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  • Polymer and Materials Science  (5,279)
  • COMMUNICATIONS AND RADAR
  • 1980-1984
  • 1975-1979  (5,638)
  • 1950-1954
  • 1978  (2,846)
  • 1976  (2,792)
Collection
Keywords
Publisher
Years
  • 1980-1984
  • 1975-1979  (5,638)
  • 1950-1954
Year
  • 1
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    An empirical spectral bandwidth model for superior conjunction (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The downlink signal from spacecraft in superior solar conjunction phases suffers a great reduction in signal-to-noise ratio. Responsible in large part for this effect is the line broadening of the signal spectrum. An analytic empirical expression was developed for spectral bandwidth as a function of heliocentric distance from 1 to 20 solar radii. The study is based on spectral broadening data obtained from the superior conjunctions of Helios 1 (1975), Helios 2 (1976), and Pioneer 6 (1968). The empirical fit is based in part on a function describing the electron content in the solar corona.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 216-223
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  • 2
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    Radio frequency interference between spacecraft in different missions (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: The possibility of separately receiving signals transmitted in a common frequency band from spacecraft in different missions was studied. For the mission pairs that were examined, co-channel operation without interference is generally possible. For some mission pairs, co-channel interference would occur during brief post-launch periods.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 180-184
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  • 3
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    System performance testing of the DSN radio science system, Mark 3-78 (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: System performance tests are required to evaluate system performance following initial system implementation and subsequent modification, and to validate system performance prior to actual operational usage. Non-real-time end-to-end Radio Science system performance tests are described that are based on the comparison of open-loop radio science data to equivalent closed-loop radio metric data, as well as an abbreviated Radio Science real-time system performance test that validates critical Radio Science System elements at the Deep Space Station prior to actual operational usage.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 129-133
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  • 4
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    Deep space telecommunications and the solar cycle: A reappraisal (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Observations of density enhancement in the near corona at solar cycle (sunspot) maximum have rather uncritically been interpreted to apply equally well to the extended corona, thus generating concern about the quality of outer planet navigational data at solar cycle maximum. Spacecraft have been deployed almost continuously during the recently completed solar cycle 20, providing two powerful new coronal investigatory data sources: (1) in-situ spacecraft plasma measurements at approximately 1 AU, and (2) plasma effects on monochromatic spacecraft signals at all signal closest approach points. A comprehensive review of these (solar cycle 20) data lead to the somewhat surprising conclusions that for the region of interest of navigational data, the highest levels of charged particle corruption of navigational data can be expected to occur at solar cycle minimum, rather than solar cycle maximum, as previously believed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 110-124
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  • 5
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    Low-noise receivers: S-band parametric up converter development (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The combination of a cryogenically-cooled parametric upconverter and a higher frequency maser post amplifier was proposed as a method of achieving maser-like receiver noise temperatures over much larger instantaneous bandwidths and tuning ranges than are presently obtainable with masers in the range of 1 to 18 GHz. An experimental 2.0- to 2.5-GHz parametric upconverter/maser system was developed to explore these possibilities. Initial tests of this system resulted in an effective input noise temperature of 3.1 K at 2295 MHz and 3.2 K at 2388 MHz. The parametric upconverter logged over 1500 hours at 4.5 K and underwent 5 thermal cycles (300 K to 4.5 K to 300 K) without degradation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 31-47
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  • 6
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    Tracking error of 100-m antenna due to wind gust (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: A procedure is shown to derive root-mean-square tracking error for an antenna system in response to wind gust loading. Example calculations are illustrated for the design of a proposed 100 m antenna. The effect of wind gust correlation is also considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 94-101
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  • 7
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    CCIR papers on telecommunications for deep space research (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Mission requirements, equipment factors, and link performance define the frequency bands that are preferred for deep space research using manned and unmanned spacecraft. The preferred bands and selection considerations are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 164-179
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  • 8
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    New X-band microwave equipment at the DSN 64-meter stations (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The performance and capabilities of the DSN 64 m antennas at X-band are considered including extensive modifications to the XRO cone assemblies. The changes include a feed assembly with a dual hybrid mode horn and orthogonal mode junction, dual traveling wave masers, and receiver mode selector.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 126-128
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  • 9
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    Simultaneous dual-frequency, round-trip calibration of Doppler data with application to radio science experiments (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: Simultaneous dual-frequency, round-trip calibration of Doppler data is discussed in light of unequal spacecraft turnaround ratios at S- and X-band. The impact of unequal turnaround ratios on calibration accuracies in the specific cases of the Gravitational Wave Detection Experiment and the Solar Gravitational Quadrupole Moment Experiment is considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 49-54
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  • 10
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    On improved ranging (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The use of a 1 MHz range code and a narrow-passband IF filter reduces waveform distortion error by a factor of as much as 20. Along with this improvement in ranging precision, ranging accuracy is enhanced by nullifying many errors caused by equipment vagaries. The IF filter and concomitant modification of ranging system software (and in the case of the planetary ranging assembly, hardware) are the most cost-effective way of improving the current generation ranging system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 40-44
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  • 11
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    JPL 2-to-the-20th-power channel 300 MHz bandwidth digital spectrum analyzer (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: A million (two to the 20th power) channel, 300 MHz bandwidth, digital spectrum analyzer was considered. The design, fabrication, and maintenance philosophy of the modular, pipelined, fast fourier transform (FFT) hardware are described. The spectrum analyzer will be used to examine the region from 1.4 GHz to 26 GHz for radio frequency interference which may be harmful to present and future tracking missions of the Deep Space Network. The design has application to the search for extraterrestrial intelligence signals and radio science phenomena.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 57-61
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  • 12
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    On estimating the phase of a periodic waveform in additive Gaussian noise, part 1 (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Motivated by recent advances in technology, a new look is taken at the problem of estimating the phase of a periodic waveform in additive Gaussian noise. The maximum a posteriori probability criterion with signal space interpretation is used to obtain the structures of optimum and some suboptimum phase estimators for the following cases: (1) known constant frequency and unknown constant phase with an a priori distribution; (2) unknown constant frequency and phase with a joint a priori distribution; (3) frequency a parameterized function of time with a joint a priori distribution on parameters and phase and (4) frequency a Gaussian random process.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 152-164
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  • 13
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    CCIR paper on the radiocommunications requirements for systems to search for extraterrestrial life (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The allocation and propagation of radio frequency bands to be used in the search for extraterrestrial intelligence is considered. Topics discussed include: propagation factors; preferred frequency bands; system characteristics and requirements; and interference.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 224-244
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  • 14
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    Pioneer Venus 1978 Deep Space Network telecommunications compatibility test program status (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Pioneer Venus 1978 flight project Deep Space Network telecommunications compatibility test program is discussed. Subsystem design tests performed during April 1977 and November 1977 are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 39-100
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  • 15
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    The Communications Technology Satellite /CTS/ Program (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The purposes of the joint Canadian-U.S. Communications Technology Satellite (CTS) Program are (1) to conduct satellite communication systems experiments using the 12- and 14-GHz bands and low-cost transportable ground terminals, (2) to develop and flight test a power amplifier tube having a greater than 50% efficiency with a saturated power output of 200 W at 12 GHz, (3) to develop and flight test a lightweight extendible solar array with an initial power output greater than 1 kW, and (4) to develop and flight test a 3-axis stabilization system to maintain accurate antenna boresight positioning on a spacecraft with flexible appendages. Brief descriptions of these experiments and of the ground facilities are provided.
    Keywords: COMMUNICATIONS AND RADAR
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  • 16
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    Television applications of interline-transfer CCD arrays (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The design features and characteristics of interline transfer (ILT) CCD arrays with 190 x 244 and 380 x 488 image elements are reviewed, with emphasis on optional operating modes and system application considerations. It was shown that the observed horizontal resolution for a TV system using an ILT image sensor can approach the aperture response limit determined by photosensor site width, resulting in enhanced resolution for moving images. Preferred camera configurations and read out clocking modes for maximum resolution and low light sensitivity are discussed, including a very low light level intensifier CCD concept. Several camera designs utilizing ILT-CCD arrays are described. These cameras demonstrate feasibility in applications where small size, low-power/low-voltage operation, high sensitivity and extreme ruggedness are either desired or mandatory system requirements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 152-156
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  • 17
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    Television cameras employing solid-state imaging sensors for manned spacecraft applications (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Space Shuttle television system incorporates a versatile complement of TV equipment which allows the positioning, quantity, and performance capabilities of the multiple TV cameras to vary as dictated by the particular mission. However, current TV camera technology employing glass enclosed, vacuum processed image sensors results in a bulky device that restricts its location and versatility. Problems and potential solutions that can be achieved through the employment of solid-state image sensors for both monochrome and color applications are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 126-128
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  • 18
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    Command detector SNR estimator and lock status monitor circuitry (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A breadboard of the command detector signal-to-noise-ratio estimator and lock status monitor was built on a wire-wrap card. The breadboard was integrated with the standard command detector, and its performance was measured. The design, design constraints, and construction of the breadboard are described. The performance is shown to agree with the theoretical model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 42-51
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  • 19
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    The scattering of obliquely incident plane waves from a corrugated conducting surface (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface. This solution is used to compute the radar cross section of the surface in the case of backscatter from irregular (i.e., stochastic) corrugations. An interesting feature of the solution is the occurrence of singularities in the scattered fields. These singularities appear to be a manifestation of focusing by the surface at its 'stationary' points. Whether or not the singularities occur in the solution depends on the manner in which one restricts the analysis to the far-field.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Nov. 197
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  • 20
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    Radio frequency boresight analysis of the low cost 64-meter antenna (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Configurations (two) of the reflector-only assemblies, using different width backup cones, are analyzed for RF boresight direction changes and wind distortions. The wider backup cone is best for minimum weight; however, there is an optimum weight which minimizes the RF boresight errors for a wind load that produces the maximum pitching moment of both configurations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 128-135
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  • 21
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    Magnitude of 64-m elevation axis movements due to alidade temperature changes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In projected very-long baseline interferometry (VLBI) work a reference point for 64-m antennas is the intersection of the elevation and azimuth axes. A minimum-level effort at DSS 14 to determine the magnitude of the effect of diurnal changes in the temperature of the alidade legs on the height of the elevation axis is described. The thermal expansion between the lowest recorded temperature -3 C (27 F) and the highest, 36 C (97 F), over the period covered was 8.9 mm (0.35 in.).
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 41-44
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  • 22
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    Remote intensity fluctuation measurements with a laser Doppler radar (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Applied Optics; 15; Sept
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  • 23
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    New sidelobe envelopes for small aperture earth stations (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The advent of domestic satellite systems and technological improvements in both space and ground equipment makes the use of small aperture earth stations economically feasible and attractive for broadcast satellite applications. With increasing use of the orbit spectrum, there is some concern that broadcast satellite systems may not be able to obtain satisfactory allocations of this orbit-spectrum resource because of interference considerations. Specifically, interference calculations based on the present envelope result in comparatively large orbit spacings for broadcast satellites. Theoretical and experimental investigations of simple sidelobe suppression techniques, plus an analysis of experimental data on small aperture antennas, indicate that much better sidelobe performance can be obtained with a very small cost or performance penalty.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Broadcasting; BC-22; June 197
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  • 24
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    The input admittance of the rectangular cavity-backed slot antenna (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The input admittance of the rectangular cavity-backed slot antenna is investigated. The slot is assumed narrow so that the voltage distribution in its aperture is sinusoidal. Equations which represent the input admittance of this slot, backed by a rectangular cavity in which a single propagating wave is assumed to exist, are given. Calculations based on these representations are compared to available measured data. As the depth of the cavity increased the resonant frequency decreased and the bandwidth became narrower. Input admittance curves as a function of electrical slot length are also presented for several size cavities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; May 1976
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  • 25
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    Implementation of the radio science subsystem in the DSN (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The functional characteristics of a subsystem for support of radio science data acquisition requirements are described. The factors that were of major importance in the design and implementation approach are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 282-287
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  • 26
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    Power conservation for reflector antennas with truncated feed patterns (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Reflector-antenna calculations using idealised truncated feed patterns can lead to incorrect values of total secondary radiated power. It is demonstrated that this discrepancy is due to the presence of higher-order spherical modes incident on the reflector. When a proper spherical-wave expansion of the incident field is used, in conjunction with the physical-optics technique, to determine the scattered field, the total power of the scattered field will equal the power radiated by the feed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Electronics Letters; 12; Mar. 18
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  • 27
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    Satellite communications at the Goddard Space Flight Center (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Starting with the 1960 Delta launch of the first Echo satellite, NASA's Goddard Space Flight Center (GSFC) became one of the pioneers in satellite communications. Attention is given to the project Syncom, the Applications Technology Satellite (ATS) program, the ATS-6 project, and current GSFC efforts. After the decision announced in January of 1973 that NASA would phase out of communications satellite programs, the communications effort at GSFC concentrates on the operation of ATS spacecraft in orbit, experiments in the 12- to 14 GHz frequency band, and advanced communications research.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Signal; 30; Mar. 197
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  • 28
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    Real-time video compression algorithm for Hadamard transform processing (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A real-time digital video processor using Hadamard transform techniques to reduce video bandwidth is described. The processor can be programmed with different parameters to investigate various algorithms for bandwidth compression. The processor is also adaptive in that it can select different parameter sets to tradeoff spatial resolution for temporal resolution in the regions of the picture that are moving. Algorithms used in programming the system are described along with results achieved at various levels of compression. The algorithms relate to spatial compression, temporal compression, and the adaptive selection of parameter sets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-18; Feb. 197
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  • 29
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    Loaded horizontal antenna over an imperfect ground (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The effect of loading for antennas over an imperfect ground is analyzed. The Fresnel reflection coefficient technique is used to derive an E-integral equation for the antenna current. An optimization method is employed to determine the critical loading parameter which enforces a traveling wave current on the antenna. Results are given for the critical loading parameters, antenna currents, input impedances, and radiation patterns for various antenna dimensions and ground parameters. Calculations of the time-domain behavior of the current are presented to show the effect of loading on antenna transient response.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-26; Nov. 197
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  • 30
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    Frequencies above 10 GHz (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper discusses some of the problems associated with extending the frequencies used by satellite communication services above 10 GHz. The principal propagation limitation above 10 GHz occurs when precipitation intercepts the earth-space propagation path and causes attenuation and depolarization of the transmitted signal. World attenuation statistics at 12 GHz for earth-space paths are discussed, revealing the effect of climate on attenuation properties. Space diversity is discussed as an effective means of overcoming precipitation-caused attenuation problems.
    Keywords: COMMUNICATIONS AND RADAR
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  • 31
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    Absolute flux density calibrations: Receiver saturation effects (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The effect of receiver saturation was examined for a total power radiometer which uses an ambient load for calibration. Extension to other calibration schemes is indicated. The analysis shows that a monotonic receiver saturation characteristic could cause either positive or negative measurement errors, with polarity depending upon operating conditions. A realistic model of the receiver was made by using a linear-cubic voltage transfer characteristic. The evaluation of measurement error for this model provided a means for correcting radio source measurements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 123-129
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  • 32
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    The DSS radio science subsystem: Data handling of Very Long Baseline Interferometry (VLBI) data (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The key characteristics functional requirements, and operation of the radio science subsystem are discussed as they pertain to usage of deep radio sources by the DSN VLBI system.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 115-122
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  • 33
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    Examination of the DSN X-band weather specification (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Effects of weather on Deep Space Network system performance at X-band are examined by comparing a record of 64 meter system noise temperatures with weather observations taken at approximately the same times and places.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 197-208
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  • 34
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    A demonstration of differenced dual-station one-way doppler conducted with Pioneer 11 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Simultaneous one way Doppler demonstrations performed on Pioneer 11 are described. The data noise of the differenced one way doppler as computed from the pseudo residuals is around 0.002 Hz, which is nearly an order of magnitude smaller than the one way Doppler noise and about the same as differenced two way/three way Doppler noise. The demonstration results and the applicability of differenced one way radio metric data to spacecraft navigation are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 104-110
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  • 35
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    Deep Space Network to Viking Orbiter telecommunications performance during the Viking extended mission, November 1976 - February 1978 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The telecommunications performance during the Viking extended mission, starting with the completion of the first superior conjunction in November 1976 and ending with the jettison of the VO-2 aft bioshield early in March 1978 is discussed. Viking Orbiter activities and problems, the ground system activities and problems, radio science activities, and communication link performance are included. The substantial involvement of the Deep Space Network and the coordination of their telecommunication planners with Viking Project telecommunications analysts in the planning and execution of complex Viking Orbiter sequences are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 7-34
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  • 36
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    Analysis of the radiation patterns of reflector antennas (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The development and application of a numerical technique for rapid calculation of the far-field radiation patterns of a reflector antenna from either a measured or computed feed pattern are reported. The reflector is defined by the intersection of a cone with any surface of revolution or an offset sector of any surface of revolution. The feed is assumed to be linearly polarized and can have an arbitrary location. Both the copolarized and the cross-polarized reflector radiation patterns are computed. Calculations using the technique compare closely with measured radiation patterns of a waveguide-fed offset parabolic reflector. Unique features of this technique are freedom from restrictive feed assumptions and the numerical methods used in preparing the aperture-plane electric-field data for integration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Jan. 197
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    Rain-rate estimates for an attenuating radar (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An iterative method has been used to produce rain-rate estimates for an attenuating frequency radar. An infinite number of higher-order estimates are shown to converge in the limit to the Hitschfeld-Bordan solution under certain conditions. An error analysis was performed by a model accounting for the randomness of the radar return power, the k-Z, Z-R relations, and offsets in the radar calibration constant. Since the behavior of the estimates strongly depends on system errors, the choice of the best estimate requires a knowledge of the variance and range of offsets in meteorological data and the calibration constant. As the errors increase, the use of the lower orders avoids significant overpredictions. In order to obtain reliable rain-rate predictions in the presence of realistic errors, an antenna pointing angles away from the horizontal at frequencies in the lower end of the X-band may be used. Such antenna configurations insure low attenuation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 13; May-June
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  • 38
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    A hybrid technique for wire antennas in a cavity (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An evaluation is conducted of two numerical techniques developed by Richmond (1961, 1966) for wire antennas and scattering bodies. It is concluded that a more efficient and accurate scheme can be devised by suitably combining the two techniques. This scheme, which is called the 'hybrid method', is well suited for a wire antenna mounted in a cavity. Reaction matching is employed in the case of the antenna, while point matching is used for the support structure. The described approach makes it possible to consider voltage generators without the use of any equivalent magnetic frill current sources. The number of unknown currents to be determined is essentially optimized by this combination of reaction matching and point matching. The resulting current distribution is a quantized distribution on the support structure and is continuous on the main radiator.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-26; May 1978
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  • 39
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    Electromagnetic pulse coupling through an aperture into a two-parallel-plate region (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Analysis of electromagnetic-pulse (EMP) penetration via apertures into cavities is an important study in designing hardened systems. In this paper, an integral equation procedure is developed for determining the frequency and consequently the time behavior of the field inside a two-parallel-plate region excited through an aperture by an EMP. Some discussion of the numerical results is also included in the paper for completeness.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-20; Aug. 197
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  • 40
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    Radio frequency and microwave subsystems section. Dual-frequency feed cone assemblies for 34-meter antennas (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: New Cassegrain cone assemblies were designed for the upgrade of three 26 meter-diameter antennas to 34 meter-diameter with improved performance. The new dual-frequency feed cone (SXD) provided both S- and X-band feed systems and traveling wave masers with a reflex reflector system to permit simultaneous operation analogous to the 64-meter antennas.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 85-88
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  • 41
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    Parametric modeling of low-frequency water-vapor-induced tropospheric path length fluctuations (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Detailed wet tropospheric fluctuation information is presented in support of proposals to search for gravitational waves in ultra-precise Doppler data. The similarities between the solar wind and tropospheric effects on apparent signal path length are used to hypothesize a parametric model for low-frequency wet tropospheric path length fluctuation. Experimental observations of wet tropospheric signal delay fluctuations are interpreted as confirmation of this parametric form. The model is used to suggest the appropriate conditions for collection of experimental tropospheric fluctuation data.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 72-76
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  • 42
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    Radio science requirements and the end-to-end ranging system (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Radio science ranging requirements negotiated between past and present flight projects and the DSN have generally focused on just the DSS and spacecraft hardware. All elements in the end-to-end system are analyzed and considered in terms of the error hierarchy. The end-to-end system is defined and examined as it applies to the generation of radio science ranging requirements. The variability of the performance levels of the system elements is emphasized with respect to the radio science experiment being performed and the DSN-spacecraft frequency band configuration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 65-71
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  • 43
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    DSN radio science system, Mark III-78 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Mark III-78, is one of eight DSN Data Systems which provide major data types and functional capabilities to flight projects. It includes the equipment, software, personnel, documentation, procedures, and resources necessary to deliver the required data to flight projects. A system definition is given along with key characteristics, functional description, system configuration, testing, implementation status, and system schedule.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 4-13
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  • 44
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    Means to achieve wide swath widths in synthetic aperture satellite borne radars (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The radar range equation including processing gains for pulse compression and synthetic aperture generation was the starting point. System geometry considerations were introduced. For simplicity, flat earth geometry was used, although it was realized that this was not a good model for satellite-borne radars. Next, the constraints were introduced. These included those needed to avoid ambiguities in both range and azimuth, those needed to acheive the desired resolution, and those needed to achieve the desired swath width.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Johnson Space Center Addendum to Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 21 p
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  • 45
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    Waveguide-excited slot arrays for synthetic array radar applications (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The basic design considerations for waveguide slottery arrays are reviewed, with emphasis on those design requirements that are most significant to both airborne and spaceborne synthetic array radar (SAR) systems. As an illustration of both design procedures and performance capability of slotted waveguide planar arrays, an L-band planar array was designed, fabricated, and tested. This array has an aperture approximately one meter wide by two meters high and was designed to be a typical submodule of a larger antenna. Measurements of radiation patterns, gain, and VSWR were recorded and are presented, together with the performance characteristics predicted on the basis of theoretical analysis.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Johnson Space Center Addendum to Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 16 p
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  • 46
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    A perspective of synthetic aperture radar for remote sensing (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The characteristics and capabilities of synthetic aperture radar are discussed so as to identify those features particularly unique to SAR. The SAR and Optical images were compared. The SAR is an example of radar that provides more information about a target than simply its location. It is the spatial resolution and imaging capability of SAR that has made its application of interest, especially from spaceborne platforms. However, for maximum utility to remote sensing, it was proposed that other information be extracted from SAR data, such as the cross section with frequency and polarization.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Johnson Space Center Addendum to Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 20 p
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  • 47
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    An unconventional approach to imaging radar calibration (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: An unconventional approach to imaging radar calibration was considered for the entire system, including the imaging processing as a measurement instrument. The technique made use of a calibrated aircraft scatterometer as a secondary standard to measure the backscatter (sigma zero) of large units of constant roughness. These measured roughness units when viewed by an imaging radar system can be used to provide gray scale level, corresponding to known degrees of roughness. To obtain a calibrated aircraft scatterometer, a homogeneous smooth surface was measured by both the aircraft scatterometer and a sphere calibrated ground system. This provided a measure of the precision and accuracy of the aircraft system. The aircraft system was then used to measure large roughness units in the Death Valley, California area. Transfer of the measured roughness units to radar imagery was demonstrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Addendum to Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 23 p
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  • 48
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    The SEASAT-A synthetic aperture radar design and implementation (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The SEASAT-A synthetic aperture imaging radar system is the first imaging radar system intended to be used as a scientific instrument designed for orbital use. The requirement of the radar system is to generate continuous radar imagery with a 100 kilometer swath with 25 meter resolution from an orbital altitude of 800 kilometers. These requirements impose unique system design problems and a description of the implementation is given. The end-to-end system is described, including interactions of the spacecraft, antenna, sensor, telemetry link, recording subsystem, and data processor. Some of the factors leading to the selection of critical system parameters are listed. The expected error sources leading to degradation of image quality are reported as well as estimate given of the expected performance from data obtained during a ground testing of the completed subsystems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 17 p
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  • 49
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    Random sampling adaptively focusing synthetic aperture radar (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A high resolution narrow angle of view imaging radar system is considered that employs an airborne synthetic aperture of 600 meters operating at X-band to produce a beamwidth of approximately 0.05 mr. This system differs from a conventional SAR in that only a smaller number of wavefront samples, spaced randomly over the aperture are processed, and adaptive beamforming with open loop scanning is used. As a result, the processing requirements are reduced to within the capability of present day small computer technology, and the tolerance on flight stability is loosened by about 100:1. The system is described and initial analysis and evaluation results are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 12 p
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  • 50
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    A system concept for wide swath constant incident angle coverage (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Multiple beam approach readily overcomes radar ambiguity constraints associated with orbital systems and therefore permits imagery over swaths much wider than 100 kilometers. Furthermore, the antenna technique permits imagery at nearly constant incident angles. When frequency scanning is employed, the center angle may be programmed. The redundant use of the antenna aperture during reception results in lower transmitted power and in shorter antenna lengths in comparison to conventional designs. Compatibility of the approach with passive imagery is also considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 19 p
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  • 51
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    Applications and limitations of very large-scale integration in SAR azimuth processing (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The major limitation of a convolution processor designed with CCD memory chips is the inability to operate in real time except for slow aircraft speeds or coarse resolutions. Two methods of summing the products were evaluated with respect to speed, power, and space requirements. A convolution processor was designed, and the number of chips as well as the power and volume requirements were determined using 4, 6, and 8 bit data words. The processor is flexible because range samples may be traded for additional azimuth samples by altering the control signals. The processor is also modular, and additional range or azimuth may be processed by adding more cards.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 11 p
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  • 52
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    Effects of range bin shape and Doppler filter response in a digital SAR data processor (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In calibrating the backscatter coefficient obtained with an imaging synthetic aperture radar (SAR) system to determine absolute values of radar cross-section and reflectivity it is common practice to use a target of known radar cross-section placed within the scene. A corner reflector acts as a point target, but the return from it may not be centered in the resolution cell. It is important, for accurate calibration, to perform straddling corrections based on the range bin and Doppler filter response curves.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 10 p
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  • 53
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    A dual polarized antenna system using a meanderline polarizer (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Certain applications of synthetic aperture radars require transmitting on one linear polarization and receiving on two orthogonal linear polarizations for adequate characterization of the surface. To meet the current need at minimum cost, it was desirable to use two identical horizontally polarized shaped beam antennas and to change the polarization of one of them by a polarization conversion plate. The plate was realized as a four-layer meanderline polarizer designed to convert horizontal polarization to vertical.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 5 p
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  • 54
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    Low loss, flexible, lightweight corporate RF feed system for SAR antenna application (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Mechanical and electrical efficiency constraints imposed by the SEASAT-A synthetic aperture radar antenna posed difficult design problems. After consideration of available standard cable and waveguide systems, it was determined that an optimum design could be obtained from a suspended substrate RF feed system. Size and mechanical flexibility constraints forced the design of a flexible, suspended substrate section capable of 180-degree flexure. Original design goal for insertion loss over power division was 1 db; measured results indicated 0.6 db maximum across the band. Multipactor testing of system components indicated system breakdown capability in excess of 4 kW compared to a specification input maximum of 1500 W.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 8 p
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  • 55
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    Mathematical modeling and simulation of the space shuttle imaging radar antennas (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Simulations of space shuttle synthetic aperture radar antennas under the influence of space environmental conditions were carried out at L, C, and X-band. Mathematical difficulties in modeling large, non-planar array antennas are discussed, and an approximate modeling technique is presented. Results for several antenna error conditions are illustrated in far-field profile patterns, earth surface footprint contours, and summary graphs.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Proc. of the 1978 Syn. Aperture Radar technol. Conf.; 14 p
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  • 56
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    Prediction of antenna array performance from subarray measurements (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Computer runs were used to determine the effect of mechanical distortions on array pattern performance. Subarray gain data, along with feed network insertion loss, and insertion phase data were combined with the analysis of Ruze on random errors to predict gain of a full array.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 16 p
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  • 57
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    Definition study of the Shuttle Imaging Radar-A (SIR-A) antenna on the second space shuttle mission (OFT-2) (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A definition is derived for an antenna configuration fixed-mounted high in the payload bay on the hybrid OFT-2 pallet which is compatible with Orbiter interface requirements. Tests showed that the combination of the selected panels and the designed corporate feed meets SIR-A performance requirement of 33 db gain. The effects of Orbiter structure proximity on performance were determined by scale model tests to be negligible. The potential for improved performance during subsequent reflights includes a multiple-beam capability and dual polarization.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 9 p
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  • 58
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    Effect of ambiguities on SAR picture quality (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The degradation of picture quality is studied for a high-resolution, large-swath SAR mapping system subjected to speckle, additive white Gaussian noise, and range and azimuthal ambiguities occurring because of the non-finite antenna pattern produced by a square aperture antenna. The effect of the azimuth antenna pattern was accounted for by calculating the aximuth ambiguity function. Range ambiguities were accounted for by adding appropriate pixels at a range separation corresponding to one pulse repetition period, but attenuated by the antenna pattern. A method of estimating the range defocussing effect which arises from the azimuth matched filter being a function of range is shown. The resulting simulated picture was compared with one degraded by speckle and noise but no ambiguities. It is concluded that azimuth ambiguities don't cause any noticeable degradation but range ambiguities might.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 15 p
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  • 59
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    Effect of pixel dimensions on SAR picture quality (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In an SAR mapping system, the product of looks per pixel and number of pixels in the scene is kept constant. Assuming that the returns from all resolution cells obey Rayleigh statistics, the expression for pixel SNR incorporating both speckle and additive white Gaussian noise was derived. It is shown that it is possible to use fine resolution and leave the large-area estimate slightly but not much worse than if a larger pixel size had been initially decided upon.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 6 p
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  • 60
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    Image synthesis for SAR system, calibration and processor design (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Point Scattering Method of simulating radar imagery rigorously models all aspects of the imaging radar phenomena. Its computational algorithms operate on a symbolic representation of the terrain test site to calculate such parameters as range, angle of incidence, resolution cell size, etc. Empirical backscatter data and elevation data are utilized to model the terrain. Additionally, the important geometrical/propagation effects such as shadow, foreshortening, layover, and local angle of incidence are rigorously treated. Applications of radar image simulation to a proposed calibrated SAR system are highlighted: soil moisture detection and vegetation discrimination.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 10 p
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    A significant post-launch calibration experiment for the SEASAT-A SAR (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A technique for periodically monitoring the impulse response function of the SEASAT-A synthetic aperture radar is outlined that yields most of the significant contributors to the overall instrument transfer function. The essential measurement involves exciting the total SAR system at L-band with a strong point source scatterer, receiving via the normal S-band analog data link, and finally sampling and processing only a small subset of data in the immediate vicinity of the strong point source.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 15 p
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  • 62
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    SAR antenna calibration techniques (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Calibration of SAR antennas requires a measurement of gain, elevation and azimuth pattern shape, boresight error, cross-polarization levels, and phase vs. angle and frequency. For spaceborne SAR antennas of SEASAT size operating at C-band or higher, some of these measurements can become extremely difficult using conventional far-field antenna test ranges. Near-field scanning techniques offer an alternative approach and for C-band or X-band SARs, give much improved accuracy and precision as compared to that obtainable with a far-field approach.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 17 p
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    Shielding of longitudinal magnetic fields with thin, closely, spaced concentric cylindrical shells with applications to atomic clocks (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A general formula is given for the longitudinal shielding effectiveness of N closed concentric cylinders. The use of these equations is demonstrated by application to the design of magnetic shields for hydrogen maser atomic clocks. Examples of design tradeoffs such as size, weight, and material thickness are discussed. Experimental results on three sets of shields fabricated by three manufacturers are presented. Two of the sets were designed employing the techniques described. Agreement between the experimental results and the design calculations is then demonstrated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the Tenth Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 131-146
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    Overview of timing/synchronization for digital communications (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Systems in general, and switched systems in particular, are explained. It pointed out some of the criteria that greatly influence timing/synchronization subsystem design for a military communications network but have little or no significance for civil systems. Timing techniques were evaluated in terms of fundamental features. Different combinations of these features covered most possibilities from which a synchronous timing system could be chosen.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the Tenth Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 393-403
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    An Evaluation of optional timing/synchronization features to support selection of an optimum design for the DCS digital communication network (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The task was to evaluate the ability of a set of timing/synchronization subsystem features to provide a set of desirable characteristics for the evolving Defense Communications System digital communications network. The set of features related to the approaches by which timing/synchronization information could be disseminated throughout the network and the manner in which this information could be utilized to provide a synchronized network. These features, which could be utilized in a large number of different combinations, included mutual control, directed control, double ended reference links, independence of clock error measurement and correction, phase reference combining, and self organizing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the Tenth Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 437-461
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    Survey of timing/synchronization of operating wideband digital communications networks (1978)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: In order to benefit from experience gained from the synchronization of operational wideband digital networks, a survey was made of three such systems: Data Transmission Company, Western Union Telegraph Company, and the Computer Communications Group of the Trans-Canada Telephone System. The focus of the survey was on deployment and operational experience from a practical (as opposed to theoretical) viewpoint. The objective was to provide a report on the results of deployment how the systems performed, and wherein the performance differed from that predicted or intended in the design. It also attempted to determine how the various system designers would use the benefit of hindsight if they could design those same systems today.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the Tenth Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 405-435
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    Effect of various features on the life cycle cost of the timing/synchronization subsystem of the DCS digital communications network (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The effect on the life cycle cost of the timing subsystem was examined, when these optional features were included in various combinations. The features included mutual control, directed control, double-ended reference links, independence of clock error measurement and correction, phase reference combining, self-organization, smoothing for link and nodal dropouts, unequal reference weightings, and a master in a mutual control network. An overall design of a microprocessor-based timing subsystem was formulated. The microprocessor (8080) implements the digital filter portion of a digital phase locked loop, as well as other control functions such as organization of the network through communication with processors at neighboring nodes.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the Tenth Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 463-489
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    Miniature interferometer terminals for earth surveying (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A system of miniature radio interferometer terminals was proposed for the measurement of vector baselines with uncertainties ranging from the millimeter to the centimeter level for baseline lengths ranging, respectively, from a few to a few hundred kilometers. Each terminal would have no moving parts, could be packaged in a volume of less than 0.1 cu m, and would operate unattended. These units would receive radio signals from low-power (10 w) transmitters on earth-orbiting satellites. The baselines between units could be determined virtually instantaneously and monitored continuously as long as at least four satellites were visible simultaneously.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Ohio State Univ. Appl. of Geodesy to Geodyn., an Intern. Symp.; p 65-85
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    VLBI and its current applications within the solar system (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 9th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 85-96
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  • 70
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    International time and frequency comparison for long term via VLF and Loran-C (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 9th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 289-296
    Format: text
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  • 71
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    Real time distribution via controlled TV transmission (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 9th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 249-276
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  • 72
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    New possibilities for time and standard frequency dissemination over TV networks (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Goddard Space Flight Center Proc. of the 9th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting; p 277-288
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    Characterization and modeling of radiation effects NASA/MSFC semiconductor devices (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A literature review of the near-Earth trapped radiation of the Van Allen Belts, the radiation within the solar system resulting from the solar wind, and the cosmic radiation levels of deep space showed that a reasonable simulation of space radiation, particularly the Earth orbital environment, could be simulated in the laboratory by proton bombardment. A 3 MeV proton accelerator was used to irradiate CMOS integrated circuits fabricated from three different processes. The drain current and output voltage for three inverters was recorded as the input voltage was swept from zero to ten volts after each successive irradiation. Device parameters were extracted. Possible damage mechanisms are discussed and recommendations for improved radiation hardness are suggested.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-161281
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    A study and experiment plan for digital mobile communication via satellite (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The viability of mobile communications is examined within the context of a frequency division multiple access, single channel per carrier satellite system emphasizing digital techniques to serve a large population of users. The intent is to provide the mobile users with a grade of service consistant with the requirements for remote, rural (perhaps emergency) voice communications, but which approaches toll quality speech. A traffic model is derived on which to base the determination of the required maximum number of satellite channels to provide the anticipated level of service. Various voice digitalization and digital modulation schemes are reviewed along with a general link analysis of the mobile system. Demand assignment multiple access considerations and analysis tradeoffs are presented. Finally, a completed configuration is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152213 , WDL-TR7957
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  • 75
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    Report for simultaneous, multiple independently steered beam study for Airborne Electronically Steerable Phased Array (AESPA) program (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Design concepts of an array for the formation of multiple, simultaneous, independently pointed beams for satellite communication links were investigated through tradeoffs of various approaches which were conceived as possible solutions to the problem. After the preferred approach was selected, a more detailed design was configured and is presented as a candidate system that should be given further consideration for development leading to a preliminary design. This array uses an attenuator and a phase shifter with every element. The aperture excitation necessary to form the four beams is calculated and then placed across the array using these devices. Pattern analysis was performed for two beam and four beam cases with numerous patterns being presented. Parameter evaluation shown includes pointing accuracy and beam shape, sidelobe characteristics, gain control, and beam normalization. It was demonstrated that a 4 bit phase shifter and a 6 bit, 30 dB attenuator were sufficient to achieve adequate pattern performances. The phase amplitude steered multibeam array offers the flexibility of 1 to 4 beams with an increase in gain of 6 dB if only one beam is selected.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-161394 , EM-911-05-78
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  • 76
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    Collapsible corrugated horn antenna (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A horn antenna that is readily collapsible while not in use is described. A number of different sized annular metal rings are arranged in a sequence such that each ring is larger than the one that precedes it in the sequence. A number of thin flexible electrically conductive members attach successive metal rings together physically and connect them together electrically. Each flexible conductive member is attached to make electrical contact between the outside surface of a metal ring and the inside surface of an adjacent metal ring in the sequence.
    Keywords: COMMUNICATIONS AND RADAR
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    Coherent generation of the terrestrial kilometric radiation by nonlinear beatings between electrostatic waves (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The propagation of electrostatic plasma waves in an inhomogeneous and magnetized plasma was studied. These waves, which are driven unstable by auroral beams of electrons, are shown to suffer a further geometrical amplification while they propagate towards resonances. Simultaneously, their group velocities tend to be aligned with the geomagnetic field. It is shown that the electrostatic energy tends to accumulate at, or near omega sub LH and omega sub UH, the local lower and upper hybrid frequencies. Due to this process, large amplitude electrostatic waves with very narrow spectra are observed near these frequencies at any place along the auroral field lines where intense beam driven instability takes place. These intense quasi-monochromatic electrostatic waves are shown to give rise to an intense electromagnetic radiation. Depending upon the ratio omega sub pe/omega sub ce between the electron plasma frequency and the electron gyro-frequency the electromagnetic wave can be radiated in the ordinary mode (at omega sub UH), or in the extraordinary (at 2 omega sub UH). As the ratio omega sub pe/omega sub ce tends to be rather small, it is shown that the most intense radiation should be boserved at 2 omega sub UH in the extraordinary mode.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-162869 , CRPE-NT-56
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  • 78
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    Cumulative slant path rain attenuation associated with COMSTAR beacon at 28.56 GHz for Wallops Island, Virginia (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Yearly, monthly, and time of day fade statistics are presented and characterized. A 19.04 GHz yearly fade distribution, corresponding to a second COMSTAR beacon frequency, is predicted using the concept of effective path length, disdrometer, and rain rate results. The yearly attenuation and rain rate distributions follow with good approximation log normal variations for most fade and rain rate levels. Attenuations were exceeded for the longest and shortest periods of times for all fades in August and February, respectively. The eight hour time period showing the maximum and minimum number of minutes over the year for which fades exceeded 12 db were approximately between 1600 to 2400, and 0400 to 1200 hours, respectively. In employing the predictive method for obtaining the 19.04 GHz fade distribution, it is demonstrated theoretically that the ratio of attenuations at two frequencies is minimally dependent of raindrop size distribution providing these frequencies are not widely separated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-159997 , APL/JHU/SIR-78U-039
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    A computer program to calculate radiation properties of reflector antennas (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A computer program to calculate the radiation properties of the reflector antennas is presented. It can be used for paraboloidal, spherical, or ellipsoidal reflector surfaces and is easily modified to handle any surface that can be expressed analytically. The program is general enough to allow any arbitrary location and pointing angle for the feed antenna. The effect of blockage due to the feed horn is also included in the computations. The computer program is based upon the technique of tracing the rays from the feed antenna to the reflector to an aperture plane. The far field radiation properties are then calculated by performing a double integration over the field points in the aperture plane. To facilitate the computation of double intergral, the field points are first aligned along the equispaced straight lines in the aperture plane. The computation time is relatively insensitive to the absolute size of the aperture and even though no limits on the largest reflector size have been determined, the program was used for reflector diameters of 1000 wavelenghts.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-78721
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  • 80
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    Study of communications data compression methods (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A simple monochrome conditional replenishment system was extended to higher compression and to higher motion levels, by incorporating spatially adaptive quantizers and field repeating. Conditional replenishment combines intraframe and interframe compression, and both areas are investigated. The gain of conditional replenishment depends on the fraction of the image changing, since only changed parts of the image need to be transmitted. If the transmission rate is set so that only one fourth of the image can be transmitted in each field, greater change fractions will overload the system. A computer simulation was prepared which incorporated (1) field repeat of changes, (2) a variable change threshold, (3) frame repeat for high change, and (4) two mode, variable rate Hadamard intraframe quantizers. The field repeat gives 2:1 compression in moving areas without noticeable degradation. Variable change threshold allows some flexibility in dealing with varying change rates, but the threshold variation must be limited for acceptable performance.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-166225 , NAS 1.26:166225
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  • 81
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    Phase-A COBE study (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A scaled version of a conical apodizing horm similar to the one used in the Cosmic Background Explorer as the antenna for the far infrared absolute spectrometer (FIRAS) was tested to determine its diffraction patterns. The test transmitter used and results are described. Calculation of the tradeoff between noise and spectral resolution for the FIRAS are examined. Flexural transports, the optical properties of the Martin-Pupplet polarizing interferometer, and radiation absorption of thin bismuth films are also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-84037
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    Hybrid receiver conceptual design and test report (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Hybrid Receiver described uses an acquisition and demodulation scheme tailored to the Jovian environment. The large Doppler offsets expected during initial acquisition led to development of the Hilbert Acquisition Aid, which provides for rapid acquisition for low signal to noise densities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-152137
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  • 83
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    Optical communication with two-photon coherent stages. I - Quantum-state propagation and quantum-noise reduction (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: To determine the ultimate performance limitations imposed by quantum effects, it is also essential to consider optimum quantum-state generation. Certain 'generalized' coherent states of the radiation field possess novel quantum noise characteristics that offer the potential for greatly improved optical communications. These states have been called two-photon coherent states because they can be generated, in principle, by stimulated two-photon processes. The use of two-photon coherent state (TCS) radiation in free-space optical communications is considered. A simple theory of quantum state propagation is developed. The theory provides the basis for representing the free-space channel in a quantum-mechanical form convenient for communication analysis. The new theory is applied to TCS radiation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Information Theory; IT-24; Nov. 197
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  • 84
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    Effect of surface roughness on the microwave emission from soils (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effect of surface roughness on the brightness temperature of a moist terrain was studied through the modification of Fresnel reflection coefficient and using the radiative transfer equation. The modification involves introduction of a single parameter to characterize the roughness. It is shown that this parameter depends on both the surface height variance and the horizontal scale of the roughness. Model calculations are in good quantitative agreement with the observed dependence of the brightness temperature on the moisture content in the surface layer. Data from truck mounted and airborne radiometers are presented for comparison. The results indicate that the roughness effects are greatest for wet soils where the difference between smooth and rough surfaces can be as great as 50K.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-79606
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    Research Plan for Study of Biological and Ecological Effects of the Solar Power Satellite Transmission System (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A programmatic research plan for a three year study is presented to generate knowledge on effects of the continuous wave 2.45 GHz microwave power transmission that the Solar Power Satellite might have on biological and ecological elements, within and around the rectenna receiving site.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-3044
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  • 86
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    Videoconferencing via satellite: Opening Congress to the people: Summary report (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Action research is presented to evaluate, through actual demonstrations, whether satellite videoconferencing can provide a new mechanism for informed dialog between congressmen and constituents and as a result strengthen the legislative process.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-157258
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    Synthetic aperture radar in geosynchronous orbit (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Radar images of the earth were taken with a synthetic aperture radar (SAR) from geosynchronous orbital ranges by utilizing satellite motion relative to a geostationary position. A suitable satellite motion was obtained by having an orbit plane inclined relative to the equatorial plane and by having an eccentric orbit. Potential applications of these SAR images are topography, water resource management and soil moisture determination. Preliminary calculations show that the United States can be mapped with 100 m resolution cells in about 4 hours. With the use of microwave signals the mapping can be performed day or night, through clouds and during adverse weather.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 5 p
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  • 88
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    The effect of wind on the microwave emission from the ocean's surface at 37 GHz (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The microwave brightness temperature measurements from the Electrically Scanned Microwave Radiometer (frequency = 37 GHz) are compared with oceanic wind measurements from data buoys. It is shown that the brightness temperature can be manipulated to yield a measure of the surface roughening which can be very well accounted for by a simple geometric optics model. The data of 1.4, 8.36 and 19.34 GHz were similarly manipulated and shown to require a surface with less slope variance than predicted by optical measurements. It is also shown that the surface may be treated as isotropic to an accuracy equivalent to the roughening produced by a 2 m/s wind speed increment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-79588
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    DSN 100-meter X and S band microwave antenna design and performance (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The RF performance is studied for large reflector antenna systems (100 meters) when using the high efficiency dual shaped reflector approach. An altered phase was considered so that the scattered field from a shaped surface could be used in the JPL efficiency program. A new dual band (X-S) microwave feed horn was used in the shaping calculations. A great many shaping calculations were made for various horn sizes and locations and final RF efficiencies are reported. A conclusion is reached that when using the new dual band horn, shaping should probably be performed using the pattern of the lower frequency
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-157555 , JPL-PUB-78-65
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    Ionosphere/microwave beam interaction study (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The microwave beam of the Solar Power Satellite (SPS) is predicted to interact with the ionosphere producing thermal runaway up to an altitude of about 100 kilometers at a power density threshold of 12 mW/cm sq (within a factor of two). The operation of the SPS at two frequencies, 2450 and 5800 MHz, is compared. The ionosphere interaction is less at the higher frequency, but the tropospheric problem scattering from heavy rain and hail is worse at the higher frequency. Microwave signals from communication satellites were observed to scintillate, but there is some concern that the uplink pilot signal may be distorted by the SPS heated ionosphere. The microwave scintillations are only observed in the tropics in the early evenings near the equinoxes. Results indicate that large phase errors in the uplink pilot signal can be reduced.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151821
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  • 91
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    Estimates of oceanic surface wind speed and direction using orthogonal beam scatterometer measurements and comparison of recent sea scattering theories (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The wind direction properties of radar backscatter from the sea were empirically modelled using a cosine Fourier series through the 4th harmonic in wind direction (referenced to upwind). A comparison with 1975 JONSWAP (Joint North Sea Wave Project) scatterometer data, at incidence angles of 40 and 65, indicates that effects to third and fourth harmonics are negligible. Another important result is that the Fourier coefficients through the second harmonic are related to wind speed by a power law expression. A technique is also proposed to estimate the wind speed and direction over the ocean from two orthogonal scattering measurements. A comparison between two different types of sea scatter theories, one type presented by the work of Wright and the other by that of Chan and Fung, was made with recent scatterometer measurements. It demonstrates that a complete scattering model must include some provisions for the anisotropic characteristics of the sea scatter, and use a sea spectrum which depends upon wind speed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-158908 , TR-186-17
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  • 92
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    Electronic SAR processors for space missions (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An experimental laboratory processor is being developed as a testbed for design of on-board processors for future space missions. The configuration of the experimental processor is described and technical factors pertaining to the design are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 19 p
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    Description of a computer simulation of an orbital SAR system (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: In order to predict the performance of a synthetic aperture radar for a wide variety of system and environmental parameters a computer simulation of the SAR system was developed. This model is a detailed description of the SAR imaging process on a pulse-by-pulse basis. The simulation is implemented as seven computer programs for a CDC Cyber 171 digital computer.
    Keywords: COMMUNICATIONS AND RADAR
    Type: New Mexico State Univ. Proc. of the 1978 Syn. Aperture Radar Technol. Conf.; 20 p
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  • 94
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    RPV application of a globally adaptive rate controlled compressor (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A globally adaptive image compression structure is introduced for use in a tactical RPV environment. The structure described would provide an operator with the flexibility to dynamically maximize the usefulness of a limited and changing data rate. The concepts would potentially simplify system design while at the same time improving overall system performance.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-157343 , JPL-PUB-78-61
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  • 95
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    RF radiation from lightning (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Radiation from lightning in the RF band from 3-300 MHz were monitored. Radiation in this frequency range is of interest as a potential vehicle for monitoring severe storms and for studying the lightning itself. Simultaneous measurements were made of RF radiation and fast and slow field changes. Continuous analogue recordings with a system having 300 kHz of bandwidth were made together with digital records of selected events (principally return strokes) at greater temporal resolution. The data reveal patterns in the RF radiation for the entire flash which are characteristic of flash type and independent of the frequency of observation. Individual events within the flash also have characteristic RF patterns. Strong radiation occurs during the first return strokes, but delayed about 20 micron sec with respect to the begining of the return stroke; whereas, RF radiation from subsequent return strokes tends to be associated with cloud processes preceding the flash with comparatively little radiation occurring during the return stroke itself.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-78095
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  • 96
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    Use of a multi-look unfocussed SAR processor on spacecraft (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two methods of processing signals from a multi-look unfocussed synthetic-aperture radar are considered. A saving in the processor complexity is achieved in comparison to a fully focussed SAR system at the expense of slightly greater clutter levels and poorer along-track resolution. In addition, lower power consumption enables the unfocussed processor to increase the number of looks to compensate in part for the reduced resolution.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156721 , RSL-TM-295-10
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  • 97
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    C-band radar calibration using GEOS-3 (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The various methods of determining tracking radar measurement error parameters are described, along with the projected accuracy of results. Typical examples and results for calibration of radars tracking the GEOS-3 satellite are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-73275
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  • 98
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    Large Active Retrodirective Arrays for Space Applications (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An active retrodirective array (ARA) electronically points a microwave beam back at the apparent source of an incident pilot signal. Retrodirectivity is the result of phase conjugation of the pilot signal received by each element of the array. The problem of supplying the correct phase reference to the phase conjugation circuit (PCC) associated with each element of the array is solved by central phasing. By eliminating the need for structural rigidity, central phasing confers a decisive advantage on ARA's as large spaceborne antennas. A new form of central phasing suitable for very large arrays is described. ARA's may easily be modified to serve both as transmitting and receiving arrays simultaneously. Two new kinds of exact, frequency translating PCC's are described. Such PCC's provide the ARA with input-output isolation and freedom from squint. The pointing errors caused by the radial and transverse components of the ARA's velocity, by the propagation medium, and by multipath are discussed. A two element ARA breadboard was built and tested at JPL. Its performance is limited primarily by multipath induced errors.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-156163 , JPL-PUB-78-20
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  • 99
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    Design of microstrip disk antenna arrays (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The radio frequency characteristics and design parameters for microstrip disk antenna elements and planar arrays are presented. Two C-band model arrays (an 8 element linear and an 8 by 8 planar) were designed, fabricated, and tested to demonstrate the technique of using microstrip elements for array applications. These arrays were designed with a cosine amplitude distribution.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-TM-78631 , L-11926
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  • 100
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    IUS/payload communication system simulator configuration definition study (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The requirements and specifications for a general purpose payload communications system simulator to be used to emulate those communications system portions of NASA and DOD payloads/spacecraft that will in the future be carried into earth orbit by the shuttle are discussed. For the purpose of on-orbit checkout, the shuttle is required to communicate with the payloads while they are physically located within the shuttle bay (attached) and within a range of 20 miles from the shuttle after they have been deployed (detached). Many of the payloads are also under development (and many have yet to be defined), actual payload communication hardware will not be available within the time frame during which the avionic hardware tests will be conducted. Thus, a flexible payload communication system simulator is required.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-151620 , R7801-3
    Format: application/pdf
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