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  • Other Sources  (451)
  • COMMUNICATIONS AND RADAR  (451)
  • 1980-1984  (451)
  • 1983  (252)
  • 1981  (199)
  • 1
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    Prediction techniques (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Prediction methods and related propagation results for the evaluation of Earth-space communication paths operating above 10 GHz are presented. Gaseous attenuation, rain, cloud, fog, sand, and dust attenuation, path diversity, signal fluctuations and low angle fading, depolarization effects, bandwidth coherence, and sky noise are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 195-348
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  • 2
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    Characteristics of rain and rain systems (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The description and measurement of the macroscopic and microscopic characteristics of rain and rain systems are discussed. The statistical relationships of these characteristics and their effect on polarization and attenuation are considered. Macroscopic characteristics include the size, distribution, and movements of rain cells, the height of melting layers, and the presence of ice crystals. Microscopic characteristics include the size distribution, density, and oblateness of rain drops and ice crystals. The estimation of a major propagation effect, specific attenuation, is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 5-39
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  • 3
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    Propagation data bases (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Existing data bases accumulated as the result of experiments to gather propagation data on millimeter wave Earth-space links are described. The satellites used are described and results of the significant experiments conducted in the United States are summarized. The data bases consist primarily of cumulative attenuation statistics, though some depolarization measurements are included. Additional summaries of propagation data are cited.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Its Propagation Effects Handbook for Satellite Systems Design; p 155-194
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  • 4
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    An overview of several rain and attenuation models (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The key features of the Rice-Holmberg, Dutton-Dougherty, Global, Lin, and Piecewise Uniform Rain Rate models for estimation of cumulative attenuation statistics on Earth-space millimeter paths are summarized. The models provide either rain rate statistics or attenuation statistics, which can be related by use of the specific attenuation and the effective path length relation. The effective path length is defined. The advantages and disadvantages of each model for specific applications are discussed. The Global model is recommended as the design tool for predicting propagation effects in Earth-space communication systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 41-101
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  • 5
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    Application of propagation predictions to Earth/space telecommunications system design (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The corresponding between a given propagation phenomenon and system performance is considered. Propagation data are related to system performance parameters, allowing the systems engineer to perform the analyses determining how well requirements are met by a given system design, and enabling the systems engineer to modify that design if necessary. The various ways of specifying performance criteria for different kinds of systems are discussed, and a general procedure for system design is presented and demonstrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 349-404
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  • 6
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    Depolarization on Earth-space paths (1981)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Sources of depolarization effects on the propagation paths of orthogonally-polarized information channels are considered. The main sources of depolarization at millimeter wave frequencies are hydrometeor absorption and scattering in the troposphere. Terms are defined. Mathematical formulations for the effects of the propagation medium characteristics and antenna performance on signals in dual polarization Earth-space links are presented. Techniques for modeling rain and ice depolarization are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Propagation Effects Handbook for Satellite Systems Design; p 103-154
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  • 7
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    Atmospheric attenuation for correlated satellite communication ground sites (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Link margin estimates are calculated for 30/20 GHz satellite communication systems employing closely-spaced (4 to 100 km) 'dual diversity' switched ground sites. The link margin estimates are based on a new analysis in which the bivariate rain attenuation density function for two correlated ground sites is modelled by an exponential density function. The results of the exponential density function analysis enable derivation of a direct relation between rain margin estimates and probability of exceedance (link availability). Margins typically in the range 2 to 12 dB are calculated for various ground site separations and summarized for seven city locations and five satellite orbit positions over the U.S. The results can be easily extended to other EHF satellite frequencies and other locations.
    Keywords: COMMUNICATIONS AND RADAR
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  • 8
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    Effects of ISI and satellite channel nonlinearity on Viterbi demodulation/decoding (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is shown that, for convolutionally coded transmission over bandwidth-constrained channels, a mere reversal of the switching direction at the encoder output produces a change in the system bit error probability performance. This change is significant when the Viterbi demodulator/decoder is matched to the total channel memory and is more significant for linear channels than for nonlinear ones. The reversal of switching direction is a simple demonstration of the fact that the well-known optimum codes for the linear AGWN channel are no longer necessarily optimum for a bandwidth-constrained channel with or without the addition of channel nonlinearity. It is concluded that potentially significant performance improvement can be obtained by matching the encoder (through the appropriate choice of tap weights and modulo-2 summers) to the channel in addition to matching the demodulator/decoder to the channel for a given encoder.
    Keywords: COMMUNICATIONS AND RADAR
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  • 9
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    Differential versus limiter-discriminator detection of narrow-band FM (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The error probability performance of differential detection of narrow-band FM is determined and compared with the analogous results for limiter-discriminator detection of the same modulation. It is shown that over a large class of benign and hostile environments, e.g., Gaussian IF filter, AWGN, partial-band noise jamming, the differential detector offers no theoretical performance advantage over the limiter-discriminator receiver with integrate-and-dump postdetection filtering.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications (ISSN 0090-6778); COM-31; 1227-123
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  • 10
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    Burst statistics of Viterbi decoding (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A mathematical model of Viterbi decoder burst error performance is presented. This model allows for computer generation of Viterbi-like error sequences quickly and inexpensively for applications where large amounts of data are required. The model is corroborated through comparisons with actual software decoder simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 187-193
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  • 11
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    An efficient technique for the performance evaluation of antenna arrays with noisy carrier reference (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An efficient computational technique is developed to evaluate the performance of coherent receivers with noisy carrier reference and multiple antennas. The received signal is assumed to be uncoded residual carrier BPSK (binary phase shift keying), with a PLL (phase locked loop) used for extracting the carrier. Explicit relationships between the error probabilities and the various system parameters are given. Specific results are given for the performance gain of combined carrier referencing over baseband only combining when the channel alignment process is ideal. A simple asymptotic expression for the performance gain is determined when the number of antennas used is increased without bound. An example using a Block 3 Deep Space Network PLL illustrates the performance of each arraying structure. The technique used is applicable to the performance evaluation for other receivers having similar decision statistics.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 194-206
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  • 12
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    The DSN VLBI system Mark 4-85 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The DSN VLBI System was established as a network system in 1978. The evolution of the VLBI System from Mark 1-79 to Mark 4-85 is described, and the system functional requirements for Mark 4-85 are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 61-76
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  • 13
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    DSN command system (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Modification of the currently operational DSN Command System MK 3-80 consisted of improvement of the uplink carrier frequency tuning capability to satisfy Voyager 2 requirements. Upgrading of Command System monitoring functions in the Network Operations Control Center is discussed. The DSN Command System requirements and functional design are described for the Mark 4 Network.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 53-60
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  • 14
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    Project ORION microwave subsystem design (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The proposed design for the microwave subsystem of Project ORION is presented. Performance characteristics and subsystem capabilities are discussed. Functional requirements and key performance parameters are stated for the subsystem as well as a proposed schedule of events.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 10-17
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  • 15
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    A multiple access communication network based on adaptive arrays (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A single frequency communication system is considered consisting of K possibly moving users distributed in space simultaneously communicating with a central station equipped with a computationally adapted array of n = or K antennas. Such a configuration could result if K spacecraft were to be simultaneously tracked by a single DSN complex consisting of an n antennas array. The array employs K sets of n weights to segregate the signals received from the K users. The weights are determined by direct computation based on known position information of the K users. Currently known techniques require (for n = K) about (4/3)K to the 4th power computer operations (multiply and add) to perform such computations. A technique that accomplishes this same goal in 8 K to the 3rd power operations, yielding a reduction by a factor K/6, was developed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 118-127
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  • 16
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    Atmospheric noise temperature measurements (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Radiometric microwave noise temperature measurements were used to estimate atmospheric transmission loss. The following lumped element model expression is used for the noise temperature contribution, T double prime = T sub p (1 - 1/L). This relationship is used to estimate the transmission loss L in terms of T double prime and the atmosphere effective physical temperature T sub p. This report evaluates T sub p in terms of assumed distributed loss and temperature models. Simplified expressions are presented for low loss applications. For these applications L was determined directly and accurately without integration or iteration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 87-96
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  • 17
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    Effects of the gaseous and liquid water content of the atmosphere on range delay and Doppler frequency (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: When high precision is required for range measurement on Earth space paths, it is necessary to correct as accurately as possible for excess range delays due to the dry air, water vapor, and liquid water content of the atmosphere. Calculations based on representative values of atmospheric parameters are useful for illustrating the order of magnitude of the expected delays. Range delay, time delay, and phase delay are simply and directly related. Doppler frequency variations or noise are proportional to the time rate of change of excess range delay. Tropospheric effects were examined as part of an overall consideration of the capability of precision two way ranging and Doppler systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 71-86
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  • 18
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    The 34-meter antenna-subreflector translations to maximize RF gain (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The extension of the 26 meter antenna to 34 meter diameter decreased the F/D ratio. This F/D change resulted in unacceptable gain losses due to the hyperboloid's lateral deflections. A three direction translating mounting device was added to the hyperboloid. This device was controlled by a microprocessor to minimize the offsets of the phase centers in the cassegrain RF system and also compensated for boresight directions. The use of the radiation program to predict the gain losses from displacements computed by a structural computing program using an analytical model of the 34 meter reflector structure is discussed. Field test results showed accurate predictions for the Y and Z hyperboloid translations. In the X direction, the prediction value was low. However, the computed gain losses vs primary foci offsets by the radiation program were verified by field tests.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 112-120
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  • 19
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    Frequency standard test facility data acquisition and processing system (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The interim frequency standards test facility tests all frequency standards used in the DSN. It is also the central testing facility for testing all ultrastable hydrogen maser frequency standards. This proposed data acquisition/processing system was designed to support the IFSTF by acquiring and processing the large amounts of data generated there.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 22-30
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  • 20
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    Station stability measurement (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Methods and instrumentation are being developed to determine the frequency stability of Deep Space Stations. The efforts are presently focused on the verification of the stability of the X-band uplink and other RF and microwave subsystems which contribute to the overall stability of the system. The measurement methodology is presented as well as frequency stability data generated with the development measurement system. The system characteristics are highlighted and the potential areas where improvements could be made are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 35-42
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  • 21
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    Control of large space antennas based on electromagnetic-structural models (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A general approach to the optimal control of large space antennas based on their RF/structural characteristics is described. The approach consists of defining a cost functional based on the degradation of the RF performance of the antenna and using the structural model as the dynamic system. The method is applied to the design of an optimal controller for a 55-m, wrap-rib offset-fed antenna. The controller's goal is to minimize the variations of the peak electric field of the antenna due to feed displacements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 181-194
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  • 22
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    DSN ground communications facility (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A functional description of the GCF and its relationships with other elements of the DSN and NASCOM is presented together with development objectives and goals and comments on implementation activites in support of flight projects.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 200-209
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  • 23
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    MV-3 communication subsystem (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The operational mobile VLBI data acquisition system (MV-3) requires that a voice link be established between the mobile data system and a fixed site. A communications subsystem was incorporated in the MV-3 design which consists of HF radio, VHF mobile radio telephone and conventional land line telephone. The HF antenna design was optimized for short and long range transmission using both inverted V and yagi antennas mounted on a self-supporting telescoping mast.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 210-219
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  • 24
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    S-band aperture efficiency of the DSS 13 26-meter antenna with the S-X common aperture feed (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Measurements of the S-band performance of the DSS 13 26-meter antenna, equipped with the second generation S-X common aperture feed, are reported. Aperture efficiency and overall antenna gain results are compared with predicted values. The elevation dependence of the aperture efficiency is reported.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 89-94
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  • 25
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    Antenna arraying performance for deep space telecommunications systems (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Antenna arraying is a crucial Deep Space Network technique in maximizing the science return of planetary and comet encounters. The equations which describe the total figure of merit for a multiple system of arrayed antennas are developed. An example is given for three Canberra DSN antennas and the Parkes 64-m antenna to be arrayed for the Voyager 2 Uranus flyby.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 83-88
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  • 26
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    VLBI collimation tower technique for time-delay studies of a large ground station communications antenna (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A need for an accurate but inexpensive method for measuring and evaluating time delays of large ground antennas for VLBI applications motivated the development of the collimation tower technique. Supporting analytical work which was performed primarily to verify time delay measurement results obtained for a large antenna when the transmitter was at a collimation distance of 1/25 of the usual far field criterion is discussed. Comparisons of theoretical and experimental results are also given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 20-29
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  • 27
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    A near-optimum receiver structure for the detection of M-ary optical PPM signals (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A class of receivers called conditionally nulling receivers is defined for quantum noise limited optical communications. These receivers have the ability to decide at each moment in time whether or not to coherently combine a predetermined local oscillator field with the received optical field, prior to performing an energy measurement (photodetection) on the combined field. Conditionally nulling receivers are applicable to pulse position modulation and related modulation schemes, which have the property that, at each moment in time, the transmitted signal is in one of only two states, on or off. The local oscillator field which may or may not be added by the receiver is an exact replica of the negative of the received on field; hence, the receiver can exactly null the on signal if the on signal is present and the receiver chooses to use the local field. An ideal conditionally nulling receiver achieves very nearly the same error probability (within a multiplicative factor varying froom 1 to 2.15) as the optimum quantum measurement for quantum noise limited detection of M-ary PPM signals. In contrast, other known receiving methods, such as direct, heterodyne, and homodyne detection, are exponentially suboptimum.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 30-42
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  • 28
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    Fundamental limitations caused by RF propagation (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Propagation phenomena affect the design of radio frequency (RF) transmission systems. Propagation phenomena limit the suitability of portions of the frequency band for some applications, limit the reliability of RF transmission systems, and provide a means of coupling unwanted signals from one system to another with the potential of producing interference. The possibility of interference is the fundamental limitation to the unrestricted use of the frequency band. Phenomena affecting suitability, reliability, and the potential for interference are considered for frequencies in the 1- to 300-GHz range.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE; vol. 69
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  • 29
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    Narrow channel bandwidth receiver for VLBI (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An introduction to the phase four receiver subsystem to be implemented into the DSN for VLBI applications is presented. The key design areas are discussed along with the design approach. Preliminary evaluation data indicate a feasible, straightforward design may be obtained.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 18-29
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  • 30
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    Capacity of a multimode direct detection optical communication channel (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The capacity is derived under both peak and average signal power constraints and without a signal bandwidth constraint. A random telegraph wave type signalling scheme of Kabanov is known to achieve capacity provided enough signalling bandwidth is available. In the absence of received background noise, an optimally coded PPM system is shown to achieve capacity with greatly reduced bandwidth as compared to Kabanov signals.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 51-70
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  • 31
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    New results on antenna arraying, part 1 (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Baseband combining with and without combined carrier referencing for antenna arrays are compared under two scenarios for the Voyager 2 Uranus encounter. The combined carrier reference scheme is estimated to outperform the baseband only scheme by less than 0.3 dB E (sub b)/N (sub 0) at a bit error probability of 0.005. These results were attained both with mathematical modeling and software Viterbi decoder simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 105-111
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  • 32
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    ISPM X-band uplink technology demonstration. Part 1: Overview (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The ground and spacecraft hardware research, design, and implementation lead to an end to end in flight technology demonstration on the International Solar Polar Mission spacecraft. An introduction to the overall effort is given and the flight experiment objectives are established. The expected improvements in the telecommunications performance are summarized. Also presented is a conceptual mission operations plant.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 50-62
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  • 33
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    Tolerence and perturbation analysis (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Rectenna deviations are described which produce errors in the since of reduced efficiency and/or scattering. Three classes of deviations are emphasized: random construction variations; systematic variations; and atmospheric induced randomness.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 93-107
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  • 34
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    Grating lobes (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The radiation patterns characteristic of an indefinite planar array of isotropic antennas was investigated. Particular emphasis was given to the grating lobe scatter from the rectenna. It is shown that an idealy arrayed rectenna of indefinite extent would produce grating lobes which are impulsive. It is further shown that a shift to finite extent or introduction of typical variations in element placement should generate more typical patterns.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 81-90
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  • 35
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    Waveguide model (1981)
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    Publication Date: 2011-08-18
    Description: A model is presented which quantifies the electromagnetic modes (field configurations) in the immediate vicinity of the rectenna element. Specifically, the waveguide model characterizes the electromagnetic modes generated by planar waves normal to the array. The model applies only to incidence normal to the array.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 59-77
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  • 36
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    A theoretical study of microwave beam absorption by a rectenna, introduction (1981)
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    Publication Date: 2011-08-18
    Description: The conditions required for a large rectenna array (i.e., reference design) to absorb nearly 100% of transmitted energy were studied. Design parameters including element spacing, and the manner in which these affect scatter were formulated. Amplitudes and directions of scatter and development of strategies for mitigation were also investigated. The effects on rectenna behavior of external factors such as weather and aircraft overflights were determined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 1-36
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    Standard format data units - Tools for automatic exchange of space mission data (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A set of standard formatting rules for the data sets, and a standard computer-readable language with which to describe the data, are two tools which are used to create the Standard Format Data Unit (SFDU). The NASA/JPL proposal for creation and utilization of SFDUs is presented, and its relationship to recommendations from the Consultative Committee for Space Data Systems (CCSDS) is discussed. Several current and planned implementations of the SFDU concept among major space flight projects are identified. The purpose of creating the concept of an SFDU is to allow members of the science community to share national and global resource data independently of project or program. The feedback from SFDU implementation efforts is considered an essential part of the CCSDS activity. Even though the CCSDS specifically deals with space data systems, the SFDU concept can be applied to practically every data system on an open network. The SFDU is in the early phase of CCSDS standard definition work, and must go through several other phases before being formally recommended as an international standard.
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  • 38
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    Control of antenna-feed attitude and reflector vibrations in large spaceborne antennas by mechanical decoupling and movable dampers (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Simple, practical methods for damping reflector vibrations and designing antenna-feed attitude control systems in large deployable spaceborne antennas are proposed. The former involves a movable damper which is positioned so that the rate-of-change of total vibrational energy is minimized. The latter introduces a mechanical decoupler between the flexible boom and the antenna-feed, whereby the feed-attitude control system can be designed independent of boom dynamics. The validity of these approaches are substantiated by analytical studies, computer simulation, and experimental studies.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Proc. of the Workshop on Appl. of Distributed System Theory to the Control of Large Space Struct.; p 143-161
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  • 39
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    Coherent detection of frequency-hopped quadrature modulations in the presence of jamming. II - QPR Class I modulation (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: This paper considers the performance of quadrature partial response (QPR) in the presence of jamming. Although a QPR system employs a single sample detector in its receiver, while quadrature amplitude shift keying (or quadrature phase shift keying) requires a matched-filter type of receiver, it is shown that the coherent detection performances of the two in the presence of the intentional jammer have definite similarities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-29; Nov. 198
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  • 40
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    Beam forming networks for mm-wave satellite communications (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Technology features of a beam forming network (BFN) employing ferrite devices to provide multiple beam antenna pattern control for satellites used in telecommunications are described. The BFN produces the phase and amplitude distribution for each horn in an antenna array, with the number of horns in the array being equal to the number of outputs in the BFN. One configuration involves microwave switches and permits illumination of a single feed horn at a time using ferrite latching circulators that function by reversing the circulation direction. A more flexible version, yielding a variable amplitude distribution across the feed horn array to accommodate changing traffic patterns or serving a TDMA system, includes the capability of forming nulls in the system with a variable phase shifter in the input ports. The antenna scan angles in phased arrays can be limited to 8 deg from center. Acceptable insertion losses have been demonstrated in BFN with hundreds of ports and switching rates as high as 10 kHz.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Microwave Journal (ISSN 0026-2897); 26; Aug. 198
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  • 41
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    Signal processing of anthropometric data (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Anthropometric Measurements Laboratory has accumulated a large body of data from a number of previous experiments. The data is very noisy, therefore it requires the application of some signal processing schemes. Moreover, it was not regarded as time series measurements but as positional information; hence, the data is stored as coordinate points as defined by the motion of the human body. The accumulated data defines two groups or classes. Some of the data was collected from an experiment designed to measure the flexibility of the limbs, referred to as radial movement. The remaining data was collected from experiments designed to determine the surface of the reach envelope. An interactive signal processing package was designed and implemented. Since the data does not include time this package does not include a time series element. Presently the results is restricted to processing data obtained from those experiments designed to measure flexibility.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
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  • 42
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    Chung-Li, Taiwan dual mode (Doppler and spaced antenna) VHF radar: Preliminary specifications (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A major unresolved question in the field of atmospheric research using VHF radar techniques is the relative merit of the two most widely used systems. These systems are the Doppler method and the spaced antenna method. It has been suggested that one radar of each type be operated side by side for a direct comparison of the two techniques. This duplication of effort is not cost effective. The major components of both systems are identical, and one radar could be operated in both modes by proper design of a suitable antenna system and by proper data analysis. The Chung-Li radar will be able to switch between modes on a time scale of seconds and is the first VHF radar to be able to directly compare the Doppler data with spaced antenna data. The system will have performance comparable with the present SOUSY spaced antenna system and will provide mesospheric data in addition to stratospheric and tropospheric data. The major specifications of the Chung-Li radar are given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intern. Council Sci. Unions Middle Atmosphere Program, Vol. 9; p 383-386
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  • 43
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    Capabilities and limitations of existing MST radars: Colorado wind profilers (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Wave Propagation Laboratory is developing a ground-based remote sensing system called PROFILER to measure troposphere parameters currently measured in operational meteorology by radiosondes. The prototype PROFILER uses two radars for wind sounding: a 6-m radar located at Platteville, Colorado, and a 33-cm radar located at Denver's Stapleton International Airport. In addition, a network of three 6-m wind-profiling radars is being installed in Colorado, and a fourth site is planned. The location of the five radars, their characteristics, and their limitations are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intern. Council Sci. Unions Middle Atmosphere Program, Vol. 9; p 325-329
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  • 44
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    Capabilities and limitations of EISCAT as an MST radar (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The European Incoherent Scatter Radar Facility also has facilities which can be used for coherent scatter research of the middle atmosphere. The observatory consists of two independent systems which allow observations of the upper, middle, and lower atmosphere: a tristatic UHF radar capable of vector drift measurements, and a monostatic VHF system. The characteristics of the components are are described including inter-site communication, on-line displays, and the real-time operating system. Analysis of about 60 hours of middle atmosphere observations in 1982 indicate that EISCAT's capabilities to measure mesospheric parameters should improve during moderately or strongly disturbed conditions, enabling measurement of profiles of wind velocity, electron density, and temperature/collision frequency, and in some instances, ion masses. Because of not yet optimized transmit-receive switching, some limitations exist in the monostatic mode when observing coherent scattering in the stratosphere at short ranges.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intern. Council Sci. Unions Middle Atmosphere Program, Vol. 9; p 305-314
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  • 45
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    The spaced antenna drift method (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The spaced antenna drift method is a simple and relatively inexpensive method for determination of atmospheric wind velocities using radars. The technique has been extensively tested in the mesosphere at high and medium frequencies, and found to give reliable results. Recently, the method has also been applied to VHF observations of the troposphere and stratosphere, and results appear to be reliable. This paper discusses briefly the principle of the method, and investigates both its strengths and weaknesses. Some discussions concerning criticisms of the technique are also given, and it is concluded that while these criticisms may be of some concern at times, appropriate care can ensure that the method is at least as viable as any other method of remote wind measurement. At times, the technique has definite advantages.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 171-186
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  • 46
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    Techniques for measurements of horizontal and vertical velocities (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Spectrum analysis and correlation methods used to measure the horizontal and vertical velocities of radar echo signals are examined mathematically. Topics include scattering/reflection geometry, monostatic versus bistatic operation, spaced antenna measurements, radar interferometry and the Doppler method. Vertical velocity determination, optimum pointing angles, and time resolution for periodic variations are also investigated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 150-163
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  • 47
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    Spectral characteristics of the return (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Doppler spectra of VHF radar returns typically indicate a Gaussian back-ground shape with superimposed spikes. An average of 10 Doppler spectra are shown which are calculated from a time series of seven min of complex data. A proper Gaussian fit to the background distribution is possible by neglecting the strong amplitude spikes. If this background distribution is due to beam width broadening, either diffuse reflection or rather isotropic scattering is required. If beam width broadening is neglected, the width of the distribution is given by turbulent velocity fluctuations. The reflected component is about 1/3 of the scattered component. It is assumed that the amplitude spikes due to diffuse reflection indicate a Gaussian frequency distribution such as for the amplitudes due to scattering.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 112-113
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  • 48
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    The effects of pulse rate, power, width and coding on signal detectability (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The effects on the signal detectability of varying the pulse repetition rate (PRF), peak pulse power (p(pk)) and pulse width (tau(p)) (tp) are examined. Both coded and uncoded pulses are considered. The following quantities are assumed to be constant; (1) antenna area, (z)echo reflectivity, (3) Doppler shift, (4) spectral width, (5) spectral resolution, (6) effective sampling rate, and (7) total incoherent spectral averagaing time. The detectability is computed for two types of targets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 100-104
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  • 49
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    Is VHF Fresnel reflectivity due to low frequency buoyancy waves? (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: VHF radar echoes are greatly enhanced near the zenith relative to other directions. This enhancement must be due to reflection from horizontally stratified laminate of refractive index. The refractivity laminate are due to the displacements of low frequency buoyancy (internal gravity) waves acting on the background vertical gradient of refractivity. VANZANDT (1982) has shown that the observed spectra of mesoscale wind fluctuations in the troposphere and lower stratosphere are modeled by a universal spectrum of buoyancy (internal gravity) waves. Since the observed frequency spectrum is red, the buoyancy wave model of the vertical displacement spectrum is strongly enhanced near the zenith. In other terms, the resulting refractivity irregularities are strongly stratified.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 78-80
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  • 50
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    Parmeterization of spectra (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Following reception and analog to digital conversion (A/D) conversion, atmospheric radar backscatter echoes need to be processed so as to obtain desired information about atmospheric processes and to eliminate or minimize contaminating contributions from other sources. Various signal processing techniques have been implemented at mesosphere-stratosphere-troposphere (MST) radar facilities to estimate parameters of interest from received spectra. Such estimation techniques need to be both accurate and sufficiently efficient to be within the capabilities of the particular data-processing system. The various techniques used to parameterize the spectra of received signals are reviewed herein. Noise estimation, electromagnetic interference, data smoothing, correlation, and the Doppler effect are among the specific points addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 535-542
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    Parameterization of spectrum (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Many radars used for wind sounding generate Doppler power spectra as output. For compact data archiving purposes, as well as for data analysis, several parameters were produced to characterize each spectrum. The parameters chosen were noise level, echo signal strength, velocity, and width. Because the derived parameters may be the only quantities available for future analysis, it was important that they did not contain biases imposed by the derivation techniques. This consideration led to a processing scheme in which the parameters were derived independently for each spectrum.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 546-547
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  • 52
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    Data analysis techniques: Spectral processing (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The individual steps in the data processing scheme applied to most radars used for wind sounding are analyzed. This processing method uses spectral analysis and assumes a pulse Doppler radar. Improvement in the signal to noise ratio of some radars is discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 528-531
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  • 53
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    Full versus limited versus no steerability (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The range of phenomena of the MST radar technique to divide the steerability versus nonsteerability problem into two broad with a third subset that lies between these two limits are studied. Processes that vary on a horizontal scale which are comparable to the area of the probing radar beam can best be fully steerable beams. The use of fixed beam systems would be a long term study of the mean wind field. Orographic effects due to mountain ridges and/or land-sea interfaces demand steerable beams, particularly if the effects are three dimensional in character. In view of their lack of moving parts fixed beam systems are more reliable. It is assumed that the reliability of a system is inversely proportioned to the number of moving parts. This is not a problem for fixed beam systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 463-464
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  • 54
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    Directivity and spacing for the antenna elements (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The optimum design choice for the MST radar antenna was considered. The following factors are required: directivity and gain; beam width and its symmetry; sidelobe levels, near and wide angle; impedance matching; feeder network losses; polarization diversity; steerability; cost effectiveness; and maintainability. The directivity and related beam forming aspects of various antenna elements and directivity aspects when such elements are formed into an array are discussed. Array performance for important variables, in particular, the spacing of the elements is considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 456-462
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  • 55
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    Design considerations for high-power VHF radar transceivers: T/R switch design (1983)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: The transceiver (TR) switch developed at NOAA's Aeronomy Laboratory for use in their 50 kW peak power, 50 MHz transmitter is described. The switch mounts inside the transmitter chassis and was designed to be compact while retaining the ability to handle well over 50 kW peak power at average power levels up to 2 kW. The TR switch is a conventional TR/ATR design with equivalent /4 transmission line sections constructed of lumped constant coils and transmitting capacitors in ''Tee' sections. Two TR sections are placed in series to achieve adequate receiver protection. The switch is set into the ''transmit' mode by forward biasing the 3 pin diodes to about 1.2 amperes each. The receive mode is achieved by back biasing the diodes to -15 volts. A directional coupler is also incorporated into the TR switch box to provide a convenient monitor point for forward and reflected transmitter power.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intern. Council Sci. Unions Middle Atmosphere Program, Vol. 9; p 431-432
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    A transceiver module of the Mu radar (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intern. Council Sci. Unions Middle Atmosphere Program, Vol. 9; p 421-423
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  • 57
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    Decoders for MST radars (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Decoding techniques and equipment used by MST radars are described and some recommendations for new systems are presented. Decoding can be done either by software in special-purpose (array processors, etc.) or general-purpose computers or in specially designed digital decoders. Both software and hardware decoders are discussed and the special case of decoding for bistatic radars is examined.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intern. Council Sci. Unions Middle Atmosphere Program, Vol. 9; p 416-420
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    The Urbana MST radar, capabilities and limitations (1983)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The 41-MHz coherent-scatter radar located northeast of the University of Illinois at Urbana is being used for studies of the troposphere, stratosphere and mesosphere regions. The antenna consists of 1008 halfwave dipoles with a physical aperture of 11000 sq m. Transmitted peak power is about 750 kW. Clear-air returns may be received from 6 km to 90 km altitude. Autocorrelation functions of the scattered signal are calculated on-line. From the autocorrelation functions the scattered power, line-of-sight velocity and signal correlation time are calculated. Some aspects of the troposphere/stratosphere and the mesosphere observations are discussed. Capabilities and limitations of the Urbana MST radar are pointed out, and recent and planned improvements to the radar are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Intern. Council Sci. Unions Middle Atmosphere Program, Vol. 9; p 346-356
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  • 59
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    A comment on some drawbacks of monostatic radars (1983)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: All Mesosphere, Stratosphere, Troposphere (MST) radars now in operation or under construction use the monostatic mode, that is to say, the same antenna for both transmitting and receiving. Consequently, it is never possible to determine more than one component of the atmospheric velocity at one point in space. Two important properties of gravity waves which are difficult if not impossible to determine by the monostatic method are discussed. The first of these is the polarization of the gravity waves; that is, the complex ratio of the wave functions of vertical and horizontal motion. A second quantity of importance is the horizontal wavelength of gravity waves. Both of these problems could be overcome by use of a bistatic system. Such a system has the additional advantage of making it possible to measure at very low altitudes, and to look away from the transmitter (for example to make a horizontal section through a thunderstorm). However, bistatic operation, in the practical sense, requires not only an additional highly directive antenna, but also that both the transmitting and receiving antennas should be fully steerable.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 170
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  • 60
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    Techniques for measurement of vertical and horizontal velocities: Monostatic versus bistatic measurements (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Three techniques of direct measurement are presented from which velocities may be obtained: (1) Doppler frequency shift, (2) spaced antenna drift, (3) spatially modulated transverse beam measurements. Emphasis is placed on the Doppler frequency measurement approach. It will compare bistatic with monostatic configurations as regards received power (or sensitivity), spatial resolution, Doppler shift and avoidance of ground clutter.
    Keywords: COMMUNICATIONS AND RADAR
    Type: International Council of Scientific Unions Middle Atmosphere Program, Vol. 9; p 164-169
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    The JPL 1.5-meter Clear Aperture Antenna with 84.5 Percent Efficiency (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: The theoretical and experimental study of a 1.5-meter offset dual shaped reflector at 31.4 GHz is detailed. An efficiency of 84.5 percent, a likely new record for reflector antennas, was ascertained through careful measurements. For larger low noise reflector systems, a 2- to 3-dB improvement in G/T performance over the state of the art ultra low noise ground stations and 90 percent or better aperture efficiency now appear feasible.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 1-14
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  • 62
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    Gain Stability Measurements at S-band and X-band (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: The Search for Extraterrestrial Intelligence (SETI) requires low noise broadband total power radiometers of high gain stability. Preliminary results of SETI field tests for a variety of receiver configurations at Deep Space Station 13 are discussed. The power spectra of Deep Space Network low noise receiving systems exhibit I/F noise whose spectral index is significantly smaller than unity. The gain stability of the S-band systems tested is almost 0.0001. An appendix presents a derivation of the power spectrum of the output of a square law detector.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 159-168
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    Planetary Radar (1983)
    In:  CASI
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    Publication Date: 2014-09-12
    Description: The application of modern planetary radar techniques to a comet passing in close proximity to Earth is discussed. These techniques have the potential to determine the nature of cometary origins, structure, and internal dynamics. Moreover, the understanding gained could very likely negate or corroborate one of the prevailing hypotheses regarding the origin of the solar system: that comets are the remainder of the primordial out of which the planets coalesced approximately 4.5 billion years ago. In 1983, two unique opportunities were presented to observe a comet very near to Earth. The last such encounter was several centuries ago.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 114-115
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  • 64
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    Atmospheric Effects (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The Earth's atmosphere consists mostly of the dry components oxygen (about 21% by volume), nitrogen (about 78% by volume) argon (about 1% by volume), and wet components (water vapor, clouds and rain). Water vapor at 100% relative humidity is approximately 1.7% by volume assuming the U.S. Standard Atmosphere, 15 C, at sea level. A communications link through the atmosphere suffers attenuation from both the dry and wet components. This results in a decreased signal to noise ratio (SNR) of the communications link due to both the signal attenuation and the increased noise temperature resulting from thermal emission.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network: A Radio Commun. Instr. for Deep Space Exploration; 18 p
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    The System View (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Analysis of spacecraft to ground communications link performance and a description of the Deep Space Network system is provided. Due to the tremendous distances involved in communicating between the spacecraft at the edge of our solar system and Earth, communications link performance is stretched to the limit of theoretical predictions. This is required in order to return the maximum amount of data possible during critical events such as planetary flybys. The link analysis provides a basis for the initial link design before spacecraft launch and performance prediction and monitoring during spacecraft flight. Additionally, it indicates what performance upgrades are required for mission extensions and new missions. Performance is improved through the use of a larger antenna collecting area, greater transmitter power, lower receiving system noise temperature and more sophisticated data coding schemes. The performance of the Deep Space Station configuration which serves as the ground portion of the communications link is assessed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network: A Radio Commun. Instr. for Deep Space Exploration; 25 p
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    New Directions: 1982-2000 (1983)
    In:  CASI
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    Publication Date: 2014-09-10
    Description: The major objective of the Deep Space Network in the period 1983-2000 is the fulfillment of the extremely diverse telecommunications requirements of the known and anticipated users. Deep space exploration projects will continue to occupy a dominant role, although in the mid-1980s, with the completion of the Networks Consolidation Program, high Earth orbiter projects will become substantial users of the Network. Also playing an increasingly important role in the Network of the next decade will be non-flight projects, such as Geodynamics, Radio Astronomy, Radar Astronomy, and the Search for Extraterrestrial Intelligence (SETI). The major challenge in meeting the primary Network objective of the next decade will be that of providing increased performance as required by users at costs which can be borne by NASA in an environment of limited resources. Emphasis will be on increased commonality, flexibility, and automation to reduce maintenance and operations costs, and lower mission costs.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network: A Radio Commun. Instr. for Deep Space Exploration; 21 p
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    Command (1983)
    In:  CASI
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    Publication Date: 2014-09-10
    Description: The Command System provides the means by which a project controls the activities of its spacecraft from the Earth. An overview of the Multimission Command (MMC) System is presented. The major components within the MMC System are discussed, with emphasis on the telecommunications related implementations. Two versions of the spacecraft command detection system the Viking Heritage command detector and the NASA standard command detector are summarized. The former prevails in the existing flight projects and the latter will likely be adopted by the missions of the near future. The preparation of Design Control Tables for the control of command link performance between Deep Space Stations and the spacecraft is also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network: A Radio Commun. Instr. for Deep Space Exploration; 24 p
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  • 68
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    Developments Related to the Future Use of the 32-ghz Allocation for Deep Space Research (1983)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: The advantage of 32-GHz links, the estimated link performance, and developments in the fields of antennas, low noise preamplifiers, radiometry, and propagation studies are discussed. A description of ways to demonstrate 32-GHz link capability concludes the discussion.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 165-175
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  • 69
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    Antenna beam solid angle relationships (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Some of the useful formulas and methods for determining antenna beam solid angle are presented. The applicability of these formulas in evaluating radiometric systems performance is illustrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 168-172
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  • 70
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    Boresighting techniques for the Antenna Control Assembly (ACA) (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Comparison of four scanning schemes including CONSCAN indicates that CONSCAN with signal cleanup and protection processes has the greatest merit in terms of accuracy, dependability and automatic unattended operation. Specific problem areas, error sources, and corrective measures are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 116-122
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  • 71
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    Radio frequency interference protection of communications between the Deep Space Network and deep space flight projects (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The increasing density of electrical and electronic circuits in Deep Space Station systems for computation, control, and numerous related functions has combined with the extension of system performance requirements calling for higher speed circuitry along with broader bandwidths. This has progressively increased the number of potential sources of radio frequency interference inside the stations. Also, the extension of spectrum usage both in power and frequency as well as the greater density of usage at all frequencies for national and international satellite communications, space research, Earth resource operations and defense, and particularly the huge expansion of airborne electronic warfare and electronic countermeasures operations in the Mojave area have greatly increased the potential number and severity of radio frequency interference incidents. The various facets of this problem and the efforts to eliminate or minimize the impact of interference on Deep Space Network support of deep space flight projects are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 125-131
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  • 72
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    Tropospheric/ionospheric transmission tests (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Four tests are described which are designed to evaluate the magnitude, type, and frequency of occurence of amplitude and phase variations in the solar power satellite power (SPS) beam as seen by the rectenna. Particular attention is given to the degree of deviation in the propagation observed under two conditions unique to the SPS: monochromaticity; and smallness of the effective aperture of individual rectenna element dipoles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 111-118
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  • 73
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    Current sheet model (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The model of a rectenna based on the current sheet equivalency of a large planar array is described. The model is mathematically characterized by expression for the fraction of the incident plane wave that is reflected from the sheet. The model is conceptually justified for normal incidence by comparing it to the waveguide model in which evanescent modes, present as beyond and cutoff, correspond to the near field components which become negligible at any significant distance from the antenna array.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 47-56
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  • 74
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    Plane wave derivation (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The characteristic of plane waves are derived from Maxwell's equations. The derivation utilizes both the transmission and reflection of plane waves as a basis for its formulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: A Theoret. Study of Microwave Beam Absorption by a Rectenna; p 39-43
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  • 75
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    Conversion of the DSN teletype subsystem to the eight-level ASCII national standard (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A functional description of the new eight level ASCII Teletype Subsystem and its constitutent Teletype Assemblies is given. An overview of the implementation of the Teletype Subsystem is presented together with a discussion of the distinct capabilities of its equipment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 95-102
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  • 76
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    Command system output bit verification (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: An automatic test was developed to test the ability of the deep space station (DSS) command subsystem and exciter to generate and radiate, from the exciter, the correct idle bit sequence for a given flight project or to store and radiate received command data elements and files without alteration. This test, called the command system output bit verification test, is an extension of the command system performance test (SPT) and can be selected as an SPT option. The test compares the bit stream radiated from the DSS exciter with reference sequences generated by the SPT software program. The command subsystem and exciter are verified when the bit stream and reference sequences are identical. It is a key element of the acceptance testing conducted on the command processor assembly (CPA) operational program (DMC-0584-OP-G) prior to its transfer from development to operations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 112-114
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  • 77
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    Historical data on characteristics of radio systems used for United States deep-space communications (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Historical data on selected communication parameters are presented in tables and charts for 14 deep space missions. Some observations are made about trends in communication capability.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition; p 7-16
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  • 78
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    Two-channel Costas loop tracking performance for UQPSK signals with arbitrary data formats (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Previous results on the tracking performance of two-channel Costas-type carrier synchronization loops are generalized and corrected, in order that they may be applied to several mixed-format cases. In particular, the mean-square phase jitter performance of these loops with active arm filters, synchronous or asynchronous symbol clocks, and arbitrary data formats on the two channels is examined. It is demonstrated that for each case, selection of the channel gain ratio, as motivated by the MAP estimation theory, does not guarantee optimum loop tracking performance: in some instances, a conventional single-channel Costas loop would outperform the two-channel version with the MAP choice of gain ratio. It is suggested that the gain ratio be chosen to directly minimize the mean-square phase tracking jitter which is equivalent to minimizing the loop's 'squaring loss'. This can, in some cases, improve the performance measure, although in all cases, the two-channel loop will still outperform the single-channel version.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-29; Sept
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  • 79
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    Investigation of a solid state power combining antenna proposed for use in the solar power satellite (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Performance tests performed on a four-feed microstrip antenna and feed network are analyzed. Frequency response with and without amplifiers, an investigation of noise threshold, phase tracking, and jitter are included. Recommendations for further development of SPS power conversion modules are also included.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 1; 28 p
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  • 80
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    Effects of rain and fog on the Shuttle Ku-band microwave scanning beam landing system range and accuracy performance (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The microwave Scanning Beam Landing System's (MSBLS) performance in fog and rain was studied. The fog and rain effects on the Shuttle Ku-band system were determined. Specifically, microwave attenuation, beam distortion, and coordinate errors resulting from operation of the MSBLS in poor weather conditions were evaluated. The main physical processes giving rise to microwave attenuation were found to be absorption and scattering by water droplets. The general theory of scattering and absorption used is discussed and a listing of applicable computer programs is provided.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The 1981 NASA ASEE Summer Fac. Fellowship Program, Vol. 1; 33 p
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  • 81
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    Shuttle Imaging Radar: A/B sensors (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The exciting discoveries of the Shuttle Imaging Radar-A (SIR-A) experiment prompted a refly of the instrument to be designated the Shuttle Imaging Radar-B. The SIR-B instrument will reuse the hardware flown for the SIR-A mission and add some interesting refinements. The two radar sensors are described in detail. The SIR-A and SIR-B instruments are both tailored for use on the Space Shuttle. They are physically configured to fit in the Shuttle's payload bay, are powered and cooled by shuttle systems, are controlled by the crew or from the ground, and record data on board or beam it to the ground using the orbiter's data links. The radars are designed to accommodate a range of orbiter altitudes and have built in operating modes to cover a wide variety of mission objectives. The flexibility and utility of these radars make them ideal, cost effective instruments for research in the Space Shuttle environment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 26-31
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  • 82
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    The finite ground plane effect on the microstrip antenna radiation patterns (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The uniform geometrical theory of diffraction (GTD) is employed for calculating the edge diffracted fields from the finite ground plane of a microstrip antenna. The source field from the radiating patch is calculated by two different methods: the slot theory and the modal expansion theory. Many numerical and measured results are presented to demonstrate the accuracy of the calculations and the finite ground plane edge effect.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); AP-31; July 198
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  • 83
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    An algorithm for the empirical optimization of antenna arrays (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A numerical technique is presented to optimize the performance of arbitrary antenna arrays under realistic conditions. An experimental-computational algorithm is formulated in which n-dimensional minimization methods are applied to measured data obtained from the antenna array. A numerical update formula is used to induce partial derivative information without requiring special perturbations of the array parameters. The algorithm provides a new design for the antenna array, and the method proceeds in an iterative fashion. Test case results are presented showing the effectiveness of the algorithm.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); AP-31; July 198
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  • 84
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    Capacity limit of the noiseless, energy-efficient optical PPM channel (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is shown that even though the capacity per photon can be made to increase without bound, the capacity per channel use (for best power efficiency) is always less than 2 nats per symbol. Furthermore, it approaches 2 nats per symbol as the bandwidth expansion factor goes to infinity. Previously announced in STAR as N82-20121
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications (ISSN 0090-6778); COM-31; April 19
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  • 85
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    Observations of internal waves in the Gulf of California by SEASAT SAR (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Internal waves which are among the most commonly observed oceanic phenomena in the SEASAT SAR imagery are discussed. These waves are associated with the vertical displacements of constant water density surfaces in the ocean. Their amplitudes are maximum at depths where the water density changes most rapidly usually at depths from 50 to 100 m, whereas the horizontal currents associated with these waves are maximum at the sea surface where the resulting oscillatory currents modulate the sea surface roughness and produce the signatures detected by SAR.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 118-120
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    Performance evaluation of the JPL interim digital SAR processor (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The performance of the Interim Digital SAR Processor (IDP) was evaluated. The IDP processor was originally developed for experimental processing of digital SEASAT SAR data. One phase of the system upgrade which features parallel processing in three peripheral array processors, automated estimation for Doppler parameters, and unsupervised image pixel location determination and registration was executed. The method to compensate for the target range curvature effect was improved. A four point interpolation scheme is implemented to replace the nearest neighbor scheme used in the original IDP. The processor still maintains its fast throughput speed. The current performance and capability of the processing modes now available on the IDP system are updated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 93-95
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  • 87
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    Processor architecture for airborne SAR systems (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Digital processors for spaceborne imaging radars and application of the technology developed for airborne SAR systems are considered. Transferring algorithms and implementation techniques from airborne to spaceborne SAR processors offers obvious advantages. The following topics are discussed: (1) a quantification of the differences in processing algorithms for airborne and spaceborne SARs; and (2) an overview of three processors for airborne SAR systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 89-92
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  • 88
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    Slotted waveguide array antennas for spaceborne SAR applications (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Starting with mission definitions and constraints for the NASA proposed Shuttle Active Microwave Experiments (SAMEX) and Free Flying Imaging Radar Experiment (FIREX), Hughes Aircraft Company has compiled and studied the technology available for slotted waveguide planar array antennas suitable for spaceborne SAR application. Antenna performance is derived, and fabrication techniques are discussed. Mission requirements will always lead to an aperture subdivided into waveguide modules, thereby validating a module definition for other mission building blocks. Finally, a specific design is proposed for a SAMEX mission using the modules as RF aperture building blocks, resulting in a (nominal) 15.1 meter by 5.5 meter extensile dual polarized L-, C-, and X-band planar array with an associated extensile graphite/epoxy support structure. Antenna development begin with a fabrication method development study involving a representative portion of an antenna module.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 35-40
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  • 89
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    Geologic application of spaceborne radars (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Geologic applications of spaceborne radar images, specifically SEASAT in southern California and SIR-A in Indonesia are illustrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 5-9
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  • 90
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    Real-time synthetic aperture radar image formation utilizing an electrooptic spatial light modulator (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The development of novel electro-optic spatial light modulators (both one and two dimensional) which allows real-time coherent optical SAR processors to be implemented is outlined. It is suggested that the availability of such processors may initiate new mission applications not presently envisioned due to current digital processor limitations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 107-109
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  • 91
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    Radar activities of the DFVLR Institute for Radio Frequency Technology (1983)
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    Publication Date: 2011-08-18
    Description: Aerospace research and the respective applications microwave tasks with respect to remote sensing, position finding and communication are discussed. The radar activities are directed at point targets, area targets and volume targets; they center around signature research for earth and ocean remote sensing, target recognition, reconnaissance and camouflage and imaging and area observation radar techniques (SAR and SLAR). The radar activities cover a frequency range from 1 GHz up to 94 GHz. The radar program is oriented to four possible application levels: ground, air, shuttle orbits and satellite orbits. Ground based studies and measurements, airborne scatterometers and imaging radars, a space shuttle radar, the MRSE, and follow on experiments are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 136-139
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    Spaceborne radar research in the 1980's (1983)
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    Publication Date: 2011-08-18
    Description: The SEASAT SAR and Shuttle Imaging Radar SIR-A experiments demonstrated that spaceborne synthetic aperture radars provide synoptic images of land and ocean features. Radar images clearly show geologic structures, morphologic features, clear cutting, subsurface features (in very arid regions), agricultural and urban land use, ocean surface waves, current boundaries, internal waves, ice floes and numerous other ocean features which affect the surface roughness.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 131-135
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    Radar image interpretation techniques applied to sea ice geophysical problems (1983)
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    Publication Date: 2011-08-18
    Description: The geophysical science problems in the sea ice area which at present concern understanding the ice budget, where ice is formed, how thick it grows and where it melts, and the processes which control the interaction of air-sea and ice at the ice margins is discussed. The science problems relate to basic questions of sea ice: how much is there, thickness, drift rate, production rate, determination of the morphology of the ice margin, storms feeling for the ice, storms and influence at the margin to alter the pack, and ocean response to a storm at the margin. Some of these questions are descriptive and some require complex modeling of interactions between the ice, the ocean, the atmosphere and the radiation fields. All involve measurements of the character of the ice pack, and SAR plays a significant role in the measurements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 116-117
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  • 94
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    Stereo imaging with spaceborne radars (1983)
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    Publication Date: 2011-08-18
    Description: Stereo viewing is a valuable tool in photointerpretation and is used for the quantitative reconstruction of the three dimensional shape of a topographical surface. Stereo viewing refers to a visual perception of space by presenting an overlapping image pair to an observer so that a three dimensional model is formed in the brain. Some of the observer's function is performed by machine correlation of the overlapping images - so called automated stereo correlation. The direct perception of space with two eyes is often called natural binocular vision; techniques of generating three dimensional models of the surface from two sets of monocular image measurements is the topic of stereology.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 53-55
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  • 95
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    Use of coregistered radar, visible and IR images for geologic remote sensing (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Shuttle Imaging Radar (SIR-A) obtained images over the southern portion of the San Rafael Swell in eastern Utah. SEASAT SAR and LANDSAT MSS images and thermal inertia data from the Heat Capacity Mapping Mission (HCMM) were correlated with the SIR-A data. Radar images obtained with different incidence angles and different illumination directions were compared with images obtained in other portions of the spectrum for geologic remote sensing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Spaceborne Imaging Radar Symp.; p 13-16
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    European Space Agency, ERS-1 program (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The objectives selected for ERS-1 which are primarily intended to facilitate the exploitation of coastal oceans, including ice infested waters, and to facilitate the development of improved global weather information through the provision of information on the weather conditions over the oceans of the word are outlined. Additionally, land objectives will be addressed using the synthetic aperture radar incorporated in the payload.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 140-142
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    Mechanisms for SAR imaging of ocean surface phenomena: Theory and experiment (1983)
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    Publication Date: 2011-08-18
    Description: Understanding the SAR response to surface wave is a central issue in the analysis of SAR ocean images. The imaging mechanism for gravity waves and the practical question of just which characteristics of the ocean wave field can be measured remotely using SAR were examined. Assessments of wave imaging theory are based primarily on comparisons of the directional wave height variance spectrum psi (K) measured by in situ buoys with estimates from SAR images. Other criteria are also recommended, e.g., the effects of focus adjustments. It is assumed that fluctuations in SAR image intensity are proportional to fluctuations in ocean surface height. If this were true, the Fourier power spectrum of a SAR image and corresponding surface measurements of psi would coincide. Differences between SAR estimates based on this hypothesis and buoy measurements of psi are then used to begin the assessment of rival wave imaging theories.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 124-127
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    Microstrip antennas for SAR applications (1983)
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    Publication Date: 2011-08-18
    Description: Current and future microstrip antenna technology development for Spaceborne Synthetic Aperture Radars (SAR) are summarized. Some of the electrical and mechanical characteristics of previously and presently developed microstrip SAR antennas are shown. The SEASAT, the SIR-A and presently the SIR-B antennas are all designed for operation at L-band with approximately 22 MHz of bandwidth. The antennas have linear polarization with minimum of 20 dB of polarization purity. Both the SEASAT and SIR-A antennas were designed for a fixed pointing angle of 20.5 deg and 47 deg, respectively. However, the SIR-B has the added feature of mechanical beam steering in elevation (range). With the exception of different mechanical characteristics, it is concluded that present spaceborne SAR antennas have only single frequency and single polarization performance. The lack of large spaceborne antennas operating at the higher degree of fabrication tolerance required for a given performance; and larger feed and radiating element losses.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 32-34
    Format: text
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  • 99
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    A fast, programmable hardware architecture for spaceborne SAR processing (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The launch of spaceborne SARs during the 1980's is discussed. The satellite SARs require high quality and high throughput ground processors. Compression ratios in range and azimuth of greater than 500 and 150 respectively lead to frequency domain processing and data computation rates in excess of 2000 million real operations per second for C-band SARs under consideration. Various hardware architectures are examined and two promising candidates and proceeds to recommend a fast, programmable hardware architecture for spaceborne SAR processing are selected. Modularity and programmability are introduced as desirable attributes for the purpose of HTSP hardware selection.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 99-104
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    Spaceborne SAR and sea ice (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A number of remote sensing systems deployed in satellites to view the Earth which are successful in gathering data on the behavior of the world's snow and ice covers are described. Considering sea ice which covers over 10% of the world ocean, systems that have proven capable to collect useful data include those operating in the visible, near-infrared, infrared, and microwave frequency ranges. The microwave systems have the essential advantage in observing the ice under all weather and lighting conditions. Without this capability data are lost during the long polar night and during times of storm passage, periods when ice activity can be intense. The margins of the ice pack, a region of particular interest, is shrouded in cloud between 80 and 90% of the time.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Spaceborne Imaging Radar Symp.; p 113-115
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