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  • COMMUNICATIONS AND RADAR  (58)
  • 1980-1984  (58)
  • 1984  (58)
  • 1
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    The spatial evolution of t he directional wave spectrum in the Southern Ocean: Its relation to extreme waves in Agulhas Current (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An experiment using the Shuttle Imaging Radar-B (SIR-B) to monitor certain properties of the ocean wave directional spectrum and to track the long swell systems as they propagate northward to encounter the Agulhas near the southeastern coast of Africa is discussed. The experiment is designed around the unique capability of SIR-B to overcome key limitations of the Seasat synthetic aperture radar data set, and to extend the existing Seasat results into new areas. Ocean wave systems will be tracked. The variable-incidence-angle capability to examine wave imaging quality will be utilized. Doppler current measurements will be attempted. An effort will be made to verify that the lower range-to-velocity ratio of SIR-B will lead to the improved response of azimuth-traveling wave systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL The SIR-B Sci. Invest. Plan; 4 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Tracking ocean wave spectrum from SAR images (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An end to end algorithm for recovery of ocean wave spectral peaks from Synthetic Aperture Radar (SAR) images is described. Current approaches allow precisions of 1 percent in wave number, and 0.6 deg in direction.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center Frontiers of Remote Sensing of the Oceans and Troposphere from Air and Space Platforms; p 159-168
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    An E-plane analysis of aperture-matched horn antennas using the moment method and the uniform geometrical theory of diffraction (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The moment method and the uniform geometrical theory of diffraction are utilized to obtain two separate solutions for the E-plane field pattern of an aperture-matched horn antenna. This particular horn antenna consists of a standard pyramidal horn with the following modifications: a rolled edge section attached to the aperture edges and a curved throat section. The resulting geometry provides significantly better performance in terms of the pattern, impedance, and frequency characteristics than normally obtainable. The moment method is used to calculate the E-plane pattern and BSWR of the antenna. However, at higher frequencies, large amounts of computation time are required. The uniform geometrical theory of diffraction provides a quick and efficient high frequency solution for the E-plane field pattern. In fact, the uniform geometrical theory of diffraction may be used to initially design the antenna; then, the moment method may be applied to fine tune the design. This procedure has been successfully applied to a compact range feed design.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-176841 , NAS 1.26:176841 , OSU-TR-716148-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    64-meter to 70-meter Antenna Extension (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The Deep Space Network 64-m antennas are being upgraded to improve their performance by increasing the diameter to 70 m, installing precision panels, and using a shaped surface. Performance improvement is expected to be 1.9 dB at X-band and 1.4 dB at S-band. The design and capabilities of the antenna are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Rept.; p 160-164
    Format: text
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  • 5
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    Mark IVA DSN 26-meter Subnet (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The Office of Space Tracking and Data Systems' Networks Consolidation Program (NCP), managed by the Jet Propulsion Laboratory (JPL), includes the implementation of a 26-meter Tracking and Communications Subnet as a part of the Mark IV A Deep Space Network (DSN). The incorporatin of this subnet into the DSN will contribute to the NCP goal of consolidating the two NASA ground tracking networks into one tracking network. The 26-meter Tracking and Communication Subnet was designed to provide the capability to support, at each Deep Space Communication Complex, the tracking and data communication requirements of the earth-orbital missions that cannot be supported by the Tracking and Data Relay Satellite System when it becomes operational. Implementation activities and planned capabilities of the subnet are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Rept.; p 152-159
    Format: text
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  • 6
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    Submilliarcsecond VLBI Using Compact Close Pairs of Radio Sources: Error Analysis (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-13
    Description: The potential accuracy attainable for (delta) VLBI positional measurements (submilliarc second level) is reached by simultaneously observing pairs of compact radio sources whose angular separation are smaller than the beamwidth of each antenna. Simultaneous (delta) VLBI (SVLBI) enables significant cancellation of measurement errors. Solar plasma is the dominant fluctuating error source in SVLBI positional measurements since there is enhanced cancellation of the troposphere and ionosphere, and complete cancellation of oscillator instabilities. Of the nonfluctuating error sources, errors due to universal time predominate. By performing SVLBI experiments over several years with many different close pairs of radio sources, limits can be placed on reference frame stability. Intrinsic properties of the sources, such as source structure and proper motion, will limit measurements. The SVLBI differential phase and corruptive noise sources will be discussed here along with estimated results.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommunications and Data Acquisition Rept.; p 1-16
    Format: text
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  • 7
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    Analysis of an infinite array of rectangular microstrip patches with idealized probe feeds (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A solution is presented to the problem of an infinite array of microstrip patches fed by idealized current probes. The input reflection coefficient is calculated versus scan angle in an arbitrary scan plane, and the effects of substrate parameters and grid spacing are considered. It is pointed out that even when a Galerkin method is used the impedance matrix is not symmetric due to phasing through a unit cell, as required for scanning. The mechanism by which scan blindness can occur is discussed. Measurement results are presented for the reflection coefficient magnitude variation with angle for E-plane, H-plane, and D-plane scans, for various substrate parameters. Measured results from waveguide simulators are also presented, and the scan blindness phenomenon is observed and discussed in terms of forced surface waves and a modified grating lobe diagram.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); AP-32; 1101-110
    Format: text
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  • 8
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    Satellite provided customer promises services, a forecast of potential domestic demand through the year 2000. Volume 4: Sensitivity analysis (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The overall purpose was to forecast the potential United States domestic telecommunications demand for satellite provided customer promises voice, data and video services through the year 2000, so that this information on service demand would be available to aid in NASA program planning. To accomplish this overall purpose the following objectives were achieved: (1) development of a forecast of the total domestic telecommunications demand; (2) identification of that portion of the telecommunications demand suitable for transmission by satellite systems; (3) identification of that portion of the satellite market addressable by consumer promises service (CPS) systems; (4) identification of that portion of the satellite market addressable by Ka-band CPS system; and (5) postulation of a Ka-band CPS network on a nationwide and local level. The approach employed included the use of a variety of forecasting models, a parametric cost model, a market distribution model and a network optimization model. Forecasts were developed for: 1980, 1990, and 2000; voice, data and video services; terrestrial and satellite delivery modes; and C, Ku and Ka-bands.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-174662 , NAS 1.26:174662
    Format: application/pdf
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  • 9
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    Microwave monolithic integrated circuit development for future spaceborne phased array antennas (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The development of fully monolithic gallium arsenide (GaAs) receive and transmit modules suitable for phased array antenna applications in the 30/20 gigahertz bands is presented. Specifications and various design approaches to achieve the design goals are described. Initial design and performance of submodules and associated active and passive components are presented. A tradeoff study summary is presented, highlighting the advantages of a distributed amplifier approach compared to the conventional single power source designs. Previously announced in STAR as N84-13399
    Keywords: COMMUNICATIONS AND RADAR
    Type: AIAA PAPER 84-0656
    Format: text
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  • 10
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    A microprocessor based anti-aliasing filter for a PCM system (1984)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Described is the design and evaluation of a microprocessor based digital filter. The filter was made to investigate the feasibility of a digital replacement for the analog pre-sampling filters used in telemetry systems at the NASA Ames-Dryden Flight Research Facility (DFRF). The digital filter will utilize an Intel 2920 Analog Signal Processor (ASP) chip. Testing includes measurements of: (1) the filter frequency response and, (2) the filter signal resolution. The evaluation of the digital filter was made on the basis of circuit size, projected environmental stability and filter resolution. The 2920 based digital filter was found to meet or exceed the pre-sampling filter specifications for limited signal resolution applications.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-177000 , NAS 1.26:177000
    Format: application/pdf
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