Summary of radio-frequency flame effects on Marshall Space Flight Center vehicles
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Ely, O. P.↗
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Results for “Radio frequency”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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The radio-frequency signal attenuation problem of rocket exhausts
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Mc Iver, D. E., Jr.↗
A very high frequency radio interferometer for investigating ionospheric disturbances using geostationary satellites. Determination of changes in exospheric electron content by a comparison of group delay and Faraday rotation
The theory and development of a VHF correlation radio interferometer for investigating ionospheric disturbances are discussed. The system was developed to receive signals from the geostationary Applications Technology Satellites. Amplitude and phase variations of the signal passing through the ionosphere can be detected by this instrument. The system consists of two superheterodyne receivers separated by a distance known as the baseline of the system. Since the system is a phase sensitive instrument, the local oscillators of the two receivers must be phase coherent. This is accomplished by using phase-locked loops for generating the local oscillators. The two signals from the separate receivers are cross-correlated by multiplying the two signals together and then time averaging the result. The sensitivity of the instrument is increased by off-setting one of the local oscillators by a small amount.
Terry, R.↗
On the effect of electron-neutral particle collisions upon the refraction of high-frequency radio waves by the lower atmosphere and ionosphere of Mars.
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Mccormick, P. T.↗
High radio frequency observations of the Omega nebula.
Observations of M17 at 0.955, 1.65, and 2.73 cm yield flux densities of 575 plus or minus 80, 644 plus or minus 64, and 644 plus or minus 64 flux units. We conclude that M17, although having a very complex angular structure over approximately one square degree of the sky, is composed of sources with thermal spectra.
Johnston, K. J.↗
Radio frequency studies in the NASA Lewis Bumay Torus
The fluctuations in potential of the plasma in the NASA Lewis Bumpy Torus were observed using capacitive probes over frequencies from 1 kHz to 25 MHz and a wide range of operating conditions. The spectra were found to differ greatly above and below a background gas pressure of 3.0.000034 torr deuterium. Above this pressure the spectrum was dominated by the ion spoke frequency and a spectral index was defined. Below this pressure the spectrum below 200 kHz was lower in lower in amplitude by a factor of ten and no spectral index could be defined. At these lower pressures, fluctuations that appeared to be ion spokes were observed, but had a dependence of frequency on operating conditions which was previously unreported.
Gerdin, G. A.↗
Surface electrical properties experiment. Part 2: Theory of radio-frequency interferometry in geophysical subsurface probing
The radiation fields due to a horizontal electric dipole laid on the surface of a stratified medium were calculated using a geometrical optics approximation, a modal approach, and direct numerical integration. The solutions were obtained from the reflection coefficient formulation and written in integral forms. The calculated interference patterns are compared in terms of the usefulness of the methods used to obtain them. Scattering effects are also discussed and all numerical results for anisotropic and isotropic cases are presented.
Kong, J. A.↗
Four Stokes parameter radio frequency polarimetry of a flare from AD Leonis
Observations of the four Stokes parameters of a 430 MHz flare from the UV Ceti-type star AD Leonis are presented. The maximum amplitude of the event was 0.52 flux units and the durations at one-half and one-tenth maximum were 12 and 40 seconds, respectively. The degree of circular polarization at maximum intensity was approximately 56 percent and was later observed to be as high as 92 percent. Linear polarization was also observed at a level of about 21 percent at flare maximum which allowed an upper limit of 440 radians - sq m to be placed on the rotation measure.
Spangler, S. R.↗
Measuring terrestrial radio frequency interference at orbit altitudes
An experiment has been designed to measure and characterize the effect of man-made interference on satellite receivers at orbital altitudes. The experiment, as designed, requires dedicated hardware on a spacecraft of specified orbit and will measure (within the frequency range from 400 MHz to 12.4 GHz) peak levels of interference in cells dimensioned in space, time, and frequency. The experiment will provide data indicative of some of the statistical characteristics of interference levels at satellite orbital altitudes and will provide designers of satellite communications links with new facilities for the prediction and prevention of interference problems.
Bayol, M. E.↗
The ATS-F radio frequency interference measurement experiment
The technical objectives of the uplink interference tests and measurements to be performed during this experiment are set forth as the determination of the integrated interference power from all 6-GHz terrestrial sources sharing the common carrier band with the RF field of view of the ATS-F satellite; the establishment of practical limits of receiver antenna gain-to-noise temperature ratios for satellites sharing the common 6-GHz carrier band; and the determination of the geographical and frequency distribution of 6-GHz terrestrial sources sharing the common carrier band. A brief description of the RF interference measurement system with some details on its hardware and subsystems is included. The performance characteristics of the mission and a measurement program are discussed.
Henry, V. F.↗
A remote operation quadrupole mass spectrometer using a custom radio-frequency link approach
A commercial quadrupole mass spectrometer (residual gas analyzer, RGA) system has been modified to operate at large separations of its electronics console and sensing head. The methods implemented have made practical applications, as well as operation, of such a system possible for the first time. This advance was stimulated by a need for placing sensors at remote (45 or 60 m) chamber locations for space simulation testing of orbital flight spacecraft. Emphasis is placed on instrument functional requirements and describing the hardware changes and adjustment techniques necessary to assure operation at the extended cable lengths.
Tashbar, P. W.↗
Mercury - Results on mass, radius, ionosphere, and atmosphere from Mariner 10 dual-frequency radio signals
Analysis of the radio-tracking data from Mariner 10 yields 6,023,600 plus or minus 600 for the ratio of the mass of the sun to that of Mercury, in very good agreement with values determined earlier from radar data alone. Occultation measurements yielded values for the radius of Mercury of 2440 plus or minus 2 and 2438 plus or minus 2 kilometers at latitudes of 2 N and 68 N, respectively, again in close agreement with the average equatorial radius of 2439 plus or minus 1 kilometers determined from radar data. The mean density of 5.44 grams per cubic centimeter deduced for Mercury from Mariner 10 data thus virtually coincides with the prior determination. No evidence of either an ionosphere or an atmosphere was found.
Esposito, P. B.↗
Radio frequency studies in the NASA Lewis Bumpy Torus
The fluctuations in potential of the plasma in the NASA Lewis Bumpy Torus are observed using capacitive probes over frequencies from 1 kHz to 25 MHz and a wide range of operating conditions. The spectra are found to differ greatly above and below a background gas pressure of .000034 torr deuterium. Above this pressure, the spectrum is dominated by the ion spoke frequency and a spectral index may be defined. Below this pressure, the spectrum below 200 kHz is lower in amplitude by a factor of ten and no spectral index can be defined. At these lower pressures, fluctuations appearing to be ion spokes are observed, but have a dependence of frequency on operating conditions which is previously unreported.
Gerdin, G. A.↗
The effect of radio frequency interference on the 136- to 138-MHz return link and 400.5- to 401.5-MHz forward link of the Tracking and Data Relay Satellite System
The purpose is to update the RFI estimates in the 136- to 138-MHz VHF band and to make estimates for the first time for the 400.5- to 401.5-MHz UHF band. These preliminary predictions are based on primarily ITU frequency-registration data, with missing data bridged by engineering judgement.
Jenny, J.↗
Design development and manufacture of a breadboard radio frequency mass gauging system. Volume 1: Phase B final report
The applicability of the RF Mode Counting technique for gauging liquid oxygen and liquid hydrogen under all attitude conditions was demonstrated using a vacuum jacketed test tank mounted on a remotely controlled gimbaling mechanism. In addition, the technique was successfully tested using liquid oxygen in a large NASA test tank as the tank was filled and emptied. To further substantiate the capabilities of the RF Mode Counting technique as applied to applications involving zero gravity conditions, a test system using benzene as a test fluid was flight tested in a KC-135 test aircraft. This testing involved a number of zero "g" maneuvers with various quantities of the test fluid. A series of tests were also performed to evaluate the relative effects of the presence of capillary liquid retention screens on the RF Gauging technique. These tests involved considerations of system Q reductions, RF leakage through retention screens, and surface wetting effects.
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Design, development and manufacture of a breadboard radio frequency mass gauging system
The feasibility of the RF gauging mode, counting technique was demonstrated for gauging liquid hydrogen and liquid oxygen under all attitude conditions. With LH2, it was also demonstrated under dynamic fluid conditions, in which the fluid assumes ever changing positions within the tank, that the RF gauging technique on the average provides a very good indication of mass. It is significant that the distribution of the mode count data at each fill level during dynamic LH2 and LOX orientation testing does approach a statistical normal distribution. Multiple space-diversity probes provide better coupling to the resonant modes than utilization of a single probe element. The variable sweep rate generator technique provides a more uniform mode versus time distribution for processing.
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A low-frequency radio survey of the planets with RAE-2
Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer-2 (RAE-2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025 to 13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE-2.
Kaiser, M. L.↗
ATS-6 - Radio Frequency Interference Measurement Experiment
The frequency band from 5.925 to 6.425 GHz is served by fixed satellites and by terrestrial microwave links. There is a possibility of microwave links pointed at the horizon causing interference to the uplinks of domestic and international communications satellites sharing the same frequency band. A mathematical model has been derived for predicting the fields at geostationary orbit based on the known characteristics and known distribution of the terrestrial microwave relay system. The Applications Technology Satellite-6 (ATS-6) is sensitive to signals in the range of 10 dBW radiated in the direction of the satellite. Signals in the range of 10-30 dBW have been recorded over various parts of the United States.
Henry, V. F.↗