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  • Polymer and Materials Science  (2,332)
  • General Chemistry  (1,021)
  • COMMUNICATIONS  (315)
  • Cell & Developmental Biology
  • 1980-1984
  • 1970-1974  (3,855)
  • 1972  (3,855)
Collection
Keywords
Publisher
Years
  • 1980-1984
  • 1970-1974  (3,855)
Year
  • 1
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    Antenna drive system for the Nimbus satellite (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: A two-axis drive system is described for pointing a high gain antenna. Motion about each axis is provided by identical drive mechanisms. Only three gear passes are required to obtain the necessary 900:1 gear reduction. The drive system is a primary element of an experiment that will provide a real time data link between Nimbus and ground stations. Data are transmitted from Nimbus to the applications technology satellite, which relays the data to ground stations.
    Keywords: COMMUNICATIONS
    Type: NASA. Ames Res. Center 6th Aerospace Mech. Symp.; p 117-120
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  • 2
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    The Intelsat 4 antenna positioner (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: The Intelsat 4 communications satellite has two spot beam antennas which are pointed to selected land masses by gimbaled positioners. The positioners employ drive motors with electromagnetic brakes and jackscrews that are self-caging during the launch. The positioner uses dry lubricants for ball bearings, spur gears, screw and nut, and various journal bearings. A coefficient of friction of approximately 0.05 was demonstrated in vacuum operation. Success of the positioner was demonstrated on the first Intelsat 4 placed in orbit in January 1971. The developmental problems that were encountered and their solutions are discussed.
    Keywords: COMMUNICATIONS
    Type: NASA. Ames Res. Center 6th Aerospace Mech. Symp.; p 109-116
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  • 3
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    Locations of solar radio bursts (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: Measurements of the positions of the sources of solar radio bursts at decameter wavelengths, 20- to 60-MHz range, provide information about physical conditions in a region of the corona extending from about one-half to several solar radii from the surface of the sun. Position measurements in the 20- to 60-MHz range were made with the Clark Lake sweep-frequency grating interferometer. Although the resolution of the instrument is sufficient to measure source position accurately, the highly variable effect of refraction in the earth's ionosphere severely limits the observations, distorting position determinations to such an extent as to make much of the position data useless unless ionospheric refraction can be taken into account. A method was developed for the removal of the refractive effect from the data to permit determination of true source position. With this technique it is considered possible to measure spatial extent of radio sources that will provide information about emission processes and physical parameters in the corona.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Sci., 1970; p 149-153
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  • 4
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    Reduction of near-in sidelobes using phase reversal aperture rings (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: A technique is described for reducing near-in sidelobes in spacecraft antennas by cancellation. This technique takes a small portion of the radiation from the antenna aperture and generates the near-in lobes, which are then fed out of phase relative to the main signal. Results of sample cases indicate that the first three lobes can be nearly eliminated at a 40% reduction in aperture efficiency.
    Keywords: COMMUNICATIONS
    Type: JPL Quart. Tech. Rev., Vol. 1, No. 4; p 34-42
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  • 5
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    The Goddard helical tape recorder (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: A spacecraft recorder was developed with the objective of functioning continuously for 5 years. The resulting design employed a metallic tape wound in a 200-turn helix. A direct drive, brushless dc torquer and servo speed control drove the recorder at 3 rpm for recording and 54 rpm for playback.
    Keywords: COMMUNICATIONS
    Type: 6th Aerospace Mech. Symp.; p 89-93
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  • 6
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    Bias and spread in extreme value theory measurements of probability of error (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: Extreme value theory is examined to explain the cause of the bias and spread in performance of communications systems characterized by low bit rates and high data reliability requirements, for cases in which underlying noise is Gaussian or perturbed Gaussian. Experimental verification is presented and procedures that minimize these effects are suggested. Even under these conditions, however, extreme value theory test results are not particularly more significant than bit error rate tests.
    Keywords: COMMUNICATIONS
    Type: JPL Quart. Tech. Rev., Vol. 1, No. 4; p 58-68
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  • 7
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    Calibration of radar data from Apollo 16 results, part X (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: Predictions of surface and near surface blockiness using earth based radar measurements were made. Two polarizations of the radar echoes were measured - polarized and depolarized. Particular attention was given to the depolarized echoes. North Ray and South Ray Craters and a 512-m diameter lunar crater in the Flamsteed Ring were used for the study.
    Keywords: COMMUNICATIONS
    Type: NASA. Lyndon B. Johnson Space Center Apollo 16 Prelim. Sci. Rept.; 3 p
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  • 8
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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
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  • 9
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    Radar augmentation device (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: The radar augmentation device (RAD) serves to increase the radar response of a target body and thus expedite radar acquisition. The design and development of the RAD are discussed with particular emphasis on technical problems that were encountered and solved. Discussions of the mode of operation of the RAD and the ground test history are also included.
    Keywords: COMMUNICATIONS
    Type: NASA. Ames Res. Center 6th Aerospace Mech. Symp.; p 65-72
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  • 10
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    Magnetospheric radio noise (1972)
    In:  CASI
    Details
    Publication Date: 2005-11-30
    Description: Observations, made by the RAE satellite, of earth magnetospheric noise are reported. The observations show radio noise exists at 700 kHz and below. The results are included in graphs.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Sci., 1970; p 75-80
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  • 11
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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
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  • 12
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    Some special cases of the electromagnetic inverse problem (1972)
    In:  CASI
    Details
    Publication Date: 2006-03-12
    Description: A review of exact techniques for determining the surface of a three-dimensional perfectly conducting body is given, followed by some new results on the uniqueness question concerning the number of measurements that may be required to explicitly determine the surface of the body. It is then shown that the inhomogeneous but spherically symmetric dielectric electromagnetic case is reducible to a scalar inverse problem that can be treated by known techniques.
    Keywords: COMMUNICATIONS
    Type: NASA. Ames Res. Center Math. of Profile Inversion; 11 p
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  • 13
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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
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  • 14
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    Interplex: An analysis of optimized power allocations for two and three channel PSK/PM telecommunications systems (1972)
    In:  CASI
    Details
    Publication Date: 2006-02-22
    Description: Optimal design concepts are presented for two- and three-channel telemetry modes in the context of the Mariner Venus-Mercury 1973 mission and the usefulness of interplex modulation techniques is discussed. These ideas are applied as an example to one Mariner Venus-Mercury 1973 telemetry mode to demonstrate that interplex can reduce the required total average power by more than 2 dB in some cases.
    Keywords: COMMUNICATIONS
    Type: JPL Quarterly Tech. Rev., Vol. 2, No. 1; p 143-151
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  • 15
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    Analysis of the failure of a polyester peripheral drive belt on the Mariner Mars 1971 flight tape recorder (1972)
    In:  CASI
    Details
    Publication Date: 2006-02-22
    Description: A peripheral drive belt on the Mariner Mars 1971 tape recorder failed when a thin longitudinal strip separated off one edge. Analysis showed that the most probable cause of failure occurred from flexural fatigue initiating in mechanically weak locations which are introduced into the belt during fabrication. Methyl ethyl ketone, which is employed as a cleaning solvent during fabrication, was found to cause permanent reduction in engineering properties of polyester and could have contributed to the reduction of the fatigue resistance. Fatigue properties of the polyester drive belt are reviewed for the operating condition, as well as the sensitivity of polyester to cleaning solvents and the origin of mechanically weak locations.
    Keywords: COMMUNICATIONS
    Type: JPL Quarterly Tech. Rev., Vol. 2, No. 1; p 82-99
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  • 16
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    Studies on the frictional behavior of magnetic recording tapes (1972)
    In:  CASI
    Details
    Publication Date: 2006-02-22
    Description: Methods were developed for measuring frictional forces acting on a magnetic tape in motion or at rest, as well as the extent of stick slip. The effects of factors such as temperature, humidity, kind of gaseous atmosphere, and tape speed on the frictional interaction between various tapes and heads were investigated. Results were instrumental in the selection of a tape for the Mariner Mars 1971 spacecraft. Studies are reported on the stick slip behavior of tapes and the performance of a metallic tape, compared with the usual plastic tapes.
    Keywords: COMMUNICATIONS
    Type: JPL Quarterly Tech. Rev., Vol. 2, No. 1.; p 100-106
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  • 17
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    Results from simultaneous radar-television observations (1972)
    In:  CASI
    Details
    Publication Date: 2006-04-24
    Description: The results of the reduction of simultaneous observations of 29 meteors are presented in tabular form. Fragmentation of the observations is discussed along with the 50 meteors not yet reduced.
    Keywords: COMMUNICATIONS
    Type: Meteor Res. Program; p 83-99
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  • 18
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    Analysis procedure for television observations and simultaneous observations (1972)
    In:  CASI
    Details
    Publication Date: 2006-04-24
    Description: The procedures used in the analysis of television and simultaneous observations are described. Starting with the right ascension and declination of the meteor, the celestrial triangle formed by Sidell and the meteor is solved, and the epochs of the beginning and end of the meteor observation as recorded on the video tape are determined.
    Keywords: COMMUNICATIONS
    Type: Meteor Res. Program; p 69-76
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  • 19
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    Simultaneous observations by television camera and radar (1972)
    In:  CASI
    Details
    Publication Date: 2006-04-24
    Description: The original image-orthicon equipment used for simultaneous radar and optical observations is described. The adaptations made to enhance its usefulness for meteor observations, and the specialized calibration and photometric procedures developed for this purpose are also described. Some brief comments concerning the use of the secondary electron conduction vidicon are included.
    Keywords: COMMUNICATIONS
    Type: Meteor Res. Program; p 29-36
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  • 20
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    Results of measurement of radio wave absorption in the ionosphere by the AI method (1972)
    In:  CASI
    Details
    Publication Date: 2006-04-26
    Description: Median noon absorption values for each month from 1964 through 1967, the diurnal variations of absorption on the regular world days, and the seasonal variations of absorption are given. The dependence of the absorption coefficient on sunspot number is analyzed.
    Keywords: COMMUNICATIONS
    Type: Morphology of the Quiet and Disturbed Ionosphere; p 99-112
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  • 21
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    Analysis procedure for radar observations (1972)
    In:  CASI
    Details
    Publication Date: 2006-04-24
    Description: Based on the assumption that the ionized column left behind a moving meteroroid is underdense, it is shown that radar observations of the column yield resonable aproximations to the meteoriod's speed and trajectory. The principles and procedures for finding a meteor's position and vector velocity from the observed data are also presented.
    Keywords: COMMUNICATIONS
    Type: Meteor Res. Program; p 51-68
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  • 22
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    Antenna calibration at Havana (1972)
    In:  CASI
    Details
    Publication Date: 2006-04-24
    Description: The procedures for calibrating the antenna patterns of the Havana radar system are described along with the reduction of the measurements made using a dipole towed behind an airplane. The power-gain pattern for the north, south, and joint troughs of sites 3 and 4 are plotted.
    Keywords: COMMUNICATIONS
    Type: Meteor Res. Program; p 37-50
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  • 23
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    Description of eight station radar near Havana, Illinois (1972)
    In:  CASI
    Details
    Publication Date: 2006-04-24
    Description: A general description is given of the eight-station system at Havana which incorporated high-gain antennas and a powerful transmitter to reach faint meteors on the order of magnitude of plus 12. The station location, principle of system design, systems connections, transmitter, receivers, logics, range measurement, and recording are described.
    Keywords: COMMUNICATIONS
    Type: Meteor Res. Program; p 19-27
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  • 24
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    Precision signal power measurement (1972)
    In:  CASI
    Details
    Publication Date: 2006-02-22
    Description: Accurate estimation of signal power is an important Deep Space Network (DSN) consideration. Ultimately, spacecraft power and weight is saved if no reserve transmitter power is needed to compensate for inaccurate measurements. Spectral measurement of the received signal has proved to be an effective method of estimating signal power over a wide dynamic range. Furthermore, on-line spectral measurements provide an important diagnostic tool for examining spacecraft anomalies. Prototype equipment installed at a 64-m-diameter antenna site has been successfully used to make measurements of carrier power and sideband symmetry of telemetry signals received from the Mariner Mars 1971 spacecraft.
    Keywords: COMMUNICATIONS
    Type: JPL Quart. Tech. Rev., Vol. 2, No. 2; p 18-24
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  • 25
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    Mode coupling in partial reflections from the ionosphere at vertical incidence. (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The effect of mode coupling has been calculated for radio waves partially reflected from the lower ionosphere at vertical incidence. Calculations were made for parameters appropriate to the partial reflection experiments (Belrose, 1970). The four reflection coefficients (two direct and two coupled) are calculated for a plane discontinuity using a matrix perturbation analysis. The ratios of coupled to direct reflection coefficients are calculated for a general one-dimensional reflecting layer using the coupled equations of Clemmow and Heading (1954). At the highest electron density considered, 10,000 per cu cm, about 10% of the reflected extraordinary wave amplitude might be due to coupling from the incident ordinary wave. The effect is smaller at lower electron density.
    Keywords: COMMUNICATIONS
    Type: Radio Science; 7; Apr. 197
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  • 26
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    Convergence of oscillator spectral estimators for counted-frequency measurements. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A common intermediary connecting frequency-noise calibration or testing of an oscillator to useful applications is the spectral density of the frequency-deviating process. In attempting to turn test data into predicts of performance characteristics, one is naturally led to estimation of statistical values by sample-mean and sample-variance techniques. However, sample means and sample variances themselves are statistical quantities that do not necessarily converge (in the mean-square sense) to actual ensemble-average means and variances, except perhaps for excessively large sample sizes. This is especially true for the flicker noise component of oscillators. This article shows, for the various types of noises found in oscillators, how sample averages converge (or do not converge) to their statistical counterparts. The convergence rate is shown to be the same for all oscillators of a given spectral type.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-20; Apr. 197
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  • 27
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    High-sensitivity receiver for infrared laser communications. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Description of a high-sensitivity wide-bandwidth 10.6-micron heterodyne receiver for space and ground operational use. The receiver includes a cooled HgCdTe infrared mixer diode, a conical scanner for spatial tracking, an acquisition channel for spatial search and station alignment, and an automatic frequency-control channel to maintain a fixed laser frequency offset. The infrared mixer is designed to provide nearly quantum-noise-limited operation over an extended range of mixer temperature, bias voltage, and intermediate frequency. The resultant experimental receiver has a measured noise equivalent power of less than 10 to the minus 19th W/Hz over the 15- to 40-MHz i.f. band for mixer temperatures from 85 to 115 K, and less than 2 x 10 to the minus 19th W/Hz up to 140 K. Mixer 3-dB cutoff frequencies as high as 420 MHz were measured at a mixer temperature of 125 K. An analysis and engineering equations are given for receiver noise components, noise equivalent power, available mixer conversion gain, mixer transducer gain, and quantum-noise factor in terms of such factors as mixer parameters, quantum efficiency, mixer temperature, dynamic conductance, bias voltage, local oscillator power, and i.f. amplifier characteristics.
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  • 28
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    Requirements for laser radar detection of a barium ion cloud at five earth radii. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The requirements for a tuned laser radar capable of detecting and ranging a high altitude barium ion cloud release are discussed. A high energy pulsed dye laser tuned to the 455.4 nm Ba II resonance line is considered as the transmitter. Photon counting detection is employed and the resultant signal is integrated over a number of successive laser firings. The solar induced radiance of the cloud is the major background noise source. Detection and ranging may be achieved with signal-to-noise ratios of the order of unity using currently available equipment. This technique has the potential of improved resolution as compared to photographic measurements previously made.
    Keywords: COMMUNICATIONS
    Type: Planetary and Space Science; 20; Mar. 197
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  • 29
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    Binary single-sideband phase-modulated communication systems. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Single-sideband phase modulation (SSBPM), in which a signal is simultaneously phase- and amplitude-modulated by a signal and its Hilbert transform, is shown to be suboptimum for binary signaling in white Gaussian noise. An alternative single-sideband technique based on the properties of binary suppressed-carrier phase modulation is proposed and shown to give performance equivalent to the double-sideband version.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Information Theory; IT-18; Jan. 197
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  • 30
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    Computations of the aperture admittance of an axial slot on a dielectric coated cylinder. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An extensive set of curves for the aperture admittance of a waveguide-fed axial slot on a coated metal cylinder is presented for both an underdense plasma and a Teflon coating. Examination of these curves shows that a slot on a cylinder with a Ka of 2 to 3 has about the same aperture admittance as the identical slot opening onto a flat ground plane.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-20; Jan. 197
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  • 31
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    Spatial-detection effects in laser radar. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Determination of a relation for the detector-aperture size for spatially coherent detection when dependent scattering is present. This relation is applied to several realistic laser-radar situations. It is concluded that no distortion of laser-radar signal signatures due to spatial-detection effects should be expected for present typical operating conditions (i.e., mean wavelength of the source = 0.6943 micrometer, and the diameter of the receiving aperture is about 10 cm). With development of longer-wavelength laser radars, in order to monitor signal returns at pollutant-gas absorption lines concomitantly larger receiver apertures must be used or else widely varying signal signatures will result even though similar conditions prevail.
    Keywords: COMMUNICATIONS
    Type: Optical Society of America; vol. 62
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  • 32
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    Electromagnetic scattering by arbitrarily oriented ice cylinders. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The scattering of electromagnetic waves by arbitrarily oriented, infinitely long circular cylinders is solved by following the procedures outlined by van de Hulst. The far-field intensities for two cases of a linearly polarized incident wave are derived. The scattering coefficients involve the Bessel functions of the first kind, the Hankel functions of the second kind, and their first derivatives. Calculations are made for ice cylinders at three wavelengths: 0.7, 3, and 10 microns. The numerical results of intensity coefficients are presented as functions of the observation angle. A significant cross-polarized component for the scattered field, which vanishes only at normal incidence, is obtained. It is also shown that the numerous interference maxima and minima of the intensity coefficients due to single-particle effects depend on the size parameter as well as on the oblique incident angle.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 11; Mar. 197
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  • 33
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    A study of microwave leakage through perforated flat plates. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A simple formula useful for predicting leakage through a circular hole array in a metallic flat plate is presented. A correction is given for plate thickness. The formula is applicable to arrays having either a 60-deg (staggered) or 90-deg (square) hole pattern, but is restricted to the case of (1) an obliquely incident plane wave with the E field polarized normal to the plane of incidence, and (2) large transmission loss. When theoretical values were compared to experimental data obtained on test samples having transmission losses greater than 20 dB, the agreement between theory and experiment was typically better than 1 dB at S band and 2 dB at X band.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Microwave Theory and Techniques; MTT-20; Mar. 197
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  • 34
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    Correction of satellite tracking data for an arbitrary tropospheric profile. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A procedure is given for deriving elevation-error and range-error correction equations in a form suitable for use in the rapid processing of satellite tracking data. The refractivity of the troposphere is assumed to have spherical symmetry, but may have any given profile that does not depart greatly from standard. When the procedure was tested for numerical accuracy by application to an exponential profile, the corrections calculated agreed with those obtained by ray tracing to 0.3% or better over a range of surface refractivity from 200 to 450 and a range of radiowave arrival angles from horizontal to vertical.
    Keywords: COMMUNICATIONS
    Type: Radio Science; 7; Feb. 197
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    Tropospheric refraction effects on satellite range measurements. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A model for predicting the atmospheric effect for earth-to-orbit range or range-rate measurements is described. The model treats the dry and wet components of refractivity (N) as different functions of its surface value and of height above the earth. It provides a zenith integral of the dry component that is consistent with the equation for the zenith range effect in dry air. For low angle use, it gives a reasonable approximation of observed N profiles. The use of the model is discussed, and data and computed positions without and with a correction for the troposphere are presented.
    Keywords: COMMUNICATIONS
    Type: APL Technical Digest; 11; Mar
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  • 36
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    On higher order discrete phase-locked loops. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An exact mathematical model is developed for a discrete loop of a general order particularly suitable for digital computation. The deterministic response of the loop to the phase step and the frequency step is investigated. The design of the digital filter for the second-order loop is considered. Use is made of the incremental phase plane to study the phase error behavior of the loop. The model of the noisy loop is derived and the optimization of the loop filter for minimum mean-square error is considered.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-8; Sept
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    Simultaneous measurements of radar reflectivity and refractive index spectra in clear air convection. (1972)
    In:  Other Sources
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    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
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  • 38
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    The short-wavelength spectrum of the microwave background. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: COMMUNICATIONS
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  • 39
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    Frame synchronization in time-multiplexed PCM telemetry with variable frame length. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-20; Oct. 197
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  • 40
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    The role of time-frequency in satellite position determination systems. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Tests were conducted by NASA on radio navigation satellite systems that employ the use of time-frequency determination. The satellites used for this purpose were the ATS 1 and 3, and the Nimbus 3 and 4. Several systems were tested in order to examine the feasibility of three satellite navigation concepts: (1) multiple satellite range measurements, (2) satellite range rate, or range and range rate measurements and (3) satellite angle measurements. Test results indicate that locations of ships and aircraft can be determined to within 3-5 km, one sigma, by these satellite methods, and that location accuracy is both a function of the RF employed and of the extent of knowledge of the satellite orbit.
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 60
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    Time synchronization via lunar radar. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The advent of round-trip radar measurements has permitted the determination of the ranges to the nearby planets with greater precision than was previously possible. When the distances to the planets are known with high precision, the propagation delay for electromagnetic waves reflected by the planets may be calculated and used to synchronize remotely located clocks. Details basic to the operation of a lunar radar indicate a capability for clock synchronization to plus or minus 20 microsec. One of the design goals for this system was to achieve a simple semiautomatic receiver for remotely located tracking stations. The lunar radar system is in operational use for deep space tracking at Jet Propulsion Laboratory and synchronizes five world-wide tracking stations with a master clock at Goldstone, Calif. Computers are programmed to correct the Goldstone transmissions for transit time delay and Doppler shifts so as to be received on time at the tracking stations; this dictates that only one station can be synchronized at a given time period and that the moon must be simultaneously visible to both the transmitter and receiver for a minimum time of 10 min.-
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 60
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  • 42
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    Dual transponder time synchronization at C band using ATS-3. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The use of artificial satellites for time synchronization of geographically distant clocks is hindered by problems due to satellite motion or equipment delay measurements. The ATS-3 satellite with its two C-band transponder channels helps solve these problems through techniques for synchronization to accuracies of tenths of microseconds. Portable cesium clocks were used to verify the accuracy of the described system.
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 60
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  • 43
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    Satellite time synchronization of a NASA network. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A satellite time synchronization technique has been used for synchronization of remotely separated clocks during the past several years. The NASA network has been successfully synchronized to an accuracy of tens of microseconds via the NASA Geodetic Earth Orbiting Satellite GEOS-11. The results indicate that a polar orbit satellite having an onboard clock can effectively be used to synchronize clocks on a global basis.
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 60
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  • 44
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    Scintillation in an earth-to-space propagation path. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Results of an experiment to measure the scintillation at a satellite from a ground-based laser transmitter. The GEOS-II satellite in a nearly circular orbit of 1250 km was illuminated by a ground-based laser tracking station using a 4880-A CW argon laser. A detector aboard the satellite measured the incident light and telemetered the data to recording equipment on the ground. Log-amplitude variance, probability distributions, and scintillation frequency distributions are derived from the data. The probability distribution is shown to be log-normal. Log-amplitude variance and normalized power spectral density are shown to be within the limits measured for stellar scintillation.-
    Keywords: COMMUNICATIONS
    Type: Optical Society of America; vol. 62
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  • 45
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    On the selection of a sampling filter bandwidth for a digital data detector. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Consideration of the problem of selecting a low-pass sampling bandwidth for the digital mechanization of a matched-filter bit-synchronizer combination. An attempt is made to determine how large a data rate can be provided for a fixed sampling rate (limited by hardware considerations on the sampling device) without paying an excessive penalty in SNR performance.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-20; June 197
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  • 46
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    Lunar subsurface exploration with coherent radar. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The Apollo Lunar Sounder Experiment that is scheduled to orbit the moon on Apollo 17 consists of a three frequency coherent radar system and an optical recorder. The coherent radar can be used to measure both phase and amplitude characteristics of the radar echo. Measurement methods that are related to the phase and amplitude will be used to determine the surface profile, locate subsurface features and ascertain near surface electrical properties of the lunar surface. The key to the coherent radar measurement is a highly stable oscillator that preserves an accurate phase reference (2 or 3 electrical degrees) over a long period of time. This reference provides a means for reducing surface clutter so that subsurface features are more easily detected and also provides a means of measuring range to the surface to within a fraction of a wavelength.
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  • 47
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    Coherent Optical Processing of Phased Array Radar Data (1972)
    In:  CASI
    Details
    Publication Date: 2014-09-09
    Description: Interfacing a coherent optical processor, which utilizes an electron-beam addressed, potassium dideuterium phosphate (KDP) crystal modulator, with a linear phased array is studied. An abbreviated development of typical radar signals from a linear array is included. A plan for formating the spatial modulator with linear array signals is presented. The theoretical expectations which include target angle and Doppler are derived. A simulated set of M signals which are typical of a linear array of M elements was devised. This set of signals was used to modulate the wave front of collimated laser light via the KDP crystal according to the format presented.
    Keywords: COMMUNICATIONS
    Type: Auburn Univ. The NASA-ASEE Summer Fac. Fellowship Program; p 495-506
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  • 48
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    Data Transmission Signal Design and Analysis (1972)
    In:  CASI
    Details
    Publication Date: 2014-09-09
    Description: The error performances of several digital signaling methods are determined as a function of a specified signal-to-noise ratio. Results are obtained for Gaussian noise and impulse noise. Performance of a receiver for differentially encoded biphase signaling is obtained by extending the results of differential phase shift keying. The analysis presented obtains a closed-form answer through the use of some simplifying assumptions. The results give an insight into the analysis problem, however, the actual error performance may show a degradation because of the assumptions made in the analysis. Bipolar signaling decision-threshold selection is investigated. The optimum threshold depends on the signal-to-noise ratio and requires the use of an adaptive receiver.
    Keywords: COMMUNICATIONS
    Type: Auburn Univ. The NASA-ASEE Summer Fac. Fellowship Program; p 399-437
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  • 49
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    Equivalence of time-multiplexed and frequency-multiplexed signals in digital communications. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: In comparing different techniques for multiplexing N binary data signals into a single channel, time-division multiplexing (TDM) is known to have a theoretic efficiency of 100 percent (neglecting sync power) and thus seems to outperform frequency-division multiplexing systems (FDM). By considering more general FDM systems, we will show that both TDM and FDM are equivalent and have an efficiency of 100 percent. The difference between the systems is in the multiplexing and demultiplexing subsystems, but not in the performance or in the generated waveforms.
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  • 50
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    On the effect of departures from spherical symmetry upon the bistatic-radar occultation experiment. (1972)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The dependence of residual phase shifts upon the angle of inclination of the orbit for a model Martian atmosphere is examined. It is found that departures from spherical symmetry in the electron number density profiles result in changes of as much as an order of magnitude in the phase shifts of radio waves passing through the atmosphere and ionosphere of the model. These results confirm the earlier findings of Pirraglia and Gross (1970).
    Keywords: COMMUNICATIONS
    Type: Planetary and Space Science; 20; May 1972
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  • 51
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    Satellite relay telemetry in the surveillance of active volcanoes and major fault zones (1972)
    In:  Other Sources
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    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
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  • 52
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    Factors affecting frequency and orbit utilization by high power transmission satellite systems (1972)
    In:  CASI
    Details
    Publication Date: 2012-05-23
    Description: The factors affecting the sharing of the geostationary orbit by high power (primarily television) satellite systems having the same or adjacent coverage areas and by satellites occupying the same orbit segment are examined and examples using the results of computer computations are given. The factors considered include: required protection ratio, receiver antenna patterns, relative transmitter power, transmitter antenna patterns, satellite grouping, and coverage pattern overlap. The results presented indicate the limits of system characteristics and orbit deployment which can result from mixing systems.
    Keywords: COMMUNICATIONS
    Type: AGARD Aerospace Telecommun. Systems; 16 p
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  • 53
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    Attitude errors arising from antenna/satellite altitude errors - Recognition and reduction (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A review is presented of the three basic types of pulsed radar altimeter designs, as well as the source and form of altitude bias errors arising from antenna/satellite attitude errors in each design type. A quantitative comparison of the three systems was also made.
    Keywords: COMMUNICATIONS
    Type: NOAA Sea Surface Topography from Space, Vol. 1; 24 p
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  • 54
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    Radar signature and systems studies at Kansas University (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The radar signature and systems studies described have concentrated in two areas: octave bandwidths radar spectrometry using a truck-mounted system, and scatterometry using primarily the 13.3 GHz system on aircraft. In addition, the results of the experiments to date have been synthesized into a pair of representative designs for spacecraft radar systems: one for small spacecraft and one for large spacecraft.
    Keywords: COMMUNICATIONS
    Type: NASA. Manned Spacecraft Center 4th Ann. Earth Resources Program Rev., Vol. 2; 37 p
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  • 55
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    Detection of oil spills using 13.3 GHz radar scatterometer (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The results of an analysis of 13.3-GHz single polarized scatterometer data collected during NASA/MSC Mission 135, flown on March 16, 1970 are reported. Data were gathered over a crude oil spill on the Gulf of Mexico off the Mississippi Delta. With the aid of RC-8 camera photographs, the scattering cross section was correlated with the extent of the oil spill. The scattering cross section at higher incidence angles decreased by 5 db to 10 db in the presence of the oil spill. This was attributed to oil's damping of small gravity and capillary waves. The composite scattering theory and the scatterometer acquired data were used to obtain an expression of radar scattering over ocean surfaces with oil spills. The study demonstrates that the presence and extent of oil spills can be detected using high frequency radar systems.
    Keywords: COMMUNICATIONS
    Type: NASA. Manned Spacecraft Center 4th Ann. Earth Resources Program Rev., Vol. 1; 27 p
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  • 56
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    The NAS-PAK Logic System (1972)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The design and fabrication of telemetry ground data processing equipment using commercial logic cards or modules are discussed. A microelectronics program was initiated to evaluate circuitry, packaging methods, and fabrication approaches necessary to produce a competitively procured logic system. The NAS-PAK logic system covering all phases of implementation is considered.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 171-180
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  • 57
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    Signal coherence studies in multiaperture arrays (1972)
    In:  CASI
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    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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  • 58
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    Dichroic subreflector for Rosman 2 (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The dichronic subreflector for the Rosman 2 dish antenna is described. Tests were conducted to make focusing adjustments, to measure the system parameters indicative of a focused condition for the Cassegrain feed, and to determine losses for the focal point feeds due to the presence of the dichroic.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 163-166
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  • 59
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    STADAN antenna gain calibration using radio stars (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An antenna gain measurement method was developed which utilizes a signal emitted from a radio star to determine absolute antenna gain at 136 MHz and 400 MHz for antennas in the STADAN network. An error analysis of the radio star method shows that the overall standard deviation uncertainty in antenna gain is + or - 0.6 db (1 sigma).
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 156-158
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  • 60
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    Computer controlled antenna system (1972)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Digital techniques are discussed for application to the servo and control systems of large antennas. The tracking loop for an antenna at a STADAN tracking site is illustrated. The augmentation mode is also considered.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 159-162
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  • 61
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    Results of FM-TV threshold reduction investigation for the ATS F trust experiment (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An investigation of threshold effects in FM TV was initiated to determine if any simple, low cost techniques were available which can reduce the subjective video threshold, applicable to low cost community TV reception via satellite. Two methods of eliminating these effects were examined: the use of standard video pre-emphasis, and the use of an additional circuit to blank the picture tube during the retrace period.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 126-128
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  • 62
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    An adaptive narrow band frequency modulation voice communication system (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A narrow band frequency modulation communication system is described which provides for the reception of good quality voice at low carrier-to-noise ratios. The high level of performance is obtained by designing a limiter and phase lock loop combination as a demodulator, so that the bandwidth of the phase lock loop decreases as the carrier level decreases. The system was built for the position location and aircraft communication equipment experiment of the ATS 6 program.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 119-121
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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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  • 64
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    Telemetry remote modules (1972)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A fully operational engineering telemetry remote module is reported that forms the basis for a decentralized telemetry system which employs small low powered modules capable of distributing the multiplexer input gates around a spacecraft. The module operates mainly as a harness reducer, allowing data to be transmitted back to a central control core for inclusion in the telemetry bit stream. Each unit is capable of accepting 32 data points in various combinations.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 87-89
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  • 65
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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
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  • 66
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    Radio wave propagation experiments to probe the ionosphere (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Ionospheric bias corrections associated with radio tracking of spacecraft depend on the following measuring techniques for integrated electron content: (1) Faraday rotation measurements from an earth synchronous satellite; (2) ranging measurements at two frequencies; and (3) group and phase velocity measurements obtained from tracking data. The extraction of the integrated electron content directly from tracking data is achieved by comparison of range-rate measurements based on Doppler shift with differentiated range measurements based on tone delay. This method is most desirable because the measured corrections pertain directly to the spacecraft whose orbit is being determined and can be used in near earth as well as deep space tracking data.
    Keywords: COMMUNICATIONS
    Type: Significant Accomplishments in Technol., GSFC, 1970; p 3-9
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  • 67
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    Methods of quantitative and qualitative analysis of bird migration with a tracking radar (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Methods of analyzing bird migration by using tracking radar are discussed. The procedure for assessing the rate of bird passage is described. Three topics are presented concerning the grouping of nocturnal migrants, the velocity of migratory flight, and identification of species by radar echoes. The height and volume of migration under different weather conditions are examined. The methods for studying the directions of migration and the correlation between winds and the height and direction of migrating birds are presented.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington Animal Orientation and Navigation; p 151-167
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  • 68
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    Information on bird navigation obtained by British long range radars (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Radar observations of the migratory habits of passerine birds over a 10 year period are presented. The relationships between intensity of cloud cover and the frequency and density of migration are illustrated. The aspects of migration which were determined by the radar were: (1) migration under total overcast, (2) compensation for wind drift, (3) changes in flight direction during migration, and (4) effects of meteorological parameters.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington Animal Orientation and Navigation; p 139-149
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  • 69
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    Use of the Doppler technique to track free roaming animals from satellites (1972)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The application of the Doppler effect to track wild animals is discussed, with artificial satellites used to provide wide range coverage. The limitations of radiotelemetry for the purpose of tracking animals are presented. The advantages of the artificial satellite, with specific reference to the Nimbus satellite, are examined.
    Keywords: COMMUNICATIONS
    Type: NASA, Washington Animal Orientation and Navigation; p 7-17
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    High power microwave components for space communications satellite (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Analyzed, developed, and tested were high power microwave components for communications satellites systems. Included were waveguide and flange configurations with venting, a harmonic filter, forward and reverse power monitors, electrical fault sensors, and a diplexer for two channel simultaneous transmission. The assembly of 8.36 GHz components was bench tested, and then operated for 60 hours at 3.5 kW CW in a high vacuum. The diplexer was omitted from this test pending a modification of its end irises. An RF leakage test showed only that care is required at flange junctions; all other components were RF tight. Designs were extrapolated for 12 GHz and 2.64 GHz high power satellite systems.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-120927
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    Optimization in the design of a 12 gigahertz low cost ground receiving system for broadcast satellites. Volume 2: Antenna system and interference (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The antenna characteristics are analyzed of a low cost mass-producible ground station to be used in broadcast satellite systems. It is found that a prime focus antenna is sufficient for a low-cost but not a low noise system. For the antenna feed waveguide systems are the best choice for the 12 GHz band, while printed-element systems are recommended for the 2.6 GHz band. Zoned reflectors are analyzed and appear to be attractive from the standpoint of cost. However, these reflectors suffer a gain reduction of about one db and a possible increase in sidelobe levels. The off-axis gain of a non-auto-tracking station can be optimized by establishing a special illumination function at the reflector aperture. A step-feed tracking system is proposed to provide automatic procedures for searching for peak signal from a geostationary satellite. This system uses integrated circuitry and therefore results in cost saving under mass production. It is estimated that a complete step-track system would cost only $512 for a production quantity of 1000 units per year.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-121184-VOL-2 , SU-SEL-72-043-VOL-2
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    On the mapping associated with the complex representation of functions and processes. (1972)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The mapping between function spaces that is implied by the representation of a real 'bandpass' function by a complex 'low-pass' function is explicitly accepted. The discussion is extended to the representation of stationary random processes where the mapping is between spaces of random processes. This approach clarifies the nature of the complex representation, especially in the case of random processes and, in addition, derives the properties of the complex representation.-
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-8; Nov. 197
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  • 73
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    Optical communication theory. (1972)
    In:  Other Sources
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    Description: An introduction is provided to the important ideas involved in the design and the evaluation of optical communication systems which transmit digital or analog data. Field representations are discussed together with background noise, a detector statistical model, quantum receivers, and turbulent and scatter channels. Free-space channels are considered, taking into account heterodyne systems, preamplifier and homodyne systems, direct-detection systems, and optimum quantum systems.
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  • 74
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    Spectral analysis program (SAP). Volume 2: Programmer's manual (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The spectral analysis program (SAP) flow diagrams, and listings are presented. The plot generation program (PLTGEN) flow diagrams and listings are also included.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-128985 , TRW-20817-H011-R0-00-VOL-2
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  • 75
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    Virginia precipitation scatter experiment: Experiment description (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A year's statistical data were acquired for the purposed of refining existing coordination procedures for the sharing of common frequency allocations between terrestrial and space services. The measurement program was conducted between October 3, 1970 and October 2, 1971, to empirically determine the cumulative distributions of scattering cross section per unit volume of hydrometeors at heights up to 9 km above the surface and of rain rate at the surface. The measurements were made in southeastern Virginia using a bistatic, continuous-wave, vertically polarized radar system operating at S- and X-band frequencies and tipping-bucket rain gages. The bistatic radar system was configured to represent an interference situation between a radio-relay system and a space communication system Earth terminal; the results may be interpreted as measured distributions of transmission loss for interference due to rain. A description of the experiment and equipment is included.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-66259 , X-750-73-54
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  • 76
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    Synchronization using pulsed edge tracking in optical PPM communication system (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A pulse position modulated (PPM) optical communication system using narrow pulses of light for data transmission requires accurate time synchronization between transmitter and receiver. The presence of signal energy in the form of optical pulses suggests the use of a pulse edge tracking method of maintaining the necessary timing. The edge tracking operation in a binary PPM system is examined, taking into account the quantum nature of the optical transmissions. Consideration is given first to pure synchronization using a periodic pulsed intensity, then extended to the case where position modulation is present and auxiliary bit decisioning is needed to aid the tracking operation. Performance analysis is made in terms of timing error and its associated statistics. Timing error variances are shown as a function of system signal to noise ratio.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-130117 , USCEE-426
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  • 77
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    Multipath propagation study for L-band, over-ocean, satellite-aircraft communication link (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The results are presented of a study of multipath propagation between an aeronautical relay satellite in synchronous earth orbit and an aircraft flying over the ocean. An analytical model for the reflected power is developed and the results of a computer solution are compared with an approximate solution obtained through integration by the method of steepest descent. The computer solution is shown to differ considerably from the approximate solution. Both methods are compared with the limited experimental results available.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-66094 , X-752-72-335
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  • 78
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    Telecommunications Systems Design Techniques Handbook (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The Deep Space Network (DSN) increasingly supports deep space missions sponsored and managed by organizations without long experience in DSN design and operation. The document is intended as a textbook for those DSN users inexperienced in the design and specification of a DSN-compatible spacecraft telecommunications system. For experienced DSN users, the document provides a reference source of telecommunication information which summarizes knowledge previously available only in a multitude of sources. Extensive references are quoted for those who wish to explore specific areas more deeply.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-129108 , JPL-TM-33-571
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  • 79
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    Amplitude fading of simultaneous transionospheric L-band and VHF signals received at the geomagnetic equator (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: At Ancon, Peru, simultaneous observations of 1550-MHz and 136-MHz signals from the ATS 5 and Intelsat-1 spacecraft showed ionospheric fading as great as 27 db at 136 MHz and 6 db at 1550 MHZ. The observations were made on 48 days during the 1970 autumnal and 1971 vernal equinox periods. Comparison of the two frequencies, in respect to rates and depths of fades, is made. Statistical distributions of the received signal levels during ionospheric scintillation occurrences are presented which may be of use to communications system engineers with operational requirements in the equatorial regions. The distributions show that during expected periods of scintillation, the L band signal typically falls 1.1 db below the median for 1.0 percent of the time, and the VHF signal falls 11.5 db below the median for 1.0 percent of the time.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-66060 , X-810-72-282
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  • 80
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    Burst decoding of binary block codes on Q-ary output channels. (1972)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The burst-b distance between two binary vectors is defined and shown to be a metric. This definition is applied to a binary-input, Q-ary output channel where errors occur in bursts. A decoding algorithm is presented for such a channel that is an extension of Weldon's (1971) weighted erasure decoding. Examples are presented illustrating the techniques.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Information Theory; IT-18; Sept
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  • 81
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    Hybrid carrier and modulation tracking loops. (1972)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The tracking loops presented herein exploit the coherency of the observed data sidebands at the carrier frequency for improvements in phase-coherent tracking, telemetry, and command system performance. The loop is motivated by one aspect of generalized harmonic analysis, viz., the so-called cross spectrum. The basic idea of the loop centers around using the power in the composite received signal (sidebands including cross-modulation components) to enhance the signal-to-noise ratio in the carrier tracking loop, thereby reducing the noisy reference loss and ultimately the subcarrier reference jitter, the symbol sync jitter, and the error probability of the data detector. The modulation from the extracted sidebands is removed in such a way that the coherence power in the data sidebands can be used for tracking at the carrier frequency.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-20; Feb. 197
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  • 82
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    Permutation codes for sources. (1972)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Source encoding techniques based on permutation codes are investigated. For a broad class of distortion measures it is shown that optimum encoding of a source permutation code is easy to instrument even for very long block lengths. Also, the nonparametric nature of permutation encoding is well suited to situations involving unknown source statistics. For the squared-error distortion measure a procedure for generating good permutation codes of a given rate and block length is described. The performance of such codes for a memoryless Gaussian source is compared both with the rate-distortion function bound and with the performance of various quantization schemes. The comparison reveals that permutation codes are asymptotically ideal for small rates and perform as well as the best entropy-coded quantizers presently known for intermediate rates. They can be made to compare favorably at high rates, too, provided the coding delay associated with extremely long block lengths is tolerable.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Information Theory; IT-18; Jan. 197
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  • 83
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    The 136 MHz/400 MHz earth station antenna-noise temperature prediction program documentation for RAE-B (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A simulation study to determine the 136 MHz and 400 MHz noise temperature of the ground network antennas which will track the RAE-B satellite during data transmission periods is described. Since the noise temperature of the antenna effectively sets the signal-to-noise ratio (SNR) of the received signal, a knowledge of SNR will be helpful in locating the optimum time windows for data transmission during low-noise periods. Antenna-noise temperatures at 136 MHz and 400 MHz will be predicted for selected earth-based ground stations which will support RAE-B. The antenna-noise temperature predictions will include the effects of galactic-brightness temperature, the sun, and the brightest radio stars. Predictions will cover the ten-month period from March 1, 1973 to December 31, 1973. The RAE-B mission will be expecially susceptible to SNR degradation during the two eclipses of the Sun occurring in this period.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-66048 , X-752-72-327
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  • 84
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    A digital simulation of message traffic for natural disaster warning communications satellite (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Various types of weather communications are required to alert industries and the general public about the impending occurrence of tornados, hurricanes, snowstorms, floods, etc. A natural disaster warning satellite system has been proposed for meeting the communications requirements of the National Oceanic and Atmospheric Administration. Message traffic for a communications satellite was simulated with a digital computer in order to determine the number of communications channels to meet system requirements. Poisson inputs are used for arrivals and an exponential distribution is used for service.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-68135 , E-7137
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  • 85
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    Numerical method and FORTRAN program for the solution of an axisymmetric electrostatic collector design problem (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The numerical calculation is described of the steady-state flow of electrons in an axisymmetric, spherical, electrostatic collector for a range of boundary conditions. The trajectory equations of motion are solved alternately with Poisson's equation for the potential field until convergence is achieved. A direct (noniterative) numerical technique is used to obtain the solution to Poisson's equation. Space charge effects are included for initial current densities as large as 100 A/sq cm. Ways of dealing successfully with the difficulties associated with these high densities are discussed. A description of the mathematical model, a discussion of numerical techniques, results from two typical runs, and the FORTRAN computer program are included.
    Keywords: COMMUNICATIONS
    Type: NASA-TN-D-6959 , E-6872
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  • 86
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    Study of optimum methods of optical communication (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Optimum methods of optical communication accounting for the effects of the turbulent atmosphere and quantum mechanics, both by the semi-classical method and the full-fledged quantum theoretical model are described. A concerted effort to apply the techniques of communication theory to the novel problems of optical communication by a careful study of realistic models and their statistical descriptions, the finding of appropriate optimum structures and the calculation of their performance and, insofar as possible, comparing them to conventional and other suboptimal systems are discussed. In this unified way the bounds on performance and the structure of optimum communication systems for transmission of information, imaging, tracking, and estimation can be determined for optical channels.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-122455
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  • 87
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    Television broadcast satellite systems, volume 1 (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Empirical expressions are derived to account for various components of the television satellite broadcast system. Computer programs are developed to determine the system weight in any general design. The factors of picture quality, propagation losses, and RF power requirements are discussed and determined.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-123818
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  • 88
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    Current distribution on a cylindrical antenna with parallel orientation in a lossy magnetoplasma (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The current distribution and impedance of a thin cylindrical antenna with parallel orientation to the static magnetic field of a lossy magnetoplasma is calculated with the method of moments. The electric field produced by an infinitesimal current source is first derived. Results are presented for a wide range of plasma parameters. Reasonable answers are obtained for all cases except for the overdense hyperbolic case. A discussion of the numerical stability is included which not only applies to this problem but other applications of the method of moments.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-128114 , SR-19 , REPT-72-3 , UILU-ENG-72-2546
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  • 89
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    On backscatter from spatially varying surfaces (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The theory of radar backscatter from rough (spatially varying) surfaces is discussed. An integral equation developed to describe the radar backscatter from a perfectly conducting surface is applied to nonsmooth surfaces. The results are compared with those obtained by Beckmann as well as those obtained by Wright. Differences between the three solutions are discussed.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-66010 , X-733-72-311
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  • 90
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    Advanced communication system time domain modeling techniques ASYSTD software description. Volume 2: Program support documentation (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The theoretical basis for the ASYSTD program is discussed in detail. In addition, the extensive bibliography given in this document illustrates some of the extensive work accomplished in the area of time domain simulation. Additions have been in the areas of modeling and language program enhancements, orthogonal transform modeling, error analysis, general filter models, BER measurements, etc. Several models have been developed which utilize the COMSAT generated orthogonal transform algorithms.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-128517 , R72-001-VOL-2
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  • 91
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    Communications terminal breadboard (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A baseline design is presented of a digital communications link between an advanced manned spacecraft (AMS) and an earth terminal via an Intelsat 4 type communications satellite used as a geosynchronous orbiting relay station. The fabrication, integration, and testing of terminal elements at each end of the link are discussed. In the baseline link design, the information carrying capacity of the link was estimated for both the forward direction (earth terminal to AMS) and the return direction, based upon orbital geometry, relay satellite characteristics, terminal characteristics, and the improvement that can be achieved by the use of convolutional coding/Viterbi decoding techniques.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-128515
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  • 92
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    Advanced communication system time domain modeling techniques ASYSTD software description. Volume 1: Program users guide (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A computer program is described which is primarily designed to simulate the transient behavior of communications systems.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-128516 , R72-001-VOL-1
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  • 93
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    A numerical study of electromagnetic scattering from ocean like surfaces (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The integral equations describing electromagnetic scattering from one dimensional conducting surfaces are formulated and numerical results are presented. The results are compared with those obtained using approximate methods such as physical optics, geometrical optics, and perturbation theory. The integral equation solutions show that the surface radius of curvature must be greater than 2.5 wavelengths for either the physical optics or geometric optics to give satisfactory results. It has also been shown that perturbation theory agrees with the exact fields as long as the root mean square surface roughness is less than one-tenth of a wavelength.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-2091 , REPT-3030-1
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  • 94
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    Multi-EVA communications system analysis (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A communications concept is analyzed to establish requirements of a confident candidate system for space shuttle. Conceptual baseline configurations, EVA's-to-spacecraft via PCM/FDM and spacecraft-to-EVA via PAM/FM, and respective functional performance requirements are discussed. The baseline system is analyzed to determine link characteristics, EMI levels at various frequency bands, and determination of desirable spectrum. Selected L- and S-Band links are analyzed to ascertain signal design parameters. A trade-off is performed, which establishes L-Band frequency as the best compromise. The results of the analysis along with the reliability/safety aspects and physical characteristics of the candidate system, indicate that the initial baseline concept meets functional requirements, but is poor from standpoint of overall space shuttle program cost.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-115766
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  • 95
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    The status of parametric studies in radar agriculture (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Outlined is an information system based on the use of remote sensor data and the design, testing, and implementation of interpretation keys for agriculture. The task of crop identification from radar imagery emphasizes dichotomous keys and the effects of frequency, angular and other microwave dependencies of crops for use in discrimination. A mosaic is formulated from imagery and used to study acres in wheat for spread of circular irrigation, spread of crops, and other phenomena.
    Keywords: COMMUNICATIONS
    Type: NASA. Manned Spacecraft Center 4th Ann. Earth Resources Program Rev., Vol. 2; 17 p
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  • 96
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    Multispectral imaging radar (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A side-looking radar, installed in a C-46 aircraft, was modified to provide it with an initial multispectral imaging capability. The radar is capable of radiating at either of two wavelengths, these being approximately 3 cm and 30 cm, with either horizontal or vertical polarization on each wavelength. Both the horizontally- and vertically-polarized components of the reflected signal can be observed for each wavelength/polarization transmitter configuration. At present, two-wavelength observation of a terrain region can be accomplished within the same day, but not with truly simultaneous observation on both wavelengths. A multiplex circuit to permit this simultaneous observation has been designed. A brief description of the modified radar system and its operating parameters is presented. Emphasis is then placed on initial flight test data and preliminary interpretation. Some considerations pertinent to the calibration of such radars are presented in passing.
    Keywords: COMMUNICATIONS
    Type: NASA. Manned Spacecraft Center 4th Ann. Earth Resources Program Rev., Vol. 2; 18 p
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  • 97
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    Space configuration as an explanation for lithology-related cross-polarized radar image anomalies (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Three rock types are described that produce dark cross-polarized images on Ka-band imagery: lava flows dating from Pleistocene and Holocene, some Tertiary volcanics, and certain massive sandstones. Their planar surfaces are large with respect to the wavelength of the Ka-band system, yet are small in comparison to the resolution. It is found that only outcrops with proper faceted surface orientations produce significant radar returns showing the dominance of specular reflectors. The omnidirectional attitude of the facets and their wide distribution on the outcrops explains the independence of look-direction that the flat-lying anomalous outcrops exhibit in production of darker cross-polarized images.
    Keywords: COMMUNICATIONS
    Type: NASA. Manned Spacecraft Center 4th Ann. Earth Resources Program Rev., Vol. 2; 9 p
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  • 98
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    A study of radiometric emission from a rough sea surface (1972)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The equations which describe the emissivity of a rough ocean surface are developed. The theory includes effects of large scale and small scale wave structure and the influence of shadowing by the large ocean waves. Also included are investigations of the emission properties of foam and the influence of the thermal boundary layer on the brightness temperature characteristics of the ocean surface.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-2088 , REPT-3000R-1
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    Prototype data terminal-multiplexer/demultiplexer (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The design and operation of a quad redundant data terminal and a multiplexer/demultiplexer (MDU) is described. The most unique feature is the design of the quad redundant data terminal. This is one of the few designs where the unit is fail/op, fail/op, fail/safe. Laboratory tests confirm that the unit will operate satisfactorily with the failure of three out of four channels. Although the design utilizes state-of-the-art technology, the waveform error checks, the voting techniques, and the parity bit checks are believed to be used in unique configurations. Correct word selection routines are also novel. The MDU design, while not redundant, utilizes, the latest state-of-the-art advantages of light coupler and interested amplifiers. Much of the technology employed was an evolution of prior NASA contracts related to the Addressable Time Division Data System. A good example of the earlier technology development was the development of a low level analog multiplexer, a high level analog multiplexer, and a digital multiplexer. A list of all drawings is included for reference and all schematic, block and timing diagrams are incorporated.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-123746 , MCR-72-123
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    Small-angle stability analysis of a linear control system for a high power communication satellite (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A small angle stability analysis is presented for one particular configuration of a high power communication satellite having a linear control system. Both the central body and the solar array are treated as rigid bodies. The control system studied consists of three-axis control of the central body and one-axis control of the solar array rotation relative to the central body. The results yield preliminary indications of the relation of stability to satellite inertias and control gains.
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    Type: NASA-TM-X-2597 , E-6865
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