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  • COMMUNICATIONS AND RADAR
  • 2000-2004
  • 1995-1999
  • 1980-1984  (208)
  • 1975-1979  (166)
  • 1970-1974
  • 1982  (208)
  • 1976  (166)
Collection
Keywords
Years
  • 2000-2004
  • 1995-1999
  • 1980-1984  (208)
  • 1975-1979  (166)
  • 1970-1974
Year
  • 1
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    A new SPS antenna design to reduce grating lobes (1982)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: In the Solar Power Satellite system, the antenna's misalignment will produce well defined grating lobes. These gratings lobe peaks occur every 440 km and are potentially hazardous to the environment. One way to suppress these peaks is to phase control every power module. The cost due to the increase in receiving electronics and processors, however, could prove to be prohibitive. A new design of the antenna involving the addition of two broad gaps, one along the x axis and another along the y axis is proposed. The gap distance is exactly one half of the distance between the center of two neighboring subarrays. Calculation of far field radiation patterns shows that the design reduces grating lobe peaks without sacrificing power in the main lobe.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The 1981 NASA(ASEE Summer Fac. Fellowship Program; 14 p
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  • 2
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    Miniature voice output communication aid (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA Technol. Appl. Team; p 20
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  • 3
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    Low gain and steerable vehicle antennas for communications with land mobile satellite (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Current development activities at JPL for ground mobile vehicle antennas to be used with the Land Mobile Satellite Service (LMSS) system are described. Both low gain and electronically steerable high gain type antennas are discussed in terms of their design concept and RF performance. For the low gain type, three classes of antennas are under various stages of development. These are the crossed-drooping dipole, quadrifilar helix, and microstrip patch designs. The antennas are intended to provide circularly-polarized radiation with a minimum of 3-dB gain in the angular region from 19 degrees to 60 deg from the horizon in elevation plane and with an omnidirectional pattern in azimuthal plane. For the electronically steerable high gain type, circularly-polarized microstrip patch phased arrays formed on a planar surface and on the surface of a truncated cone are under study. The arrays are intended to provide a minimum of 12 dB gain in the same angular region in elevation plane at all azimuthal angles. This coverage is accomplished by scanning the high gain pencil beam in both elevation and azimuthal directions. Both types of antennas are to transmit at 821-831 MHz band and to receive at 866-876 MHz band. They must be of low cost design and reasonably conformal to the vehicle.
    Keywords: COMMUNICATIONS AND RADAR
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  • 4
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    Concept for advanced satellite communications and required technologies (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The advanced communications technology satellite (ACTS) program of NASA is aimed at the development of high risk technologies that will enable exploiting higher frequency bands and techniques for improving frequency reuse. The technologies under development include multiple beam spacecraft antennas, on-board switching and processing, RF devices and components and advanced earth stations. The program focus is on the Ka-band (30/20 GHz) as the implementing frequency since it has five times the bandwidth of either the C- or Ku-bands. However, the technology being developed is applicable to other frequency bands as well and will support a wide range of future communications systems required by NASA, other Government agencies and the commercial sector. An overview is presented of an operational 30/20 GHz satellite system that may evolve. How the system addresses service requirements is discussed, and the technology required and being developed is considered. Previously announced in STAR as N83-11210
    Keywords: COMMUNICATIONS AND RADAR
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  • 5
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    An advanced generation land mobile satellite system and its critical technologies (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A conceptual design for a Land Mobile Satellite System (LMSS) for the 1990s is presented. LMSS involves small tranceivers accessing satellites directly, with ground reception through small car-top antennas. The satellite would have a large antenna and blanket coverage areas in the UHF. The call may originate from a home, be carried by wire to a gateway, transmitted to satellite on the S-band, converted to UHF on the satellite, and transmitted to the vehicle. The system design is constrained by the number of users in an area during the busiest hours, Shuttle storage, controllability factors, and the total area served. A 55-m antenna has been selected, with 87 spot beams and two 10 MHz UHF bands in the 806-890 MHz band. A 17 dB interbeam isolation level is required, implying that sufficient sub-bands can be generated to assure 8265 total channels. The mobile satellite (MSAT) would have an 83 m mast lower segment, a 34 m upper segment, and a second, 10 m antenna made of a deployable mesh. Various antenna function modes are considered.
    Keywords: COMMUNICATIONS AND RADAR
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  • 6
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    TDM/FM/FDMA - A modulation technique for multiple-beam satellites which precludes cochannel interference and allows non-uniform geographic distribution of user channels (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The technique outlined in this paper is intended to eliminate the problems of cochannel interference and uniform geographic distribution of user channels which arise in conventional designs for a multiple spot beam communication satellite to serve mobile telephony users across the CONUS. By time multiplexing FM/FDMA signal ensembles so that only those beams operating on distinct frequency subbands are allowed to transmit concurrently, cochannel interference arising from simultaneous frequency subband reuse is precluded. Thus, time disjoint frequency reuse is accomplished over a repetitive sequence of fixed time slots. By assigning different size subbands to each time slot, a market of nonuniform users can be accommodated. The technique results in a greatly simplified antenna feed system design for the satellite, at a cost of imposing the need for time slot synchronization on the mobile FM receivers whose ability for rejecting adjacent channel interference is somewhat diminished.
    Keywords: COMMUNICATIONS AND RADAR
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  • 7
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    Space Shuttle and TDRSS telecommunications system interfaces (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The telecommunications system interfaces between the spacecraft and the space shuttle, and between the spacecraft and the Tracking and Data Relay Satellite System (TDRSS) are discussed. The payload/shuttle/ground communications network, principle end-to-end link configurations, and requirements for attached and detached payloads are addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 557-596
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  • 8
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    Telecommunications performance analysis and monitoring software (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The computer software used for telecommunications performance analysis and monitoring is discussed. The utilization of the TPAP analysis program for the Viking 1975 project and the Voyager 1977 project is described. The functional and design requirements for the successor system, TPAS, are also given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 491-516
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  • 9
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    Radio frequency selection and interference prevention (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The bands available for deep-space communications, and the choice of particular mission frequencies are discussed. The more general susceptibility of deep-space Earth stations to various kinds of interference is then presented. An associated topic is the development of protection criteria that specify maximum allowable levels of interference. Next, the prediction of interference from near-Earth satellites is described, with particular emphasis on the problems and uncertainties of such predictions. Finally, a brief description of other activities aimed at the prevention or avoidance of interference to deep-space radio communications is given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 517-555
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  • 10
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    Spacecraft antennas (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A tutorial description is given for spacecraft antennas used for deep-space-to-Earth communication. Radiation pattern parameters, pointing errors, pointing and polarization loss, and noise characteristics are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 413-460
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  • 11
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    Spacecraft radio frequency subsystem (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The historical background for the development of the planetary (RFS) is reviewed, and the performance capabilities of the various functional subassemblies are described. The flight radio frequency subsystem is a valid component for the three spacecraft telecommunications functions of tracking, command, and telemetry. It is the radio and the signal processing equipment residing in the spacecraft that interfaces with the control & data subsystem and performs two-way communications with the Earth-based Deep Space Network. The RFS consists of all the elements for RF reception, demodulation, modulation, and transmission, including those for command detection and telemetry modulation.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 383-412
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  • 12
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    Command system (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Multimission Command (MMC) System is described. The major components within the MMC System are discussed, with the emphasis on the telecommunication-related implementations. Two versions of the spacecraft command detection system (the Viking heritage command detector and the NASA standard command detector) are discussed in detail. The former prevails in the existing flight projects and the latter will likely be adopted by the missions of the near future. The preparation of design control tables for the control of command link performance between deep space stations and the spacecraft is also discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 343-381
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  • 13
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    Receiver design and performance characteristics (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The basic design, principles of operation, and characteristics of deep space communications receivers are examined. In particular, the basic fundamentals of phase-locked loop and Costas loop receivers used for synchronization, tracking, and demodulation of phase-coherent signals in residual carrier and suppressed carrier systems are addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telcommun. Systems Eng.; p 49-121
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  • 14
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    Special characteristics of digital modulations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The importance of the bandwidth required for transmitting the chosen signaling or modulation technique in evaluating efficiency of a communication system is noted. The direct relation between bandwidth and the power spectral density (PSD) of the signaling scheme makes efficient analytical methods for calculating the PSD essential to specifying the spectral occupancy of the transmission channel. Several techniques for calculating the PSD of synchronous data pulse streams are reviewed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 23-47
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  • 15
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    Telecommunications systems design (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The general configuration of deep space telecommunication systems is reviewed with regard to the design criteria necessary to insure the integrity of the system's telemetry, command, and tracking functions. The signal to noise spectral density ratios that characterize telecommunications performance are defined in terms of the link parameters. For design control, a statistical approach to predict link performance and to assess its uncertainty is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Deep Space Telecommun. Systems Eng.; p 1-22
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  • 16
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    Adaptive arrays - A new approach to the steady-state analysis (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A closed-form expression for the steady-state output signal-to-noise ratio (SNR) of an n-element adaptive array excited by one desired narrow-band signal and K - 1 narrow-band jammers is obtained. This is facilitated by representing each excitation by a complex n-dimensional vector - the excitation vector. It is shown that the important system parameters are functions of scalar products of pairs of these excitation vectors. In particular, the normalized output SNR of the array is shown to be the ratio of determinants whose elements involve these scaler products. Such determinants are also shown to be involved in the expressions for the optimal array weights.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; Jan. 198
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  • 17
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    New CCIR papers on telecommunications for deep space research (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The selection of preferred frequency bands for deep space telecommunications in the 20 to 120 GHz range is discussed. The performance of links between Earth stations and stations in deep space is affected by the atmosphere of the Earth. Attenuation and emission by the atmosphere generally limits deep space telecommunications to frequencies below 20 GHz. There are, however, certain frequency bands in the 20 to 120 GHz range where atmospheric attenuation is low enough to permit links between Earth stations and deep space stations. Additionally there are certain other bands in the 20 to 120 GHz range that would be particularly suitable for links between an Earth orbiting relay station and deep space stations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 86-102
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  • 18
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    An experimental investigation of the changes of VLBI time delays due to antenna structural deformations (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Structural deformations primarily occur as functions of antenna elevation angle due to gravity loading. For a Cassegrain antenna, one of the major effects of structural deformation on measured VLBI time delays are those delay changes associated with axial subreflector displacement from its nominal position. Two types of time delay changes that occur when the subreflector is axially defocused are: a change which is a linear function of subreflector defocus position; and a cyclical change caused by multipath. Test results show that for the 64-m DSN antenna, the linear change is 1.8 times the subreflector defocus position, while the peak-to-peak change in cyclical variation is about + or - 3 cm when a spanned bandwidth of 38 MHz at 2290 MHz is used.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 8-16
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  • 19
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    Sideband-aided receiver arraying (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Efforts to increase the amount of data that can be received from outer planet missions by coherently combining signals from ground antennas in such a way as to increase the total effective aperture of the receiving system are discussed. As these signals become weaker, the baseband arraying technique in current use degrades somewhat due to carrier jitter. One solution to this problem is Sideband-Aided Receiver Arraying (SARA). In SARA, sidebands demodulated to baseband in a master receiver at the largest antenna are used to allow slave receivers in the other antennas to track the sideband power in the signal rather than the carrier power. The already existing receivers can be used in the slaves to track and demodulate the signals in either a residual carrier or a suppressed carrier environment. The resultant baseband signals from all the antennas can then be combined using existing baseband combining equiment. Computer simulations of SARA show increases in throughput (measured in data bits per second) over baseband-only combining 17 percent at Voyager 2 Uranum encounter and 31 percent at Neptune for a four-element antenna array and (7, 1/2) convolutional coding.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 39-54
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  • 20
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    The DSN radio science system Mark 3, 1980 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The DSN Radio Science System supported the Voyager 2 Saturn encounter radio science experiments in August 1981. Support for these experiments was provided by all the Deep Space Stations of the DSN. However, the critical support for the Saturn occultation and ring scattering experiment was provided at DSS 43 by the medium-band open-loop recording system. The DSN Radio Science System is descried and the recent implementation at DSS 43 is emphasized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 6-11
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  • 21
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    Selection of frequencies for deep-space telecommunications (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The procedures used by the Jet Propulsion Laboratory to select and recommend frequencies to be used for deep space telecommunications are explained. The frequency selection process described deals only with the potential for radio frequency interference between deep space telecommunication links. Channel plans based on bandwidth, hardware implementation, and frequency ratio considered are used. The channel selection process is based on calculations and analysis of interference-to-signal power ratios as a function of time for each possible pair of missions. The modes of interference and the interference protection ratio are explained, and the interference analysis procedure described. Equations used in calculating the downlink and uplink interference analyses are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 49-61
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  • 22
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    The Communications Technology Satellite /CTS/ Program (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The purposes of the joint Canadian-U.S. Communications Technology Satellite (CTS) Program are (1) to conduct satellite communication systems experiments using the 12- and 14-GHz bands and low-cost transportable ground terminals, (2) to develop and flight test a power amplifier tube having a greater than 50% efficiency with a saturated power output of 200 W at 12 GHz, (3) to develop and flight test a lightweight extendible solar array with an initial power output greater than 1 kW, and (4) to develop and flight test a 3-axis stabilization system to maintain accurate antenna boresight positioning on a spacecraft with flexible appendages. Brief descriptions of these experiments and of the ground facilities are provided.
    Keywords: COMMUNICATIONS AND RADAR
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  • 23
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    Television applications of interline-transfer CCD arrays (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The design features and characteristics of interline transfer (ILT) CCD arrays with 190 x 244 and 380 x 488 image elements are reviewed, with emphasis on optional operating modes and system application considerations. It was shown that the observed horizontal resolution for a TV system using an ILT image sensor can approach the aperture response limit determined by photosensor site width, resulting in enhanced resolution for moving images. Preferred camera configurations and read out clocking modes for maximum resolution and low light sensitivity are discussed, including a very low light level intensifier CCD concept. Several camera designs utilizing ILT-CCD arrays are described. These cameras demonstrate feasibility in applications where small size, low-power/low-voltage operation, high sensitivity and extreme ruggedness are either desired or mandatory system requirements.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 152-156
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  • 24
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    Television cameras employing solid-state imaging sensors for manned spacecraft applications (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Space Shuttle television system incorporates a versatile complement of TV equipment which allows the positioning, quantity, and performance capabilities of the multiple TV cameras to vary as dictated by the particular mission. However, current TV camera technology employing glass enclosed, vacuum processed image sensors results in a bulky device that restricts its location and versatility. Problems and potential solutions that can be achieved through the employment of solid-state image sensors for both monochrome and color applications are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; p 126-128
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  • 25
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    Command detector SNR estimator and lock status monitor circuitry (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A breadboard of the command detector signal-to-noise-ratio estimator and lock status monitor was built on a wire-wrap card. The breadboard was integrated with the standard command detector, and its performance was measured. The design, design constraints, and construction of the breadboard are described. The performance is shown to agree with the theoretical model.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 42-51
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  • 26
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    The scattering of obliquely incident plane waves from a corrugated conducting surface (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface. This solution is used to compute the radar cross section of the surface in the case of backscatter from irregular (i.e., stochastic) corrugations. An interesting feature of the solution is the occurrence of singularities in the scattered fields. These singularities appear to be a manifestation of focusing by the surface at its 'stationary' points. Whether or not the singularities occur in the solution depends on the manner in which one restricts the analysis to the far-field.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Nov. 197
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  • 27
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    Radio frequency boresight analysis of the low cost 64-meter antenna (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Configurations (two) of the reflector-only assemblies, using different width backup cones, are analyzed for RF boresight direction changes and wind distortions. The wider backup cone is best for minimum weight; however, there is an optimum weight which minimizes the RF boresight errors for a wind load that produces the maximum pitching moment of both configurations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 128-135
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  • 28
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    Magnitude of 64-m elevation axis movements due to alidade temperature changes (1976)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In projected very-long baseline interferometry (VLBI) work a reference point for 64-m antennas is the intersection of the elevation and azimuth axes. A minimum-level effort at DSS 14 to determine the magnitude of the effect of diurnal changes in the temperature of the alidade legs on the height of the elevation axis is described. The thermal expansion between the lowest recorded temperature -3 C (27 F) and the highest, 36 C (97 F), over the period covered was 8.9 mm (0.35 in.).
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Deep Space Network; p 41-44
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  • 29
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    Remote intensity fluctuation measurements with a laser Doppler radar (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A coaxial focused CW scanning laser Doppler velocimeter (SLDV) radar equipment applying heterodyne detection at 10.6 microns can measure intensity fluctuations under field conditions. The set includes a 20 W CO2 laser, a coaxial Cassegrainian telescope, standard heterodyne equipment, and a SAW spectrum analyzer with 100 kHz signal resolution. Operation of the equipment and techniques for taking remote measurements are described briefly. Applications to remote measurements of transverse component of wind speed, as a complement to the traditional Doppler method of determining axial velocity, are under study. SLDV equipment has been used in detection, tracking, and measurements of atmospheric turbulence associated with aircraft wing-tip vortices or with dust devils, and in measurement of general atmospheric wind profiles.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Applied Optics; 15; Sept
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  • 30
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    New sidelobe envelopes for small aperture earth stations (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The advent of domestic satellite systems and technological improvements in both space and ground equipment makes the use of small aperture earth stations economically feasible and attractive for broadcast satellite applications. With increasing use of the orbit spectrum, there is some concern that broadcast satellite systems may not be able to obtain satisfactory allocations of this orbit-spectrum resource because of interference considerations. Specifically, interference calculations based on the present envelope result in comparatively large orbit spacings for broadcast satellites. Theoretical and experimental investigations of simple sidelobe suppression techniques, plus an analysis of experimental data on small aperture antennas, indicate that much better sidelobe performance can be obtained with a very small cost or performance penalty.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Broadcasting; BC-22; June 197
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  • 31
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    The input admittance of the rectangular cavity-backed slot antenna (1976)
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    Publication Date: 2011-08-16
    Description: The input admittance of the rectangular cavity-backed slot antenna is investigated. The slot is assumed narrow so that the voltage distribution in its aperture is sinusoidal. Equations which represent the input admittance of this slot, backed by a rectangular cavity in which a single propagating wave is assumed to exist, are given. Calculations based on these representations are compared to available measured data. As the depth of the cavity increased the resonant frequency decreased and the bandwidth became narrower. Input admittance curves as a function of electrical slot length are also presented for several size cavities.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; May 1976
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  • 32
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    Power conservation for reflector antennas with truncated feed patterns (1976)
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    Publication Date: 2011-08-16
    Description: Reflector-antenna calculations using idealised truncated feed patterns can lead to incorrect values of total secondary radiated power. It is demonstrated that this discrepancy is due to the presence of higher-order spherical modes incident on the reflector. When a proper spherical-wave expansion of the incident field is used, in conjunction with the physical-optics technique, to determine the scattered field, the total power of the scattered field will equal the power radiated by the feed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Electronics Letters; 12; Mar. 18
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    Satellite communications at the Goddard Space Flight Center (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Starting with the 1960 Delta launch of the first Echo satellite, NASA's Goddard Space Flight Center (GSFC) became one of the pioneers in satellite communications. Attention is given to the project Syncom, the Applications Technology Satellite (ATS) program, the ATS-6 project, and current GSFC efforts. After the decision announced in January of 1973 that NASA would phase out of communications satellite programs, the communications effort at GSFC concentrates on the operation of ATS spacecraft in orbit, experiments in the 12- to 14 GHz frequency band, and advanced communications research.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Signal; 30; Mar. 197
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  • 34
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    Real-time video compression algorithm for Hadamard transform processing (1976)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A real-time digital video processor using Hadamard transform techniques to reduce video bandwidth is described. The processor can be programmed with different parameters to investigate various algorithms for bandwidth compression. The processor is also adaptive in that it can select different parameter sets to tradeoff spatial resolution for temporal resolution in the regions of the picture that are moving. Algorithms used in programming the system are described along with results achieved at various levels of compression. The algorithms relate to spatial compression, temporal compression, and the adaptive selection of parameter sets.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Electromagnetic Compatibility; EMC-18; Feb. 197
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  • 35
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    Signalling characteristics in satellite-aided land mobile communications (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The feasibility of land mobile radio communications has been demonstrated by a large number of experiments with NASA's ATS satellites. Significant differences in the propagation characteristics of satellite and terrestrial mobile signal paths were observed in the experiments. Terrestrial paths are best in cities where they can provide frequency reuse and assure communication by bouncing signals around obstructions. Satellites may be best in thinly populated areas because they eliminate the need for many tower mounted relays. The satellite paths do not have the severe Rayleigh fading that limits the range and signal quality of terrestrial paths if the satellite is above approximately ten degrees elevation, a value easily achieved for the United States. The experiments verified that high quality voice communications and other functions, such as data transmission and vehicle position surveillance, are easily accomplished through geostationary satellites with vehicle transmitter power and antenna gain no different than those of terrestrial mobile communications.
    Keywords: COMMUNICATIONS AND RADAR
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  • 36
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    Observations of tropospheric phase scintillations at 5 GHz on vertical paths (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The article presents observations of turbulence-induced tropospheric phase fluctuations measured at 5 GHz on the near-vertical paths relevant to many astronomical and geophysical measurements. The data are summarized as phase power spectra, structure functions, and Allan variances. Comparisons to other microwave observations indicate relatively good agreement in both the level and shape of the power spectrum of these tropospheric phase fluctuations. Implications for precision Doppler tracking of spacecraft and geodesy/radio interferometry are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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  • 37
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    An explanation for the systematic flow of plasma in the solar transition region (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Using numerical simulations, it is shown that the systematic flow of plasma along a coronal magnetic flux tube is easily produced by a change in the spatial dependence of the heating rate from a symmetric deposition which supports a stationary equilibrium to a time-independent asymmetric deposition. The velocity of the flow is roughly proportional to the heating symmetry and is directed to the side of the loop away from the bulk of the energy deposition.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Astrophysical Journal; vol. 258
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  • 38
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    Environmentally induced discharges on satellites (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A discharge process whose trigger conditions are a negative exposed metallic surface surrounded by a less negative dielectric, and a large voltage gradient at a dielectric/metal interface is proposed. Analysis of SCATHA data for a discharge substantiates the postulation. Surface discharges cause a small transient charge transfer to space which results in voltage transients. A method of computing these transients, based on the charge lost through the capacitance to space and a fraction of charge stored in the dielectric at the discharge source was developed. It gives an estimate of the discharge transients at the discharge site, which is used as input for coupling code analysis of structure/system response. The transient computations were applied to a three-axis stabilized, geosynchronous satellite for both sunlight and eclipse charging. The energy of the transient pulses are about 1 mJ for sunlight discharge and 8 mJ for eclipse. Changing of selected coatings on the satellite would relieve the stress.
    Keywords: COMMUNICATIONS AND RADAR
    Type: ESA 2nd ESTEC Spacecraft Electromag. Compatibility Seminar; p 161-172
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  • 39
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    Input impedance of microstrip antennas (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Using Richmond's reaction integral equation, an expression is derived for the input impedance of microstrip patch antennas excited by either a microstrip line or a coaxial probe. The effects of the finite substrate thickness, a dielectric protective cover, and associated surface waves are properly included by the use of the exact dyadic Green's function. Using the present formulation the input impedance of a rectangular microstrip antenna is determined and compared with experimental and earlier calculated results.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; July 198
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  • 40
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    Far-field radiation patterns of Y and T shaped arrays with Chebyshev loading (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The far-field radiation patterns for Chebyshev loaded Y- and T-shaped array antennas are given for a number of cases. Included are full- and half-length loaded array arms. The goal of the investigation is to determine the effect of different Chebyshev loading arrangements on this type of array. It is found that in both the Y- and T-shaped arrays, the main lobes are defined by the shape of the array and that the level of the side-lobes is mainly dependent on the Chebyshev loading (that is, complete or partial).
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; July 198
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  • 41
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    Scattering by Pruppacher-Pitter raindrops at 30 GHz (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N81-30327)
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; July-Aug
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  • 42
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    Microwave noise temperature and attenuation of clouds - Statistics of these effects at various sites in the United States, Alaska, and Hawaii (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The microwave attenuation and noise temperature effects of clouds can result in serious degradation of telecommunications link performance, especially for low-noise systems presently used in deep-space communications. Although cloud effects are generally less than rain effects, the frequent presence of clouds will cause some amount of link degradation a large portion of the time. This paper presents a general review of cloud types and their water particle densities, attenuation and noise temperature calculations, and basic link signal-to-noise ratio calculations. Tabular results of calculations for 12 different cloud models are presented for frequencies in the range 10-50 GHz. Curves of average-year attenuation and noise temperature statistics at frequencies ranging from 10 to 90 GHz, calculated from actual surface and radiosonde observations, are given for 15 climatologically distinct regions in the contiguous United States, Alaska, and Hawaii. Nonuniform sky cover is considered in these calculations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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  • 43
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    Frequencies above 10 GHz (1976)
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    Publication Date: 2011-08-17
    Description: The paper discusses some of the problems associated with extending the frequencies used by satellite communication services above 10 GHz. The principal propagation limitation above 10 GHz occurs when precipitation intercepts the earth-space propagation path and causes attenuation and depolarization of the transmitted signal. World attenuation statistics at 12 GHz for earth-space paths are discussed, revealing the effect of climate on attenuation properties. Space diversity is discussed as an effective means of overcoming precipitation-caused attenuation problems.
    Keywords: COMMUNICATIONS AND RADAR
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  • 44
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    Analysis of the radiation patterns of reflector antennas (1976)
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    Publication Date: 2011-08-16
    Description: The development and application of a numerical technique for rapid calculation of the far-field radiation patterns of a reflector antenna from either a measured or computed feed pattern are reported. The reflector is defined by the intersection of a cone with any surface of revolution or an offset sector of any surface of revolution. The feed is assumed to be linearly polarized and can have an arbitrary location. Both the copolarized and the cross-polarized reflector radiation patterns are computed. Calculations using the technique compare closely with measured radiation patterns of a waveguide-fed offset parabolic reflector. Unique features of this technique are freedom from restrictive feed assumptions and the numerical methods used in preparing the aperture-plane electric-field data for integration.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-24; Jan. 197
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  • 45
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    Special activity utilization of GDSCC antennas during 1981 (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The activities are categorized as advanced systems program, radio astronomy program, crustal dynamics program, and operations and support activities. The goals of each of the activities that received tracking support at Goldstone during 1981 are discussed. All Goldstone stations (DSSs 11, 12, 13 and 14) provided a total of 2353.55 hours of support to special activities during the period.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 121-126
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  • 46
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    Noise temperature and noise figure concepts: DC to light (1982)
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    Publication Date: 2011-08-18
    Description: The Deep Space Network is investigating the use of higher operational frequencies for improved performance. Noise temperature and noise figure concepts are used to describe the noise performance of these receiving systems. It is proposed to modify present noise temperature definitions for linear amplifiers so they will be valid over the range (hf/kT) 1 (hf/kT). This is important for systems operating at high frequencies and low noise temperatures, or systems requiring very accurate calibrations. The suggested definitions are such that for an ideal amplifier, T sub e = (hg/k) = T sub q and F = 1. These definitions revert to the present definition for (hf/kT) 1. Noise temperature calibrations are illustrated with a detailed example. These concepts are applied to system signal-to-noise analysis. The fundamental limit to a receiving system sensitivity is determined by the thermal noise of the source and the quantum noise limit of the receiver. The sensitivity of a receiving system consisting of an ideal linear amplifier with a 2.7 K source, degrades significantly at higher frequencies.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 100-111
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  • 47
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    Provision of 9.6-kbps wideband data rate capability in the DSN (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The new 9.6-kbps wideband data rate capability in the DSN is reviewed. A functional description of the completed implementation is presented, together with a plan to upgrade the central communications terminal for additional 9.6 s operational flexibility.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 189-193
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  • 48
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    RFI measurement survey at Goldstone in November and December 1981 (1982)
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    Publication Date: 2011-08-18
    Description: A measurement survey was conducted to measure the emissions from the transmitters at Deep Space Station 14 and the Spaceflight Tracking and Data Network station. Both intended and spurious emissions were measured from DSN operational transmitters. The quiescent electromagnetic environment was also measured.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 110-121
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  • 49
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    An efficient sampling technique for sums of bandpass functions (1982)
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    Publication Date: 2011-08-18
    Description: A well known sampling theorem states that a bandlimited function can be completely determined by its values at a uniformly placed set of points whose density is at least twice the highest frequency component of the function (Nyquist rate). A less familiar but important sampling theorem states that a bandlimited narrowband function can be completely determined by its values at a properly chosen, nonuniformly placed set of points whose density is at least twice the passband width. This allows for efficient digital demodulation of narrowband signals, which are common in sonar, radar and radio interferometry, without the side effect of signal group delay from an analog demodulator. This theorem was extended by developing a technique which allows a finite sum of bandlimited narrowband functions to be determined by its values at a properly chosen, nonuniformly placed set of points whose density can be made arbitrarily close to the sum of the passband widths.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 3-7
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  • 50
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    Receiver-exciter controller design (1982)
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    Publication Date: 2011-08-18
    Description: A description of the general design of both the block 3 and block 4 receiver-exciter controllers for the Deep Space Network (DSN) Mark IV-A System is presented along with the design approach. The controllers are designed to enable the receiver-exciter subsystem (RCV) to be configured, calibrated, initialized and operated from a central location via high level instructions. The RECs are designed to be operated under the control of the DMC subsystem. The instructions are in the form of standard subsystem blocks (SSBs) received via the local area network (LAN). The centralized control provided by RECs and other DSCC controllers in Mark IV-A is intended to reduce DSN operations costs from the Mark III era.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 117-125
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    DSN RFI susceptibility models development program overview (1982)
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    Publication Date: 2011-08-18
    Description: The RFI model development described intended to provide an understanding of the interference susceptibility of DSN receivers. An overview of interference types and effects, analytic modelling and experimental verification is presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 103-109
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  • 52
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    Goldstone radio spectrum signal identification, March 1980 - March 1982 (1982)
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    Publication Date: 2011-08-18
    Description: The signal identification process is described. The Goldstone radio spectrum environment contains signals that are a potential source of electromagnetic interference to the Goldstone tracking receivers. The identification of these signals is accomplished by the use of signal parameters and environment parameters. Statistical data on the Goldstone radio spectrum environment from 2285 to 2305 MHz are provided.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 197-199
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  • 53
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    Applicaton of radiative transfer theory to microwave transmission medium calibrations (1982)
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    Publication Date: 2011-08-18
    Description: Precise determinations of the transmission medium loss and noise temperature contribution which are important to the performance characterization of low noise microwave receiving systems and thermal noise standards are discussed. Tropospheric loss is frequently inferred from microwave radiometer noise temperature measurements. Interpretation of these measurements requires an inversion of the radiative transfer integral equation. This is inconvenient even with computer techniques. Solutions of a rapidly convergent power series of the radiative transfer equations are presented. This solution is applicable to a low loss medium with either uniform or nonuniform loss distributions. A four layer atmosphere model is investigated to demonstrate the accuracy of the solution relative to the model. Applications include thermal noise standards and single- and dual-frequency water radiometers.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 179-188
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  • 54
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    Analysis, prediction and control of radio frequency interference with respect to DSN (1982)
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    Publication Date: 2011-08-18
    Description: Susceptibility modeling, prediction of radio frequency interference from satellites, operational radio frequency interference control, and international regulations are considered. The existing satellite interference prediction program DSIP2 is emphasized. A summary status evaluation and recommendations for future work are given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 81-100
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  • 55
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    RF processing (1982)
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    Publication Date: 2011-08-18
    Description: The Loran-C radio frequency processing is discussed. A diagram which generally illustrates the automatic gain control is presented. The augmented differentiator for pulse envelopes adapts conventional communications receiver with wideband AM capability to detect pulse signals such as Loran-C. The circuit enhances reception for surveillance and observation of HF over-the-horizon radar signals or others where time difference estimates between pulse returns are of interest. The high resolution VLF spectrum which receives weak VLF signals by using an HP 3581A wave analyzer detecting signals with a very narrow bandwidth of only 3 Hz is also presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Langley Research Center Joint Univ. Program for Air Transportation Res., 1981; p 165-172
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  • 56
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    Operations of the reconfigured Ground Communications Facility Central Communications Terminal and the Network Operations Control Center (1982)
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    Publication Date: 2011-08-18
    Description: The ground communications facility (GCF) central communications terminal and network operations control center (NOCC) hardware was rearranged, supplemented, and modified, and software programs changed to provide an improved GCF and NOCC operational environment and capability. Control center operations section activities required to make the changeover from the old to the new GCF and NOCC configuration are addressed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 122-129
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  • 57
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    Field interface module for antenna control assembly (1982)
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    Publication Date: 2011-08-18
    Description: The hardware aspects and capabilities of the field interface module (FIM) developed for monitor and control functions in the antenna mechanical subsystems of the deep space network and in the technical facilities controllers for the various complexes are described. The FIM is capable of monitoring and responding to a range of anaog and digital inputs and controlling external elements. The flexibility of the design makes it applicable to other control needs, using software developed for those specific applications.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 107-112
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    New CCIR papers on telecommunications for deep space research (1982)
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    Publication Date: 2011-08-18
    Description: Three draft reports submitted by JPL to the International Radio Consultative Committee (CCIR) for inclusion in their 1982 edition of reports and recommendations are presented. Potential interference between deep space telecommunications and the fixed satellite and broadcasting satellite services in harmonically related bands, protection criteria and sharing considerations relating to deep space research, and preferred frequencies and bandwidths for deep space research are considered.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Rept.; p 62-80
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  • 59
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    Radiation patterns of interfacial dipole antennas (1982)
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    Publication Date: 2011-08-18
    Description: The radiation pattern of an infinitesimal electric dipole is calculated for the case where the dipole is vertically located on the plane interface of two dielectric half spaces and for the case where the dipole is lying horizontally along the interface. For the vertical case, it is found that the radiation pattern has nulls at the interface and along the dipole axis. For the horizontal case, it is found that the pattern has a null at the interface; that the pattern in the upper half space, whose index of refraction is taken to be less than that of the lower half space, has a single lobe whose maximum is normal to the interface; and that in the lower half space, in the plane normal to the interface and containing the dipole, the pattern has three lobes, whereas in the plane normal to the interface and normally bisecting the dipole, the pattern has two maxima located symmetrically about a minimum. Interpretation of these results in terms of the Cerenkov effect is given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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    Multiple scattering calculations of rain effects (1982)
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    Publication Date: 2011-08-18
    Description: The multiple scattering calculations of rain effects are studied on the basis of calculating the incoherent intensity at 30, 60, 90, and 120 GHz. The Mie solution and the Laws-Parsons distribution are used to determine scattering and absorption characteristics. The equation of transfer and the Stokes parameters are used to determine incoherent intensities for the horizontal and vertical polarizations. The ratio of the copolarized incoherent intensity to the copolarized coherent intensity is defined as the incoherent copolarized discrimination. The ratio of the cross-polarized incoherent intensity is defined as the incoherent cross-polarized discrimination. These ratios are calculated in terms of copolarized attenuation, rain rate, and field of view. The results show that multiple scattering effects may become significant during heavy rains.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; Nov
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    Real-time optical synthetic aperture radar /SAR/ processor (1982)
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    Publication Date: 2011-08-18
    Description: A description is given of a real-time optical synthetic aperture radar (SAR). The processor employs an acoustooptic device as the input electronic-to-optical transducer and a CCD camera that serves as the optical detector and simultaneously performs the focusing of the SAR image in the azimuth direction. The performance criteria of the optical processor that are discussed include azimuth resolution, image size in azimuth, range resolution, image size in range, flexibility, and dynamic range.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Optical Engineering; 21; Sept
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    Recent advances in electromagnetic synthesis and analysis of dual-shaped reflector antennas (1982)
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    Publication Date: 2011-08-18
    Description: Dual-shaped reflectors have been used for many years. Thus, these reflectors have been used as high gain antennas on Voyagers 1 and 2. The objectives of the geometrical optics (GO) dual shaped synthesis are considered. Concerning the synthesis of dual shaped reflectors, it has been shown for circular symmetric reflectors that an exact GO solution can be found to the problem of transforming, by two reflections, any feed pattern into any aperture distribution. This problem involves solving two simultaneous nonlinear ordinary differential equations. The same approach for offset geometry leads to two simultaneous nonlinear partial differential equations. It is shown that these equations could also be integrated numerically, except that in general these equations are not total and therefore, in general, they do not have a 'smooth' solution. It is further shown that the offset partial differentials often very nearly form a total differential in many cases of practical importance.
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    The performance of M-ary FH-DPSK in the presence of partial-band multitone jamming (1982)
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    Publication Date: 2011-08-18
    Description: Using a geometric approach, the performance of M-ary FH-DPSK in the presence of partial-band multitone jamming is evaluated. The optimal jamming strategy is determined as a function of the number of signaling levels M and the ensuing results are used to determine worst case bit error probability performance as a function of this same parameter. It is demonstrated that, for M = 2 to the m power (where m is an integer), the best performance is obtained for M = 4.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; May 1982
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  • 64
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    Differentially coherent detection of QASK for frequency-hopping systems. II - Performance in the presence of jamming (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The performance of differentially coherent detection of frequency-hopped QASK in the presence of partial-band noise and partial-band multitone jamming is presented. In each case, the worst case jamming strategy is determined which consists of specifying the worst case partial-band fraction and the corresponding maximum average error probability. The results obtained are compared with those of M-ary FH-DPSK operating in the same jamming environment.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; Jan. 198
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  • 65
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    Differentially coherent detection of QASK for frequency-hopping systems. I - Performance in the presence of a Gaussian noise environment (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Bandwidth-conserving modulation techniques, which trade average power for bandwidth in a favorable exchange, have recently found widespread application in digital radio and satellite communication systems. Quadrature amplitude-shift-keying (QASK) is a particular type of the considered techniques. QASK makes use of multilevel signals to amplitude modulate the in-phase and quadrature components of a carrier. Frequency hopping (FH) is used to protect a conventional communication system from radio frequency interference (RFI) or jamming. Differentially coherent detection provides a possible solution to the effect of phase discontinuities introduced by FH. The application of such a detection technique to QASK signals is discussed. A receiver structure is proposed and its symbol error probability performance for an additive white Gaussian noise (AWGN) background is investigated.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; Jan. 198
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    The application of digital signal processing techniques to a teleoperator radar system (1982)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: A digital signal processing system was studied for the determination of the spectral frequency distribution of echo signals from a teleoperator radar system. The system consisted of a sample and hold circuit, an analog to digital converter, a digital filter, and a Fast Fourier Transform. The system is interfaced to a 16 bit microprocessor. The microprocessor is programmed to control the complete digital signal processing. The digital filtering and Fast Fourier Transform functions are implemented by a S2815 digital filter/utility peripheral chip and a S2814A Fast Fourier Transform chip. The S2815 initially simulates a low-pass Butterworth filter with later expansion to complete filter circuit (bandpass and highpass) synthesizing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center The 1982 NASA(ASEE Summer Fac. Fellowship Program; 20 p
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    Deep Space Communications Complex Command Subsystem Mark IVA (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Deep Space Communications Complex Command Subsystem will require major changes for the Mark IVA era. A description of the subsystem and its assemblies is contained in this article.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 129-136
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  • 68
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    Direct comparison of Viking 2.3-GHz signal phase fluctuation and columnar electron density between 2 and 160 solar radii (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The relationship between solar wind induced signal phase fluctuation and solar wind columnar electron density has been the subject of intensive analysis during the last two decades. In this article, a sizeable volume of 2.3-GHz signal phase fluctuation and columnar electron density measurements separately and concurrently inferred from Viking spacecraft signals are compared as a function of solar geometry. These data demonstrate that signal phase fluctuation and columnar electron density are proportional over a very wide span of solar elongation angle. A radially dependent electron density model which provides a good fit to the columnar electron density measurements and, when appropriately scaled, to the signal phase fluctuation measurements, is given. This model is also in good agreement with K-coronameter observations at 2 solar radii (2r0), with pulsar time delay measurements at 10r0, and with spacecraft in situ electron density measurements at 1 AU.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 117-128
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  • 69
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    Viterbi decoder node synchronization losses in the Reed-Solomon/Veterbi concatenated channel (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Viterbi decoders currently used by the Deep Space Network (DSN) employ an algorithm for maintaining node synchronization that significantly degrades at bit signal-to-noise ratios (SNRs) of below 2.0 dB. In a recent report by the authors, it was shown that the telemetry receiving system, which uses a convolutionally encoded downlink, will suffer losses of 0.85 dB and 1.25 dB respectively at Voyager 2 Uranus and Neptune encounters. This report extends the results of that study to a concatenated (255,223) Reed-Solomon/(7, 1/2) convolutionally coded channel, by developing a new radio loss model for the concatenated channel. It is shown here that losses due to improper node synchronization of 0.57 dB at Uranus and 1.0 dB at Neptune can be expected if concatenated coding is used along with an array of one 64-meter and three 34-meter antennas.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 73-80
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  • 70
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    Thermal background noise limitations (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Modern detection systems are increasingly limited in sensitivity by the background thermal photons which enter the receiving system. Expressions for the fluctuations of detected thermal radiation are derived. Incoherent and heterodyne detection processes are considered. References to the subject of photon detection statistics are given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 53-59
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  • 71
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    Performance of differenced range data types in Voyager navigation (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Voyager radio navigation made use of a differenced rage data type for both Saturn encounters because of the low declination singularity of Doppler data. Nearly simultaneous two-way range from two-station baselines was explicitly differenced to produce this data type. Concurrently, a differential VLBI data type (DDOR), utilizing doubly differenced quasar-spacecraft delays, with potentially higher precision was demonstrated. Performance of these data types is investigated on the Jupiter-to-Saturn leg of Voyager 2. The statistics of performance are presented in terms of actual data noise comparisons and sample orbit estimates. Use of DDOR as a primary data type for navigation to Uranus is discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 40-52
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  • 72
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    DSN Monitor and Control System Mark III-82 (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A description of the DSN Monitor and Control System, Mark III-82 is presented. The major implementations required to evolve from the Mark III-80 to the Mark III-82 configuration are identified.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 20-22
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  • 73
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    Performance of an optical relay satellite using Reed-Solomon coding over a cascaded optical PPM and BPSK channel (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The nature of the optical/microwave interface aboard the relay satellite is considered. To allow for the maximum system flexibility, without overburdening either the optical or RF channel, demodulating the optical on board the relay satellite but leaving the optical channel decoding to be performed at the ground station is examined. The occurrence of erasures in the optical channel is treated. A hard decision on the erasure (i.e., the relay selecting a symbol at random in case of erasure occurrence) seriously degrades the performance of the overall system. Coding the erasure occurrences at the relay and transmitting this information via an extra bit to the ground station where it can be used by the decoder is suggested. Many examples with varying bit/photon energy efficiency and for the noisy and noiseless optical channel are considered. It is shown that coding the erasure occurrences dramatically improves the performance of the cascaded channel relative to the case of hard decision on the erasure by the relay.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 117-131
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  • 74
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    The 2.5 bit/detected photon demonstration program: Phase 2 and 3 experimental results (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The experimental program for laboratory demonstration of and energy efficient optical communication channel operating at a rate of 2.5 bits/detected photon is described. Results of the uncoded PPM channel performance are presented. It is indicated that the throughput efficiency can be achieved not only with a Reed-Solomon code as originally predicted, but with a less complex code as well.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 95-104
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  • 75
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    The DSN VLBI System Mark IV-86 (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Use of the system for wide channel bandwidth very long base interferometry is described. System requirements, description, and implementation plans are given.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 16-20
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  • 76
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    DSN Command System Mark IV-85 (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A functional description of command subsystem software modifications providing computer-controlled prepass data transfer, validation tests, and revised displays are described. The Mark 4-A implementation schedule is presented and subsystems configurations for the Mark 4-85 system summarized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 8-15
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  • 77
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    Study of and proposals for the correction of errors in a radar ranging device designed to facilitate docking of a teleoperator maneuvering system (1982)
    In:  Other Sources
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    Publication Date: 2016-06-07
    Description: A frequency modulated continuous wave radar system was developed. The system operates in the 35 gigahertz frequency range and provides millimeter accuracy range and range rate measurements. This level of range resolution allows soft docking for the proposed teleoperator maneuvering system (TMS) or other autonomous or robotic space vehicles. Sources of error in the operation of the system which tend to limit its range resolution capabilities are identified. Alternative signal processing techniques are explored with emphasis on determination of the effects of inserting various signal filtering circuits in the system. The identification and elimination of an extraneous low frequency signal component created as a result of zero range immediate reflection of radar energy from the surface of the antenna dish back into the mixer of the system is described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA. Marshall Space Flight Center The 1982 NASA(ASEE Summer Fac. Fellowship Program; 17 p
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  • 78
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    The fabrication and surface tolerance measurements of the JPL clear aperture microwave antenna (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Present ground station microwave antennas of the Deep Space Network are of the symmetric dual reflector (cassegrainian) type. An investigation is being made of alternative high-performance offset antenna designs which have a clear aperture (no reflector or structural blockage) with shaped reflector surfaces. A 1.5-m, 32-GHz clear aperture model was built for experimental studies. The unique processes of fabrication, surface measurement, and alignment are described.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 104-116
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  • 79
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    Performance of concatenated Reed-Solomon/Viterbi channel coding (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The concatenated Reed-Solomon (RS)/Viterbi coding system is reviewed. The performance of the system is analyzed and results are derived with a new simple approach. A functional model for the input RS symbol error probability is presented. Based on this new functional model, we compute the performance of a concatenated system in terms of RS word error probability, output RS symbol error probability, bit error probability due to decoding failure, and bit error probability due to decoding error. Finally we analyze the effects of the noisy carrier reference and the slow fading on the system performance.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 81-94
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  • 80
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    X-band noise temperature effects of rain on DSN antenna feedhorns (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Simulated rain tests were carried out to determine the noise temperature contribution of liquid water adhering to the aperture cover material on both a standard DSN X-band feedhorn and on an S/X-band common aperture feedhorn. It was found that for the particular common aperture feedhorn tested, system noise temperature increases were much greater when the plastic horn cover material was old and weathered than when it was new. The age and condition of the aperture cover material is believed to be a major factor in the amount of degradation experienced by a telecommunications system during rain events.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 66-72
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  • 81
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    K sub A-band weather-dependent system performance estimates for Goldstone (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A K sub A band atmospheric noise temperature and attenuation statistical model is developed for Goldstone, based on water vapor radiometer measurements at 31.4 GHz made during winter and spring 1981. An equivalent X-band model is derived from these measurements, and the two sets of data are compared to determine the possible advantages of developing DSN telecommunications links at 32 GHz. For a nominal elevation angle of 30 degrees and identical antennas, it is found that a K sub A band system at Goldstone will show a 5 to 1 dB signal-to-noise ratio advantage oer an X-band system more than 99 percent of the time.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 60-65
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  • 82
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    Improved downlink frequency calculations for Voyager 2 (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Voyager 2 and her sister Voyager 1 were launched, respectively, in August and September 1977. The object of these spacecraft was to conduct exploratory investigations of the Jupiter and Saturn planetary systems and the interplanetary medium between Earth and Saturn. In April 1978 the Voyager 2 redundant receiver and the loop capacitor in the prime spacecraft receiver failed, leaving the Voyager Project with a major problem: how to communicate with the spacecraft and get the data back.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. J.; p 27-39
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  • 83
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    GCF Mark IV development (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Mark IV ground communication facility (GCF) as it is implemented to support the network consolidation program is reviewed. Changes in the GCF are made in the area of increased capacity. Common carrier circuits are the medium for data transfer. The message multiplexing in the Mark IV era differs from the Mark III era, in that all multiplexing is done in a GCF computer under GCF software control, which is similar to the multiplexing currently done in the high speed data subsystem.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 161-172
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  • 84
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    Thermal analysis of antenna backup structure. Part 1. Methodology development (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An analytic method was devised to predict the temperature distribution in typical antenna structural back-up members. The results are in agreement with those obtained by a numerical shooting method. The analytic method shows potential in simplifying the thermal analysis process for complex back-up antenna structures.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 110-116
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  • 85
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    A note on deep space optical communication link parameters (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Topical communication in the context of a deep space communication link. Communication link analysis at the optical frequencies differs significantly from that at microwave frequencies such as the traditional S and X-bands used in deep space applications, due to the different technology of transmitter, antenna, modulators, and receivers. In addition, the important role of quantum noise in limiting system performance is quite different than that of thermal noise. The optical link design is put in a design control table format similar to a microwave telecom link design. Key considerations unique to the optical link are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 105-109
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  • 86
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    PPM demodulation for Reed-Solomon decoding for the optical space channel (1982)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The use of Reed-Solomon (RS) block codes over the pulse position modulated (PPM) frames to obtain the largest degree of error correction is considered. Since RS codes can correct both symbol errors and symbol erasures, a question arises as to the best way to demodulate the PPM laser fields in order to generate the input symbols for the RS decoder. The method selected for demodulating (converting the received laser field to digital symbols) defines the erasure and transmitted symbols of the laser link, and therefore determines the work error probabilities of the system. Several demodulating schemes are considered, and the effect of each on RS decoding performance computed. This computation was carried out for various optical receiver models. It is shown that simple threshold decisioning of pulse slots produces performance that degrades as the background noise increases. This is caused by the generation of too many erasures for the RS decoder to handle. A decision scheme, delta-max demodulation which offers improvement over threshold decisioning by redefining the generation of an erasure is proposed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Report; p 47-59
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  • 87
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    Speed-dependent collision effects on radar back-scattering from the ionosphere (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The question whether the differences between fluctuation spectra for linearly speed-dependent and speed-independent collision frequencies could account for disagreements between rocket and incoherent scatter estimate was addressed. The basic theory used for computing the fluctuation spectrum is outlined. The speed-dependence of the charge-neutral collision frequency is discussed, with special emphasis on its derivation from the mobility measurements. Various developments of the computer code used for the computation of the fluctuation spectrum are described. The range of values of input parameters typical to the collision-dominated ionosphere are briefly described. The computational results are presented, and the significance and limitation of these results and the future scope of the research are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-173077 , NAS 1.26:173077
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  • 88
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    Integrated command, control, communication and computation system design study. Summary of tasks performed (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A summary of tasks performed on an integrated command, control, communication, and computation system design study is given. The Tracking and Data Relay Satellite System command and control system study, an automated real-time operations study, and image processing work are discussed.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-170611 , NAS 1.26:170611
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  • 89
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    Introduction to the concepts of TELEDEMO and TELEDIMS (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An introduction to the system concepts: TELEDEMO and TELEDIMS is provided. TELEDEMO is derived primarily from computer graphics and, via incorporation of sophisticated image data compression, enables effective low cost teleconferencing at data rates as low as 1K bit/second using dial-up phone lines. Combining TELEDEMO's powerful capabilities for the development of presentation material with microprocessor-based Information Management Systems (IMS) yields a truly all electronic IMS called TELEDIMS.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-170294 , NAS 1.26:170294 , JPL-PUB-82-108
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  • 90
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    New advances in the partial-reflection-drifts experiment using microprocessors (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Improvements to the partial reflection drifts experiment are completed. The results of the improvements include real time processing and simultaneous measurements of the D region with coherent scatter. Preliminary results indicate a positive correlation between drift velocities calculated by both methods during a two day interval. The possibility now exists for extended observations between partial reflection and coherent scatter. In addition, preliminary measurements could be performed between partial reflection and meteor radar to complete a comparison of methods used to determine velocities in the D region.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-169891 , NAS 1.26:169891 , AERONOMY-106 , UILU-ENG-82-2506 , (ISSN 0568-0581)
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  • 91
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    RF model of the distribution system as a communication channel, phase 2. Volume 1: Summary Report (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The design, implementation, and verification of a computerized model for predicting the steady-state sinusoidal response of radial (tree) configured distribution feeders was undertaken. That work demonstrated the feasibility and validity based on verification measurements made on a limited size portion of an actual live feeder. On that basis a follow-on effort concerned with (1) extending the verification based on a greater variety of situations and network size, (2) extending the model capabilities for reverse direction propagation, (3) investigating parameter sensitivities, (4) improving transformer models, and (5) investigating procedures/fixes for ameliorating propagation trouble spots was conducted. Results are summarized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-169626 , NAS 1.26:169626 , SRD-82-055-1-VOL-1
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  • 92
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    RF model of the distribution system as a communication channel, phase 2. Volume 4: Sofware source program and illustrations ASCII database listings (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Listings of source programs and some illustrative examples of various ASCII data base files are presented. The listings are grouped into the following categories: main programs, subroutine programs, illustrative ASCII data base files. Within each category files are listed alphabetically.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-169629 , NAS 1.26:169629 , SRD-82-055-4-VOL-4
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  • 93
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    Coded error probability evaluation for antijam communication systems (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: We present a general union-Chernoff bound on the bit error probability for coded communication systems and apply it to examples of antijam systems. The key feature of this bound is the decoupling of the coding aspects of the system from the remaining part of the communication system which includes jamming, suboptimum detectors, and arbitrary decoding metrics which may or may not use jammer state knowledge
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; May 1982
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  • 94
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    Outline of a multiple-access communication network based on adaptive arrays (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Attention is given to a narrow-band communication system consisting of a central station trying to receive signals simultaneously from K spatially distinct mobile users sharing the same frequencies. One example of such a system is a group of aircraft and ships transmitting messages to a communication satellite. A reasonable approach to such a multiple access system may be based on equipping the central station with an n-element antenna array where n is equal to or greater than K. The array employs K sets of n weights to segregate the signals received from the K users. The weights are determined by direct computation based on position information transmitted by the users. A description is presented of an improved technique which makes it possible to reduce significantly the number of required computer operations in comparison to currently known techniques.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications; COM-30; May 1982
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  • 95
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    Wave scattering from a periodic dielectric surface for a general angle of incidence (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Electromagnetic waves scattered from a periodic dielectric and perfectly conducting surface are studied for a general angle of incidence. It is shown that the one-dimensional corrugated surface can be solved by using two scalar functions: the components of the electric and magnetic fields along the row direction of the surface, and appropriate boundary conditions to obtain simple matrix equations. Results are compared to the case where the incident angle wave vector is perpendicular to the row direction. Numerical results demonstrate that energy conservation and reciprocity are obeyed for scattering by sinusoidal surfaces for the general case, which checks the consistency of the formalism.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Radio Science; 17; May-June
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  • 96
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    Wave transmission through a spherical dielectric shell (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: (Previously announced in STAR as N81-17321)
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; May 1982
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  • 97
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    Radiation from an open-ended waveguide with beam equalizer - A spectral domain analysis (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A septum and an impedance matching post are used as a beam equalizer in an open-ended waveguide feed for reflectors used in satellite communications systems. The performance of this design over a frequency band is evaluated using a spectral domain approach. The computed radiation patterns in the E- and H-planes, as well as the results for the impedance match are presented.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Antennas and Propagation; AP-30; Jan. 198
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  • 98
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    A two-component rain model for the prediction of attenuation and diversity improvement (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A new model was developed to predict attenuation statistics for a single Earth-satellite or terrestrial propagation path. The model was extended to provide predictions of the joint occurrences of specified or higher attenuation values on two closely spaced Earth-satellite paths. The joint statistics provide the information required to obtain diversity gain or diversity advantage estimates. The new model is meteorologically based. It was tested against available Earth-satellite beacon observations and terrestrial path measurements. The model employs the rain climate region descriptions of the Global rain model. The rms deviation between the predicted and observed attenuation values for the terrestrial path data was 35 percent, a result consistent with the expectations of the Global model when the rain rate distribution for the path is not used in the calculation. Within the United States the rms deviation between measurement and prediction was 36 percent but worldwide it was 79 percent.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-169198 , NAS 1.26:169198
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  • 99
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    A new antenna concept for satellite communications (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A novel antenna configuration of two reflecting surfaces and a phased array is examined for application to satellite communications and shown to be superior in every respect to earlier designs for service to the continental United States from synchronous orbit. The vignetting that afflicts other two reflector optical systems is eliminated by use of a reflecting field element. The remaining aberrations, predominantly coma, are isolated in the time delay distribution at the surface of the array and can be compensated by ordinary array techniques. The optics exhibits infinite bandwidth and the frequency range is limited only by the design of the array.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-167924 , NAS 1.26:167924
    Format: application/pdf
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  • 100
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    Coaxial prime focus feeds for paraboloidal reflectors (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A TE11 - TM11 dual mode coaxial feed for use in prime focus paraboloidal antenna systems is investigated. The scattering matrix parameters of the internal bifurcation junction was determined by the residue calculus technique. The scattering parameters and radiation fields of the aperture were found from the Weinstein solution. The optimum modeing ratio for minimum cross-polarization was determined along with the corresponding optimum feed dimensions. A peak cross-polarization level of -58 dB is predicted. The frequency characteristics were also investigated and a bandwidth of 5% is predicted over which the cross-polarization remains below -30 dB, the input VSWR is below 1.15, and the phase error is less than 10 deg. Theoretical radiation patterns and efficiency curves for a paraboloidal reflector illuminated by this feed were computed. The predicted sidelobe level is below -30 dB and aperture efficiencies greater than 70% are possible. Experimental results are also presented that substantiates the theoretical results. In addition, experimental results for a 'short-cup' coaxial feed are given. The report includes extensive design data for the dual-mode feed along with performance curves showing cross-polarization as a function of feed parameters. The feed is useful for low-cost ground based receiving antennas for use in direct television satellite broadcasting service.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-167934 , NAS 1.26:167934
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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