Activities of the Office of Telecommunications Management
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Morris, F. W., Jr.↗
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A Practical Statistical Model for Telecommunications Performance Uncertainty
A statistical method, the probability distribution method, is presented which will give the probability of link performance values. The advantages of a design control procedure are preserved and optimum use of the system capabilities is permitted by improving the accuracy and completeness of the system model.
Yuen, J. H.↗
Study plan to identify long term national telecommunications need and priorities applying Delphi techniques (handbook)
A handbook that explains the basic Delphi methodology and discusses modified Delphi techniques is presented. The selection of communications experts to participate in a study, the construction of questionnaires on potential communications developments, and requisite technology is treated. No two modified Delphi studies were the same, which reflects the flexibility and adaptability of the technique. Each study must be specifically tailored to a particular case, and consists of seeking a consensus of opinion among experts about a particular subject and attendant conditions that may prevail in the future.
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117.6 kilobit telemetry from Mercury - A major deep space telecommunication advance
On March 29, 1974, Mariner 10 transmitted 562 clear, sharp pictures of Mercury in real time at 117.6 kilobits per second. The methods by which large area coverage at roughly 1 km resolution was achieved are described. In particular, it is shown how link performance was effectively improved by carefully assessing picture quality and coverage versus bit rate and bit error rate. A number of improvements as compared to the 1971 Mars Orbiter, Mariner 9, are outlined.
Clarke, V. C., Jr.↗
Telecommunications Division fourth harmonic power analyzer
A microprocessor-based instrumentation system was developed to be used in the measurement and analysis of fourth harmonic power generated by the DSN high-power transmitters.
Foster, C.↗
ATS-6 - Technical aspects of the Health/Education Telecommunications Experiment
An overview is given of the HET experiment on ATS-6. The paper is divided into nine parts, including a technical overview, a preliminary evaluation of the HET demonstration, a review of operations at the Denver uplink terminal, a discussion of remote ground terminals, a review of C-band comprehensive terminals and of S-band comprehensive terminals, and parts devoted to general network operations, technical management and effectiveness of the network, and the site equipment operator.
Boor, J. L.↗
Encoding and decoding a telecommunication standard command code
A simple encoder/decoder implementation scheme is described for the (63,56) BCH code which can be used to correct single errors and to detect any even-number of errors. The scheme is feasible for onboard-spacecraft implementation.
Benjauthrit, B.↗
A real time, low cost, data acquisition telecommunication network
The real time, low cost data acquisition communication network described features the use of asynchronous ASCII code transmissions operating at 30 characters per second on the dial-up telephone system. The network features an elaborate, but easily generated error checking system, operating in a line-by-line demand-response mode. The system is readily adaptable for any low speed computer-to-computer data transmissions requiring high reliability in data transmission. The network was developed for the acquisition of prelaunch wind data from the Eastern Test Range at Cape Kennedy.
Schulte, R. R.↗
TDRSS telecommunication system PN code analysis
The pseudonoise (PN) code library for the Tracking and Data Relay Satellite System (TDRSS) Services was defined and described. The code library was chosen to minimize user transponder hardware requirements and optimize system performance. Special precautions were taken to insure sufficient code phase separation to minimize cross-correlation sidelobes, and to avoid the generation of spurious code components which would interfere with system performance.
Gold, R.↗
Deep Space Network to Viking Orbiter telecommunication link effects during 1976 superior conjunction
Planning of the Viking superior conjunction by the Viking Project and the Deep Space Network is reviewed. Spacecraft and ground station activities and configuration during the three month superior conjunction period are presented and observations made are described.
Taylor, F. H. J.↗
Innovative telecommunications for law enforcement
The operation of computer-aided dispatch, mobile digital communications, and automatic vehicle location systems used in law enforcement is discussed, and characteristics of systems used by different agencies are compared. With reference to computer-aided dispatch systems, the data base components, dispatcher work load, extent of usage, and design trends are surveyed. The capabilities, levels of communication, and traffic load of mobile digital communications systems are examined. Different automatic vehicle location systems are distinguished, and two systems are evaluated. Other aspects of the application of innovative technology to operational command, control, and communications systems for law enforcement agencies are described.
Sohn, R. L.↗
State criminal justice telecommunications (STACOM). Volume 1: Executive summary
Techniques for identifying user requirements and network designs for criminal justice networks on a state wide basis are discussed. Topics covered include: methods for determining data required; data collection and survey; data organization procedures, and methods for forecasting network traffic volumes. Developed network design techniques center around a computerized topology program which enables the user to generate least cost network topologies that satisfy network traffic requirements, response time requirements and other specified functional requirements. The developed techniques were applied in Texas and Ohio, and results of these studies are presented.
Fielding, J. E.↗
Deep space telecommunications and the solar cycle: A reappraisal
Observations of density enhancement in the near corona at solar cycle (sunspot) maximum have rather uncritically been interpreted to apply equally well to the extended corona, thus generating concern about the quality of outer planet navigational data at solar cycle maximum. Spacecraft have been deployed almost continuously during the recently completed solar cycle 20, providing two powerful new coronal investigatory data sources: (1) in-situ spacecraft plasma measurements at approximately 1 AU, and (2) plasma effects on monochromatic spacecraft signals at all signal closest approach points. A comprehensive review of these (solar cycle 20) data lead to the somewhat surprising conclusions that for the region of interest of navigational data, the highest levels of charged particle corruption of navigational data can be expected to occur at solar cycle minimum, rather than solar cycle maximum, as previously believed.
Berman, A. L.↗
CCIR papers on telecommunications for deep space research
Mission requirements, equipment factors, and link performance define the frequency bands that are preferred for deep space research using manned and unmanned spacecraft. The preferred bands and selection considerations are presented.
Degroot, N. F.↗
The Qualification of a large electron irradiation facility for telecommunication satellite differential charging simulation
The definition and procurement program is presented for the set up of a test simulating an electron environment on a model of a communication satellite to study the degradation of the thermal insulation materials during electron bombardment.
Serene, B. E. H.↗
Telecommunication service markets through the year 2000 in relation to millimeter wave satellite systems
NASA is currently conducting a series of millimeter wave satellite system and market studies to develop 30/20 GHz satellite system concepts that have commercial potential for the period 1980-2000. The results of the market studies to-date focusing on the overall demand forecasts and distributions by geographic location, distance, and user category are discussed. Tables are presented indicating baseline market forecast voice and video services, data service category, impacted baseline forecast, and traffic/distance distribution voice services. It is concluded that the total market and system activity will be influential in determining the potential role of millimeter wave systems in the overall transmission needs of the nation, and the amount of the total forecasted traffic suitable for millimeter wave systems.
Stevenson, S. M.↗
Simulation program of nonlinearities applied to telecommunication systems
In any satellite communication system, the problems of distorsion created by nonlinear devices or systems must be considered. The subject of this paper is the use of the Fast Fourier Transform (F.F.T.) in the prediction of the intermodulation performance of amplifiers, mixers, filters. A nonlinear memory-less model is chosen to simulate amplitude and phase nonlinearities of the device in the simulation program written in FORTRAN 4. The experimentally observed nonlinearity parameters of a low noise 3.7-4.2 GHz amplifier are related to the gain and phase coefficients of Fourier Service Series. The measured results are compared with those calculated from the simulation in the cases where the input signal is composed of two, three carriers and noise power density.
Thomas, C.↗
Performance evaluation of telecommunication systems using computer simulation
The SYSTID time domain digital simulation technique is reviewed. A technique is illustrated which estimates the signal to noise ratio at a point in the simulation of a communication system. Signals having a lowpass or bandpass spectra are utilized. Simulation results show the technique to be accurate over a wide range of signal to noise ratios. Examples which illustrate application to both analog and digital communication systems are provided.
Tranter, W. H.↗