)
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An expanded system for vehicles and individuals could use an integrated set of satellites at geosynchronous orbit (for continuous detection) or at low earth orbit (for simplified Doppler positioning)
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that would help people prepare for natural disasters, and by providing postdisaster communications for assessment and rescue control. Multimode Land and Maritime Remote-Area Service Radio is the practical medium in the vast thinly populated areas of the earth's surface for communications related to safety, survival, business, and education.
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From page 70... ...
An unmanned geosynchronous-orbit operational platform could serve as the support platform for varied communications missions. The desired characteristics of orbit, power, attitude control, and thermal control for such a platform are: Orbit -- 0° angle inclination with 24-hour synchronous orbit Power -- 25-kW power level initially with an eventual l00-kW power level Attitude control -- l° to 3° inclination about three axes with finer control by individual payload subsystems Thermal control -- centralized thermal control-heat rejection system sized to approximately 75 percent of the power available If a low-earth-orbit service station is planned, the Panel recommends the following characteristics in relation to orbit, power, attitude control, and fuel storage: Orbit -- altitude consistent with long life and inclination in the 28° to 0° range consistent with requirements for raising and lowering orbits of spacecraft Power -- sufficient to operate station/platform housekeeping services, estimated to be in the l5- to 25-kW range Attitude control -- flexible requirements (few degrees acceptable)
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From page 71... ...
Western Union, Final Project Review at NASA Lewis Research Center, Cleveland, Ohio. Regional Administrative Radio Conference Advisory Committee.
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