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  • COMMUNICATIONS  (61)
  • LUNAR AND PLANETARY EXPLORATION
  • ASTROPHYSICS
  • 1975-1979
  • 1970-1974  (62)
  • 1972  (62)
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  • 1975-1979
  • 1970-1974  (62)
Year
  • 1
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    ATS-F COMSAT millimeter wave propagation experiment. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Description of the transmitting and receiving system configurations to be used in an ATS-F propagation experiment designed to gather data on the attenuation of satellite uplink signals (at approximately 13.2 and 17.8 GHz) due to atmospheric hydrometeors (mostly rain). The data will be used for statistical determination of system power margins required for operational communications systems at frequencies above 10 GHz. A secondary analysis will study site diversity as a means of reducing the required system margins. A spacecraft transponder receives signals from 15 dual-frequency ground transmitter stations and retransmits these signals to a central ground receiving terminal at a frequency of 4 GHz.
    Keywords: COMMUNICATIONS
    Type: NTC ''72; National Telecommunications Conference; Dec 04, 1972 - Dec 06, 1972; Houston, TX
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Numerical solution for propagation of longitudinal waves along the geomagnetic field using a three-fluid ionosphere model. (1972)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-20; Nov. 197
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Bistatic-radar investigation (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: The purpose of the reported experiment was to determine the principal electromagnetic and structural properties of the lunar surface from the observation of command and service module (CSM) radio transmissions that were reflected from the lunar surface and received on earth. These transmissions emanate from the CSM communication systems at wavelengths of 13 cm (S-band) and 116 cm (very high frequency (VHF)). Lunar crustal properties such as dielectric constant, average slope and slope probability, density, small-scale surface roughness, and embedded rocks to a depth of 20 m may be determined. The results are proving to be most useful in understanding the processes that have produced and modified the crust and in distingushing between adjacent and subjacent geological units. The experimental observations are also of intrinsic interest in the study of electromagnetic scattering.
    Keywords: COMMUNICATIONS
    Type: NASA. Lyndon B. Johnson Space Center Apollo 16 Prelim. Sci. Rept.; 13 p
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    Error analysis of bent ray radio occultation measurments (1972)
    In:  CASI
    Details
    Publication Date: 2006-03-12
    Description: There are two types of experimental measurement errors of the Doppler data associated with the radio occultation, random and systematic. Random errors are due to thermal noise in the transmission channel, and the phase lock loop, and quantization error in the digital circuitry. These are called noise type errors. The systematic errors are due to geometric uncertainty and equipment phase instability. Considered is the amount of uncertainty, due to random measurement errors, in the refractivity profiles reconstructed by this type of indirect sensing experiment. A class of refractivity profiles is defined which approximately fit the set of measured data. Bounds are placed on the extent of this class of solution profiles. To accomplish this, the sensivity of the reconstructed refractivity profiles to errors in the measured quantity and the statistics of the errors in the measurement are examined.
    Keywords: COMMUNICATIONS
    Type: NASA. Ames Res. Center Math. of Profile Inversion; 5 p
    Format: text
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  • 5
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    Spacecraft ion beam noise effects (1972)
    In:  CASI
    Details
    Publication Date: 2006-02-22
    Description: An estimate of the antenna noise temperature and the uplink signal-to-noise ratio has been made for Bremsstrahlung radiation emitted by a spacecraft ion beam; a worst-case situation in which the spacecraft antenna is located in the exit plane of the ion beam and directed at varying angles into the ion beam is assumed. Numerical results of the antenna noise temperature versus antenna pointing angle are given for a typical set of ion beam and antenna pattern parameters. The uplink signal-to-noise ratio due to the ion beam noise alone is given in terms of a critical range in AU at which a typical ranging transmission is received with S/N = 0 db. The effects of the ion beam divergence angle and antenna distance on the ion beam are also presented. Results of the study show typical increases in the antenna noise temperature of about 0.2 K and critical ranges of the order of 3-5 AU. An ion engine thus generally introduces an undetectable level of noise into a spacecraft receiver.
    Keywords: COMMUNICATIONS
    Type: JPL Quart. Tech. Rev., Vol. 2, No. 2; p 61-71
    Format: text
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  • 6
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    Simultaneous measurements of radar reflectivity and refractive index spectra in clear air convection. (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Simultaneous measurements of radar reflectivity and radio refractive index at several altitudes in clear air convection have been made. The experimental data were compared with the theoretical relationship which relates the reflectivity to the refractivity spectrum. The agreement between the measurements and the theory is excellent and shows that the radar returns in clear air are the result of, and can be quantitatively described as being from, fine-scale refractivity fluctuations due to turbulent mixing. Further, the data give strong support to the -5/3 spectral decay of the refractivity spectrum in the inertial subrange.
    Keywords: COMMUNICATIONS
    Type: Journal of Applied Meteorology; 11; Oct. 197
    Format: text
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  • 7
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    Satellite relay telemetry in the surveillance of active volcanoes and major fault zones (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A review was made of efforts to develop a dense telemetered microearthquake network to study earthquake mechanics along the San Andreas fault and the strain mechanics of the Kilauea Volcano. The principle elements and objectives of the ERTS-A proposal are outlined. Some of the aspects of the earthquake network and the results obtained from it as well as some promising experiments in computerized record processing are discussed.
    Keywords: COMMUNICATIONS
    Type: NASA. Manned Spacecraft Center 4th Ann. Earth Resources Program Rev., Vol. 3; 17 p
    Format: text
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  • 8
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    Signal coherence studies in multiaperture arrays (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A two-element array was constructed to measure the gain improvement that can be realized while tracking spacecraft. Measurements were made at VHF and S band. An automatically controlled time delay correction system was developed and tested for this program.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 167-170
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  • 9
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    Millimeter wave propagation measurements using the ATS 5 satellite (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The ATS 5 millimeter wave propagation experiment determines long- and short-term attenuation statistics of operational millimeter wavelength earthspace links as functions of defined meteorological conditions. A preliminary analysis of results with 15 GHz downlink and 32 GHz uplink frequency bands indicates that both frequency bands exhibit an excellent potential for utilization in reliable high data rate earth-space communications systems.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 100-102
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  • 10
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    Ku-band high gain antenna (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An exposed four element array of 12.8 m diameter elements mounted on a common pedestal is the recommended ground antenna configuration in support of the 2 GHz bandwidth Ku-band downlink from tdr satellites. The array provides three channel phase monopulse tracking capability with only listening feeds in each element. The array is as cost effective as a single aperture antenna and offers significant advantages in tracking and reliability.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 74-78
    Format: application/pdf
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