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  • COMMUNICATIONS AND RADAR  (237)
  • 1980-1984
  • 1975-1979  (237)
  • 1950-1954
  • 1977  (237)
  • 1
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    A radio lens in the ionosphere (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Using a modified version of the classical Cornu spiral, fading patterns in agreement with observations of radio signals on 140 and 360 MHz from the geostationary satellite ATS6, have been obtained. The particular fading patterns chosen show modulated quasi-periodic fading before and after a deep central minimum. It is shown that a cylindrical lens in the ionosphere required to produce this is only about 100 m across (an order of magnitude smaller than the size of the pattern on the ground) and if it were circular in cross-section would have a maximum plasma frequency of over 40 MHz. This suggests the reason why calculations based on a transparent phase screen did not give the observed fading pattern for 40 MHz signals. It was not possible to deduce the height of the lens above the ground, though we would incline to an E-region origin.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Journal of Atmospheric and Terrestrial Physics; 39; Mar. 197
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  • 2
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    Limitations on oceanographic use of beam-limited target-referenced radars (1977)
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    Publication Date: 2011-08-17
    Description: A general development is undertaken to determine the limitations on the use of beam-limited target-referenced radars in the measurement of ocean wave height. This class of radars is concerned only with the range extent of the target, not the range to the target. The nonzero range extent of a flat waveless sea and the compounding effect of pointing errors due to radar platform instability cause difficulty in measuring low wave heights and impose a maximum operating altitude on such systems. It is seen that it is impractical to obtain accurate measurements for wave heights of interest at altitudes above those used by commercial aircraft (10,000 m). Additionally, the typical ratio of dominant wavelength to significant wave height (SWH) of 30 for wind-driven gravity waves imposes an upper limit on the SWH measurable for a given altitude and beamwidth.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; May 1977
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  • 3
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    Tracking performance of symbol synchronizers for Manchester coded data (1977)
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    Publication Date: 2011-08-17
    Description: The implementation and tracking performance of symbol synchronizers for Manchester coded data is presented with motivation provided by maximum a posteriori (MAP) estimation theory. Certain physically relizable closed-loop structures, readily implemented in practice, are suggested by the theory for uncoded data symbols with arbitrary data transition probabilities. The tracking performance of these loops is optimized and comparisons are made among the various configurations over a wide range of system parameters. Although not the major intent of the paper, the acquisition problem is briefly addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Apr. 197
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  • 4
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    An antenna for limited scan in one plane - Design criteria and numerical simulation (1977)
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    Publication Date: 2011-08-17
    Description: Aperture illumination is synthesized through the use of overlapping subarrays with independently controlled excitations. Detailed analysis and design criteria are provided for a specific limited-scan antenna configuration scanning in one plane. The number of phase shifts is the theoretical minimum corresponding to specified aperture size and field of view. Beam pointing and width are approximately constant for moderate frequency variation, and ultralow sidelobes outside the field of view can be produced at the cost of a slight loss of illumination efficiency. Accurate aperture illumination control makes for excellent independently specified sum and difference patterns in beamforming.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; Mar. 197
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  • 5
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    Optimum performance of suppressed carrier receivers with Costas loop tracking (1977)
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    Publication Date: 2011-08-17
    Description: The performance of suppressed carrier receivers with Costas loop tracking is optimized by proper choice of loop arm filter bandwidth. In particular, it is shown that for a variety of passive arm filter types, there exists, for a given data rate and data signal-to-noise ratio, an optimum filter bandwidth in the sense of minimizing the loop's squaring loss. For the linear theory case, this is equivalent to minimizing the loop's tracking jitter. When symbol synchronization is known, it is shown that by replacing the passive arm filters with active filters, i.e., integrate-and-dump circuits, one can achieve an improvement in carrier-to-noise ratio of as much as 4 to 6 dB depending on the passive arm filter type used for comparison and the value of data signal-to-noise ratio.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Feb. 197
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  • 6
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    Optimum design and performance of Costas receivers containing soft bandpass limiters (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: This paper investigates several key questions concerning the mechanization and design of a Costas receiver for reconstruction of a carrier from a suppressed carrier signal. For baseband NRZ encoded data symbols and a soft bandpass limiter preceding the loop, several design issues which are considered herein and which affect acquisition and tracking performance are: (1) The choice of an IF bandwidth. (2) The optimum choice of the Costas arm filter bandwidths as well as the spectral roll-off characteristics. (3) The optimum choice of loop bandwidth to data rate ratio for a given signal-to-noise ratio. (4) The signal suppression factor and the combined limiter-squaring loss. (5) The variations in loop bandwidth and damping with signal level. (6) The choice of the limiter transfer characteristic. (7) Performance degradation due to the presence of a limiter. Various new results in system design are presented and typical numerical results are given and graphically demonstrated in SNR regions of practical interest. The theory is applicable to the design of carrier reconstruction loops required in the implementation of spread spectrum communication receivers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-25; Aug. 197
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  • 7
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    Polarization loss of a satellite - Data collection sensor link (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: It is noted that the stringent economy of data-collection systems consisting of several widely dispersed satellite-monitored sensor platforms can be partially achieved by using an inexpensive linearly polarized antenna on each platform and that due to Faraday rotation of the ionosphere, the satellite antenna must be circularly polarized to avoid a prohibitive polarization loss. The cumulative probability distribution of polarization loss between a linearly polarized platform antenna and an elliptically polarized satellite antenna is computed for satellite-antenna axial ratios of 3 and 4 dB. The results indicate that a polarization loss of 4.5 dB must be expected for a reliability of 85% and an axial ratio of 3 dB. It is suggested that the conventional assignment of a 3-dB polarization loss to the communication link considered may not insure the required link reliability.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-13; July 197
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  • 8
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    Analysis of a discrete spectrum analyzer for the detection of radio frequency interference (1977)
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    Publication Date: 2011-08-17
    Description: As the radio frequency spectrum becomes increasingly overcrowded, interference with mission-critical DSN operations is rising at an alarming rate. To alleviate this problem the DSN is developing a wideband surveillance system for on-site detection and identification of potential sources of radio frequency interference (RFI), which will complement the existing frequency coordination activities. The RFI monitoring system is based on a wideband, multi-look discrete spectrum analyzer operating on fast Fourier transform principles. An extensive general statistical analysis is presented of such spectrum analyzers and derives threshold detection performance formulas for signals of interest. These results are then applied to the design of the RFI spectrum analyzer under development.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 83-98
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  • 9
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    Walsh transforms and signal detection (1977)
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    Publication Date: 2011-08-17
    Description: The detection of signals using Walsh power spectral estimates is analyzed. In addition, a generalization of this method of estimation is evaluated. The conclusion is that Walsh transforms are not suitable tools for the detection of weak signals in noise.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 127-131
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  • 10
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    Radio frequency interference from near-earth satellites (1977)
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    Publication Date: 2011-08-17
    Description: A pessimistic statistical model was developed for predicting the extent of radio frequency interference (RF1). Based on the assumptions underlying the model, DSN S-band operations can expect one RF1 interruption every 4.1 days, with the average incident lasting 24 s. This implies that 52 or more such satellites, with uncorrelated orbital trajectories, will cause in excess of 5 min of RF1 per day at a DSN station.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 69-77
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  • 11
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    Modification of the DSN radio frequency angular tropospheric refraction model (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The previously derived DSN Radio Frequency Angular Tropospheric Refraction Model contained an assumption which was subsequently seen to be at a variance with the theoretical basis of angular refraction. The modification necessary to correct the model is minor in that the value of a constant is changed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 184-186
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  • 12
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    Synchronization strategies for RFI channels (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An RFI channel to be a multiple-access channel is defined in which no sender can know when any other starts, and the problem of determining the relative phases of the senders at the receiver is studied. A new result is proved about binary DEBruijn sequences.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 103-108
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  • 13
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    Proportionality between Doppler noise and integrated signal path electron density validated by differenced S-X range (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of Viking differenced S-band/X-band (S-X) range are shown to correlate strongly with Viking Doppler noise. A ratio of proportionality between downlink S-band plasma-induced range error and two-way Doppler noise is calculated. A new parameter (similar to the parameter epsilon which defines the ratio of local electron density fluctuations to mean electron density) is defined as a function of observed data sample interval (Tau) where the time-scale of the observations is 15 Tau. This parameter is interpreted to yield the ratio of net observed phase (or electron density) fluctuations to integrated electron density (in RMS meters/meter). Using this parameter and the thin phase-changing screen approximation, a value for the scale size L is calculated. To be consistent with Doppler noise observations, it is seen necessary for L to be proportional to closest approach distance a, and a strong function of the observed data sample interval, and hence the time-scale of the observations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 172-183
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  • 14
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    The Deep Space Network-Mariner Jupiter/Saturn 1977 flight project telecommunications compatibility (1977)
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    Publication Date: 2011-08-17
    Description: The DSN-Mariner Jupiter/Saturn 1977 telecommunications compatibility tests conducted during the periods 15-20 November 1976, 7-16 December 1976 and 5 January 1977, are an ongoing series of engineering level tests to determine the flight-ground interface compatibility and performance characteristics between these two systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 16-37
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  • 15
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    Selectable polarization at X-band (1977)
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    Publication Date: 2011-08-17
    Description: The X-band feeds in the Deep Space Network were upgraded to include selectable polarization in time for the Voyager missions to the outer planets. The modified antenna feed has the following major items added: two circular waveguide rotary joints, drive motor and gear reducer, gear assembly, two microswitches, and a polarization control junction box. The overall length of the feed remains the same because circular waveguide spacing sections were designed into the original feed to readily permit such modifications. There is no significant increase in antenna noise temperature compared to the original feed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 177-180
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  • 16
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    DSS 13 automated antenna pointing subsystem phase 1 hardware (1977)
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    Publication Date: 2011-08-17
    Description: An automated antenna pointing subsystem (APS) is being installed at DSS 13 as part of the unattended station project. The function of the APS is to track an instructed position with the 26 meter antenna and to monitor the antenna servo system and meteorological conditions to ensure a proper operational environment. This article discusses the now-completed first phase of the digital hardware portion of the APS development.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 100-109
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  • 17
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    X-band antenna gain and system noise temperature of 64-meter deep space stations (1977)
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    Publication Date: 2011-08-17
    Description: A set of measured data on the X-band performance of the three 64-meter deep space stations was obtained for use in future mission telecommunication design and predictions. The test configuration and measurement procedure is described. A method of modelling attenuation due to the atmosphere is given. Radio source brightness temperature and flux density are reviewed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 76-99
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  • 18
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    Investigation of package sealing using organic adhesives (1977)
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    Publication Date: 2011-08-17
    Description: A systematic study was performed to evaluate the suitability of adhesives for sealing hybrid packages. Selected adhesives were screened on the basis of their ability to seal gold-plated Kovar butterfly-type packages that retain their seal integrity after individual exposures to increasingly severe temperature-humidity environments. Tests were also run using thermal shock, temperature cycling, mechanical shock and temperature aging. The four best adhesives were determined and further tested in a 60 C/98% RH environment and continuously monitored in regard to moisture content. Results are given, however, none of the tested adhesives passed all the tests.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Proc. of the 1977 NASA(ISHM Microelectronics Conf.; p 77-94
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  • 19
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    The 26-meter S-X Conversion Project (1977)
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    Publication Date: 2011-08-17
    Description: The 26-meter S-X conversion project provides for the conversion of an existing 26-meter S-band subnet to a 34-meter S- and X-band subnet. The subnet chosen for conversion consists of the following stations: DSS 12 near Barstow, DSS 44 in Australia, and DSS 62 in Spain. The main subsystems effected by this project are the antenna mechanical, antenna microwave, and receiver-exciter. In addition to these, there are many project-related electronic equipments that have been added to the existing station equipment. The major subsystems are essentially through the design stage with the antenna mechanical subsystem completed through detail design with procurement in process.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 157-167
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  • 20
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    Minimum-weight codewords in the (128,64) BCH (1977)
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    Publication Date: 2011-08-17
    Description: Techniques of combinational algebra and computer simulation are combined to determine the number of weight 22 codewords in the (128,64) BCH code which is being studied for use on future deep-space missions.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network p92-94 (SEE N78-24161 15-12)
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  • 21
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    Complex mixer system modifications (1977)
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    Publication Date: 2011-08-17
    Description: Modifications of the complex mixer system to increase bandwidth and number of channels were made. Three modified complex mixers were installed at DSS 14 and were used to process planetary radar signals in March and April of 1977.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 88-91
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  • 22
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    Viking extended mission support (1977)
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    Publication Date: 2011-08-17
    Description: The period from 1 July through 31 August 1977 is covered and included is the remainder of post DSN Mark 3 Data Subsystem Implementation Project Viking-related testing at DSS14. Also included are reports on the Viking DSN Discrepancy Reporting System, Viking command support, tracking support, and periodic tests conducted with the Viking spacecraft.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 28-33
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  • 23
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    Voyager flight project: DSN Telecommunications Compatibility Test Program (1977)
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    Publication Date: 2011-08-17
    Description: The Voyager Flight Project - DSN Telecommunications Compatibility Test Program consisted of three phases: Subsystem Design, System Design, and System Verification Tests. Subsystem Design Tests were performed during mid 1976. System Design Tests were performed during late 1976 and early 1977. System Verification Tests were performed during the spring and summer of 1977. This article describes the System Design Tests and test results that provided the basis for establishment of telecommunications design between the DSN and the Voyager Flight Project.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 13-27
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  • 24
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    DSN radio science system description and requirements (1977)
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    Publication Date: 2011-08-17
    Description: The data system created to collect the functions performed by the Deep Space Network in support of spacecraft radio science experiments is described. Some of the major functional requirements presently being considered for the system are delineated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network, Vol. 39; p 119-129
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  • 25
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    EMI survey for maritime satellite 1535-1645-MHz shipboard terminal (1977)
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    Publication Date: 2011-08-17
    Description: A 15,690-ton commercial container ship was selected as lead ship for an onboard electromagnetic-interference (EMI) survey prior to installation of 1535-1645-MHz (L-Band) shipboard terminals for communication via a maritime satellite. In general, the EMI survey revealed tolerable interference levels on board ship. Radiometer measurements indicate antenna-noise temperatures less than 70 K at elevation angles of 5 deg and greater at 1559 MHz at the output terminals of the 1.2-m diameter parabolic-dish antenna for the L-band shipboard terminal. Other EMI measurements include field intensity from 3-cm and 10-cm wavelength pulse radars, and conducted-emission tests of primary power lines to both onboard radars.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-19; Nov. 197
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  • 26
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    VLBI (Very Long Baseline Interferometry) instrumental effects, part 1 (1977)
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    Publication Date: 2011-08-17
    Description: Very Long Baseline Interferometry (VLBI) is a method for observation of extragalactic radio sources which appears to have potential for precise long-distance earth surveying, clock synchronization and spacecraft navigation. Many researchers have been working to establish the accuracy of VLBI observations. The intent of the work reported here is to review the principal components of the VLBI instrument in order to estimate and/or bound the systematic error contributions. In this first of a series of articles, the definitions and tools which are needed in order to apply filter transfer-function analysis to the VLBI receiver are established and they are used to estimate the sensitivity of the VLBI receiver to plausible filter variations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 54-80
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  • 27
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    Statistical assessment of speech system performance (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Methods for the normalization of performance tests results of speech recognition systems are presented. Technological accomplishments in speech recognition systems, as well as planned research activities are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 265-284
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  • 28
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    The Army word recognition system (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The application of speech recognition technology in the Army command and control area is presented. The problems associated with this program are described as well as as its relevance in terms of the man/machine interactions, voice inflexions, and the amount of training needed to interact with and utilize the automated system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 207-215
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  • 29
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    Speech systems research at Texas Instruments (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: An assessment of automatic speech processing technology is presented. Fundamental problems in the development and the deployment of automatic speech processing systems are defined and a technology forecast for speech systems is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 289-299
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  • 30
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    Automatic speech recognition research at NASA-Ames Research Center (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A trainable acoustic pattern recognizer manufactured by Scope Electronics is presented. The voice command system VCS encodes speech by sampling 16 bandpass filters with center frequencies in the range from 200 to 5000 Hz. Variations in speaking rate are compensated for by a compression algorithm that subdivides each utterance into eight subintervals in such a way that the amount of spectral change within each subinterval is the same. The recorded filter values within each subinterval are then reduced to a 15-bit representation, giving a 120-bit encoding for each utterance. The VCS incorporates a simple recognition algorithm that utilizes five training samples of each word in a vocabulary of up to 24 words. The recognition rate of approximately 85 percent correct for untrained speakers and 94 percent correct for trained speakers was not considered adequate for flight systems use. Therefore, the built-in recognition algorithm was disabled, and the VCS was modified to transmit 120-bit encodings to an external computer for recognition.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 143-170
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  • 31
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    Multi-user real time word recognition system (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Technological accomplishments in speech recognition systems are presented. A discrete word recognition system which contains an audio spectrum analyzer is described in detail.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 301-304
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  • 32
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    Practical applications of interactive voice technologies: Some accomplishments and prospects (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A technology assessment of the application of computers and electronics to complex systems is presented. Three existing systems which utilize voice technology (speech recognition and speech generation) are described. Future directions in voice technology are also described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 217-234
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  • 33
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    Automatic speech recognition technology development at ITT Defense Communications Division (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: An assessment of the applications of automatic speech recognition to defense communication systems is presented. Future research efforts include investigations into the following areas: (1) dynamic programming; (2) recognition of speech degraded by noise; (3) speaker independent recognition; (4) large vocabulary recognition; (5) word spotting and continuous speech recognition; and (6) isolated word recognition.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 305-316
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  • 34
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    An analysis technique for microstrip antennas (1977)
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    Publication Date: 2011-08-17
    Description: The paper presents a combined numerical and empirical approach to the analysis of microstrip antennas over a wide range of frequencies. The method involves representing the antenna by a fine wire grid immersed in a dielectric medium and then using Richmond's reaction formulation (1974) to evaluate the piecewise sinusoidal currents on the grid segments. The calculated results are then modified to account for the finite dielectric discontinuity. The method is applied to round and square microstrip antennas.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-25; Nov. 197
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  • 35
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    S-X conversion for the block 3 receiver--exciter (1977)
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    Details
    Publication Date: 2011-08-17
    Description: An S-X conversion modification was designed for the Block 3 receiver-exciter to be used in the 26 meter S-X Conversion Project. The description, design, specifications, and data are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 141-148
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    CCIR papers on telecommunications for deep space research (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A brief description is given of United States participation in the process of developing the technical basis for international allocation and regulation of the radio frequency spectrum. The telecommunication requirements for deep space research are considered. Topics include functional requirements, methods and techniques, and equipment characteristics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 162-183
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    Dual coupler configuration at DSS 14 for the Voyager era (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A description is given of the dual coupler configuration which was installed at DSS 14 for station delay calibrations during the Voyager era. The Z correction values determined for these new and previous configurations are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 184-192
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    The 1977 WARC on broadcasting satellites - Spectrum management aspects and implications (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Broadcasting satellites are allocated as a primary service in the band 11.7-12.2 GHz (11.7-12.5 GHz in Europe, Africa, and the USSR), but the band is also allocated on a primary basis (equal sharing) to other services - fixed, mobile, broadcasting, and fixed satellite. Presented with these difficult sharing situations, delegates from over 100 countries met at an ITU World Administrative Radio Conference in 1977 to develop a plan for broadcasting satellites. Many nations wanted a plan that would assign to them now, reserved orbital locations and channel asignments for their future use. Other countries wanted a plan adopted now for future broadcasting satellites which assigned specific channels to specific areas on the ground so that they could use the remaining frequencies to provide terrestrial service right away. This paper describes the 'Plan' developed at the conference and points out how the principles of spectrum management were employed. It also discusses the implications for future international management of the spectrum growing out of this meeting.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-19; Aug. 197
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    Research on speech understanding and related areas at SRI (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Research capabilities on speech understanding, speech recognition, and voice control are described. Research activities and the activities which involve text input rather than speech are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 45-63
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    Voice integrated systems (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The program at Naval Air Development Center was initiated to determine the desirability of interactive voice systems for use in airborne weapon systems crew stations. A voice recognition and synthesis system (VRAS) was developed and incorporated into a human centrifuge. The speech recognition aspect of VRAS was developed using a voice command system (VCS) developed by Scope Electronics. The speech synthesis capability was supplied by a Votrax, VS-5, speech synthesis unit built by Vocal Interface. The effects of simulated flight on automatic speech recognition were determined by repeated trials in the VRAS-equipped centrifuge. The relationship of vibration, G, O2 mask, mission duration, and cockpit temperature and voice quality was determined. The results showed that: (1) voice quality degrades after 0.5 hours with an O2 mask; (2) voice quality degrades under high vibration; and (3) voice quality degrades under high levels of G. The voice quality studies are summarized. These results were obtained with a baseline of 80 percent recognition accuracy with VCS.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 123-140
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    Multi-system approach to speech understanding (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Harpy and Hearsay-2 systems are described. The performance of these systems was tabulated. The large number of design decisions which confront a speech understanding system are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 11-23
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    Voice data entry in air traffic control (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Several of the keyboard data languages were tabulated and analyzed. The key language chosen as a test vehicle was that used by the nonradar or flight data controllers. This application was undertaken to minimize effort in a cost efficient way and with less research and development.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 171-196
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    Voice input/output capabilities at Perception Technology Corporation (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Condensed resumes of key company personnel at the Perception Technology Corporation are presented. The staff possesses recognition, speech synthesis, speaker authentication, and language identification. Hardware and software engineers' capabilities are included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 95-106
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    Voice technology and BBN (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The following research was discussed: (1) speech signal processing; (2) automatic speech recognition; (3) continuous speech understanding; (4) speaker recognition; (5) speech compression; (6) subjective and objective evaluation of speech communication system; (7) measurement of the intelligibility and quality of speech when degraded by noise or other masking stimuli; (8) speech synthesis; (9) instructional aids for second-language learning and for training of the deaf; and (10) investigation of speech correlates of psychological stress. Experimental psychology, control systems, and human factors engineering, which are often relevant to the proper design and operation of speech systems are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 65-75
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    Real-time interactive speech technology at Threshold Technology, Incorporated (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Basic real-time isolated-word recognition techniques are reviewed. Industrial applications of voice technology are described in chronological order of their development. Future research efforts are also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 235-261
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    Military applications of automatic speech recognition and future requirements (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An updated summary of the state-of-the-art of automatic speech recognition and its relevance to military applications is provided. A number of potential systems for military applications are under development. These include: (1) digital narrowband communication systems; (2) automatic speech verification; (3) on-line cartographic processing unit; (4) word recognition for militarized tactical data system; and (5) voice recognition and synthesis for aircraft cockpit.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 197-205
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    Sperry Univac speech communications technology (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Technology and systems for effective verbal communication with computers were developed. A continuous speech recognition system for verbal input, a word spotting system to locate key words in conversational speech, prosodic tools to aid speech analysis, and a prerecorded voice response system for speech output are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NADC, Proceedings: Voice Technology for Interactive Real-Time Command(Control Systems Application; p 77-93
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    Qualification model spacecraft tests for DEMP, SGEMP, and ESD effects (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The development of a satellite design demonstration test program is described. The test approach is comprehensive in that it includes the effects from electrostatic discharge (ESD), system generated electromagnetic pulse (SGEMP), as well as dispersed electromagnetic pulses (DEMP). The comprehensive test concept is based on the similarity of the satellite's response to several environments.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Lewis Res. Center Proc. of the Spacecraft Charging Technol. Conf.; p 815-828
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    Plasma charging testing of communication satellites (1977)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A discussion is given of ESD as a radiated electromagnetic environment and compares the ESD environment to a standard EMI test environment. An arc generator used to assess the sensitivity of typical spacecraft electronics is described. The results of radiated susceptibility tests conducted on breadboard circuits and a satellite electrical model of a communication satellite are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Lewis Res. Center Proc. of the Spacecraft Charging Technol. Conf.; p 805-813
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    Low frequency electric field variations during HF transmissions on a mother-daughter rocket (1977)
    In:  CASI
    Details
    Publication Date: 2017-10-02
    Description: HF wave propagation experiments were conducted on Mother-Daughter rockets in the polar ionosphere. Swept frequency transmissions from the Mother, nominally covering the range from 0.5 to 5 MHz in both CW and pulse modes, are received by the Daughter. In the most recent rocket of the series, the Mother also contained an AC electric field spectrometer covering the frequency range from 10 Hz to 100 kHz in four decade bands. The low frequency response of the ionosphere with respect to waves emitted from the onboard HF transmitter is examined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: AGARD Artificial Modification of Propagation Media; 11 p
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    Contributions of speech science to the technology of man-machine voice interactions (1977)
    In:  CASI
    Details
    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
    Details
    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
    Details
    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
    Details
    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
    Details
    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
    Details
    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
    Details
    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
    Details
    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
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    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
    Details
    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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    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
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    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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    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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  • 71
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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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  • 72
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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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  • 73
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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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  • 74
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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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  • 75
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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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  • 76
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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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  • 77
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    Propagation along azimuthally magnetized ferrite-loaded circular waveguides (1977)
    In:  Other Sources
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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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  • 78
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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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  • 79
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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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  • 80
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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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  • 81
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    Communications Link Characterization Experiment (CLCE) technical data report, volume 2 (1977)
    In:  CASI
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    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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  • 82
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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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  • 83
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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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  • 84
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    Survey of adaptive image coding techniques (1977)
    In:  Other Sources
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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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  • 85
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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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  • 86
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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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  • 87
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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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  • 88
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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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  • 89
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    Survey: Federal Aviation Administration National Communication Center (1977)
    In:  CASI
    Details
    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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  • 90
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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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  • 91
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    Probe corrected far-field reconstruction from measurements on a cylinder: A novel formulation and efficient algorithm (1977)
    In:  Other Sources
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    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
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  • 92
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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
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  • 93
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    Modes and cutoff frequencies of crossed rectangular waveguides (1977)
    In:  Other Sources
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    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
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  • 94
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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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  • 95
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    Noncoherent pseudonoise code tracking performance of spread spectrum receivers (1977)
    In:  Other Sources
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    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
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  • 96
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    A spectral domain method for remotely probing stratified media (1977)
    In:  Other Sources
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    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
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  • 97
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    Limitations on Ku-band communications due to multipath (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The earth and orbiter body reflections involving the Tracking Data Relay Satellite (TDRS)/orbiter communications link are evaluated. Recommendations address operational conditions in order to avoid critical multipath impacts, modulation preferences during acquisition, and preferred scan limit implementation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151490 , DN-1.2-DN-B0703-008
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  • 98
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    Pseudo noise code and data transmission method and apparatus (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Pseudo noise ranging codes, having a predetermined chipping rate, and a pair of binary data sources, each having a bit rate no greater than one tenth the chipping rate, quadriphase, digitally modulate a suppressed carrier wave having a first frequency are examined. Two additional binary data sources, each having a bit rate that is not restricted by the chipping rate of the first carrier, quadriphase, digitally modulate a suppressed carrier wave having a second frequency. The first and second frequencies are only slightly displaced so that there is overlap in the frequency bands which modulate the two carriers. The two suppressed carrier waves are linearly combined and transmitted from a first station to a second station so that the amplitude of the transmitted first wave is controlled so as not to degrade the detectability of the second wave at the second station.
    Keywords: COMMUNICATIONS AND RADAR
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  • 99
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    Integrated source and channel encoded digital communication system design study (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The analysis of the forward link signal structure for the shuttle orbiter Ku-band communication system was carried out, based on the assumptions of a 3.03 Mcps PN code. It is shown that acquisition requirements for the forward link can be met at the acquisition threshold C/N0 sub 0 value of about 60 dB-Hz, which corresponds to a bit error rate (BER) of about 0.001. It is also shown that the tracking threshold for the forward link is at about 57 dB-Hz. The analysis of the bent pipe concept for the orbiter was carried out, along with the comparative analysis of the empirical data. The complexity of the analytical approach warrants further investigation to reconcile the empirical and theoretical results. Techniques for incorporating a text and graphics capability into the forward link data stream are considered and a baseline configuration is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151344 , R77-04-1
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  • 100
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    Radar speckle reduction in synthetic aperture radar processors by a moving diffuser (1977)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Some theoretical and experimental results are presented demonstrating the reduction of synthetic aperture radar speckle when a moving diffuser is placed in the processor image plane and is reimaged with a lens whose resolution is not better than the radar resolution. The resolution of the resulting radar image is determined by the resolution of this output lens.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Optics Communications; 20; Feb. 197
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