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  • Other Sources  (6,027)
  • COMMUNICATIONS
  • FACILITIES, RESEARCH, AND SUPPORT
  • 1
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    The tracking system analytic calibration activity for Mariner Mars 1971: Its function and scope (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The functions of the Tracking System Analytic Calibration activity for Mariner Mars 1971 (MM'71), its objectives for this and future missions, and the support provided to the MM'71 Navigation Team during operations are described. Support functions encompass calibration of tracking data by estimating physical parameters whose uncertainties represent limitations to navigational accuracy, and detailed analysis of the tracking data to uncover and resolve any anomalies. Separate articles treat the activities and results of producing calibrations for the various error sources: Deep Space Station Locations, timing and polar motion, charged particles, and the troposphere. Two other articles are also included discussing the effects of the media error sources on orbit determination and the merits of the smoothing technique used for DRIVID.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 1-12
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  • 2
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    Radio communications with extra-terrestrial civilizations (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Communications between civilizations within our galaxy at the present level of radio engineering is possible, although civilizations must begin to search for each other to achieve this. If an extra-terrestrial civilization possessing a technology at our level wishes to make itself known and will transmit special radio signals to do this, then it can be picked up by us at a distance of several hundreds of light years using already existing radio telescopes and specially built radio receivers. If it wishes, this civilization can also send us information without awaiting our answer.
    Keywords: COMMUNICATIONS
    Type: Inhabited Space, Pt. 2 (NASA-TT-F-820); p 79-82
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  • 3
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    Concerns of the Institute of Transport Study and Research for reducing the sound level inside completely repaired buses (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Sound level measurements on noise sources on buses are used to observe the effects of attenuating acoustic pressure levels inside the bus by sound-proofing during complete repair. A spectral analysis of the sound level as a function of motor speed, bus speed along the road, and the category of the road is reported.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: The 4th Natl. Conf. on Acoustics, Vol. 1A (NASA-TT-F-15375); p 205-211
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  • 4
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    Intermediate memory devices (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Several methods of transfer and processing of data whose practical implementation requires operational memory devices are described. Devices incorporating multistable elements are proposed and their main parameters are given. The possibility of using the proposed devices for storing information for transmission in space radio communications channels is examined.
    Keywords: COMMUNICATIONS
    Type: Space Res. in the Ukraine, No. 3 (NASA-TT-F-15537); p 155-162
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  • 5
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    Electromagnetic processes in the atmosphere of pulsars (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The work consists of two parts. The first deals with the fine structure of radio pulses. Based on kinetic theory, processes occurring in the plasma shell of a pulsar when external electromagnetic radiation is present are investigated. It is shown that electromagnetic waves cause electrons to drift relative to ions, and initiate longitudinal oscillations. A dispersion equation describing the longitudinal oscillations in magnetized plasma is derived. Conditions for excitation of oscillations are found. Correlation functions of electron density are calculated, along with the coefficients of electromagnetic wave scattering. It is shown that variations in the amplitude of pulsar pulses are associated with scintillations caused by fluctuations in the plasma electron density. The second part of the study presents a mechanism for the radio emission of pulsars. The model of a rotating and a pulsating star, a neutron star with dipolar or more complex magnetic field, is examined.
    Keywords: COMMUNICATIONS
    Type: Space Res. in the Ukraine, No. 3, (NASA-TT-F-15537); p 44-53
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  • 6
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    Calibration effects on orbit determination (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The effects of charged particle and tropospheric calibrations on the orbit determination (OD) process are analyzed. The calibration process consisted of correcting the Doppler observables for the media effects. Calibrated and uncalibrated Doppler data sets were used to obtain OD results for past missions as well as Mariner Mars 1971. Comparisons of these Doppler reductions show the significance of the calibrations. For the MM'71 mission, the media calibrations proved themselves effective in diminishing the overall B-plane error and reducing the Doppler residual signatures.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 83-96
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  • 7
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    The tropospheric calibration model for Mariner Mars 1971 (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The effects of the troposphere on arrival time, range, and range rate measurement of radio signals propagating from spacecraft are examined. A tropospheric calibration model which takes into account seasonal variations, various elevations, and apparent location changes was developed. A comparison was made of the effects before and after calibration. Without calibration, a 16-m change in the distance off the spin axis, is induced for a 10-deg minimum elevation symmetrical pass. Even after calibration with the old model, the error in spin axis is still greater than 1 m. Calibration results and estimated uncertainties of the model are given in tabular form. Test results also show that the model met the required accuracy for the Mariner Mars 1971 mission.
    Keywords: COMMUNICATIONS
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 61-76
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  • 8
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    Polynomial smoothing of DRVID data (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Charged particle calibrations based on differenced range versus integrated Doppler (DRVID) are smoothed and fitted with a polynomial prior to its application in the orbit determination process. A description is given of the results of the tests performed on the computer program performing these calculations to determine its characteristics and to evaluate the acceptability of its computations. This program, called MEDIA, is described.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 97-103
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  • 9
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    Charged particles (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: Calibrations compensating for the effects of charged particles in the ionosphere and in the interplanetary medium were applied to the Doppler tracking data acquired during Mariner 9 missions on a demonstration basis. The combined effects of the space plasma and the ionosphere were measured by a comparison of the range and Doppler observables (Differenced Range Versus Integrated Doppler (DRVID). Independent measurements of the ionospheric effects were obtained from polarimeter devices located at the Goldstone, California, tracking complex.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 43-60
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  • 10
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    Time and polar motion (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The time and polar motion calibration support provided to the MM'71 mission is discussed. Specifically, a description is given of the data gathering system and the data processing system by which calibrations were obtained. An introductory discussion of the effects of timing and polar motion error on spacecraft navigation, along with a description of the system used to support Mariners 6 and 7, is given. A complete discussion of the way in which timing is used in orbit determination is also given.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 77-82
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  • 11
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    Station locations (1974)
    In:  CASI
    Details
    Publication Date: 2006-01-11
    Description: The extended process of providing station location estimates for use in orbit determination at launch and during the course of the mission, is outlined. Station location sets provided for Mariner Mars 1971 navigation support are given. Data cover set construction, basis for construction, and a comparison of estimated sets with final sets.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Tracking System Analytic Calibration Activities for the Mariner Mars 1971 Mission; p 13-42
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  • 12
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    Optical antenna gain. II - Receiving antennas (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Expressions are developed for the gain of a centrally obscured, circular optical antenna used as the collecting and focusing optics in a laser receiver, involving losses due to (1) incoming light blockage by central obscuration, (2) energy spillover at the detector, and (3) the effect of local oscillator distribution in the case of heterodyne or homodyne detection. Numerical results are presented for direct detection and for three types of local oscillator distribution (uniform, Gaussian, and matched).
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; Oct. 197
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  • 13
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    Optical antenna gain. I - Transmitting antennas (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The gain of centrally obscured optical transmitting antennas is analyzed in detail. The calculations, resulting in near- and far-field antenna gain patterns, assume a circular antenna illuminated by a laser operating in the TEM-00 mode. A simple polynomial equation is derived for matching the incident source distribution to a general antenna configuration for maximum on-axis gain. An interpretation of the resultant gain curves allows a number of auxiliary design curves to be drawn that display the losses in antenna gain due to pointing errors and the cone angle of the beam in the far field as a function of antenna aperture size and its central obscuration. The results are presented in a series of graphs that allow the rapid and accurate evaluation of the antenna gain which may then be substituted into the conventional range equation.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; Sept
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  • 14
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    The subsequence weight distribution of summed maximum length digital sequences (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An attempt is made to develop mathematical formulas to provide the basis for the design of pseudorandom signals intended for applications requiring accurate knowledge of the statistics of the signals. The analysis approach involves calculating the first five central moments of the weight distribution of subsequences of hybrid-sum sequences. The hybrid-sum sequence is formed from the modulo-two sum of k maximum length sequences and is an extension of the sum sequences formed from two maximum length sequences that Gilson (1966) evaluated. The weight distribution of the subsequences serves as an approximation to the filtering process. The basic reason for the analysis of hybrid-sum sequences is to establish a large group of sequences with good statistical properties. It is shown that this can be accomplished much more efficiently using the hybrid-sum approach rather than forming the group strictly from maximum length sequences.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-22; Aug. 197
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  • 15
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    Computer simulation of the Pioneer 10 microwave occultation experiment (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: As Pioneer 10 approaches the planet Jupiter, its trajectory will carry it behind the planet, as seen from the earth. The microwave telemetry signal from the spacecraft will then pass through the Jovian atmosphere on its way to the earth, and analysis of the effects of the atmosphere on the signal should yield information on the atmospheric structure. To help define the capabilities of this experiment and to aid the analysis of the real data, we have simulated the occultation experiment on a computer by using model Jovian atmospheres and a predicted trajectory. The results indicate that the useful depth of penetration of the microwave signal will be governed by ammonia absorption rather than superrefractivity. The experiment is apparently far more sensitive to variations in cloud-top temperature than to variations in the hydrogen-helium ratio. Characteristic 'flashes' in the attenuation record of the signal may yield information on the location of the top of the Jovian convective zone.
    Keywords: COMMUNICATIONS
    Type: Journal of Geophysical Research; 79; May 1
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  • 16
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    Mutual coupling in a finite planar array of circular apertures (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Equations are presented for the calculation of the interelement mutual coupling in a finite-size planar array of waveguide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures, and the mutual coupling calculations are verified experimentally for two Te-(11) mode excited apertures. Qualitative agreement between calculations for a 183-element array and an infinite array establishes the validity of the finite-array theoretical model.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 17
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    ERTS operations and data processing (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The overall communications and data flow between the ERTS spacecraft and the ground stations and processing centers are generally described. Data from the multispectral scanner and the return beam vidicon are telemetered to a primary ground station where they are demodulated, processed, and recorded. The tapes are then transferred to the NASA Data Processing Facility (NDPF) at Goddard. Housekeeping data are relayed from the prime ground stations to the Operations Control Center at Goddard. Tracking data are processed at the ground stations, and the calculated parameters are transmitted by teletype to the orbit determination group at Goddard. The ERTS orbit has been designed so that the same swaths of the ground coverage pattern viewed during one 18-day coverage cycle are repeated by the swaths viewed on all subsequent cycles. The Operations Control Center is the focal point for all communications with the spacecraft. NDPF is a job-oriented facility which processes and stores all sensor data, and which disseminates large quantities of these data to users in the form of films, computer-compatible tapes, and data collection system data.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Journal of Environmental Sciences; 17; Mar
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  • 18
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    Channel simulation for optical communication systems (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A technique is reported for simulating the signal fading that will be experienced by typical optical communication systems. The desired irradiance or amplitude fading statistics can be simulated by incorporating a linearized optical modulator subsystem between the transmitter and receiver. This technique has been implemented in the design and construction of a laboratory channel simulator. The design of the processing electronics is discussed along with the results of tests performed for each mode of operation.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; June 197
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  • 19
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    On first cycle slip time of phase-locked loops in cascade (1974)
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    Publication Date: 2011-08-16
    Description: Precise measurement and spacecraft tracking are obtained by using phase-locked loops in cascade in two-way communications links. Statistics on cycle slip time are of vital importance in system planning and design. This paper presents: (1) results of a computer simulation study of the mean time to first cycle slip of cascade phase-locked loops preceded by bandpass limiters, and (2) the determination of probability distributions of cycle slip. Numerical results are obtained for a typical coherent communication system.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-10; May 1974
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  • 20
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    Bistatic scatter from rain (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: An experimental investigation of bistatic scatter from rain was conducted, using a 143-km scatter path at frequencies of 4.5 and 7.7 GHz. The ratio of transmitted to received power (transmission loss) was measured for scattering angles ranging from 6 to 130 deg. Simultaneous weather radar observations were made at a frequency of 1.3 GHz. Transmission loss estimates for the bistatic scatter path were computed, using the weather radar data, the bistatic radar equation, and a model for the scattering cross section per unit volume of rain based upon Rayleigh scattering by an ensemble of water spheres. The measured and estimated transmission loss values were compared to test the use of the scattering model for the estimation of interference. The averaged ratio of measured-to-calculated transmission loss for the 4.5 GHz data is 1.2 plus or minus 0.4 dB. The averaged ratio for the 7.7 GHz data is -1.6 plus or minus 0.5 dB.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 21
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    Integrated laser/radar satellite ranging and tracking system (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A laser satellite ranging system that is mounted upon and integrated with a microwave tracking radar is reported. The 1-pulse/sec ruby laser transmitter is attached directly to the radar's elevation axis and radiates through a new opening in the radar's parabolic dish. The laser photomultiplier tube receiver utilizes the radar's existing 20-cm diam f/11 boresight telescope and observes through a similar symmetrically located opening in the dish. The laser system possesses separate ranging system electronics but shares the radar's timing, computer, and data handling/recording systems. The basic concept of the laser/radar is outlined together with a listing of the numerous advantages over present singular laser range-finding systems. The developmental laser hardware is described along with preliminary range-finding results and expectations.
    Keywords: COMMUNICATIONS
    Type: Applied Optics; 13; Oct. 197
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  • 22
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    Ground testing and simulation. II - Aerodynamic testing and simulation: Saving lives, time, and money (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The present work discusses in general terms the various kinds of ground facilities, in particular, wind tunnels, which support aerodynamic testing. Since not all flight parameters can be simulated simultaneously, an important problem consists in matching parameters. It is pointed out that there is a lack of wind tunnels for a complete Reynolds-number simulation. Using a computer to simulate flow fields can result in considerable reduction of wind-tunnel hours required to develop a given flight vehicle.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Astronautics and Aeronautics; 12; June 197
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  • 23
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    Four years of meteor spectra patrol (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The development of the NASA-Langley Research Center meteor spectra patrol is described in general terms. The recording of very faint meteors was made possible by three great strides in optical and photographic technology in the 1960's: (1) the availability of optical-grade fused silica at modest cost, (2) the development of large transmission gratings with high blaze efficiency, and (3) the development of a method for avoiding plate fogging due to background skylight, which consisted of using a photoelectric meteor detector which actuates the spectrograph shutter when a meteor occurs in the field. The classification scheme for meteor spectra developed by Peter M. Millman is described.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Sky and Telescope; 47; June 197
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  • 24
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    Shortwave telemetric system (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: The application of frequency modulation when constructing a telemetric system in the shortwave band. The operating principles, the construction of the system and the decision making device are described and experimental data are presented. The equipment can be used on sounding balloons.
    Keywords: COMMUNICATIONS
    Type: Technol. for the Production of Space Equipment (NASA-TT-F-15766); p 59-65
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  • 25
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    Anechoic chamber in industrial plants (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: A light anechoic chamber for routine acoustical measurements in the machine building industry is reported. The outer housing of the chamber consists of modules cast in glass fiber reinforced polyester resin; the inner housing consists of pyramidal modules cut out of sound absorbing slates. The parameters of this anechoic chamber facilitate acoustical measurements according to ISO and CAEM recommendations.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: The 4th Natl. Conf. on Acoustic, Vol. 1, C (NASA-TT-F-15376); p 29-31
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  • 26
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    Stand for studying technological processes under conditions simulating space (1974)
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    Publication Date: 2011-08-16
    Description: A test stand for conducting processing experiments under conditions simulating space is described. The most important units of the stand are discussed. Tests of the stand and research studies using the stand demonstrated that it is a reliable and universal research facility which makes it possible to study processes such as metal melting, welding, and deposition.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Space Studies in the Ukraine, No. 1 (NASA-TT-F-15535); p 1-8
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  • 27
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    Automated life-detection experiments for the Viking mission to Mars (1974)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: As part of the Viking mission to Mars in 1975, an automated set of instruments is being built to test for the presence of metabolizing organisms on that planet. Three separate modules are combined in this instrument so that samples of the Martian surface can be subjected to a broad array of experimental conditions so as to measure biological activity. The first, the Pyrolytic Release Module, will expose surface samples to a mixture of C-14O and C-14O2 in the presence of Martian atmosphere and a light source that simulates the Martian visible spectrum. The assay system is designed to determine the extent of assimilation of CO or CO2 into organic compounds. The Gas Exchange Module will incubate surface samples in a humidified CO2 atmosphere. At specified times, portions of the incubation atmosphere will be analyzed by gas chromatography to detect the release or uptake of CO2 and several additional gases. The Label Release Module will incubate surface samples with a dilute aqueous solution of simple radioactive organic substrates in Martian atmosphere, and the gas phase will be monitored continuously for the release of labeled CO2.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Origin of Life; 5; July-Oct
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  • 28
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    Diffraction theory techniques applied to aperture antennas on finite circular and square ground planes (1974)
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    Publication Date: 2011-08-16
    Description: Expressions which represent the elevation-plane patterns of a large TEM mode coax aperture and a TM-01 mode circular aperture on finite circular and square ground planes have been derived using geometrical theory of diffraction; design curves for the coax case are presented. The expressions for the field pattern were obtained by superposing the infinite ground plane solutions, the first-order diffracted field solutions, and the axial caustic solutions in their respective regions of validity. The pattern analyses for the coax and circular apertures are verified experimentally.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; May 1974
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  • 29
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    Diffused optical waveguides (1974)
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    Publication Date: 2011-08-16
    Description: Diffused optical waveguides are studied using the modal and the ray tracing approach, with an emphasis on the case of a hollow waveguide with diffuse cladding. The properties of the guided modes are investigated in detail. The applications of these structures to optical circuits, integrated optics lasers and capillary gas lasers are discussed.
    Keywords: COMMUNICATIONS
    Type: vol. 43; July 197
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  • 30
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    The Langley cryogenic high Reynolds number wind-tunnel program (1974)
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    Publication Date: 2011-08-16
    Description: A pilot version of a new type of transonic tunnel was placed in operation in the fall of 1973. In the tunnel the cryogenic method is used to obtain a high Reynolds number. The cryogenic concept employs low temperatures to increase the Reynolds number through reducing the viscous forces rather than increasing the inertia forces. The cryogenic approach offers the desired Reynolds-number increase with no increase in dynamic pressure, and therefore no increase in model loads. A series of aerodynamic experiments have been made in the pilot tunnel to confirm the cryogenic concept at transonic speeds. A brief description is given of the project for a large tunnel which has evolved from the investigations.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Astronautics and Aeronautics; 12; Oct. 197
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  • 31
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    The Apollo Lunar Sounder radar system (1974)
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    Publication Date: 2011-08-16
    Description: The objectives of the Apollo 17 Lunar Sounder Experiment (ALSE) were to detect subsurface geologic structures, to generate a continuous lunar profile, and to image the moon at radar wavelengths. A three-wavelength synthetic-aperture radar (SAR) operating at 60, 20, and 2 m wavelengths was designed to attain these objectives. The design choices reflected a balance of scientific requirements versus Apollo mission and hardware constraints. The radar data from the lunar mission were recorded on photographic film in a conventional SAR format, and were returned to earth for processing. A combination of optical and digital processing and exploitation techniques was applied to the scientific interpretation of the data. Some preliminary results from the lunar mission have been obtained.
    Keywords: COMMUNICATIONS
    Type: IEEE; vol. 62
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  • 32
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    Mutual coupling in a finite planar array of circular apertures (1974)
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    Publication Date: 2011-08-16
    Description: Equations are presented for the calculation of the interelement mutual coupling in a finite size planar array of wave-guide-fed apertures in an infinite flat conductor. The general mutual admittance expression is evaluated for circular apertures and the mutual coupling calculations are verified experimentally for two TE11 mode excited apertures. Qualitative agreement between calculations for a 183 element array and an infinite array establishes the validity of the finite array theoretical model.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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    Simulation study of communication link for Pioneer Saturn/Uranus atmospheric entry probe (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A digital simulation is presented for a candidate modem in a modeled atmospheric scintillation environment with Doppler, Doppler rate, and signal attenuation typical of the radio link conditions for an outer planets atmospheric entry probe. The results indicate that the signal acquisition characteristics and the channel error rate are acceptable for the system requirements of the radio link. The simulation also outputs data for calculating other error statistics and a quantized symbol stream from which error correction decoding can be analyzed.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-114739
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    Gas flow analysis during thermal vacuum test of a spacecraft (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The self-contamination of the IMP-H spacecraft, while it was undergoing thermal and solar vacuum tests, has been investigated in conjunction with the outgassing evaluation and detection of molecular flow anomalies occurring in the test chamber. The pressures indicated by two tubulated ionization gauges were used to calculate flow kinetics in the vacuum chamber. The fluxes of emitted molecules and chamber wall reflected molecules were monitored during the entire test. Representative equations and graphs are presented. Test results indicate that from 3 to 9 of every 100 emitted molecules returned to the spacecraft surface; that self-contamination by noncondensable gases was more severe than that by condensable gases; and that outgassing of the spacecraft was approximately 1.18 x 0.01 g/s after 10 hours and 1.18 x 0.001 after 90 hours of vacuum exposure. Testing deficiencies have been identified, and the type and location of instruments required to measure the outgassing, the degree of contamination, and return flow are discussed.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TN-D-7492 , G-7346
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    Testing a satellite automatic nutation control system (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Testing of a particular nutation control system for the synchronous meteorological satellite (SMS) is described. The test method and principles are applicable to nutation angle control for other satellites with similar requirements. During its ascent to synchronous orbit, a spacecraft like the SMS spins about its minimum-moment-of-inertia axis. An uncontrolled spacecraft in this state is unstable because torques due to fuel motion increase the nutation angle. However, the SMS is equipped with an automatic nutation control (ANC) system which will keep the nutation angle close to zero. Because correct operation of this system is critical to mission success, it was tested on an air-bearing table. The ANC system was mounted on the three-axis air-bearing table which was scaled to the SMS and equipped with appropriate sensors and thrusters. The table was spun up in an altitude chamber and nutation induced so that table motion simulated spacecraft motion. The ANC system was used to reduce the nutation angle. This dynamic test of the ANC system met all its objectives and provided confidence that the ANC system will control the SMS nutation angle.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TN-D-7596 , G-7426
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    Low cost ground receiving systems for television signals from high-powered communications satellites. Volume 2: Parts list and engineering drawings (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Parts lists for the 2.25 GHz indoor- and antenna-unit assemblies are followed by drawings that constitute the drafting package for three converter types and the tunnel diode amplifier.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-120933
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    Task 60 test report, evaluation of IRIG-A 21 channel constant bandwith FM multiplexer for shuttle development flight instrumentation (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A frequency modulated (FM) multiplexer, consisting of 21 IRIG-A constant bandwidth (CBW) voltage-controlled oscillators (VCO's) was tested to determine its suitability for use in multiplexing 21 data signals which have frequency ranges of dc to 2 kHz. Tests were preformed with the composite signal, consisting of the mixed outputs of the 21 VCO's connected directly to a set of subcarrier discriminators, with the signal recorded on magnetic tape and played back through the discriminators and with the signal transmitted by a frequency-modulated FM S-band radio frequency RF transmitter to a FM receiver and through the subcarrier discriminators. Tape speed flutter was induced to determine the reduction in flutter noise which can be obtained by the tape speed compensation equipment. The RF transmission test included transmitting the composite signal at a nominal RF received signal of -73 dbm and at RF levels of -83 and -86 dbm.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134304 , LEC-3558 , JSC-09017
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  • 38
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    Integrated source and channel encoded digital communications system design study (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Studies on the digital communication system for the direct communication links from ground to space shuttle and the links involving the Tracking and Data Relay Satellite (TDRS). Three main tasks were performed:(1) Channel encoding/decoding parameter optimization for forward and reverse TDRS links,(2)integration of command encoding/decoding and channel encoding/decoding; and (3) modulation coding interface study. The general communication environment is presented to provide the necessary background for the tasks and to provide an understanding of the implications of the results of the studies.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134183 , R7401-2
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  • 39
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    Effects of turbulence in a planetary atmosphere on radio occultation (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: A formulation is given for the correlation functions for the log-amplitude and phase fluctuations of both spherical and plane waves propagating in a turbulent medium whose correlation function for refractive index fluctuations is described by the product of a function of the average coordinate and a function of the difference coordinate. The results are applied to radio occultation of a flyby space probe by the atmosphere of Venus, assuming that the turbulence in the atmosphere exists as a layer, that it is localized, isotropic, and smoothly varying, and that the localized turbulence is described by the Kolmogorov spectrum. Closed-form solutions for both variances and frequency spectra of the log-amplitude and phase fluctuations are obtained using Rytov's method, and it is seen that the shape of the frequency spectra depends greatly on the characteristics and extent of the turbulence.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; July 197
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  • 40
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    The interpretation of ionospheric radio drift measurements. VII - Diffraction methods applied to E-region echo fading: Evidence of a focusing model (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: COMMUNICATIONS
    Type: Journal of Atmospheric and Terrestrial Physics; 36; May 1974
    Format: text
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  • 41
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    Properties of cutoff corrugated surfaces for corrugated horn design (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Corrugated horns involve a junction between the corrugated surface and a conducting ground plane. Proper horn design requires an understanding of the electromagnetic properties of the corrugated surface and this junction. An integral equation solution has been used to study the influence of corrugation density and tooth thickness on the power loss, surface current, and the scattering from a ground plane/corrugated surface junction.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Mar. 197
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  • 42
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    Application of an integral equation formulation to the prediction of space shuttle annular slot antenna radiation patterns (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Pitch and roll plane radiation patterns computed by use of an integral equation formulation are presented for a space shuttle annular slot communications antenna. The excellent agreement between computed patterns and experimental patterns obtained from 1/35 scale models supports the use of this method as a design tool for similar spacecraft/aircraft antenna applications.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Antennas and Propagation; AP-22; Jan. 197
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  • 43
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    Operation and performance of a lunar laser ranging station (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The Lunar Laser Ranging Experiment has been in continuous operation for about 4 years using the McDonald Observatory 2.7-m telescope. Occupying only a small percentage of the available telescope time, the system is now measuring 350 lunar ranges per year, each with an accuracy of from 10 to 15 cm. This article tabulates the observed signal strengths, the success ratios, and the major operating restrictions that have characterized the daily performance of the experiment. These empirical data can be used to optimize the design of such installations in the future.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Applied Optics; 13; Mar. 197
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  • 44
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    Abating exhaust noises in jet engines (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A noise abating improvement for jet engines including turbojets, turbofans, turboprops, ramjets, scramjets, and hybrid jets is introduced. A provision is made for an apparatus in the primary and/or secondary flow streams of the engines; the apparatus imparts to the exhaust gases a component rotation or swirl about the engine's longitudinal axis. The rotary component in the exhaust gases causes a substantial suppression of sound energy build up normally produced by an axial flow exhaust system.
    Keywords: COMMUNICATIONS
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  • 45
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    Design of a 12 channel fm microwave receiver (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The design, fabrication, and performance of elements of a low cost FM microwave satellite ground station receiver is described. It is capable of accepting 12 contiguous color television equivalent bandwidth channels in the 11.72 to 12.2 GHz band. Each channel is 40 MHz wide and incorporates a 4 MHz guard band. The modulation format is wideband FM and the channels are frequency division multiplexed. Twelve independent CATV compatible baseband outputs are provided. The overall system specifications are first discussed, then consideration is given to the receiver subsystems and the signal branching network.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140056 , R(T)-74/2
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  • 46
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    High temperature antenna development for space shuttle, volume 2 (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An S-band antenna system and a group of off-the-shelf aircraft antenna were exposed to temperatures simulating shuttle orbital cold soak and entry heating. Radiation pattern and impedance measurements before and after exposure to the thermal environments were used to evaluate the electrical performance. The results of the electrical and thermal testing are given. Test data showed minor changes in electrical performance and established the capability of these antenna to withstand both the low temperatures of space flight and the high temperatures of entry.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140226 , MDC-E0896-VOL-2
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  • 47
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    Noise suppressor (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A tuned noise suppressor is described consisting of annular acoustically porous elements for incorporation into the inlet and exhaust ducts of turbofan engines. The apparatus uses sound wave absorption, reflection, and incompatibility for achieving high noise reduction in the short distance. In addition, it has a duct of uniform inner diameter which does not block the duct flow.
    Keywords: COMMUNICATIONS
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  • 48
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    Dual frequency dichroic feed performance (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The NASA Deep Space Net (DSN) in support of the Viking Mars Project in 1976, and for science and technology demonstrations during the Mariner-Venus-Mercury mission in 1974, has developed and implemented a dual (S- and X-band) feed for large ground microwave antennas. This feed provides for a multiplicity of functions; very low listening capability at each downlink (spacecraft-to-earth) band as well as simultaneous diplexed very high cw power uplink (earth-to-spacecraft) at the S-band frequency. Total 64-m antenna system performance, is considered in terms of gain, operating noise temperature and dual beam pointing or boresight coincidence. Because of the unique ability to fold or stow the dual band feed elements for single band operations, the performance definition between single and dual band operations will be reliable and accurate.
    Keywords: COMMUNICATIONS
    Type: AGARD Antennas for Avionics; 10 p
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  • 49
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    Recognition of three dimensional obstacles by an edge detection scheme (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The need for an obstacle detection system on the Mars roving vehicle was assumed, and a practical scheme was investigated and simulated. The principal sensing device on this vehicle was taken to be a laser range finder. Both existing and original algorithms, ending with thresholding operations, were used to obtain the outlines of obstacles from the raw data of this laser scan. A theoretical analysis was carried out to show how proper value of threshold may be chosen. Computer simulations considered various mid-range boulders, for which the scheme was quite successful. The extension to other types of obstacles, such as craters, was considered. The special problems of bottom edge detection and scanning procedure are discussed.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-139661 , RPI-TR-MP-45
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  • 50
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    Effects of turbulence in the atmosphere of Venus on Pioneer Venus radio, phase 2 (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two problems related to the effects of turbulence in the atmosphere of Venus on the Pioneer entry probe radio link were studied. In the first problem, the cross correlation between the log amplitude and phase fluctuations of the Pioneer Venus communications link is examined. Data show that for fluctuation frequencies above approximately 1 Hz there is little or no correlation. For frequencies below this region the correlation is weak and the square root of the coherence has a peak value close to 0.65. The second problem consists of interferring turbulence characteristics of the Venus atmosphere from the Mariner 5 phase fluctuations. Data show that with the data processing techniques developed and currently available, the phase error due to oscillator drift, assumed trajectory delay, and spline curve fit exceed the turbulence induced fluctuations. Results show that it is not possible to interfere with the turbulence characteristics from Mariner 5 phase fluctuations.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139657 , JPL-TM-33-702
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    The potential for congressional use of emergent telecommunications: An exploratory assessment (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A study of the use of newly emerging communications technology for improving the understanding between members of Congress and their constituents was conducted. The study employed a number of specific methodologies such as interdisciplinary systems model building, technology analysis, a sample survey, and semi-structured interviews using sketches of the emergent channels. The following configurations were identified as representative of emergent channel characteristics: (1) the teleconference, (2) the videoconference, (3) the videophone, (4) cable television, (5) cable television polling, and (6) information retrieval. Analysis of the interview data resulted in an overview of the current congressional-constituent communication system and an assessment of the potential for emergent telecommunications, as perceived by congressmen and senior staff from 40 offices in the stratified judgement sample.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139669 , GWPS-MON-20
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  • 52
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    Variably positioned guide vanes for aerodynamic choking (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A choking device to cause a sonic barrier to be formed which reduces the transmission of noise in a direction opposed to the direction of air flow in a compressor that may be part of an aircraft gas turbine engine is described. The noise reduction is accomplished by proper shaping and movement of inlet guide vanes, and an actuator is connected to selected guide vanes to effect movement by programmed amounts as required to choke or partially choke within the design range of the axial-flow-air compressor.
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  • 53
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    Performance evaluation of a second-generation elastic loop mobility system (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Tests were conducted to evaluate the mobility performance of a second-generation Elastic Loop Mobility System (ELMS II). Performance on level test lanes and slopes of lunar soil simulant (LSS) and obstacle-surmounting and crevasse-crossing capabilities were investigated. In addition, internal losses and contact pressure distributions were evaluated. To evaluate the soft-soil performance, two basic soil conditions were tested: loose (LSS1) and dense (LSS5). These conditions embrace the spectrum of soil strengths tested during recent studies for NASA related to the mobility performance of the LRV. Data indicated that for the tested range of the various performance parameters, performance was independent of unit load (contact pressure) and ELMS II drum angular velocity, but was influenced by soil strength and ELMS pitch mode. Power requirements were smaller at a given system output for dense soil than for loose soil. The total system output in terms of pull developed or slope-climbing capability was larger for the ELMS II operating in restrained-pitch mode than in free-pitch mode.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-139531 , M-74-7
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    MSFC Skylab neutral buoyancy simulator (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The use of a neutral buoyancy simulator for developing extravehicular activity systems and for training astronauts in weightless activities is discussed. The construction of the facility and the operations are described. The types of tests and the training activities conducted in the simulator are reported. Photographs of the components of the simulator and actual training exercises are included.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-64844
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  • 55
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    CVT/GPL phase 2 integrated testing (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Experiments representing earth observations, space physics, and material sciences disciplines were installed in the General Purpose Laboratory (GPL). The experiments and the GPL are described. The experiments interfaces the GPL and GPL support systems are assessed. The experiments were cloud physics, ionospheric disturbances, material sciences, high energy astronomy, and superfluid helium.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-64861
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  • 56
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    Analysis of the proposed utilization of TDRS system by the HEAO-C satellite (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The primary function of the study was to assess the impact upon the HEAO telecommunications system of the proposed relay satellite-to-ground-link configuration. The system is designed to perform the function of most of the NASA ground tracking and communications network at a net cost savings for NASA.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139393
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    An application of queueing theory to the design of channel requirements for special purpose communications satellites (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Special purpose satellites are very cost sensitive to the number of broadcast channels, usually will have Poisson arrivals, fairly low utilization (less than 35%), and a very high availability requirement. To solve the problem of determining the effects of limiting C the number of channels, the Poisson arrival, infinite server queueing model will be modified to describe the many server case. The model is predicated on the reproductive property of the Poisson distribution.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-71590
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  • 58
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    Simulators' validation study: Problem solution logic (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A study was conducted to validate the ground based simulators used for aircraft environment in ride-quality research. The logic to the approach for solving this problem is developed. The overall problem solution flow chart is presented. The factors which could influence the human response to the environment on board the aircraft are analyzed. The mathematical models used in the study are explained. The steps which were followed in conducting the validation tests are outlined.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-138305 , MEMO-403213
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  • 59
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    Tracking and Data Relay Satellite System (TDRSS), users' guide (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The system concept and characteristics are described along with support and orbital coverage capabilities. Information on user acquisition procedures is given. System impact on single and multiple access users is discussed.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70710 , X-805-74-176
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  • 60
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    An integral equation formulation for predicting radiation patterns of a space shuttle annular slot antenna (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An integral equation formulation is applied to predict pitch- and roll-plane radiation patterns of a thin VHF/UHF (very high frequency/ultra high frequency) annular slot communications antenna operating at several locations in the nose region of the space shuttle orbiter. Digital computer programs used to compute radiation patterns are given and the use of the programs is illustrated. Experimental verification of computed patterns is given from measurements made on 1/35-scale models of the orbiter.
    Keywords: COMMUNICATIONS
    Type: NASA-TN-D-7594 , L-9279
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  • 61
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    Channel coding and data compression system considerations for efficient communication of planetary imaging data (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: End-to-end system considerations involving channel coding and data compression which could drastically improve the efficiency in communicating pictorial information from future planetary spacecraft are presented.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139362 , JPL-TM-33-695
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    The cryogenic wind tunnel for high Reynolds number testing (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Experiments performed at the NASA Langley Research Center in a cryogenic low-speed continuous-flow tunnel and in a cryogenic transonic continuous-flow pressure tunnel have demonstrated the predicted changes in Reynolds number, drive power, and fan speed with temperature, while operating with nitrogen as the test gas. The experiments have also demonstrated that cooling to cryogenic temperatures by spraying liquid nitrogen directly into the tunnel circuit is practical and that tunnel temperature can be controlled within very close limits. Whereas most types of wind tunnel could operate with advantage at cryogenic temperatures, the continuous-flow fan-driven tunnel is particularly well suited to take full advantage of operating at these temperatures. A continuous-flow fan-driven cryogenic tunnel to satisfy current requirements for test Reynolds number can be constructed and operated using existing techniques. Both capital and operating costs appear acceptable.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-70207
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    System design optimization for a Mars-roving vehicle and perturbed-optimal solutions in nonlinear programming (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Work in two somewhat distinct areas is presented. First, the optimal system design problem for a Mars-roving vehicle is attacked by creating static system models and a system evaluation function and optimizing via nonlinear programming techniques. The second area concerns the problem of perturbed-optimal solutions. Given an initial perturbation in an element of the solution to a nonlinear programming problem, a linear method is determined to approximate the optimal readjustments of the other elements of the solution. Then, the sensitivity of the Mars rover designs is described by application of this method.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-138817 , RPI-TR-MP-43
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    Low-cost, air mass 2 solar simulator (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A low cost air mass 2 solar simulator for testing flat-plate solar collectors was developed and operated at Lewis. Total cost was less than $10,800/sq m ($1000/sq ft). It consists of an array of 143 tungsten-halogen 300-watt lamps, each having integral dichroic coated reflectors. A second array of 143 respective hexagonal-shaped plastic Fresnel lenses are located approximately 1 focal length from the lamps. The simulator will produce a uniform collimated beam covering an area of 1.2 by 1.2m(4 by 4 ft). Design features, construction details, and component costs are given, as well as measured results on a 12-lamp prototype.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-3059 , E-7885
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    Engineering information on an Analog Signal to Discrete Time Interval Converter (ASDT-IC) (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An electronic control system for nondissipative dc power converters is presented which improves (1) the routinely attainable static output voltage accuracy to the order of + or - 1% for ambient temperatures from -55 to 100 C and (2) the dynamic stability by utilizing approximately one tenth of the feedback gain needed otherwise. Performance is due to a functional philosophy of deterministic pulse modulation based on pulse area control and to an autocompensated signal processing principle. The system can be implemented with commercially available unselected components.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-134544
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    Flush-mounted dielectric-loaded axial slot on circular cylinder (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: The theory, computer program, and numerical results of an investigation of an axial slot antenna on a circular cylinder are discussed. The cylinder is partially coated with a dielectric layer and the antenna radiates through a flush mounted window. The study was conducted to determine the effects of a high temperature dielectric layer on the performance of antennas mounted on a space shuttle. Mathematical models are developed to show the relationships of the parameters. Curves are developed to compare the theoretical and actual far field radiation patterns.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138752 , ESL-2902-17
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    Mode conversion in periodically disturbed thin-film waveguides (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Mode conversion in a periodically perturbed thin-film optical waveguide is studied in detail. Three different types of perturbations are considered: periodic index of refraction of the film, periodic index of refraction of the substrate, and periodic boundary. The applications in filters, mode converters, and distributed feedback lasers are discussed.
    Keywords: COMMUNICATIONS
    Type: Journal of Applied Physics; 45; Aug. 197
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    Optimum frame synchronization for biorthogonally coded data (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Many recent American unmanned planetary probes have used biorthogonally coded spacecraft-to-earth telemetry links. An examination of the frame-synchronization (sync) techniques employed on these missions revealed that they were not specifically designed for coded data. This led to a consideration of the optimum frame-sync problem for biorthogonally coded data received over the additive white Gaussian noise (AWGN) channel and decoded prior to sync acquisition. A frame-sync algorithm for biorthogonally coded data based on a super-symbol distance rule is proposed, along with a corresponding selection criterion for the sync sequence. It is argued heuristically that this approach is optimum with regard to minimizing the probability of false synchronization.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Communications; COM-22; Aug. 197
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    Ionospheric irregularities causing scintillation of GHz frequency radio signals (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Consideration of the recently observed phenomenon of scintillation of satellite signals at GHz frequency range. Based on the scintillation data and results from in situ measurements, several ionospheric irregularity models with different power spectra are studied. Scintillation index is computed for the various models and compared with observed results. Both magnitude and frequency dependence of the scintillation index are investigated. It is found that a thick irregularity slab of the order of 200 km with an electron density fluctuation of about 20 per cent of its background value and with a nonmonotonic power spectrum may account for the maximum observed values of the scintillation index as well as its frequency dependence. Some future observations and measurements are suggested.
    Keywords: COMMUNICATIONS
    Type: Journal of Atmospheric and Terrestrial Physics; 36; May 1974
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    Design features and operational characteristics of the Langley pilot transonic cryogenic tunnel (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A fan-driven transonic cryogenic tunnel was designed, and its purging, cooldown, and warmup times were determined satisfactory. Cooling with liquid nitrogen is at the power levels required for transonic testing. Good temperature distributions are obtained by using a simple nitrogen injection system.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-72012
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    Calibration of the Langley 16-foot transonic tunnel with test section air removal (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The Langley 16-foot transonic tunnel with test section air removal (plenum suction) was calibrated to a Mach number of 1.3. The results of the calibration, including the effects of slot shape modifications, test section wall divergence, and water vapor condensation, are presented. A complete description of the wind tunnel and its auxiliary equipment is included.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TR-R-423 , L-9326
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    KSC maintenance capability (laboratories and shops) (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A summary of laboratory and shop facilities at Kennedy Space Center that are available to provide a baseline to the offline maintenance requirements for the space shuttle program is provided.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-70380 , KSC-GP-1037
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    Lunar module voice recorder (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: A feasibility unit suitable for use as a voice recorder on the space shuttle was developed. A modification, development, and test program is described. A LM-DSEA recorder was modified to achieve the following goals: (1) redesign case to allow in-flight cartridge change; (2) time code change from LM code to IRIG-B 100 pps code; (3) delete cold plate requirements (also requires deletion of long-term thermal vacuum operation at 0.00001 MMHg); (4) implement track sequence reset during cartridge change; (5) reduce record time per cartridge because of unavailability of LM thin-base tape; and (6) add an internal Vox key circuit to turn on/off transport and electronics with voice data input signal. The recorder was tested at both the LM and shuttle vibration levels. The modified recorder achieved the same level of flutter during vibration as the DSEA recorder prior to modification. Several improvements were made over the specification requirements. The high manufacturing cost is discussed.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140305
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    Computer Program for Thin Wire Antenna over a Perfectly Conducting Ground Plane (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A computer program is presented for a thin-wire antenna over a perfect ground plane. The analysis is performed in the frequency domain, and the exterior medium is free space. The antenna may have finite conductivity and lumped loads. The output data includes the current distribution, impedance, radiation efficiency, and gain. The program uses sinusoidal bases and Galerkin's method.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140622 , Technical Report 2902-19
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    Channel coding and data compression system considerations for efficient communication of planetary imaging data (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: End-to-end system considerations involving channel coding and data compression are reported which could drastically improve the efficiency in communicating pictorial information from future planetary spacecraft. In addition to presenting new and potentially significant system considerations, this report attempts to fill a need for a comprehensive tutorial which makes much of this very subject accessible to readers whose disciplines lie outside of communication theory.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-140181 , JPL-TM-33-695-REV-1
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    Dynamic Docking Test System (DDTS) active table frequency response test results (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results are presented of the frequency response test performed on the dynamic docking test system (DDTS) active table. Sinusoidal displacement commands were applied to the table and the dynamic response determined from measured actuator responses and accelerometers mounted to the table and one actuator.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-140285 , D2-118546-1
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    Mathematical model for the simulation of Dynamic Docking Test System (DDST) active table motion (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The mathematical model developed to describe the three-dimensional motion of the dynamic docking test system active table is described. The active table is modeled as a rigid body supported by six flexible hydraulic actuators which produce the commanded table motions.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-140288 , D2-118544-1
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    Analyses of the dynamic docking test system for advanced mission docking system test programs (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Results are given of analytical studies performed in support of the design, implementation, checkout and use of NASA's dynamic docking test system (DDTS). Included are analyses of simulator components, a list of detailed operational test procedures, a summary of simulator performance, and an analysis and comparison of docking dynamics and loads obtained by test and analysis.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-140286 , D2-118470-2
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    Optimal filter design subject to output sidelobe constraints - Theoretical considerations (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The design of filters for detection and estimation in radar and communications systems is considered, with inequality constraints on the maximum output sidelobe levels. A constrained optimization problem in Hilbert space is formulated, incorporating the sidelobe constraints via a partial ordering of continuous functions. Generalized versions (in Hilbert space) of the Kuhn-Tucker and duality theorems allow the reduction of this problem to an unconstrained one in the dual space of regular Borel measures.
    Keywords: COMMUNICATIONS
    Type: Journal of Optimization Theory and Applications; 14; Aug. 197
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    A novel method for measuring the polarization angle of satellite radio waves (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: One of the most important parameters for the study of the physics of the ionosphere is the columnar electron content. This can be obtained indirectly by measuring the Faraday rotation of signals emitted from satellites. Many different types of polarimeters have been developed for this purpose. Efforts to develop a new type of polarimeter, suitable for extensive network operation, led to a novel technique for measuring the polarization angle.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-10; July 197
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    Computer algorithm for coding gain (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Development of a computer algorithm for coding gain for use in an automated communications link design system. Using an empirical formula which defines coding gain as used in space communications engineering, an algorithm is constructed on the basis of available performance data for nonsystematic convolutional encoding with soft-decision (eight-level) Viterbi decoding.
    Keywords: COMMUNICATIONS
    Type: IEEE Transactions on Aerospace and Electronic Systems; AES-10; Mar. 197
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    A new wideband, fully steerable, decametric array at Clark Lake (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A new, fully steerable, decametric array for radio astronomy is under construction at the Clark Lake Radio Observatory near Borrego Springs, California. This array will be a T of 720 conical spiral antennas (teepee-shaped antennas, hence the array is called the TPT), 3.0 by 1.8 km capable of operating between 15 and 125 MHz. Both its operating frequency and beam position will be adjustable in less than one msec, and the TPT will provide a 49-element picture around the central beam position for extended-source observations. Considerable experience has been gained in the operation of completed portions of the array, and successful operation of the final array is assured. This paper describes the results of the tests which have been conducted with the conical spirals and outlines the planned electronics.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: Radio Science; 9; Mar. 197
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    Multiple beam communicating satellites with remote beam steering and beam shaping (1974)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Multiple beam phased arrays are shown to enhance the performance of several anticipated geostationary communications satellite programs because of the greater efficiency and flexibility of the phased array. It is shown that the efficiency of arrays can be significantly greater than corresponding multiple feed dishes and that the problems of crossover loss and performance degradation with parts failures are thereby avoided. On an open loop basis, it is shown that a multiple beam array can provide higher EIRP over a coverage area. On a closed loop basis, it is shown that an adaptive array can provide nulling of unwanted signals while simultaneously providing gain in the direction of a desired signal.
    Keywords: COMMUNICATIONS
    Type: AIAA PAPER 72-566
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    Skylab extravehicular mobility unit thermal simulator (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The analytical methods, thermal model, and user's instructions for the Skylab Extravehicular Mobility Unit (SEMU) routine are presented. This digital computer program was developed for detailed thermal performance predictions of the SEMU on the NASA-JSC Univac 1108 computer system. It accounts for conductive, convective, and radiant heat transfer as well as fluid flow and special component characterization. The program provides thermal performance predictions for a 967 node thermal model in one thirty-sixth (1/36) of mission time when operated at a calculating interval of three minutes (mission time). The program has the operational flexibility to: (1) accept card or magnetic tape data input for the thermal model describing the SEMU structure, fluid systems, crewman and component performance, (2) accept card and/or magnetic tape input of internally generated heat and heat influx from the space environment, and (3) output tabular or plotted histories of temperature, flow rates, and other parameters describing system operating modes.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-134389 , T194-06
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    Roll plane analysis of on-aircraft antennas (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The roll plane radiation patterns of on-aircraft antennas are analyzed using high frequency solutions. This is a basic study of aircraft-antenna pattern performance in which the aircraft is modelled in its most basic form. The fuselage is assumed to be a perfectly conducting elliptic cylinder with the antennas mounted near the top or bottom. The wings are simulated by arbitrarily many sided flat plates and the engines by circular cylinders. The patterns in each case verified by measured results taken on simple models as well as scale models of actual aircraft.
    Keywords: COMMUNICATIONS
    Type: AGARD Antennas for Avionics; 23 p
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    Propeller modulation effects on a scanning beam microwave landing system (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An investigation to assess the modulation effects on microwave signals transmitted through rotating propeller blades. Interruption of the antenna line-of-sight signal by the rotating propeller causes a variation of path loss, which produces essentially an amplitude modulation of the received signal. This interruption or blockage effect is generally only partial because of edge diffraction around the particular interfering propeller blade. Signals reflected from the rotating propeller will also cause Doppler frequency shifts to be present in the received signals. A scanning beam microwave landing system (MLS) known as MODILS (modular instrument landing system) was used to process the received signals for display. The effects of propeller modulation were studied by varying the following parameters: (1) spacing between propeller and receiving antenna, (2) propeller dimensions, (3) propeller speed (rpm), (4) number of propeller blades, (5) system data rate, (6) receiver response time, and (7) receiver antenna aperture.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-62368
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    A wind model for an elevated STOL-port configuration (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Measurements of mean velocity magnitude and direction as well as three-dimensional turbulence intensity were made in the flow over a model of an elevated STOL-port. A 1:300 scale model was placed in a wind tunnel flow simulating the mean velocity profile and turbulence characteristics of atmospheric winds over a typical city environment excluding detailed wake structures of possible nearby buildings. Hot-wire anemometer measurements of velocity and turbulence were made along approach and departure paths of aircraft operating on the runway centerline and at specified lateral distances from the centerline. Approach flow directions simulated were 0 and 30 degrees to the runway centerline.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-CR-2450
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    The use of an aircraft test stand for VTOL handling qualities studies (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The VTOL flight tests stand for testing control concepts on the X-14B VSS aircraft in hover, is described. This stand permits realistic and safe piloted evaluation and checkout of various control systems and of parameter variations within each system to determine acceptability to the pilot. Pilots can use it as a practical training tool to practice procedures and flying techniques and become familiar with the aircraft characteristics. Some examples of test experience are given. The test stand allows the X14B to maneuver in hover from centered position + or - 9.7 deg in roll and + or - 9.3 deg in pitch, about + or - 6 deg in yaw, and + or - 15 cm in vertical translation. The unique vertical free flight freedom enables study of liftoffs and landings with power conditions duplicated. The response on the stand agrees well with that measured in free hovering flight, and pilot comments confirm this.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-62218
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    Supersonic fan blading (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Radially extending rotor blades are disposed on a hub to form a supersonic propulsion fan for a turbofan engine. The peripheral spacing of the blades is such as to avoid forming a channel or passageway between adjacent blades. Each has a flat trailing surface extending from the leading edge at least as far to the rear as to cause any pressure waves which might originate on the blade surface to strike the leading surface of the following blade rather than propagate upstream of the blade row. The flat trailing surface of each blade makes an angle with the axis of rotation such that the blade is parallel to a gas inflow into the blades.
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    Jet exhaust noise suppressor (1974)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Noise suppression for a jet engine exhaust is provided by an annular divergent body attached to an exhaust nozzle. The smallest diameter of the divergent body is larger than the diameter of the exhaust nozzle exit to form an annular step which produces a shock wave in the exhaust as it passes the step. An annular shroud is disposed around the divergent body and causes outside air to pass through voids in the divergent body to mix with the jet exhaust gas. The divergent body includes a plurality of channels with separators between the channels.
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    The influence of polarization on millimeter wave propagation through rain (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The influence of polarization on millimeter wave propagation through rain is investigated. The experimental equipment consisted of a 1.43 km line-of-sight path with 4-foot diameter dual-polarized parabolic reflector antennas at each end. Linearly polarized 17.65 GHz signals were transmitted with the electric field vectors at plus 45 degrees and minus 45 degrees from the vertical. These polarizations were initially chosen to maximize the measured depolarization at any given rainfall rate. Later it was discovered that the cross polarization levels measured with plus or minus 45 degree linearly polarized signals are theoretically the least sensitive to variations in drop canting angle and this choice of polarization reduces the scatter in the data.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138150 , IR-2
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    A study of KC-135 aircraft antenna patterns (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Numerical solutions for the radiation patterns of aircraft antennas are evaluated. Designing and locating antennas in order to achieve the desired performance is discussed. The high frequency solutions presented in this report are based on fuselage antennas mounted on a general-type aircraft but applied specifically to the KC-135 aircraft. The roll and elevation plane patterns are computed for a monopole, axial slot, and circumferential slot mounted both over and forward of the wings. In each case the calculated patterns compare very favorably with the measured patterns. The precision pattern measurements were taken on a 1/25 scale model of the KC-135 aircraft at NASA (Langley, Virginia) with special emphasis on reducing the mount and background effects.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138585 , ESL-3001-9
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    NASA Lewis 8 by 6 foot supersonic wind tunnel (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Performance data are presented for the tunnel, which has a Mach number range from 0.36 to 2.0. The tunnel circuit, test section, model support systems, auxiliary systems, instrumentation, control room equipment, and automatic recording and computing equipment are also described. Information is presented on criteria for designing models and on shop facilities available to prospective users.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-71542 , E-7949
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    Mission and spacecraft support functions of the Materials Engineering Branch: A space oriented technology resource (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The capabilities of the Materials Engineering Branch (MEB) of the Goddard Space Flight Center, Greenbelt, Maryland, are surveyed. The specific functions of spacecraft materials review, materials processing and information dissemination, and laboratory support, are outlined in the Activity Report. Further detail is provided by case histories of laboratory satellite support and equipment. Project support statistics are shown, and complete listings of MEB publications, patents, and tech briefs are included. MEB staff, and their respective discipline areas and spacecraft liaison associations, are listed.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-70663 , X-755-74-152
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    Operating characteristics of the Langley Mach 10 high Reynolds number helium tunnel (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Operating characteristics of the Langley Mach 10 high Reynolds number helium tunnel are presented for stagnation pressures from 138 N/sq cm to 1655 N/sq cm. The characteristics include detailed Mach number surveys in the test section from which usable core size and regions of disturbed flow were determined, preliminary blockage test results, and maximum run time to be expected at various stagnation pressures. Important tunnel dimensions including details of the model mounting apparatus are given. Measurements show the variation in average core Mach number in the test section to be between 9.4 and 10 for the present range of test conditions. The core radius is from 23 cm to 31.5 cm, depending on stagnation pressure and axial location in the test section.
    Keywords: FACILITIES, RESEARCH, AND SUPPORT
    Type: NASA-TM-X-2955 , L-9259
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    Satellite to aircraft multipath signals over the ocean (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A satellite-to-aircraft communication link over the ocean may include a specularly reflected signal and a diffusely scattered signal, as well as the direct path transmission. A computer program is provided for estimating two statistical properties of the diffuse signal, namely the Doppler spectrum and the delay spectrum. A convenient representation of the total signal is also provided. Examples of the Doppler and delay spectra for a number of representative link geometries are given to illustrate the features of the diffuse signal.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-138578 , ESL-3266-2
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    Aperture excited dielectric antennas (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.
    Keywords: COMMUNICATIONS
    Type: NASA-TN-D-7342 , L-8920
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    Variable-beamwidth monopulse antennas (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The merits of nine methods for zooming microwave amplitude-sensing monopulse antenna patterns are discussed. Of these, six are directly related to the TDRSS (Tracking Data Relay Satellite System) and are compatible with a deployable-mesh pseudo-paraboloidal main reflector. The remaining three methods utilize radically different geometrical configurations that depart considerably from the TDRSS parameters existing at this time. Preservation of the monopulse postulates is considered to be of prime importance for any variable-beamwidth candidate, however, it is allowed that approximate satisfaction of the postulates should be accepted for practical reasons. All of the methods discussed admit free choice of the polarization state, and the zooming function is never predicated on polarization. Exploration of the zooming techniques was carried out almost entirely by means of the Kirchhoff-Kottler vector diffraction program. The program generates electric and magnetic field intensity, associated phase, and time-average Poynting vector power flow in the intermediate near-field and far-field zones in both receive and transmit modes of operation. A few of the concepts have been verified experimentally with excellent agreement between theory and practice.
    Keywords: COMMUNICATIONS
    Type: NASA-TM-X-70650 , X-811-74-62
    Format: application/pdf
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    Channel simulation for direct-detection optical communication systems (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A technique is described for simulating the random modulation imposed by atmospheric scintillation and transmitter pointing jitter on a direct-detection optical communication system. The system is capable of providing signal fading statistics which obey log-normal, beta, Rayleigh, Ricean, or chi-square density functions. Experimental tests of the performance of the channel simulator are presented.
    Keywords: COMMUNICATIONS
    Type: NASA-TN-D-7641 , G-7439
    Format: application/pdf
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    Spaceborne synthetic aperture radar pilot study (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A pilot study of a spaceborne sidelooking radar is summarized. The results of the system trade studies are given along with the electrical parameters for the proposed subsystems. The mechanical aspects, packaging, thermal control and dynamics of the proposed design are presented. Details of the data processor are given. A system is described that allows the data from a pass over the U. S. to be in hard copy form within two hours. Also included are the proposed schedule, work breakdown structure, and cost estimate.
    Keywords: COMMUNICATIONS
    Type: NASA-CR-139004
    Format: application/pdf
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