SATELLITE RELAYS FOR POINT-TO-POINT COMMUNICATION
Satellite relays for point-to-point communication
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Satellite relays for point-to-point communication
Point-to-point communication on the moon by ground-wave propagation
Ground wave propagation over an atmosphereless, lunar surface model is studied, with reference to point-to-point communication systems on the moon
Conference nets of operational voice communications subsystem
Reliability analyses of global point-to-point communications system network for supporting manned and unmanned space missions
Global point-to-point communications system network ground station reliability analyses
Lunar surface transmission loss for Apollo astronaut point-to-point communications
Existing and future developments for worldwide commercial or common carrier point to point communication satellite systems
Determining optimum frequency for point-to-point communication in vicinity of line-of-sight horizon on lunar surface
The results are presented of observations by the University of Texas of the 15.3 GHz experiment associated with the ATS-5 satellite and of related experiments designed to provide information on earth-satellite communication links at 15.3 and 31.65 GHz. The 15.3 GHz transmissions were observed at Austin, Texas over an eighteen month interval primarily during periods of rain. Measurements were also made at Mount Locke, near Fort Davis, Texas but only for a period of two months. Essentially continuous measurements were made at Austin, Texas of the sky temperature at 35 GHz looking in the direction of the ATS-5 satellite over an interval of four months. Point-to-point transmissions over the earth's surface at 15 and 35 GHz and various meteorological parameters were studied as possible means of predicting performance over a satellite-earth path.
The data management system for the Large Space Telescope (LST) must be capable of meeting requirements of 160 million bits per 95 min orbit with a bit error rate of less than 0.00001 for data. The system will be supported by the Tracking and Data Relay Satellite System of the Space Tracking and Data Network. The on-board system includes a general purpose computer that controls the vehicle as a stable observation platform and the array of instruments used for data collection. The ground-based system comprises a Mission Operations Center (MOC), a Science Institute where instrument data is processed, and a communications service for the space and point-to-point data flow. The allocation of hardware and software between on-board and ground-based components to achieve design objectives of maximum flexibility at minimum cost is discussed.
The identification of technologies necessary for development of millimeter spectrum communication satellites was examined from a system point of view. Development of methodology based on the technical requirements of potential services that might be assigned to millimeter wave bands for identifying the viable and appropriate technologies for future NASA millimeter research and development programs, and testing of this methodology with selected user applications and services were the goals of the program. The entire communications network, both ground and space subsystems was studied. Cost, weight, and performance models for the subsystems, conceptual design for point-to-point and broadcast communications satellites, and analytic relationships between subsystem parameters and an overall link performance are discussed along with baseline conceptual systems, sensitivity studies, model adjustment analyses, identification of critical technologies and their risks, and brief research and development program scenarios for the technologies judged to be moderate or extensive risks. Identification of technologies for millimeter satellite communication systems, and assessment of the relative risks of these technologies, was accomplished through subsystem modeling and link optimization for both point-to-point and broadcast applications.
The present study identifies potential satellite services, examines the technology necessary for efficient implementation of these services, and determines minimum service cost versus user network size. The generic satellite services evaluated comprise TV and radio distribution (for retransmission), video teleconferencing (interactive), audio/facsimile teleconferencing (interactive), multiplexed data/voice (point-to-point), and satellite-supported land mobile. Satellite costs are based on extrapolations from ongoing commercial satellite programs. Production methods, new technology, and effect of production quantities on present and future production costs are examined to provide information on earth station equipment cost versus the variable 'buy'. Six different launch vehicles from a Delta 2914 to a dedicated Shuttle and three frequency bands and both broadcast (no eclipse capability) and fixed service satellites are considered to assess the effect of satellite size on cost and performance. It is assumed that the user pays only for his prorata share of the space segment costs.
Telesat-D (Anik-B) is the first of a series of three (Telesat-D, -E, -F) second generation satellites developed for Telesat/Canada. These second generation satellites will replace three first generation HS-333 satellites (Telesat-A, -B, -C) developed for Telesat/CNADA AND LAUNCHED BY Delta 2914 vehicles in 1972, 1973, and 1975 and successfully placed in orbit as Anik-A1, -A2, -A3. The Telesat-D(Anik-B) satellite will be place in sync-transfer orbit by a Delta 3914 launch vehicle, currently scheduled for launch on December 15, 1978. The Telesat-E and -F(Anik-C1 and -C2) missions are scheduled for launch on the Space Shuttle in 1981 to replace the function of the Anik-A2 and -A3 (Telesat-B, and -C) satellites. The Anik-B will provide point-to-point voice, TV, and data communications traffic to Canada's ten provinces.
The objectives of the program were: (1) development of methodology based on the technical requirements of potential services that might be assigned to millimeter wave bands for identifying the viable and appropriate technologies for future NASA millimeter research and development programs, and (2) testing of this methodology with user applications and services. The scope of the program included the entire communications network, both ground and space subsystems. The reports include: (1) cost, weight, and performance models for the subsystems, (2) conceptual design for point-to-point and broadcast communications satellites, (3) analytic relationships between subsystem parameters and an overall link performance, (4) baseline conceptual systems, (5) sensitivity studies, (6) model adjustment analyses, (7) identification of critical technologies and their risks, (8) brief R&D program scenarios for the technologies judged to be moderate or extensive risks.
Identification of technologies for millimeter satellite communication systems, and assessment of the relative risks of these technologies, were accomplished through subsystem modeling and link optimization for both point-to-point and broadcast applications. The results, in terms of annual cost per channel to the user from a commercial view point, are described.
The frequency reuse capability is demonstrated for a Ku-band multiple beam antenna which provides contiguous low sidelobe spot beams for point-to-point communications between any two points within the continental United States (CONUS), or regional coverage beams for direct broadcast systems. A spot beam antenna in the 14/21 GHz band which provides contiguous overlapping beams covering CONUS and two discrete beams covering Hawaii and Alaska were designed, developed, and tested. Two reflector antennas are required for providing contiguous coverage of CONUS. Each is comprised of one offset parabolic reflector, one flat polarization diplexer, and two separate planar array feeds. This antenna system provides contiguous spot beam coverage of CONUS, utilizing 15 beams. Also designed, developed and demonstrated was a shaped contoured beam antenna system which provides contiguous four time zone coverage of CONUS from a single offset parabolic reflector incorporating one flat polarization diplexer and two separate planar array feeds. The beams which illuminate the eastern time zone and the mountain time zone are horizontally polarized, while the beams which illuminate the central time zone and the pacific time zone are vertically polarized. Frequency reuse is achieved by amplitude and polarization isolation.
Additional antenna design options made available by subreflector concept for converting cylindrical waves into spherical waves. Waves used to feed main reflector that shapes radiation pattern into pencil beam for point-to-point communication or into fan beam for aircraft tracking, space surveillance, or directional beacon transmission.