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  • COMMUNICATIONS  (1,377)
  • 1970 - 1974  (1,377)
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Years
Year
  • 1
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    In:  CASI
    Publication Date: 2016-03-07
    Description: A tuned noise suppressor is described consisting of annular acoustically porous elements for incorporation into the inlet and exhaust ducts of turbofan engines. The apparatus uses sound wave absorption, reflection, and incompatibility for achieving high noise reduction in the short distance. In addition, it has a duct of uniform inner diameter which does not block the duct flow.
    Keywords: COMMUNICATIONS
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  • 2
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    In:  CASI
    Publication Date: 2016-03-07
    Description: Noise suppression for a jet engine exhaust is provided by an annular divergent body attached to an exhaust nozzle. The smallest diameter of the divergent body is larger than the diameter of the exhaust nozzle exit to form an annular step which produces a shock wave in the exhaust as it passes the step. An annular shroud is disposed around the divergent body and causes outside air to pass through voids in the divergent body to mix with the jet exhaust gas. The divergent body includes a plurality of channels with separators between the channels.
    Keywords: COMMUNICATIONS
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  • 3
    Publication Date: 2012-05-22
    Description: The roll plane radiation patterns of on-aircraft antennas are analyzed using high frequency solutions. This is a basic study of aircraft-antenna pattern performance in which the aircraft is modelled in its most basic form. The fuselage is assumed to be a perfectly conducting elliptic cylinder with the antennas mounted near the top or bottom. The wings are simulated by arbitrarily many sided flat plates and the engines by circular cylinders. The patterns in each case verified by measured results taken on simple models as well as scale models of actual aircraft.
    Keywords: COMMUNICATIONS
    Type: AGARD Antennas for Avionics; 23 p
    Format: text
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  • 4
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    In:  CASI
    Publication Date: 2012-05-22
    Description: The NASA Deep Space Net (DSN) in support of the Viking Mars Project in 1976, and for science and technology demonstrations during the Mariner-Venus-Mercury mission in 1974, has developed and implemented a dual (S- and X-band) feed for large ground microwave antennas. This feed provides for a multiplicity of functions; very low listening capability at each downlink (spacecraft-to-earth) band as well as simultaneous diplexed very high cw power uplink (earth-to-spacecraft) at the S-band frequency. Total 64-m antenna system performance, is considered in terms of gain, operating noise temperature and dual beam pointing or boresight coincidence. Because of the unique ability to fold or stow the dual band feed elements for single band operations, the performance definition between single and dual band operations will be reliable and accurate.
    Keywords: COMMUNICATIONS
    Type: AGARD Antennas for Avionics; 10 p
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  • 5
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The objectives, functions, and organization, of the Deep Space Network are summarized. Deep Space stations, ground communications, and network operations control capabilities are described. The network is designed for two-way communications with unmanned spacecraft traveling approximately 1600 km from earth to the farthest planets in the solar system. It has provided tracking and data acquisition support for the following projects: Ranger, Surveyor, Mariner, Pioneer, Apollo, Helios, Viking, and the Lunar Orbiter.
    Keywords: COMMUNICATIONS
    Type: JPL-PR-42-22 , NASA-CR-139582
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  • 6
    Publication Date: 2013-08-31
    Description: The Tracking and Data Relay Satellite with a set of circularly-polarized, amplitude-sensing monopulse patterns suitable for acquiring and tracking user spacecraft at Ku-band (15.0 GHz) is discussed. The possibility of increasing the less than 0.4-degree half-power beamwidth of the data beam to almost 1.0 degree during the acquisition phase is predicated on the use of feeds situated in the first bright-ring of the Airy diffraction structure. A complex-vector simulation equivalent to the Kirchhoff-Kottler or Franz formulations is used to compute transmitted and received field information for a dual-reflector (Cassegrain) antenna configuration in a three-dimensional space.
    Keywords: COMMUNICATIONS
    Type: X-811-74-170 , NASA-TM-X-70737
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  • 7
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The fluctuations in potential of the plasma in the NASA Lewis Bumpy Torus were observed using capacitive probes over frequencies from 1 kHz to 25 MHz and a wide range of operating conditions. The spectra were found to differ greatly above and below a background gas pressure of 3.0.000034 torr deuterium. Above this pressure the spectrum was dominated by the ion spoke frequency and a spectral index was defined. Below this pressure the spectrum below 200 kHz was lower in lower in amplitude by a factor of ten and no spectral index could be defined. At these lower pressures, fluctuations that appeared to be ion spokes were observed, but had a dependence of frequency on operating conditions which was previously unreported.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-71567 , E-8003 , Intern. Conf. on Plasma Sci.; 15-17 May 1974; Knoxville, TN; United States
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  • 8
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The theory, computer program, and numerical results of an investigation of an axial slot antenna on a circular cylinder are discussed. The cylinder is partially coated with a dielectric layer and the antenna radiates through a flush mounted window. The study was conducted to determine the effects of a high temperature dielectric layer on the performance of antennas mounted on a space shuttle. Mathematical models are developed to show the relationships of the parameters. Curves are developed to compare the theoretical and actual far field radiation patterns.
    Keywords: COMMUNICATIONS
    Type: ESL-2902-17 , NASA-CR-138752
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  • 9
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The objectives, functions, and organization of the deep space network are summarized. Progress in flight project support, tracking and data acquisition research and technology, network engineering, hardware and software implementation, and operations is reported. Interface support for the Mariner Venus Mercury 1973 flight and Pioneer 10 and 11 missions is included.
    Keywords: COMMUNICATIONS
    Type: JPL-PR-42-21 , NASA-CR-138803
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  • 10
    Publication Date: 2013-08-31
    Description: Parts lists for the 2.25 GHz indoor- and antenna-unit assemblies are followed by drawings that constitute the drafting package for three converter types and the tunnel diode amplifier.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-120933
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  • 11
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The solar radio spectra were recorded in real time, both on film and magnetic tape, during the period from November 1972 to February 1974. A catalogue of the observations is given for the frequency range 565-1000 MHz and includes descriptions of the bursts, intensity scales, and pertinent remarks. Some theoretical considerations resulting from the research are given. Equipment modified for the experiment is described and the text of the final report which summarizes the research on type IV solar radio bursts is included.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138669 , S1P-198-74
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  • 12
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    In:  CASI
    Publication Date: 2013-08-31
    Description: Progress on predicting the patterns of high-frequency antennas on aircraft and shuttles is reported. Patterns are presented for an axial slot antenna on a circular cylinder partially coated with a dielectric layer. Results are shown for Omega signal disturbance by a conducting vertical pole.
    Keywords: COMMUNICATIONS
    Type: ESL-2902-16 , NASA-CR-138605
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  • 13
    Publication Date: 2013-08-31
    Description: A frequency modulated (FM) multiplexer, consisting of 21 IRIG-A constant bandwidth (CBW) voltage-controlled oscillators (VCO's) was tested to determine its suitability for use in multiplexing 21 data signals which have frequency ranges of dc to 2 kHz. Tests were preformed with the composite signal, consisting of the mixed outputs of the 21 VCO's connected directly to a set of subcarrier discriminators, with the signal recorded on magnetic tape and played back through the discriminators and with the signal transmitted by a frequency-modulated FM S-band radio frequency RF transmitter to a FM receiver and through the subcarrier discriminators. Tape speed flutter was induced to determine the reduction in flutter noise which can be obtained by the tape speed compensation equipment. The RF transmission test included transmitting the composite signal at a nominal RF received signal of -73 dbm and at RF levels of -83 and -86 dbm.
    Keywords: COMMUNICATIONS
    Type: JSC-09017 , LEC-3558 , NASA-CR-134304
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  • 14
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    In:  CASI
    Publication Date: 2013-08-31
    Description: Abstracts are reported relating to the techniques used in the research concerning optical transmission of information. Communication through the turbulent atmosphere, quantum mechanics, and quantum communication theory are discussed along with the results.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138672
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  • 15
    Publication Date: 2013-08-31
    Description: Numerical solutions for the radiation patterns of aircraft antennas are evaluated. Designing and locating antennas in order to achieve the desired performance is discussed. The high frequency solutions presented in this report are based on fuselage antennas mounted on a general-type aircraft but applied specifically to the KC-135 aircraft. The roll and elevation plane patterns are computed for a monopole, axial slot, and circumferential slot mounted both over and forward of the wings. In each case the calculated patterns compare very favorably with the measured patterns. The precision pattern measurements were taken on a 1/25 scale model of the KC-135 aircraft at NASA (Langley, Virginia) with special emphasis on reducing the mount and background effects.
    Keywords: COMMUNICATIONS
    Type: ESL-3001-9 , NASA-CR-138585
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  • 16
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    In:  CASI
    Publication Date: 2013-08-31
    Description: Digital multiplication of two waveforms using delta modulation (DM) is discussed. It is shown that while conventional multiplication of two N bit words requires N2 complexity, multiplication using DM requires complexity which increases linearly with N. Bounds on the signal-to-quantization noise ratio (SNR) resulting from this multiplication are determined and compared with the SNR obtained using standard multiplication techniques. The phase locked loop (PLL) system, consisting of a phase detector, voltage controlled oscillator, and a linear loop filter, is discussed in terms of its design and system advantages. Areas requiring further research are identified.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138606
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  • 17
    Publication Date: 2013-08-31
    Description: Development of a dual polarized L-band radar imaging system to be used in conjunction with the present dual polarized X-band radar is described. The technique used called for heterodyning the transmitted frequency from X-band to L-band and again heterodyning the received L-band signals back to X-band for amplification, detection, and recording.
    Keywords: COMMUNICATIONS
    Type: ERIM-198200-1-F , NASA-CR-134212
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  • 18
    Publication Date: 2013-08-31
    Description: Studies on the digital communication system for the direct communication links from ground to space shuttle and the links involving the Tracking and Data Relay Satellite (TDRS). Three main tasks were performed:(1) Channel encoding/decoding parameter optimization for forward and reverse TDRS links,(2)integration of command encoding/decoding and channel encoding/decoding; and (3) modulation coding interface study. The general communication environment is presented to provide the necessary background for the tasks and to provide an understanding of the implications of the results of the studies.
    Keywords: COMMUNICATIONS
    Type: R7401-2 , NASA-CR-134183
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  • 19
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    In:  CASI
    Publication Date: 2016-03-07
    Description: A choking device to cause a sonic barrier to be formed which reduces the transmission of noise in a direction opposed to the direction of air flow in a compressor that may be part of an aircraft gas turbine engine is described. The noise reduction is accomplished by proper shaping and movement of inlet guide vanes, and an actuator is connected to selected guide vanes to effect movement by programmed amounts as required to choke or partially choke within the design range of the axial-flow-air compressor.
    Keywords: COMMUNICATIONS
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  • 20
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    In:  CASI
    Publication Date: 2013-08-31
    Description: An S-band antenna system and a group of off-the-shelf aircraft antenna were exposed to temperatures simulating shuttle orbital cold soak and entry heating. Radiation pattern and impedance measurements before and after exposure to the thermal environments were used to evaluate the electrical performance. The results of the electrical and thermal testing are given. Test data showed minor changes in electrical performance and established the capability of these antenna to withstand both the low temperatures of space flight and the high temperatures of entry.
    Keywords: COMMUNICATIONS
    Type: MDC-E0896-VOL-2 , NASA-CR-140226
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  • 21
    Publication Date: 2013-08-31
    Description: Two problems related to the effects of turbulence in the atmosphere of Venus on the Pioneer entry probe radio link were studied. In the first problem, the cross correlation between the log amplitude and phase fluctuations of the Pioneer Venus communications link is examined. Data show that for fluctuation frequencies above approximately 1 Hz there is little or no correlation. For frequencies below this region the correlation is weak and the square root of the coherence has a peak value close to 0.65. The second problem consists of interferring turbulence characteristics of the Venus atmosphere from the Mariner 5 phase fluctuations. Data show that with the data processing techniques developed and currently available, the phase error due to oscillator drift, assumed trajectory delay, and spline curve fit exceed the turbulence induced fluctuations. Results show that it is not possible to interfere with the turbulence characteristics from Mariner 5 phase fluctuations.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139657 , JPL-TM-33-702
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  • 22
    Publication Date: 2013-08-31
    Description: An integral equation formulation is applied to predict pitch- and roll-plane radiation patterns of a thin VHF/UHF (very high frequency/ultra high frequency) annular slot communications antenna operating at several locations in the nose region of the space shuttle orbiter. Digital computer programs used to compute radiation patterns are given and the use of the programs is illustrated. Experimental verification of computed patterns is given from measurements made on 1/35-scale models of the orbiter.
    Keywords: COMMUNICATIONS
    Type: L-9279 , NASA-TN-D-7594
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  • 23
    Publication Date: 2013-08-31
    Description: An electronic control system for nondissipative dc power converters is presented which improves (1) the routinely attainable static output voltage accuracy to the order of + or - 1% for ambient temperatures from -55 to 100 C and (2) the dynamic stability by utilizing approximately one tenth of the feedback gain needed otherwise. Performance is due to a functional philosophy of deterministic pulse modulation based on pulse area control and to an autocompensated signal processing principle. The system can be implemented with commercially available unselected components.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134544
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  • 24
    Publication Date: 2013-08-31
    Description: Results are presented of a comprehensive study of the performance of Viterbi-decoded convolutional codes in the presence of nonideal carrier tracking and bit synchronization. A constraint length 7, rate 1/3 convolutional code and parameters suitable for the space shuttle coded communications links are used. Mathematical models are developed and theoretical and simulation results are obtained to determine the tracking and acquisition performance of the system. Pseudorandom sequence spread spectrum techniques are also considered to minimize potential degradation caused by multipath.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134310
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  • 25
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    In:  CASI
    Publication Date: 2013-08-31
    Description: A satellite-to-aircraft communication link over the ocean may include a specularly reflected signal and a diffusely scattered signal, as well as the direct path transmission. A computer program is provided for estimating two statistical properties of the diffuse signal, namely the Doppler spectrum and the delay spectrum. A convenient representation of the total signal is also provided. Examples of the Doppler and delay spectra for a number of representative link geometries are given to illustrate the features of the diffuse signal.
    Keywords: COMMUNICATIONS
    Type: ESL-3266-2 , NASA-CR-138578
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  • 26
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The instability of the ordinary electromagnetic mode propagating perpendicular to an external magnetic field is studied for a single-species plasma with ring velocity distribution. The marginal instability boundaries for both the purely growing mode and the propagating growing modes are calculated from the instability criteria. The dispersion characteristics for various sets of plasma parameters are also given. The typical growth rates are of the order of the cyclotron frequency.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138451 , U-OF-IOWA-74-19
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  • 27
    Publication Date: 2013-08-31
    Description: Large amplitude Alfvenic disturbances of arbitrary spatial shape and polarization are described by MHD equations, without resort to the usual assumption of planarity. However, because of their nonplanar nature, the direction of propagation of these disturbances cannot, in general, be determined by looking for minima in a variance matrix constructed from observed field fluctuations. When such minima exist, one is observing that subset of interplanetary Alfven waves that is essentially planar.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70640 , X-692-74-106
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  • 28
    Publication Date: 2013-08-31
    Description: A technique is described for simulating the random modulation imposed by atmospheric scintillation and transmitter pointing jitter on a direct-detection optical communication system. The system is capable of providing signal fading statistics which obey log-normal, beta, Rayleigh, Ricean, or chi-square density functions. Experimental tests of the performance of the channel simulator are presented.
    Keywords: COMMUNICATIONS
    Type: G-7439 , NASA-TN-D-7641
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  • 29
    Publication Date: 2013-08-31
    Description: The constraints that are imposed on the Outer Planet Missions (OPM) imager design are of critical importance. Imager system modeling analyses define important parameters and systematic means for trade-offs applied to specific Jupiter orbiter missions. Possible image sequence plans for Jupiter missions are discussed in detail. Considered is a series of orbits that allow repeated near encounters with three of the Jovian satellites. The data handling involved in the image processing is discussed, and it is shown that only minimal processing is required for the majority of images for a Jupiter orbiter mission.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-114745
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  • 30
    Publication Date: 2013-08-31
    Description: A digital simulation is presented for a candidate modem in a modeled atmospheric scintillation environment with Doppler, Doppler rate, and signal attenuation typical of the radio link conditions for an outer planets atmospheric entry probe. The results indicate that the signal acquisition characteristics and the channel error rate are acceptable for the system requirements of the radio link. The simulation also outputs data for calculating other error statistics and a quantized symbol stream from which error correction decoding can be analyzed.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-114739
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  • 31
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    In:  CASI
    Publication Date: 2013-08-31
    Description: A feasibility unit suitable for use as a voice recorder on the space shuttle was developed. A modification, development, and test program is described. A LM-DSEA recorder was modified to achieve the following goals: (1) redesign case to allow in-flight cartridge change; (2) time code change from LM code to IRIG-B 100 pps code; (3) delete cold plate requirements (also requires deletion of long-term thermal vacuum operation at 0.00001 MMHg); (4) implement track sequence reset during cartridge change; (5) reduce record time per cartridge because of unavailability of LM thin-base tape; and (6) add an internal Vox key circuit to turn on/off transport and electronics with voice data input signal. The recorder was tested at both the LM and shuttle vibration levels. The modified recorder achieved the same level of flutter during vibration as the DSEA recorder prior to modification. Several improvements were made over the specification requirements. The high manufacturing cost is discussed.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140305
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  • 32
    Publication Date: 2013-08-31
    Description: An analysis of the measurement accuracy requirement of a high resolution meteor radar for observing short period, atmospheric waves is presented, and a system which satisfies the requirements is described. A medium scale, real time computer is programmed to perform all echo recognition and coordinate measurement functions. The measurement algorithms are exercised on noisy data generated by a program which simulates the hardware system, in order to find the effects of noise on the measurement accuracies.
    Keywords: COMMUNICATIONS
    Type: UILU-ENG-74-2502 , AERONOMY-59 , NASA-CR-139650
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  • 33
    Publication Date: 2013-08-31
    Description: A study of the use of newly emerging communications technology for improving the understanding between members of Congress and their constituents was conducted. The study employed a number of specific methodologies such as interdisciplinary systems model building, technology analysis, a sample survey, and semi-structured interviews using sketches of the emergent channels. The following configurations were identified as representative of emergent channel characteristics: (1) the teleconference, (2) the videoconference, (3) the videophone, (4) cable television, (5) cable television polling, and (6) information retrieval. Analysis of the interview data resulted in an overview of the current congressional-constituent communication system and an assessment of the potential for emergent telecommunications, as perceived by congressmen and senior staff from 40 offices in the stratified judgement sample.
    Keywords: COMMUNICATIONS
    Type: GWPS-MON-20 , NASA-CR-139669
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  • 34
    Publication Date: 2013-08-31
    Description: An investigation to assess the modulation effects on microwave signals transmitted through rotating propeller blades. Interruption of the antenna line-of-sight signal by the rotating propeller causes a variation of path loss, which produces essentially an amplitude modulation of the received signal. This interruption or blockage effect is generally only partial because of edge diffraction around the particular interfering propeller blade. Signals reflected from the rotating propeller will also cause Doppler frequency shifts to be present in the received signals. A scanning beam microwave landing system (MLS) known as MODILS (modular instrument landing system) was used to process the received signals for display. The effects of propeller modulation were studied by varying the following parameters: (1) spacing between propeller and receiving antenna, (2) propeller dimensions, (3) propeller speed (rpm), (4) number of propeller blades, (5) system data rate, (6) receiver response time, and (7) receiver antenna aperture.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-62368
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  • 35
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The functions of the Tracking and Data Relay Satellite System (TDRSS) are discussed. The primary purpose of the system is to transmit signals to and receive signals from earth orbiting user spacecraft, and provide data from which user spacecraft ephemerides can be calculated. The system configuration is described and illustrated. The frequency plan is analyzed to show the frequency coverage and the signal handling capability of the system. The characteristics of the components of the system are tabulated.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70730 , X-805-74-230
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  • 36
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The system concept and characteristics are described along with support and orbital coverage capabilities. Information on user acquisition procedures is given. System impact on single and multiple access users is discussed.
    Keywords: COMMUNICATIONS
    Type: X-805-74-176 , NASA-TM-X-70710
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  • 37
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The investigations conducted for the Millimeter Wavelength Propagation Studies during the period December, 1966, to June 1974 are reported. These efforts included the preparation for the ATS-5 Millimeter Wavelength Propagation Experiment and the subsequent data acquisition and data analysis. The emphasis of the OSU participation in this experiment was placed on the determination of reliability improvement resulting from the use of space diversity on a millimeter wavelength earth-space communication link. Related measurements included the determination of the correlation between radiometric temperature and attenuation along the earth-space propagation path. Along with this experimental effort a theoretical model was developed for the prediction of attenuation statistics on single and spatially separated earth space propagation paths. A High Resolution Radar/Radiometer System and Low Resolution Radar System were developed and implemented for the study of intense rain cells in preparation for the ATS-6 Millimeter Wavelength Propagation Experiment.
    Keywords: COMMUNICATIONS
    Type: FR-2374-18 , ESL-2374-18 , NASA-CR-139366
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  • 38
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    In:  CASI
    Publication Date: 2013-08-31
    Description: A design study on adding a radar altimeter to the Pioneer Venus small probe is review. Block and timing diagrams are provided. The inherent and interface ambiguities, resolution, and data handling logic for radar altimeters are described.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-137549
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  • 39
    Publication Date: 2013-08-31
    Description: Special purpose satellites are very cost sensitive to the number of broadcast channels, usually will have Poisson arrivals, fairly low utilization (less than 35%), and a very high availability requirement. To solve the problem of determining the effects of limiting C the number of channels, the Poisson arrival, infinite server queueing model will be modified to describe the many server case. The model is predicated on the reproductive property of the Poisson distribution.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-71590
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  • 40
    Publication Date: 2013-08-31
    Description: The primary function of the study was to assess the impact upon the HEAO telecommunications system of the proposed relay satellite-to-ground-link configuration. The system is designed to perform the function of most of the NASA ground tracking and communications network at a net cost savings for NASA.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139393
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  • 41
    Publication Date: 2013-08-31
    Description: End-to-end system considerations involving channel coding and data compression which could drastically improve the efficiency in communicating pictorial information from future planetary spacecraft are presented.
    Keywords: COMMUNICATIONS
    Type: JPL-TM-33-695 , NASA-CR-139362
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  • 42
    Publication Date: 2013-08-31
    Description: The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.
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    Type: L-8920 , NASA-TN-D-7342
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  • 43
    Publication Date: 2013-08-31
    Description: Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138238 , UILU-ENG-74-2540 , TR-53
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  • 44
    Publication Date: 2013-08-31
    Description: The influence of polarization on millimeter wave propagation through rain is investigated. The experimental equipment consisted of a 1.43 km line-of-sight path with 4-foot diameter dual-polarized parabolic reflector antennas at each end. Linearly polarized 17.65 GHz signals were transmitted with the electric field vectors at plus 45 degrees and minus 45 degrees from the vertical. These polarizations were initially chosen to maximize the measured depolarization at any given rainfall rate. Later it was discovered that the cross polarization levels measured with plus or minus 45 degree linearly polarized signals are theoretically the least sensitive to variations in drop canting angle and this choice of polarization reduces the scatter in the data.
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    Type: IR-2 , NASA-CR-138150
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  • 45
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    In:  CASI
    Publication Date: 2013-08-31
    Description: Request procedures are described for Mariner 9 TV picture data. Image processing laboratory, user's guides, mosaics, catalogues, and microfiches are briefly discussed. Samples of the limb picture microfiche index and catalogue are presented.
    Keywords: COMMUNICATIONS
    Type: NSSDC-74-05-SUPPL-1 , NASA-TM-X-69982
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  • 46
    Publication Date: 2013-08-31
    Description: The development of a harness to hold the transmitter is discussed along with satellite systems for monitoring the flight paths of the birds, and incorporating biological information into the tracking signal.
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    Type: NASA-CR-137369
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  • 47
    Publication Date: 2013-08-31
    Description: A piecewise-sinusoidal reaction technique is developed for scattering and radiation from perfectly conducting bodies of arbitrary shape. The theory and numerical results for scattering patterns of rectangular plates and radiation patterns of corner-reflector antennas are presented. Experimental measurements are included for comparison with the calculated data.
    Keywords: COMMUNICATIONS
    Type: ESL-2902-11 , NASA-CR-137302
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  • 48
    Publication Date: 2013-08-31
    Description: The method utilizes computer programs developed for the forthcoming ATS-F/NIMBUS-F tracking and data relay experiment where the basic tracking measurements are multiple path round-trip propagation times and rates. This method of orbit computation has recently been successfully evaluated by tracking a geostationary satellite (ATS-3) using an existing VHF (150 MHz) network of automatic transponders. A master station sequentially interrogates each transponder via the ATS-3. The master site is located at Schenectady, N. Y. and four automatic transponders were located at Shannon, Reykajavik, Buenos Aires, and Seattle respectively. Data at hourly intervals were collected during a 24 hour period on April 18-19, 1973. After correcting this data for known systematic errors it was provided as input to an orbit determination program where all satellite motions during signal propagation are rigorously accounted for. The resulting estimated ATS-3 orbit yielded observational residuals on the order of 100 meters. By using more than one satellite the present scheme is further capable of accurately locating several stationary or mobile terminals as part of the overall orbital solution.
    Keywords: COMMUNICATIONS
    Type: X-591-74-2 , NASA-TM-X-70587 , American Geophysical Union Fall Annual Meeting; 10-13 Dec. 1973; San Francisco
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  • 49
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The progress is reported in the DSN for Nov. and Dec. 1973. Research is described for the following areas: functions and facilities, mission support for flight projects, tracking and ground-based navigation, spacecraft/ground communication, network control and operations technology, and deep space stations.
    Keywords: COMMUNICATIONS
    Type: JPL-TR-32-1526-VOL-19 , NASA-CR-136730
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  • 50
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The objectives, functions, and organization of the Deep Space Network are summarized. Deep space station, ground communication, and network operations control capabilities are described.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140514 , JPL-PR-42-23
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  • 51
    Publication Date: 2013-08-31
    Description: End-to-end system considerations involving channel coding and data compression are reported which could drastically improve the efficiency in communicating pictorial information from future planetary spacecraft. In addition to presenting new and potentially significant system considerations, this report attempts to fill a need for a comprehensive tutorial which makes much of this very subject accessible to readers whose disciplines lie outside of communication theory.
    Keywords: COMMUNICATIONS
    Type: JPL-TM-33-695-REV-1 , NASA-CR-140181
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  • 52
    Publication Date: 2013-08-31
    Description: The design, fabrication, and performance of elements of a low cost FM microwave satellite ground station receiver is described. It is capable of accepting 12 contiguous color television equivalent bandwidth channels in the 11.72 to 12.2 GHz band. Each channel is 40 MHz wide and incorporates a 4 MHz guard band. The modulation format is wideband FM and the channels are frequency division multiplexed. Twelve independent CATV compatible baseband outputs are provided. The overall system specifications are first discussed, then consideration is given to the receiver subsystems and the signal branching network.
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    Type: R(T)-74/2 , NASA-CR-140056
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  • 53
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The merits of nine methods for zooming microwave amplitude-sensing monopulse antenna patterns are discussed. Of these, six are directly related to the TDRSS (Tracking Data Relay Satellite System) and are compatible with a deployable-mesh pseudo-paraboloidal main reflector. The remaining three methods utilize radically different geometrical configurations that depart considerably from the TDRSS parameters existing at this time. Preservation of the monopulse postulates is considered to be of prime importance for any variable-beamwidth candidate, however, it is allowed that approximate satisfaction of the postulates should be accepted for practical reasons. All of the methods discussed admit free choice of the polarization state, and the zooming function is never predicated on polarization. Exploration of the zooming techniques was carried out almost entirely by means of the Kirchhoff-Kottler vector diffraction program. The program generates electric and magnetic field intensity, associated phase, and time-average Poynting vector power flow in the intermediate near-field and far-field zones in both receive and transmit modes of operation. A few of the concepts have been verified experimentally with excellent agreement between theory and practice.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70650 , X-811-74-62
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  • 54
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    In:  CASI
    Publication Date: 2013-08-31
    Description: A pilot study of a spaceborne sidelooking radar is summarized. The results of the system trade studies are given along with the electrical parameters for the proposed subsystems. The mechanical aspects, packaging, thermal control and dynamics of the proposed design are presented. Details of the data processor are given. A system is described that allows the data from a pass over the U. S. to be in hard copy form within two hours. Also included are the proposed schedule, work breakdown structure, and cost estimate.
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    Type: NASA-CR-139004
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  • 55
    Publication Date: 2013-08-31
    Description: A derivation is presented for the calculation of the interelement mutual coupling in a finite-size planar array of waveguide-fed apertures covered by a multilayered dielectric and/or plasma. The general mutual admittance expression is evaluated for circular apertures and the mutual coupling calculations are verified experimentally for two transverse electric circular waveguide mode excited apertures. A parametric study of higher order mode aperture fields indicates that the only significant change in the circular aperture mutual coupling is due to the transverse magnetic mode, which introduces an additional phase shift. Qualitative agreement between calculations for a 183-element array of circular apertures and an infinite array establishes the validity of the finite-array theoretical model.
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    Type: NASA-TR-R-408 , L-8919
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  • 56
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    Publication Date: 2013-08-31
    Description: Communications equipment for use with the Skylab project is examined to show compliance with contract requirements. The items of equipment considered are: (1) communications carrier assemblies, (2) filter bypass adapter assemblies, and (3) sub-assemblies, parts, and repairs. Additional information is provided concerning contract requirements, test requirements, and failure investigation actions.
    Keywords: COMMUNICATIONS
    Type: DCR-SIC-2944-00 , NASA-CR-134220
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  • 57
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    In:  CASI
    Publication Date: 2016-03-07
    Description: A noise abating improvement for jet engines including turbojets, turbofans, turboprops, ramjets, scramjets, and hybrid jets is introduced. A provision is made for an apparatus in the primary and/or secondary flow streams of the engines; the apparatus imparts to the exhaust gases a component rotation or swirl about the engine's longitudinal axis. The rotary component in the exhaust gases causes a substantial suppression of sound energy build up normally produced by an axial flow exhaust system.
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  • 58
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    In:  CASI
    Publication Date: 2016-03-07
    Description: Radially extending rotor blades are disposed on a hub to form a supersonic propulsion fan for a turbofan engine. The peripheral spacing of the blades is such as to avoid forming a channel or passageway between adjacent blades. Each has a flat trailing surface extending from the leading edge at least as far to the rear as to cause any pressure waves which might originate on the blade surface to strike the leading surface of the following blade rather than propagate upstream of the blade row. The flat trailing surface of each blade makes an angle with the axis of rotation such that the blade is parallel to a gas inflow into the blades.
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  • 59
    Publication Date: 2006-01-11
    Description: Several methods of transfer and processing of data whose practical implementation requires operational memory devices are described. Devices incorporating multistable elements are proposed and their main parameters are given. The possibility of using the proposed devices for storing information for transmission in space radio communications channels is examined.
    Keywords: COMMUNICATIONS
    Type: Space Res. in the Ukraine, No. 3 (NASA-TT-F-15537); p 155-162
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  • 60
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    In:  CASI
    Publication Date: 2006-01-11
    Description: The work consists of two parts. The first deals with the fine structure of radio pulses. Based on kinetic theory, processes occurring in the plasma shell of a pulsar when external electromagnetic radiation is present are investigated. It is shown that electromagnetic waves cause electrons to drift relative to ions, and initiate longitudinal oscillations. A dispersion equation describing the longitudinal oscillations in magnetized plasma is derived. Conditions for excitation of oscillations are found. Correlation functions of electron density are calculated, along with the coefficients of electromagnetic wave scattering. It is shown that variations in the amplitude of pulsar pulses are associated with scintillations caused by fluctuations in the plasma electron density. The second part of the study presents a mechanism for the radio emission of pulsars. The model of a rotating and a pulsating star, a neutron star with dipolar or more complex magnetic field, is examined.
    Keywords: COMMUNICATIONS
    Type: Space Res. in the Ukraine, No. 3, (NASA-TT-F-15537); p 44-53
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  • 61
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    In:  CASI
    Publication Date: 2006-01-11
    Description: Communications between civilizations within our galaxy at the present level of radio engineering is possible, although civilizations must begin to search for each other to achieve this. If an extra-terrestrial civilization possessing a technology at our level wishes to make itself known and will transmit special radio signals to do this, then it can be picked up by us at a distance of several hundreds of light years using already existing radio telescopes and specially built radio receivers. If it wishes, this civilization can also send us information without awaiting our answer.
    Keywords: COMMUNICATIONS
    Type: Inhabited Space, Pt. 2 (NASA-TT-F-820); p 79-82
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  • 62
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: The experiment described was conducted to demonstrate a procedure for tracking a near-earth satellite via a geostationary satellite without the aid of multiple ground station tracking. Another objective of the experiment was connected with the utilization of the broad tracking coverage provided by the geostationary satellite to obtain an improved geopotential solution. Questions of overall experiment implementation are discussed along with details regarding ground equipment, the ATS-F transponder, and the Nimbus-F transponder. Aspects of measurement evaluation are also examined, taking into account basic measurements, measurement interpretation, and approaches for orbit computation.
    Keywords: COMMUNICATIONS
    Type: International Convention and Exposition; March 26-29, 1974; New York, NY
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  • 63
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    Publication Date: 2011-08-16
    Description: Solar support for the ATM PIs (Apollo Telescope Mount Principle Investigators) and NASA was provided by NOAA's real-time data network through the NOAA-SOLAR facility in the ATM Science Support Room at Mission Control in Houston, Tex. Support was in the form of solar data - e.g., ground-based photographs of H-alpha (hydrogen-alpha), calcium, and magnetograms; voice/teletype reports of activity; analysis and forecasts; and assistance to the PIs and NASA as needed. This required establishing a communication system to a worldwide network of observatories, acquiring data transmission and dissemination equipment, and developing techniques to improve ATM related forecasts. This support began about one month before the first launch of the Skylab series and continued until splashdown of the last mission.
    Keywords: COMMUNICATIONS
    Type: AAS PAPER 74-170 , Annual Meeting; Aug. 20-22, 1974; Los Angeles, CA
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  • 64
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    Publication Date: 2011-08-16
    Description: Many recent American unmanned planetary probes have used biorthogonally coded spacecraft-to-earth telemetry links. An examination of the frame-synchronization (sync) techniques employed on these missions revealed that they were not specifically designed for coded data. This led to a consideration of the optimum frame-sync problem for biorthogonally coded data received over the additive white Gaussian noise (AWGN) channel and decoded prior to sync acquisition. A frame-sync algorithm for biorthogonally coded data based on a super-symbol distance rule is proposed, along with a corresponding selection criterion for the sync sequence. It is argued heuristically that this approach is optimum with regard to minimizing the probability of false synchronization.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-22; Aug. 197
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  • 65
    Publication Date: 2011-08-16
    Description: The objectives of the Apollo 17 Lunar Sounder Experiment (ALSE) were to detect subsurface geologic structures, to generate a continuous lunar profile, and to image the moon at radar wavelengths. A three-wavelength synthetic-aperture radar (SAR) operating at 60, 20, and 2 m wavelengths was designed to attain these objectives. The design choices reflected a balance of scientific requirements versus Apollo mission and hardware constraints. The radar data from the lunar mission were recorded on photographic film in a conventional SAR format, and were returned to earth for processing. A combination of optical and digital processing and exploitation techniques was applied to the scientific interpretation of the data. Some preliminary results from the lunar mission have been obtained.
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 62
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  • 66
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    Publication Date: 2011-08-16
    Description: Any electromagnetic field - e.g., a contoured antenna pattern may be expanded into a sum of spherical waves, similar to a one-dimensional Fourier expansion. This expanded wave could then be scattered from a source reflector to determine a resulting required feed field in the vicinity of the focal region. This is of questionable value, and the more significant information to produce would be the required feed pattern itself. Hence the required contour pattern is instead scattered from the back of the reflector, and the result is the required feed pattern with origin at the focus of the chosen reflector.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 74-487 , Communications Satellite Systems Conference; Apr. 22-24, 1974; Los Angeles, CA
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  • 67
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    Publication Date: 2011-08-16
    Description: Laser data relays potentially offer continuous 1 Gb/sec bandwidths, drastically increasing low-altitude satellite data collection capacity over present store-and-dump techniques. Availability of the laser link as a reliable alternative, operating within conventional low-altitude communication subsystem weight and power allocations, will create customer pressure for adoption. Major communication relay system impacts are discussed including reliability, mechanical design, attitude control, on-board data handling, contamination control, and traffic-net management. Interface parameters which drive the fundamental relay satellite design concepts are discussed, and conditions requiring early quantitative analysis are identified.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 74-484 , Communications Satellite Systems Conference; Apr. 22-24, 1974; Los Angeles, CA
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  • 68
    Publication Date: 2011-08-16
    Description: Multiple beam phased arrays are shown to enhance the performance of several anticipated geostationary communications satellite programs because of the greater efficiency and flexibility of the phased array. It is shown that the efficiency of arrays can be significantly greater than corresponding multiple feed dishes and that the problems of crossover loss and performance degradation with parts failures are thereby avoided. On an open loop basis, it is shown that a multiple beam array can provide higher EIRP over a coverage area. On a closed loop basis, it is shown that an adaptive array can provide nulling of unwanted signals while simultaneously providing gain in the direction of a desired signal.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 72-566
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  • 69
    Publication Date: 2011-08-16
    Description: The degradation of the performance of digital communication systems because of ionospheric scintillation effects can be reduced either by diversity techniques or by coding. The effectiveness of traditional space-diversity, frequency-diversity and time-diversity techniques is reviewed and design considerations isolated. Time-diversity signaling is then treated as an extremely simple form of coding. More advanced coding methods, such as diffuse threshold decoding and burst-trapping decoding, which appear attractive in combatting scintillation effects are discussed and design considerations noted. Finally, adaptive coding techniques appropriate when the general state of the channel is known are discussed.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 74-55 , Aerospace Sciences Meeting; Jan. 30-Feb. 1, 1974; Washington, DC
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  • 70
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    Publication Date: 2011-08-16
    Description: The application of frequency modulation when constructing a telemetric system in the shortwave band. The operating principles, the construction of the system and the decision making device are described and experimental data are presented. The equipment can be used on sounding balloons.
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    Type: Technol. for the Production of Space Equipment (NASA-TT-F-15766); p 59-65
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  • 71
    Publication Date: 2011-08-16
    Description: With applications to geophysical subsurface probings, electromagnetic fields due to a horizontal electric dipole laid on the surface of a two-layer medium are solved by a combination of analytic and numerical methods. Interference patterns are calculated for various layer thickness. The results are interpreted in terms of normal modes, and the accuracies of the methods are discussed.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Sept
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  • 72
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    Publication Date: 2011-08-16
    Description: A laser satellite ranging system that is mounted upon and integrated with a microwave tracking radar is reported. The 1-pulse/sec ruby laser transmitter is attached directly to the radar's elevation axis and radiates through a new opening in the radar's parabolic dish. The laser photomultiplier tube receiver utilizes the radar's existing 20-cm diam f/11 boresight telescope and observes through a similar symmetrically located opening in the dish. The laser system possesses separate ranging system electronics but shares the radar's timing, computer, and data handling/recording systems. The basic concept of the laser/radar is outlined together with a listing of the numerous advantages over present singular laser range-finding systems. The developmental laser hardware is described along with preliminary range-finding results and expectations.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; Oct. 197
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  • 73
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    Publication Date: 2011-08-16
    Description: The improved system performance resulting from the use of path diversity on earth-space satellite links operating above 10 GHz is discussed. Diversity gain is defined, and it is noted that the optimum diversity gain may be determined quite simply from the knowledge of a simple terminal fade distribution only. This approach may be extended to an arbitrary number of diversity terminals. The available diversity gain data are compared and shown to be consistent. These data, resulting from measurements in Ohio and New Jersey, indicate that diversity gain becomes relatively independent of separation distance for separations greater than approximately 8 km.
    Keywords: COMMUNICATIONS
    Type: Journal de Recherches Atmospheriques; 8; Jan
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  • 74
    Publication Date: 2011-08-16
    Description: Rytov's method is used to formulate the correlation functions for log-amplitude and phase fluctuations for both spherical and plane wave propagation in a turbulent medium whose correlation function for refractive index fluctuations is described by the product of a function of the average coordinate and a function of the difference coordinate. The results are applied to the study of radio occultation effects due to the atmosphere of Venus in the case of a flyby space probe. It is assumed that turbulence of isotropic and smoothly varying characteristics occurs in the Venusian atmosphere.
    Keywords: COMMUNICATIONS
    Type: Symposium on Electromagnetic Wave Theory; July 9-12, 1974; London
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  • 75
    Publication Date: 2011-08-16
    Description: Range measurements to the Pioneer 10 and Mariner 10 spacecraft were made, without the use of a ranging system per se, by using the Jet Propulsion Laboratory Deep Space Network's new digitally controlled oscillator (DCO) device. These measurements were accomplished by controlling the linear ramps of the transmitted carrier frequency with a recently installed DCO instrument at the Goldstone facility and analyzing the received linearly ramped Doppler data with a computer program. The accuracy of these range measurements is on the order of 1.5 km.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 74-830 , Mechanics and Control of Flight Conference; Aug. 5-9, 1974; Anaheim, CA
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  • 76
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    Publication Date: 2011-08-16
    Description: Equations are presented for the calculation of the interelement mutual coupling in a finite size planar array of wave-guide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures and the mutual coupling calculations are verified experimentally for two TE11 mode excited apertures. Qualitative agreement between calculations for a 183 element array and an infinite array establishes the validity of the finite array theoretical model.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 77
    Publication Date: 2011-08-16
    Description: Recent development in the optical scintillation theory has been adapted to the ionospheric geometry in order to study the ionospheric scintillation phenomenon in the presence of multiple scattering. Under approximations well satisfied in typical ionospheres for a frequency above about 20 MHz, the first through fourth moment equations have been derived and some analytic solutions given. The fourth moment equation has also been solved numerically. The numerical results show clearly the occurrence of focusing and saturation phenomena. The new multiple-scatter effects are emphasized.
    Keywords: COMMUNICATIONS
    Type: Radio Science; 9; June 197
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  • 78
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    Publication Date: 2011-08-16
    Description: As Pioneer 10 approaches the planet Jupiter, its trajectory will carry it behind the planet, as seen from the earth. The microwave telemetry signal from the spacecraft will then pass through the Jovian atmosphere on its way to the earth, and analysis of the effects of the atmosphere on the signal should yield information on the atmospheric structure. To help define the capabilities of this experiment and to aid the analysis of the real data, we have simulated the occultation experiment on a computer by using model Jovian atmospheres and a predicted trajectory. The results indicate that the useful depth of penetration of the microwave signal will be governed by ammonia absorption rather than superrefractivity. The experiment is apparently far more sensitive to variations in cloud-top temperature than to variations in the hydrogen-helium ratio. Characteristic 'flashes' in the attenuation record of the signal may yield information on the location of the top of the Jovian convective zone.
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    Type: Journal of Geophysical Research; 79; May 1
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  • 79
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    Publication Date: 2011-08-16
    Description: Absolute spectral energy distributions for the large-redshift quasars OQ 172 and OH 471 are discussed along with similar data for two other quasars: 4C 05.34 and PHL 957. If the redshift are assumed to be cosmological, OQ 172 and OH 471 are not as luminous as PHL 957. If these quasars are basically similar and if radiative processes dominate, the strength of alpha and the behavior of the continuum at the Lyman limit strongly suggest that these objects consist of a central ionizing source surrounded by discrete clouds, filaments, or a gaseous structure such as a disk. This gaseous matter does not cover the whole solid angle surrounding the source.
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    Type: Astrophysical Journal; 189; Apr. 15
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  • 80
    Publication Date: 2011-08-16
    Description: Corrugated horns involve a junction between the corrugated surface and a conducting ground plane. Proper horn design requires an understanding of the electromagnetic properties of the corrugated surface and this junction. An integral equation solution has been used to study the influence of corrugation density and tooth thickness on the power loss, surface current, and the scattering from a ground plane/corrugated surface junction.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 81
    Publication Date: 2011-08-16
    Description: The reception theory for quasi-monochromatic partially polarized emissions is employed to describe the antenna temperature when observing a flat scene from within or above an absorbing/emitting atmosphere. When the polarization aspects of the antenna and scene are carefully observed, the resulting integral expression for the antenna temperature differs significantly from that reported for polarization invariant temperature distributions. It is observed that the antenna couples to both emitted surface polarizations, and the phase character of the antenna introduces a term involving the product of the polarized and cross-polarized antenna patterns. A matrix approximation of the integral expression is suggested and developed as a means for inverting polarized antenna temperature observations for the underlying partially polarized apparent temperature distributions.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; May 1974
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  • 82
    Publication Date: 2011-08-16
    Description: Expressions which represent the elevation-plane patterns of a large TEM mode coax aperture and a TM-01 mode circular aperture on finite circular and square ground planes have been derived using geometrical theory of diffraction; design curves for the coax case are presented. The expressions for the field pattern were obtained by superposing the infinite ground plane solutions, the first-order diffracted field solutions, and the axial caustic solutions in their respective regions of validity. The pattern analyses for the coax and circular apertures are verified experimentally.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; May 1974
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  • 83
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: A technique is reported for simulating the signal fading that will be experienced by typical optical communication systems. The desired irradiance or amplitude fading statistics can be simulated by incorporating a linearized optical modulator subsystem between the transmitter and receiver. This technique has been implemented in the design and construction of a laboratory channel simulator. The design of the processing electronics is discussed along with the results of tests performed for each mode of operation.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; June 197
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  • 84
    Publication Date: 2011-08-16
    Description: With wideband pseudo-noise (PN) communications systems, it is sometimes desirable to supplement the inherent interference rejection capabilities by adding notch filters to attenuate relatively narrowband interference. This correspondence presents an investigation of the effects of notch filters on the performance of PN correlation receivers. A theoretical analysis of the correlation drop due to filter distortion has been conducted and confirmed by experimentation. Additional measurements and analysis have established the trade-off between correlation drop and interference suppression as a function of interference bandwidth. A typical result is that by incurring a penalty of a 1-dB drop in correlation peak, interfering signals having bandwidths of 2 to 3% of the PN chip rate can be attenuated by 25 dB.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-10; May 1974
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  • 85
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: Analyses of AGC analog data from the Small Astronomy Satellite (SAS) at VHF (136 MHz) have shown amplitude fluctuations in the signals received at several equatorial tracking sites operated by NASA. Coincident digital telemetry data, transmitted from SAS at 1 kbps, has also been analyzed. Errors in data are shown to increase markedly for nighttime satellite passes around the periods of the two equinoxes as compared to the errors observed during other periods. This paper establishes the qualitative and quantitative correlations between the ionospheric scintillation phenomenon and the occurrence of errors. Strong time and geographic cause and effect relationships are established by determining the statistical correlation between scintillation indices and bit error rates.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 74-51 , Aerospace Sciences Meeting; Jan. 30-Feb. 1, 1974; Washington, DC
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  • 86
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: Diffused optical waveguides are studied using the modal and the ray tracing approach, with an emphasis on the case of a hollow waveguide with diffuse cladding. The properties of the guided modes are investigated in detail. The applications of these structures to optical circuits, integrated optics lasers and capillary gas lasers are discussed.
    Keywords: COMMUNICATIONS
    Type: vol. 43; July 197
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  • 87