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  • COMMUNICATIONS AND RADAR  (237)
  • Engineering  (234)
  • 1975-1979  (471)
  • 1977  (471)
  • 1
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    Different approaches of spectral analysis (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Several approaches to the problem of the calculation of spectral power density of a random function from an estimate of the autocorrelation function were studied. A comparative study was presented of these different methods. The principles on which they are based and the hypothesis implied were pointed out. Some indications on the optimization of the length of the estimated correlation function was given. An example of application of the different methods discussed in this paper was included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-75224
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    NASA teleconferencing pilot project - An evaluation of teleconferencing as a substitute for travel (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: NASA conducted a Pilot Project during 1975-1976 to determine the extent to which teleconferencing could replace travel to meetings. The network consisted of approximately 34 teleconference rooms and 50 fast facsimile machines, all interconnected on private lines to a master switchboard in Huntsville, Alabama. In addition, portable conference telephones augmented the voice network and experimental video conferences were attempted. Evaluations showed that the teleconferences saved travel costs approximating 21% of the travel budget at a communications cost of 3% of this budget.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: International Telemetering Conference; Oct 18, 1977 - Oct 20, 1977; Los Angeles, CA
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    NASA TECHNICAL REPORTS
  • 3
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    Analysis of economics of a TV broadcasting satellite for additional nationwide TV programs (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: The influence of a TV broadcasting satellite, transmitting four additional TV networks was analyzed. It is assumed that the cost of the satellite systems will be financed by the cable TV system operators. The additional TV programs increase income by attracting additional subscribers. Two economic models were established: (1) each local network is regarded as an independent economic unit with individual fees (cost price model) and (2) all networks are part of one public cable TV company with uniform fees (uniform price model). Assumptions are made for penetration as a function of subscription rates. Main results of the study are: the installation of a TV broadcasting satellite improves the economics of CTV-networks in both models; the overall coverage achievable by the uniform price model is significantly higher than that achievable by the cost price model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-75128 , BMFT-FB-T-76-5 , BMFT-NT-581
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    NASA TECHNICAL REPORTS
  • 4
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    ATS-6 ascending: Near horizon measurements over water at 30 GHz (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The return of the ATS 6 satellite to a western longitude during the fall of 1976 presented a unique opportunity to perform low angle of elevation measurements at 30 GHz. For this purpose a receiver using a 1.5 m antenna was set up at Port Aransas, Texas, resulting in a propagation path entirely over water. The 30 GHz beacon was monitored daily for at least one hour from 8 September 1976 to 21 September 1976. During the time the elevation angle changed from 1.5 deg to 17.3 deg, the mean attenuation decreased from 20 dB to 2 dB and the standard deviation from over 6 dB to less than .2 dB. The deep fades at angles below 4 deg show significantly sharper nulls than peaks on a log scale. Spectra of the log amplitude fluctuations vary as the (-8/3) power of the spectral frequency in the limit. A flattening is noticeable at the low frequencies. A precipitation event at 8.5 deg elevation produced a 16 dB fade and significantly increased the variance.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159966 , URSI Comm. of Open Symp. on Propagation in Nonionized Media; Apr 28, 1977 - May 06, 1977; LaBaule; France
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    NASA TECHNICAL REPORTS
  • 5
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    Aircraft measurement of radio frequency noise at 121.5 MHz, 243MHz and 406MHz (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An airborne survey measurement of terrestrial radio-frequency noise over U.S. metropolitan areas has been made at 121.5, 243 and 406 MHz with horizontal-polarization monopole antennas. Flights were at 25,000 feet altitude during the period from December 30, 1976 to January 8, 1977. Radio-noise measurements, expressed in equivalent antenna-noise temperature, indicate a steady-background noise temperature of 572,000 K, at 121.5 MHz, during daylight over New York City. This data is helpful in compiling radio-noise temperature maps; in turn useful for designing satellite-aided, emergency-distress search and rescue communication systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Symposium and Technical Exhibition; Jun 28, 1977 - Jun 30, 1977; Montreux; Switzerland
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  • 6
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    The proposed coding standard at GSFC (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: As part of the continuing effort to introduce standardization of spacecraft and ground equipment in satellite systems, NASA's Goddard Space Flight Center and other NASA facilities have supported the development of a set of standards for the use of error control coding in telemetry subsystems. These standards are intended to ensure compatibility between spacecraft and ground encoding equipment, while allowing sufficient flexibility to meet all anticipated mission requirements. The standards which have been developed to date cover the application of block codes in error detection and error correction modes, as well as short and long constraint length convolutional codes decoded via the Viterbi and sequential decoding algorithms, respectively. Included are detailed specifications of the codes, and their implementation. Current effort is directed toward the development of standards covering channels with burst noise characteristics, channels with feedback, and code concatenation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: EASCON-77; Electronics and Aerospace Systems Convention; Sep 26, 1977 - Sep 28, 1977; Arlington, VA
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  • 7
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    Public Service Communication Satellite Program (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The proposed NASA Public Service Communication Satellite Program consists of four different activities designed to fulfill the needs of public service sector. These are: interaction with the users, experimentation with existing satellites, development of a limited capability satellite for the earliest possible launch, and initiation of an R&D program to develop the greatly increased capability that future systems will require. This paper will discuss NASA efforts in each of these areas.
    Keywords: COMMUNICATIONS AND RADAR
    Type: EASCON-77; Electronics and Aerospace Systems Convention; Sep 26, 1977 - Sep 28, 1977; Arlington, VA
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  • 8
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    Communication satellite services for special purpose users (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: 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.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intelcom ''77 Symposium; Oct 09, 1977 - Oct 15, 1977; Atlanta, GA
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    NASA TECHNICAL REPORTS
  • 9
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    Low cost Ku-band earth terminals for voice/data/facsimile (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A Ku-band satellite earth terminal capable of providing two way voice/facsimile teleconferencing, 128 Kbps data, telephone, and high-speed imagery services is proposed. Optimized terminal cost and configuration are presented as a function of FDMA and TDMA approaches to multiple access. The entire terminal from the antenna to microphones, speakers and facsimile equipment is considered. Component cost versus performance has been projected as a function of size of the procurement and predicted hardware innovations and production techniques through 1985. The lowest cost combinations of components has been determined in a computer optimization algorithm. The system requirements including terminal EIRP and G/T, satellite size, power per spacecraft transponder, satellite antenna characteristics, and link propagation outage were selected using a computerized system cost/performance optimization algorithm. System cost and terminal cost and performance requirements are presented as a function of the size of a nationwide U.S. network. Service costs are compared with typical conference travel costs to show the viability of the proposed terminal.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intelcom ''77 Symposium; Oct 09, 1977 - Oct 15, 1977; Atlanta, GA
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  • 10
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    Multiple-access channels without synchronization (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper discusses models for multiple-access communications which take into account the fact that the channel users may not be able to synchronize their transmissions. It is shown that for a broad class of such channels, the capacity region is the same as it would be with user synchronization. Some open problems are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 12, 1977 - Jun 15, 1977; Chicago, IL
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  • 11
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    Carrier synchronization techniques for unbalanced QPSK signals. I (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper uses MAP estimation techniques to obtain carrier reconstruction circuits for unbalanced QPSK signals. In addition, the performance analysis of these circuits is carried out to the extent that a loop design can proceed. Numerical results are presented in order to demonstrate the utility of the theory developed. This signal design will be used in the development of the Tracking and Data Relay Satellite System (TDRSS) and the Navigation Satellite Timing and Ranging Global Positioning System (NAVSTAR GPS).
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 12, 1977 - Jun 15, 1977; Chicago, IL
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  • 12
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    Spectrally efficient modulation (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Spectrally efficient modulation, involving the maximization of the transmitted data rate through a specified bandwidth, may aid in alleviating the problem of spectral congestion in the electromagnetic spectrum. Attention is given to pulse-shaping and nonbinary modulation, and particularly to combined amplitude- and phase-modulation. Theoretical performance limits, such as Shannon's bound, are used to assess the effectiveness of the systems described. Consideration is also allotted to spectrally efficient modulation for terrestrial microwave systems, required to provide 1000 voice channels in the 4- and 6-GHz band.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 12, 1977 - Jun 15, 1977; Chicago, IL
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  • 13
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    System design for the digitally implemented communications experiment /DICE/ (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Full-duplex digital television providing a teleconference capability is to be evaluated in an experimental program utilizing the Communications Technology Satellite. The digitally implemented communications experiment employs a QPSK modulator-demodulator capable of operation over a wide range of bit rates. In addition to simultaneous data transmission (used for digital high-speed facsimiles and remote computer terminals), voice transmission through four-to-one compression will be studied.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Conference on Communications; Jun 12, 1977 - Jun 15, 1977; Chicago, IL
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  • 14
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    Interaction of electromagnetic and acoustic waves in a stochastic atmosphere (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper considers the interaction of electromagnetic and acoustic waves where a Radio Acoustic Sounding System (RASS) is operated in a stochastic environment characterized by turbulence, winds and mean-temperature gradients. It has been shown that for a RASS operating at acoustic frequencies below a few kilohertz propagating under typical atmospheric conditions, turbulence has little effect on the strength of the received radio signal scattered from the pulse at heights up to a few kilometers. This result implies that the received RF signal level (power) is primarily a function of sound intensity which decreases as x exp minus 2 where x is the altitude.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Union Radio Scientifique Internationale Open Symposium; Apr 28, 1977 - May 06, 1977; Loire-Atlantique; France
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    NASA TECHNICAL REPORTS
  • 15
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    Rain depolarization and attenuation measurements at 11.7, 19.04, and 28.56 GHz - A description of the experiment and some preliminary results (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The considered investigation made use of the Communications Technology Satellite (CTS) downlink and the beacons carried by the Comstar satellites. The general behavior of rain attenuation and depolarization is illustrated with the aid of data from a storm which took place on July 15, 1976. The effect of the rain on the copolarized signal is indicated in a graph. Another graph shows the behavior of the cross-polarized signal component. Phase effects are also considered together with statistical curves for attenuation. The considered data from CTS indicate that, at least during summer convective storms, attenuation at 11.7 GHz is much more severe than anticipated. Attenuation may be a more serious impediment to dual polarized satellite links at this frequency than is depolarization.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Union Radio Scientifique Internationale Open Symposium; Apr 28, 1977 - May 06, 1977; Loire-Atlantique; France
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    NASA TECHNICAL REPORTS
  • 16
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    CTS /Hermes/ - United States experiments and operations summary (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The U.S. experiments conducted with the Communications Technology Satellite, a joint Canadian-U.S. venture launched in 1976, are discussed. The 14/12 GHz frequencies employed by the 200-W transmitter on board the satellite provide two-way television and voice communications. Applications of the satellite in the categories of health care, community services and education are considered; experiments have also made use of the special properties of the super-high frequency band (e.g. link characterization and digital communications). Time-sharing of the 14/12 GHz communication between the U.S. and Canada has functioned well.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Symposium on Hermes (Communications Technology Satellite): Its Performance and Applications; Nov 29, 1977 - Dec 01, 1977; Ottawa; Canada
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    NASA TECHNICAL REPORTS
  • 17
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    A digitally implemented communications experiment utilizing the Hermes /CTS/ satellite (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Attention is given to an investigation being conducted by NASA-Lewis and Comsat Laboratories which uses the Hermes (CTS) satellite to explain digital link implementation and the advantages it provides over conventional analog systems. The experiment concentrates on developing several video, audio, and data digital communications techniques.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Symposium on Hermes (Communications Technology Satellite): Its Performance and Applications; Nov 29, 1977 - Dec 01, 1977; Ottawa; Canada
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    NASA TECHNICAL REPORTS
  • 18
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    Utilization of NASA Lewis mobile terminals for the Hermes satellite (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The paper describes the portable earth terminal (PET) and the transportable earth terminal (TET) which enable two-way television and voice communication. Both terminals were developed by NASA and utilize the high power of the Hermes satellite. PET is a bus-type vehicle which has receiving equipment for full duplex color television and which can transmit programs originating in either the on-board PET studio or in nearby buildings. PET has a collapsible 2.4-m diameter parabolic antenna interfacing with a 500-watt 14-GHz wideband TV transmitter and a 12-GHz wideband TV receiver system. TET uses two parabolic reflector antennas, 3 m and 1.2 m in diameter, mounted on a flat trailer towed by a truck. TET can receive and relay color TV signals, and its narrowband transmitter can serve as a return audio link permitting a question-and-answer format. Also described are uplink and downlink performance characteristics, operation procedures, and field demonstrations which enabled personnel at several hospitals to participate in a distant medical conference.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Symposium on Hermes (Communications Technology Satellite): Its Performance and Applications; Nov 29, 1977 - Dec 01, 1977; Ottawa; Canada
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    NASA TECHNICAL REPORTS
  • 19
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    A compendium of millimeter wave propagation studies performed by NASA (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Key millimeter wave propagation experiments and analytical results were summarized. The experiments were performed with the Ats-5, Ats-6 and Comstar satellites, radars, radiometers and rain gage networks. Analytic models were developed for extrapolation of experimental results to frequencies, locations, and communications systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156781
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    NASA TECHNICAL REPORTS
  • 20
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    CTS attenuation and cross-polarization measurements at 11.7 GHz (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The results of data obtained 80 days preceding the solar eclipse shutdown of the CTS 11.7 GHz righthand circularly polarized beacon transmitter are presented. Attenuation and cross polarization isolation were measured. It was determined that depolarization presents a serious limitation to satellite system reliability when frequency reuse by polarization diversity is employed. A 27 db isolation margin would reduce reliability below 99.95%. For the same percentage the required fade margin was below 3 db.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156771
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    NASA TECHNICAL REPORTS
  • 21
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    Design and demonstration of an advanced data collection/position location system (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The final report on a breadboard evaluation and demonstration program is reported concerning the applicability of MSK modulation and chirp-z transformer technology in Advanced Data Collection/Position Location (ADC/PL) systems. The program effort consisted of three phases - design, testing, and evaluation. Section 2 describes the breadboard hardware built during the design phase of the program, Section 3 describes the tests conducted on the breadboard and the results of the tests, and Section 4 presents a brief analysis and summary of the findings of the breadboard tests and develops a sample ADC/PL system which incorporates both MSK modulation and a chirp-z transformer.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156748
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    NASA TECHNICAL REPORTS
  • 22
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    Analysis of synthetic aperture radar imagery (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Some problems faced in applications of radar measurements in hydrology are: (1) adequate calibration of the radar systems and direct digital data will be required in order that repeatable data can be acquired for hydrologic applications; (2) quantitative hydrologic research on a large scale will be prohibitive with aircraft mounted synthetic aperture radar systems due to the system geometry; (3) spacecraft platforms appear to be the best platforms for radar systems when conducting research over watersheds larger than a few square kilometers; (4) experimental radar systems should be designed to avoid use of radomes; and (5) cross polarized X and L band data seem to discriminate between good and poor hydrologic cover better than like polarized data.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156743 , RSC-3359-2
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    NASA TECHNICAL REPORTS
  • 23
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    Electromagnetic plasma wave emissions from the auroral field lines (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The most important types of auroral radio emissions are reviewed, both from a historical perspective as well as considering the latest results. Particular emphasis is placed on four types of electromagnetic emissions which are directly associated with the plasma on the auroral field lines. These emissions are (1) auroral hiss, (2) saucers, (3) ELF noise bands, and (4) auroral kilometric radiation. Ray tracing and radio direction finding measurements indicate that both the auroral hiss and auroral kilometric radiation are generated along the auroral field lines relatively close to the earth, at radial distances from about 2.5 to 5 R sub e. For the auroral hiss the favored mechanism appears to be amplified Cerenkov radiation. For the auroral kilometric radiation several mechanisms have been proposed, usually involving the intermediate generation of electrostatic waves by the precipitating electrons.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155172 , U-OF-IOWA-77-36 , Gen. Sci. Assembly of the Intern. Assoc. of Geomagnetism and Aeronomy; Jan 01, 1977; Seattle
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  • 24
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    Communication system analysis for manned space flight (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: One- and two-dimensional adaptive delta modulator (ADM) algorithms are discussed and compared. Results are shown for bit rates of two bits/pixel, one bit/pixel and 0.5 bits/pixel. Pictures showing the difference between the encoded-decoded pictures and the original pictures are presented. The effect of channel errors on the reconstructed picture is illustrated. A two-dimensional ADM using interframe encoding is also presented. This system operates at the rate of two bits/pixel and produces excellent quality pictures when there is little motion. The effect of large amounts of motion on the reconstructed picture is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151508
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    NASA TECHNICAL REPORTS
  • 25
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    Solid state Ku-band spacecraft transmitters (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A transmitter is considered that consists of GaAs IMPATT and Read diodes operating in a microstrip circuit environment to provide amplification with a minimum of 63 db small signal gain and a minimum compressed gain at 5 W output of 57 db. Reported are Schottky-Read diode design and fabrication, microstrip and circulator optimization, preamplifier development, power amplifier development, dc-to-dc converter design, and integration of the breadboard transmitter modules. A four-stage power amplifier in cascade with a three-stage preamplifier had an overall gain of 56.5 db at 13.5 GHz with a power output of 4.5 W. A single-stage Read amplifier delivered 5.9 W with 4 db gain at 22% efficiency.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152590 , TI-08-77-11
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    NASA TECHNICAL REPORTS
  • 26
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    Final report on technical work accomplished under contract NASw-2953 (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A report is given on the technical work accomplished in the area of plasma physics. The subjects covered are: (1) oblique whistler instabilities, (2) current-limited electron beam injection, (3) three-dimensional ion sound turbulence, (4) theoretical aspects of sounder antenna operation and (5) whistler modes in bow shock structures.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-153294 , TRW-29697-6002-RU-00
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    NASA TECHNICAL REPORTS
  • 27
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    Research in millimeter wave techniques (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The following is investigated; (1) the design of a 183 GHz single ended fundamental mixer to serve as a back up mixer to the subharmonic mixer for airborne applications, (2) attainment of 6 db single sideband conversion loss with the 6 GHz subharmonic mixer model, together with initial tests to determine the feasibility of pumping the mixer at w sub s/4, (3) additional ground based radiometric measurements, and (4) derivation of equations for power transmission of wire grid interferometers, and initial tests to verify these equations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156762 , SATR-6
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    NASA TECHNICAL REPORTS
  • 28
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    A depolarization and attenuation experiment using the CTS satellite (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Rain attenuation and depolarization data collected on the communications technology satellite 11.7 GHz downlink, and changes made in equipment following rain leak damage to the parametric amplifier are discussed. A 15 GHz radar system is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152535 , QTPR-1
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    NASA TECHNICAL REPORTS
  • 29
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    Aircraft measurement of radio frequency noise at 121.5 MHz, 243 MHz and 406 MHz (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An airborne survey measurement of terrestrial radio-frequency noise over U.S. metropolitan areas was carried out at 121.5, 243 and 406 MHz with horizontal-polarization monopole antennas. Flights were at 25,000 feet altitude. Radio-noise measurements, expressed in equivalent antenna-noise temperature, indicate a steady-background noise temperature of 572,000 K, at 121.5 MHz, during daylight over New York City. This data is helpful in compiling radio-noise temperature maps; in turn useful for designing satellite-aided, emergency-distress search and rescue communication systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-71283 , X-952-77-11 , Symp. and Technical Exhibition on Electromagnetic Compatibility; Jun 28, 1977 - Jun 30, 1977; Montreux; Switzerland
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    NASA TECHNICAL REPORTS
  • 30
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    A depolarization and attenuation experiment using the CTS satellite. Volume 2: Data (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experiment for measuring precipitation attenuation and depolarization on the CTS 11.7 GHz downlink is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152482
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    NASA TECHNICAL REPORTS
  • 31
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    Repeater in the sky (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Public Service Communications Satellite (PSCS) program is intended to develop and demonstrate a space system aimed at stimulating future commercial markets in fixed and mobile applications. The services are envisioned for rural areas, regions beyond access to terrestrial systems, or for continuous cross-country applications. The system incorporates a UHF repeater for mobile voice and data experiments; 8 MHz of spectrum is specified for serving 70 channels. This paper describes the PSCS program and discusses some demonstration experiments. A future concept based on large structure multibeam antennas is also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: National Electronics Conference; Oct 10, 1977 - Oct 12, 1977; Chicago, IL
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    Carrier synchronization techniques for unbalanced QPSK signals. II (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper develops a theory for assessing the tracking performance and designing carrier synchronization loops which are to be matched to an unbalanced QPSK signal design. It is assumed that the power split and the I and Q channel data rates are arbitrary. Bit synchronization is assumed to be unavailable for both carrier reconstruction techniques which have been suggested via MAP estimation theory. Numerical results are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: NTC ''77; National Telecommunications Conference; Dec 05, 1977 - Dec 07, 1977; Los Angeles, CA
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    Bit timing with pulse distortion and intersymbol interference (1977)
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    Publication Date: 2019-07-13
    Description: Pulse distortion and intersymbol interference due to insufficient filtering in PCM and PSK channels cause performance degradation in terms of both bit error probabilities and timing errors. This paper reports the results of a study analyzing these effects on bit timing subsystems. Consideration is given to both the filter-rectifier and transition tracking type of timing subsystem. Although both these systems perform similarly in high SNR and ideal pulse models, pulse distortion and intersymbol affects each differently. The primary effects in both systems is to cause the presence of an irreducible mean squared timing error due to the intersymbol which limits the ultimate performance. Design procedures to minimize the anomalies of both systems are presented, and indicate modifications of the standard timing subsystems. It is found that specific design directions depend on whether the intersymbol or the receiver noise tends to dominate.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: NTC ''77; National Telecommunications Conference; Dec 05, 1977 - Dec 07, 1977; Los Angeles, CA
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    Non-parametric PCM to ADM conversion (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An all-digital technique to convert pulse code modulated (PCM) signals into adaptive delta modulation (ADM) format is presented. The converter developed is shown to be independent of the statistical parameters of the encoded signal and can be constructed with only standard digital hardware. The structure of the converter is simple enough to be fabricated on a large scale integrated circuit where the advantages of reliability and cost can be optimized. A concise evaluation of this PCM to ADM translation technique is presented and several converters are simulated on a digital computer. A family of performance curves is given which displays the signal-to-noise ratio for sinusoidal test signals subjected to the conversion process, as a function of input signal power for several ratios of ADM rate to Nyquist rate.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: NTC ''77; National Telecommunications Conference; Dec 05, 1977 - Dec 07, 1977; Los Angeles, CA
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    Minimax decoding of cyclic block codes (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A minimax decoding algorithm utilizing soft bit detection of an (n,k) cyclic block code is described which will permit the correction of up to n-k bit errors interspersed at random locations throughout the block. The decoding solution consists of: (1) identifying the ordered soft bit set and, (2) finding the minimum order solution to the resulting syndrome equations where the nonzero error vector components are constrained to be a subset of the soft bit set. An efficient implementation of the decoding operation is described. In essence, this algorithm focuses the correction capability of the code on those bit positions which have the lowest a posteriori probabilities of correct detection.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: NTC ''77; National Telecommunications Conference; Dec 05, 1977 - Dec 07, 1977; Los Angeles, CA
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    On signal design by the R/0/ criterion for non-white Gaussian noise channels (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The use of the cut-off rate criterion for modulation system design is investigated for channels with non-white Gaussian noise. A signal space representation of the waveform channel is developed, and the cut-off rate for vector channels with additive non-white Gaussian noise and unquantized demodulation is derived. When the signal input to the channel is a continuous random vector, maximization of the cut-off rate with constrained average signal energy leads to a water-filling interpretation of optimal energy distribution in signal space. The necessary condition for a finite signal set to maximize the cut-off rate with constrained energy and an equally likely probability assignment of signal vectors is presented, and an algorithm is outlined for numerically computing the optimum signal set. As an example, the rectangular signal set which has the water-filling average energy distribution and the optimum rectangular set are compared.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: NTC ''77; National Telecommunications Conference; Dec 05, 1977 - Dec 07, 1977; Los Angeles, CA
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    Comparison of convolutional and block code performance on the Rician channel (1977)
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    Publication Date: 2019-07-13
    Description: The paper is concerned with the relative performance of short constraint length convolutional codes vis-a-vis block codes when used in conjunction with either BPSK or DPSK modulation on the classical Rician fading channel. A variety of soft-decision decoding algorithms is considered for block codes while the Viterbi algorithm is used exclusively for decoding convolutional codes. Results indicate a substantial performance/complexity advantage in favor of short constraint length convolutional codes and Viterbi decoding which increases with fading severity. The work reported here extends the well-known performance advantage of convolutional codes on the AWGN channel to representative fading channels.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: NTC ''77; National Telecommunications Conference; Dec 05, 1977 - Dec 07, 1977; Los Angeles, CA
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    Measured results of polarization crosstalk cancellation using LMS control (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper discusses the use of wideband decoupling networks for the cancellation of polarization crosstalk in dual-polarized communication links. Measured cancellation performance for an all-electronic IF network and an RF electro-mechanical waveguide network are presented. Each of these networks utilizes LMS-type adaptive control techniques to adjust the cancellation network.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: NTC ''77; National Telecommunications Conference; Dec 05, 1977 - Dec 07, 1977; Los Angeles, CA
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  • 39
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    Antenna bias rigging for performance objective (1977)
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    Publication Date: 2019-07-13
    Description: An optimum bias rigging for a paraboloidal antenna can be used to minimize the expected average mean-square half-pathlength surface deviations. Statistics of deep space planetary missions are employed to develop weighting factors for antenna elevation angles during these missions. A procedure is shown to compute the optimum rigging angle from these weights.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Mechanical Engineering in Radar Symposium; Nov 08, 1977 - Nov 10, 1977; Arlington, VA
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  • 40
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    Evaluating computed distortions of parabolic reflectors (1977)
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    Publication Date: 2019-07-13
    Description: Distortion outputs from structural analysis of a 64-m paraboloidal reflector are analyzed by two computer programs for their radio-frequency performance characteristics. The computed and field measured values are compared.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Mechanical Engineering in Radar Symposium; Nov 08, 1977 - Nov 10, 1977; Arlington, VA
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  • 41
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    Approximations to microwave attenuation in precipitation (1977)
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    Publication Date: 2019-07-13
    Description: A three-term approximation and a discrete drop-size distribution have been used to obtain an analytical expression for the microwave attenuation coefficient for precipitation. Results compared to an exact calculation using the same drop size distribution showed a relative difference of 50% or less over a broad range of rainrates (5-150 mm/hr) and wavelengths (2-5 cm). Since the use of a discrete drop-size distribution is computationally complex, the exponential size distribution formulated by Marshall and Palmer (1948) was studied. This distribution resulted in an overprediction of the attenuation coefficient of as much as 100% at a 2 cm wavelength and a 150 mm/hr rainrate, although the prediction was much closer at lower rainrates and different wavelengths.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Conference on Radar Meteorology; Oct 26, 1976 - Oct 29, 1976; Seattle, WA
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  • 42
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    K-band attenuation by rain at constant reflectivity (1977)
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    Publication Date: 2019-07-13
    Description: The paper considers a radar method of determining rain intensity which uses a dual wavelength system to measure both reflectivity Z and attenuation A and solving for the constants in an assumed exponential drop size distribution. Calculations are confined to the K-band, relations between A and the rain intensity R being determined for different values of Z for wavelengths of 0.86 and 1.24 cm. It is shown that measurements of reflectivity and attenuation by a dual wavelength radar can provide separate derivations of rain intensity. Available data on errors in an A-R relation indicate that the derivation from the attenuation measurement will be no better than from the Z-R relation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Conference on Radar Meteorology; Oct 26, 1976 - Oct 29, 1976; Seattle, WA
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    A digitally implemented communications experiment utilizing the Hermes (CTS) satellite (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The Hermes (CTS) experiment program made possible a significant effort directed toward new developments which will reduce the costs associated with the distribution of satellite services. Advanced satellite transponder technology and small inexpensive earth terminals were demonstrated as part of the Hermes program. Another system element that holds promise for reduced transmission cost is associated with the communication link implementation. An experiment is described which uses CTS to demonstrate digital link implementation and its advantages over conventional analog systems. A Digitally Implemented Communications experiment which demonstrates the flexibility and efficiency of digital transmission of television video and audio, telephone voice and high-bit-rate data is also described. Presentation of the experiment concept which concentrates on the evaluation of full-duplex digital television in the teleconferencing environment is followed by a description of unique equipment that was developed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-73827 , Symp. on Hermes (Comm. Technol. Satellite) its Performance and Appl.; Nov 29, 1977 - Dec 01, 1977; Ottawa, Ontario; Canada
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    New lidar concept for measuring the slant range transmission in aircraft landing approaches (1977)
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    Publication Date: 2019-07-13
    Description: The single-scatter, single-wavelength, scalar-backscatter lidar equation is investigated to determine the transmission along a line from a point on the ground to what is known as the decision point on the 3 degree aircraft glide slope. It may be applied in aircraft landing approaches for measuring the slant range transmission.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Laser Radar Conference on Laser Atmospheric Studies; Jun 06, 1977 - Jun 09, 1977; Philadelphia, PA; US
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  • 45
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    A Technique for Measuring Rotocraft Dynamic Stability in the 40 by 80 Foot Wind Tunnel (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: An on-line technique is described for the measurement of tilt rotor aircraft dynamic stability in the Ames 40- by 80-Foot Wind Tunnel. The technique is based on advanced system identification methodology and uses the instrumental variables approach. It is particulary applicable to real time estimation problems with limited amounts of noise-contaminated data. Several simulations are used to evaluate the algorithm. Estimated natural frequencies and damping ratios are compared with simulation values. The algorithm is also applied to wind tunnel data in an off-line mode. The results are used to develop preliminary guidelines for effective use of the algorithm.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151955
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    Meteorological radar facility (MRF) slot conductance investigations (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A preliminary meteorological radar facility (MRF) array design was completed in support of the slot conductance measurement program. Three different slot measurement techniques were evaluated. The selection of the probe comparison measurement technique was selected as the principal experimental method with the impedance measurement technique chosen to measure a few higher conductance slots to be used as reference slots. The impedance of 43 slots in 0.9 x 0.4 inch standard waveguide and of 40 slots in 0.835 x 0.4 inch waveguide was measured. Also, impedance measurements were made of a few slots using image planes to simulate mutual coupling effects. The measured and theoretical conductance, susceptance, and radiation phase data are presented in graphic form as a function of slot displacement for constant slot length, and of slot length for constant slot displacement. It is concluded that the proposed MRF array design approach is a feasible one.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152465 , P77-20 , HAC-REF-D7036
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    Proceedings: Voice Technology for Interactive Real-Time Command/Control Systems Application (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Speech understanding among researchers and managers, current developments in voice technology, and an exchange of information concerning government voice technology efforts are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152283 , NAS 1.26:152283 , Voice Technology for Interactive Real-Time Command/Control Systems Application; Dec 06, 1977 - Dec 08, 1977; Moffett Field, CA; United States
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    A forecast of broadcast satellite communications (1977)
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    Publication Date: 2019-07-13
    Description: This paper presents forecasts of likely changes in broadcast satellite technology, the technology of ground terminals, and the technology of terrestrial communications competitive with satellites. The impacts of these changes in technology are then assessed, using a cross-impact model of U.S. domestic telecommunications, to determine the consequences of various possible changes in communications satellite technology. These consequences are discussed in terms of various possible services, for households, businesses, and specialized customers, which might become economically viable as a result of improvements in satellite technology.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NAECON ''77: National Aerospace and Electronics Conference; May 17, 1977 - May 19, 1977; Dayton, OH
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    Experiments in data collection technology using satellites (1977)
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    Publication Date: 2019-07-13
    Description: A variety of techniques potentially useful to data collection have been tested. An automatic data collection platform with a minicomputer collects and preprocesses data, then sends desired information when interrogated through a communication satellite. Position surveillance by tone-code ranging through communication satellites is automatic, real time and accurate. Emergency medical data transmissions from ambulances to hospitals can be extended to rural and remote areas by direct satellite links. A small platform can send emergency-related data through a satellite while the satellite is routinely relaying powerful communication signals. A low orbit satellite provides means to locate existing emergency locator beacons.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 77-1563 , Conference on Satellite applications to marine technology; Nov 15, 1977 - Nov 17, 1977; New Orleans, LA
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    Effect of interference on delta modulator encoded video signals (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-154523
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    Utilization of NASA Lewis mobile terminals for the Hermes satellite (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The high power of the Hermes satellite enables two-way television and voice communication with small ground terminals. The Portable Earth Terminal (PET) and the Transportable Earth Terminal (TET) were developed and built by NASA-Lewis to provide communications capability to short-term users. The NASA-Lewis mobile terminals are described in terms of vehicles and onboard equipment, as well as operation aspects, including use in the field. The section on demonstrations divides the uses into categories of medicine, education, technology and government. Applications of special interest within each category are briefly described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-73859 , E-9448 , Symp. of Hermes, Commun. Technol. Satellite: Its Performance and Appl.; Nov 29, 1977 - Dec 01, 1977; Ottawa
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    Performance of the 12GHz, 200 watt transmitter experiment package for the Hermes satellite (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Performance characteristics from on-orbit tests of the Transmitter Experiment Package (TEP) for the Hermes Satellite are presented. The TEP consists of a Power Processing System (PPS), an Output Stage Tube (OST) and a Variable Conductance Heat Pipe System (VCHPS), all of which are described. The OST is a coupled-cavity Traveling Wave Tube (TWT) with a Multistage Depressed Collector (MDC) and a stepped velocity-tapered slow wave structure for efficiency enhancement. It has an RF output power of 233 watts and overall efficiency of 50.75 percent at a center band frequency of 12.080 GHz. The PPS provides the required operating voltages, regulation, control and protection for the OST. The VCHPS consists of a fin radiator and three dual-artery stainless steel heat pipes using methanol and a mixture of inert gases. Test results presented include efficiencies, RF output power and body current. A discussion of thermal anomalies which occurred is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-73804 , E-9385 , Symp. on Hermes (Communications Technol. Satellite) its Performance and Applications; Nov 29, 1977 - Dec 01, 1977; Ottawa
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    Coherent optical processing of synthetic aperture radar data (1977)
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    Publication Date: 2019-07-13
    Description: Consideration is given to the data processing algorithm used in synthetic aperture radar (SAR) systems. Examples are presented of radar imagery obtained with the ERIM X-band SAR system and processed with a precision optical processor. An optical recording of the data is the input to the coherent optical processing channel. The encoding technique, spatial format, and quality of the stored data are discussed. Several optical processor configurations are outlined, noting particularly the tilted-plane system. A scanning photodetector serves to convert the optical processor output image data into an electronic signal stream. Solid-state two-dimensional photodetector arrays may provide this function at increased speeds and with greater accuracy.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Effective utilization of optics in radar systems; Symposium; Sep 27, 1977 - Sep 29, 1977; Huntsville, AL
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    Study of large adaptive arrays for space technology applications (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The research in large adaptive antenna arrays for space technology applications is reported. Specifically two tasks were considered. The first was a system design study for accurate determination of the positions and the frequencies of sources radiating from the earth's surface that could be used for the rapid location of people or vehicles in distress. This system design study led to a nonrigid array about 8 km in size with means for locating the array element positions, receiving signals from the earth and determining the source locations and frequencies of the transmitting sources. It is concluded that this system design is feasible, and satisfies the desired objectives. The second task was an experiment to determine the largest earthbound array which could simulate a spaceborne experiment. It was determined that an 800 ft array would perform indistinguishably in both locations and it is estimated that one several times larger also would serve satisfactorily. In addition the power density spectrum of the phase difference fluctuations across a large array was measured. It was found that the spectrum falls off approximately as f to the minus 5/2 power.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152593 , VFRC-112
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    Contributions of speech science to the technology of man-machine voice interactions (1977)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Research in speech understanding was reviewed. Plans which include prosodics research, phonological rules for speech understanding systems, and continued interdisciplinary phonetics research are discussed. Improved acoustic phonetic analysis capabilities in speech recognizers are suggested.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 25-44
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    RF environment survey of Space Shuttle related EEE frequency bands (1977)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Radio frequency assignments within the continental United States in frequency bands between 121 MHz abd 65 GHz were surveyed and analyzed in order to determine current utilization of anticipated frequency bands for the shuttle borne electromagnetic environment experiment. Data from both government and nongovernment files were used. Results are presented in both narrative form and in histograms which show the total number of unclassified assignments versus frequency and total assigned power versus frequency.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-160081 , NSL-21-136
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    Clutter free synthetic aperture radar correlator (1977)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A synthetic aperture radar correlation system including a moving diffuser located at the image plane of a radar processor is described. The output of the moving diffuser is supplied to a lens whose impulse response is at least as wide as that of the overall processing system. A significant reduction in clutter results is given.
    Keywords: COMMUNICATIONS AND RADAR
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    Concatenated coding systems employing a unit-memory convolutional code and a byte-oriented decoding algorithm (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Concatenated coding systems utilizing a convolutional code as the inner code and a Reed-Solomon code as the outer code are considered. In order to obtain very reliable communications over a very noisy channel with relatively modest coding complexity, it is proposed to concatenate a byte-oriented unit-memory convolutional code with an RS outer code whose symbol size is one byte. It is further proposed to utilize a real-time minimal-byte-error probability decoding algorithm, together with feedback from the outer decoder, in the decoder for the inner convolutional code. The performance of the proposed concatenated coding system is studied, and the improvement over conventional concatenated systems due to each additional feature is isolated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Oct. 197
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    Prediction of attenuation of the 28 GHz COMSTAR beacon signal using radar and measured rain drop spectra (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Disdrometer measurements and radar reflectivity measurements were injected into a computer program to estimate the path attenuation of the signal. Predicted attenuations when compared with the directly measured ones showed generally good correlation on a case by case basis and very good agreement statistically. The utility of using radar in conjunction with disdrometer measurements for predicting fade events and long term fade distributions associated with earth-satellite telecommunications is demonstrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156810 , APL/JHU-S1R78U-009
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    Absolute flux density calibrations of radio sources: 2.3 GHz (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A detailed description of a NASA/JPL Deep Space Network program to improve S-band gain calibrations of large aperture antennas is reported. The program is considered unique in at least three ways; first, absolute gain calibrations of high quality suppressed-sidelobe dual mode horns first provide a high accuracy foundation to the foundation to the program. Second, a very careful transfer calibration technique using an artificial far-field coherent-wave source was used to accurately obtain the gain of one large (26 m) aperture. Third, using the calibrated large aperture directly, the absolute flux density of five selected galactic and extragalactic natural radio sources was determined with an absolute accuracy better than 2 percent, now quoted at the familiar 1 sigma confidence level. The follow-on considerations to apply these results to an operational network of ground antennas are discussed. It is concluded that absolute gain accuracies within + or - 0.30 to 0.40 db are possible, depending primarily on the repeatability (scatter) in the field data from Deep Space Network user stations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156132 , JPL-TM-33-806
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    Survey: Automated Field Operations and Services (AFOS) (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The National Weather Service (NWS) is currently implementing a program for improving operations through automation of routine functions, improved communications capability, and improved management and presentation of data. The program, designated as Automation of Field Operations and Services (AFOS), uses high-speed data circuits, minicomputers, and dynamic display devices to rapidly collect, disseminate, and present data to forecasters and users on both a broadcast and a request basis. The initial system will be configured to serve facilities within the continental United States, Alaska, Hawaii, and Puerto Rico, with eventual expansion to provide international capability. This report discusses AFOS users, functions, and network and site configurations. The sections discuss current and future capability and workload in terms of the 10 data systems elements designated by NASA.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-150548 , SD77-MSFC-2150
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    Hardware simulation of shuttle Ku-band antenna acquisition, volume 5 (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: For abstract, see N78-17252.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151614 , TR-7810-0675-VOL-5
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    Experiments for improved positioning by means of integrated Doppler satellite observations and the NNSS broadcast ephemeris (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: An effort to improve station position recovery using broadcast ephemeris in Doppler data reduction was studied. A comparison of precise and broadcast ephemerides, treating the former as the standard, yielded information about the state disturbance that can be associated with the broadcast ephemeris. Statistical information about the state disturbance was used with current observational data for improved position recovery. The rank deficiency problem encountered in the short arc geodetic adjustment procedure was analysed and it was deduced that the fundamental rank deficiency is six, scale information being derivable from the wavelength of transmission. Coordinate differences between stations coobserving a pass are estimable. The uncertainty of the broadcast ephemeris, now in the WGS72 system, was assessed. It was conservatively estimated that its positional uncertainty may vary between 19 to 26 m in-track, 15 to 20 m cross-track and 9 to 10 m in radial directions depending on the incidence of the epoch of observations in the interinjection period.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155735 , REPT-258
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    TELEC laser experiment (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: An experimental thermoelectronic laser energy converter (TELEC) was constructed and tested with a 40 kW combustion laser operating at a wave length of 10.6 microns. The objective of the test was to demonstrate the feasibility of the TELEC concept for converting a laser beam into electric power. The TELEC System is intended as the receiver for a laser power transmission system in space.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152077
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    Ku-band antenna acquisition and tracking performance study, volume 4 (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results pertaining to the tradeoff analysis and performance of the Ku-band shuttle antenna pointing and signal acquisition system are presented. The square, hexagonal and spiral antenna trajectories were investigated assuming the TDRS postulated uncertainty region and a flexible statistical model for the location of the TDRS within the uncertainty volume. The scanning trajectories, shuttle/TDRS signal parameters and dynamics, and three signal acquisition algorithms were integrated into a hardware simulation. The hardware simulation is quite flexible in that it allows for the evaluation of signal acquisition performance for an arbitrary (programmable) antenna pattern, a large range of C/N sub O's, various TDRS/shuttle a priori uncertainty distributions, and three distinct signal search algorithms.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151613 , TR-7810-0675-VOL-4
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    State criminal justice telecommunications (STACOM). Volume 3: Requirements analysis and design of Texas criminal Justice Telecommunications Network (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: For abstract, see N78-16218.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155556 , JPL-PUB-77-53-VOL-3
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    State criminal justice telecommunications (STACOM). Volume 4: Network design software user's guide (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A user's guide to the network design program is presented. The program is written in FORTRAN V and implemented on a UNIVAC 1108 computer under the EXEC-8 operating system which enables the user to construct least-cost network topologies for criminal justice digital telecommunications networks. A complete description of program features, inputs, processing logic, and outputs is presented, and a sample run and a program listing are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155555 , JPL-PUB-77-53-VOL-4
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    State criminal justice telecommunications (STACOM). Volume 2: Requirements analysis and design of Ohio Criminal Justice Telecommunications Network (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: For abstract, see N78-16218.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155557 , JPL-PUB-77-53-VOL-2
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    US Search and Rescue Mission Control Center functions (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A satellite aided Search and Rescue (SAR) Mission concept consisting of a local coverage bent pipe system, and a global coverage system is described. The SAR instrument is to consist of a Canadian repeater and a French processor for which Canada and France, respectively are to evaluate health and trends. Performance evaluations of each system were provided. The United States and Canada will each have a Search and Rescue Mission Control Center (MCC) and their functions were also examined. A summary of the interface requirements necessary to perform each function was included as well as the information requirements between the USMCC and each of its interfaces. Physical requirements such as location, manning etc. of the USMCC were discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155572
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  • 70
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    State criminal justice telecommunications (STACOM). Volume 1: Executive summary (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: 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.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155558 , JPL-PUB-77-53-VOL-1
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    Radar image processing module development program, phase 3 (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The feasibility of using charge coupled devices in an IPM for processing synthetic aperture radar signals onboard the NASA Convair 990 (CV990) aircraft was demonstrated. Radar data onboard the aircraft was recorded and processed using a CCD sampler and digital tape recorder. A description of equipment and testing was provided. The derivation of the digital presum filter was documented. Photographs of the sampler/tape recorder, real time display and circuit boards in the IPM were also included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155579
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  • 72
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    Volumetric pattern analysis of airborne antennas (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: By blending together the roll and elevation plane high frequency solutions, a very efficient technique was developed for the volumetric pattern analysis of antennas mounted on the fuselage of a generalized aircraft. The fuselage is simulated by an infinitely long, perfectly conducting, elliptic cylinder in cross-section and a composite elliptic cylinder in profile. The wings, nose section, stabilizers, and landing gear doors may be modeled by finite flat or bent plates. Good agreement with accurate scale model measurements was obtained for a variety of airborne antenna problems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-78327 , ESL-78-2902 , FR-2902-27
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    Ultra stable frequency distribution system (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A system is presented for synchronizing a signal at a remotely located slave station with the phase and frequency of a signal generated at a master station. The signal transmitted at the master station and received by the slave station provides compensation for the phase shift caused by the transmission path delays between the master and slave station. The slave station transmits a signal to the master station at a frequency that is different from the frequency of the signal being transmitted by the master station. The signal transmitted by the slave station is received by the master station while the master station transmitter is off. The signal transmitted by the master station is received by the slave station while the slave station transmitter is off.
    Keywords: COMMUNICATIONS AND RADAR
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    Shuttle Experimental Radar for Geological Exploration (SERGE); antenna and integration concept definition study (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The baseline configuration defined has the SERGE antenna panel array mounted on the OFT-2 pallet sufficiently high in the bay that negligible amounts of radiation from the beam are reflected from orbiter surfaces into the shuttle payload bay. The array is symmetrically mounted to the pallet along the array long dimension with the pallet at the center. It utilizes a graphite epoxy trusswork support structure. The antenna panels are of SEASAT engineering model design and construction. The antenna array has 7 panels and a 7-way naturally tapered coax corporate feed system. The performance of the system is predicted to exceed 33 db gain, have -15 db sidelobes in the E-plane and even lower in the H-plane, and have and E-plane beamwidth less than 2.2 deg, all within performance specification. The primary support structure is predicted to exceed the specified greater than 25 hertz fundamental frequency, although individual panels will have hertz fundamental frequency.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151581 , F77-23
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    Unipolar pulse and bipolar noise testing of wideband signal noise conditioner (MC476-0132-0034) (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Information is presented on performance characteristics of the shuttle orbiter wideband signal conditioner when subjected to special types of input signals. Design analysis of the signal flow path through the signal conditioning amplifier was performed followed by acutal testing of the amplifier with various signal inputs. Results indicate that the signal conditioner should perform acceptably if the shuttle orbiter flight vibration signal levels are in accord with preflight predictions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151569 , LEC-10628
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    Study to investigate and evaluate means of optimizing the Ku-band combined radar/communication functions for the space shuttle (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The Ku band radar system on the shuttle orbiter operates in both a search and a tracking mode, and its transmitter and antennas share time with the communication mode in the integrated system. The power allocation properties and the Costa subloop subcarrier tracking performance associated with the baseline digital phase shift implementation of the three channel orbiter Ku band modulator are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151562 , R7710-5
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  • 77
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    Sharing the 620-790 MHz band allocated to terrestrial television with an audio-bandwidth social service satellite system (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A study was carried out to identify the optimum uplink and downlink frequencies for audio-bandwidth channels for use by a satellite system distributing social services. The study considered functional-user-need models for five types of social services and identified a general baseline system that is appropriate for most of them. Technical aspects and costs of this system and of the frequency bands that it might use were reviewed, leading to the identification of the 620-790 MHz band as a perferred candidate for both uplink and downlink transmissions for nonmobile applications. The study also led to some ideas as to how to configure the satellite system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155268 , JPL-PUB-77-71
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    A study of worldwide communications markets: The relationship between federally sponsored research and development and competitiveness of US industry in this market (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Many factors have been reviewed in an attempt to seek criteria for the establishment of regions or nations as potential customers for space communication systems. These include economic measures, demographic distributions, topographic variations, physical size, national dispersion, telephones available, investment credit viability, and the general level of technology within the population. A major consideration is the fact that essentially all nations are subject to significant financial constraints. Consequently, some form of national investment priorities becomes necessary, and these priorities are generally perceived differently according to the factors mentioned above and also according to the personalities and interests of each nation's decision makers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-155324 , REPT-77-263-3
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    An approximate analysis of delay for fixed and variable length packets in an unslotted ALOHA channel (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: In this paper we compute the mean delay for an unslotted ALOHA random access channel for both fixed and variable length packets. The analysis is based on the concept of a user cycle and obtains steady state results. When the channel is 'stable', the results seem quite accurate. The input parameters to the model are the number of users, the mean think time, and mean retransmission time. The model yields total traffic, throughput and delay but only the latter is emphasized here. Because of the steady state nature of the analysis, no information is obtained on stability. The results are verified by simulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; July 197
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    Calculations of antenna temperature, horizontal path attenuation, and zenith attenuation due to water vapor in the frequency band 150-700 GHz (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS AND RADAR
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    Propagation along azimuthally magnetized ferrite-loaded circular waveguides (1977)
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    Publication Date: 2019-06-27
    Description: The paper describes the modal dispersion characteristics of electromagnetic waves traveling along the azimuthally magnetized ferrite-loaded coaxial transmission line and the ferrite-loaded wire. The modal dispersion curves are used to determine the pass and stop bands of normal propagation. Boundary-value problems were solved with Bolle-Heller functions. The dispersion characteristics of transverse electric modes are presented as plots of the normalized propagation constant vs the normalized frequency.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Journal of Applied Physics; 48; June 197
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  • 82
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    Mathematical models for the reflection coefficients of lossy dielectric half-spaces with application to transient responses of chirped pulses (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Reflection coefficients are found at normal incidence for a large class of homogeneous lossy half-spaces with a one-dimensionally inhomogeneous or stratified lossy layer on top. Solutions are in terms of Hankel functions of complex argument to decrease cancellation error at high frequencies. One special case is that of layers on a homogeneous half-space where the dielectric constant in each layer may vary in a quite general manner. A Wronskian is used to insure the critical computations are correct. The reflection of chirped pulses is considered. Solutions are obtained by applying the fast Fourier transform. It is found that for a typical relatively long normalized 'long' pulse the power reflected as a function of time is essentially the power reflection coefficient for the frequencies swept out, whereas for a relatively short 'long' pulse, with the same relative change in frequency and the same number of oscillations there is only the uniform attenuation by the power reflection coefficient of the center frequency. By a 'long' pulse we mean a pulse whose spatial length is long compared to the thickness of the reflecting layer.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; July 197
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  • 83
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    Low-cost high-performance VLF receiver front-end (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A VLF receiver front end has been designed using standard linear IC's. The basic methods have been evaluated extensively on the omega 10.2-kHz channel but are readily adaptable to any other VLF frequency in the 10.2-20 kHz region. Applications for the modules exist in position location, time-frequency measurements, and signal propagation. The set provides control gates, zero-crossing signals, and analog outputs to interface with any type of digital logic, microprocessor, or analog signal processor.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Instrumentation and Measurement; IM-26; Mar. 197
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    Communications Link Characterization Experiment (CLCE) (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Results of the data which were acquired, reduced, and analyzed from the Communications Link Characterization Experiment (CLCE) while utilizing the CTS satellite are presented. The test data obtained from the stations consisted of the results of various TV tests, attenuation and rain rate data. An additional meteorological parameter was measured and it consists of the back scatter returns of the multifrequency weather radar.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156784 , FIS-76-4039A
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    Communications Link Characterization Experiment (CLCE) technical data report, volume 2 (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results are presented of the long term rain rate statistical analysis and the investigation of determining the worst month statistical from the measured attenuation data caused by precipitation. The rain rate statistics cover a period of 11 months from July of 1974 to May of 1975 for measurements taken at the NASA, Rosman station. The rain rate statistical analysis is a continuation of the analysis of the rain rate data accumulated for the ATS-6 Millimeter Wave Progation Experiment. The statistical characteristics of the rain rate data through December of 1974 is also presented for the above experiment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156808 , FIS-77-4007-VOL-2
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    Low cost miniature data collection platform (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The development of the RF elements of a telecommunications package involved detailed study and analysis of concepts and techniques followed by laboratory testing and evaluation of designs. The design goals for a complete telecommunications package excluding antenna were a total weight of 300 grams, in a total volume of 400 cu cm with a capability of unattended operation for a period of six months. Of utmost importance is extremely low cost when produced in lots of 10,000. Early in the program it became apparent that a single Miniature Data Collection Platform would not satisfy all users. A single high efficiency system would not satisfy a user who had available a large battery capacity but required a low cost system. Conversely, the low cost system would not satisfy the end user who had a very limited battery capacity. A system design to satisfy these varied requirements was implemented by designing several versions of the system building blocks and then constructing three systems from these building blocks.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156707 , REPT-10173
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  • 87
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    A Depolarization and Attenuation Experiment Using the CTS and COMSTAR Satellites. Mathematical Formulations and Definitions for Dual Polarized Reception of a Wave Passing Through a Depolarizing Medium (A Polarization Primer) (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The theoretical fundamentals and mathematical definitions for calculations involved with dual polarized radio links are given. Detailed derivations and results are discussed for several formulations applied to a general dual polarized radio link.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156644 , SUPPL-1
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    Survey of adaptive image coding techniques (1977)
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    Publication Date: 2019-06-27
    Description: The general problem of image data compression is discussed briefly with attention given to the use of Karhunen-Loeve transforms, suboptimal systems, and block quantization. A survey is then conducted encompassing the four categories of adaptive systems: (1) adaptive transform coding (adaptive sampling, adaptive quantization, etc.), (2) adaptive predictive coding (adaptive delta modulation, adaptive DPCM encoding, etc.), (3) adaptive cluster coding (blob algorithms and the multispectral cluster coding technique), and (4) adaptive entropy coding.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Nov. 197
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  • 89
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    Communications Link Characterization Experiment (CLCE), volume 3 (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The results of data which were acquired, reduced and analyzed as of June 1977, from the Communications Link Characterization Experiment while utilizing the Communications Link Characterization Experiment while utilizing the Communications Technology Satellite is presented. The long term yearly and worst month propagation data from both stations are presented for the defined yearly period and the test results of the Goddard Television Experiment are described. The data for the continuing path length analysis are updated. Progress on the continuing analysis of utilizing the weather radars for attenuation prediction is given and the concept of the weather radar ratio is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156801 , FIS-77-4057-VOL-3
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  • 90
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    Amplitude scintillation at 2 and 30 GHz on earth space paths (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Extensive amplitude scintillation measurements were made simultaneously at 2.075 and 30 GHz on earth-space propagation paths. These measurements were performed as the Applications Technology Satellite (ATS-6) was moved slowly from a synchronous position over India to a new synchronous position over the United States. The variance, path loss, covariance, and spectra are discussed as functions of the path elevation angle. These results are also compared with earlier simultaneous scintillation measurements at 20 and 30 GHz during the movement of ATS-6 to its position over India.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156780 , REPT-4299-3
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  • 91
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    Synthetic aperture radar correlator phase histories (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: This report supplements the design of the following subsystems: (1) zoom azimuth telescope, zooming range from 3X to 6X. (2) range curvature correcting lenses. (3) Sphero-cylindrical shift lens. (4) Auxiliary lenses (tilted cylinder and matching lens).
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-157086 , REPT-6590
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  • 92
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    Signal-to-noise ratio estimation in digital computer simulation of lowpass and bandpass systems with applications to analog and digital communications, volume 3 (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Techniques are developed to estimate power gain, delay, signal-to-noise ratio, and mean square error in digital computer simulations of lowpass and bandpass systems. The techniques are applied to analog and digital communications. The signal-to-noise ratio estimates are shown to be maximum likelihood estimates in additive white Gaussian noise. The methods are seen to be especially useful for digital communication systems where the mapping from the signal-to-noise ratio to the error probability can be obtained. Simulation results show the techniques developed to be accurate and quite versatile in evaluating the performance of many systems through digital computer simulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151712 , CSR-77-6-VOL-3
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    Survey: Federal Aviation Administration National Communication Center (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The National Communication (NATCOM) Center (commonly known as the FAA Weather Message Switching Center), is a Federal Aviation Administration (FAA) facility with responsibility for providing communication switching services to the National Weather Service (NWS), the FAA, commercial and private flight organizations under the auspices of the FAA, and DoD. Data handled by NATCOM include weather data, flight plans, and Notices to Airmen (NOTAMS) on both national and international networks. The communications and data management functions are handled through four computer-controlled communication networks designated as WMSC, AFTN, A-BDIS, and NASNET. The functions of these networks are discussed with emphasis on those networks that support the different elements of the NWS. The primary network of concern to NASA, the WMSC (Weather Message Switching Center) network, performs approximately 60 percent of its work for the NWS, 20 percent for the State Department, and 20 percent for the FAA. This document discusses the current and future systems capabilities and workload of NATCOM in terms of new roles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-150552 , SD-77-MSFC-2149
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    Monte Carlo simulation of wave sensing with a short pulse radar (1977)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A Monte Carlo simulation is used to study the ocean wave sensing potential of a radar which scatters short pulses at small off-nadir angles. In the simulation, realizations of a random surface are created commensurate with an assigned probability density and power spectrum. Then the signal scattered back to the radar is computed for each realization using a physical optics analysis which takes wavefront curvature and finite radar-to-surface distance into account. In the case of a Pierson-Moskowitz spectrum and a normally distributed surface, reasonable assumptions for a fully developed sea, it has been found that the cumulative distribution of time intervals between peaks in the scattered power provides a measure of surface roughness. This observation is supported by experiments.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-X-71412 , X-953-77-239
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    Probe corrected far-field reconstruction from measurements on a cylinder: A novel formulation and efficient algorithm (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A novel and numerically efficient method of far field evaluation from measurements taken on a cylinder is based on the representation of both the antenna and the probe fields as superpositions of plane waves. A system of two integral equations are established whose unknown functions are the azimuthal and elevation components of the antenna pattern and whose known terms are the set of measurement data taken with two different probes - the second probe in most practical instances being simply the same probe with a different geometrical orientation. The equations express the known data - for each angular position of the antenna under measurement - as the integrals of the products of the corresponding components of the unknown antenna and known probe patterns multiplied by a phase term. The convolutional nature of the integral equations makes their solutions straight-forward. If, as is virtually always the case, the probe is small or of moderate size so that the axis of rotation of the antenna mount is in the far field of the probe, the intervention of asymptotic techniques makes the solution numerically very efficient. The agreement of calculated and experimental patterns is excellent.
    Keywords: COMMUNICATIONS AND RADAR
    Type: ESA Antenna Testing Tech.; p 143-149
    Format: text
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  • 96
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    Communications systems technology assessment study. Volume 2: Results (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The cost and technology characteristics are examined for providing special satellite services at UHF, 2.5 GHz, and 14/12 GHz. Considered are primarily health, educational, informational and emergency disaster type services. The total cost of each configuration including space segment, earth station, installation operation and maintenance was optimized to reduce the user's total annual cost and establish preferred equipment performance parameters. Technology expected to be available between now and 1985 is identified and comparisons made between selected alternatives. A key element of the study is a survey of earth station equipment updating past work in the field, providing new insight into technology, and evaluating production and test methods that can reduce costs in large production runs. Various satellite configurations were examined. The cost impact of rain attenuation at Ku-band was evaluated. The factors affecting the ultimate capacity achievable with the available orbital arc and available bandwidth were analyzed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-135224
    Format: application/pdf
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  • 97
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    Modes and cutoff frequencies of crossed rectangular waveguides (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: One complete solution is presented for determining the electromagnetic field of a generalized crossed rectangular waveguide. The method adopted is that of partial regions. Cutoff frequencies of symmetrical crossed waveguides are presented as an example. The results, even for low-order approximations, correspond well with the only experimental results available in the literature.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Microwave Theory and Techniques; MTT-25; July 197
    Format: text
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  • 98
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    Theory for microwave thermal emission from a layer of cloud or rain (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Microwave thermal emission from a layer of cloud or rain consisting of spherical particles has been investigated. Scattering effects are studied in great detail with both numerical and analytical approaches. In the absence of ground emission, it is found that scattering induces brightening for optically thin layers and vice versa for optically thick layers. As a function of observation angle, brightening occurs near nadir, while darkening occurs at large angles in the case of small optical thickness. For large optical thickness, darkening occurs at all angles because of backscattering effects. When the layer of cloud or rain is above an air layer and an ocean surface at a higher temperature, it is found that the darkening effect at large optical thickness is much more pronounced. The darkening effect is also larger for vertical polarizations because the ocean emits more vertically polarized components. The effect of thermal emission and molecular absorption by atmospheric gases is also taken into account. Results obtained from analytical formulas under single-scattering assumptions are compared and illustrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AD-A064462 , IEEE Transactions on Antennas and Propagation; AP-25; Sept
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  • 99
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    Noncoherent pseudonoise code tracking performance of spread spectrum receivers (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The optimum design and performance of two noncoherent PN tracking loop configurations, namely, the delay-locked loop and tau-dither loop, are described. In particular, the bandlimiting effects of the bandpass arm filters are considered by demonstrating that for a fixed data rate and data signal-to-noise ratio, there exists an optimum filter bandwidth in the sense of minimizing the loop's tracking jitter. Both the linear and nonlinear loop analyses are presented, and the region of validity of the former relative to the latter is indicated. In addition, numerical results are given for several filter types. For example, assuming ideal bandpass arm filters, it is shown that the tau-dither loop requires approximately 1 dB more signal-to-noise ratio than the delay-locked loop for equal rms tracking jitters.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Mar. 197
    Format: text
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  • 100
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    A spectral domain method for remotely probing stratified media (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The problem of remotely probing a stratified, lossless, dielectric medium is formulated using the spectral domain method of probing. The response of the medium to a spectrum of plane waves incident at various angles is used to invert the unknown profile. For TE polarization, the electric field satisfies a Helmholtz equation. The inverse problem is solved by means of a new representation for the wave function. The principal step in this inversion is solving a second kind Fredholm equation which is very amenable to numerical computations. Several examples are presented including some which indicate that the method can be used with experimentally obtained data. When the fields exhibit a surface wave behavior, a unique inversion can be obtained only if information about the magnetic field is also available. In this case, the inversion is accomplished by a two-step procedure which employs a formula of Jost and Kohn. Some examples are presented, and an approach which greatly shortens the computations without greatly deteriorating the results is discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; Mar. 197
    Format: text
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