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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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At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1968

Dual frequency (20.0-19.9 kHz) VLF data

Data are presented from 24 months of operation of radio station WWVL. Daily measurements of the 20.0 kHz and 20.0/19.9 kHz signal phase angles corrected in accordance with the NBS measurements are presented in tabular form. The 20.0/19.9 kHz data is a function of the phase angle of the 100 Hz information inherent in the 20.0/19.9 transmissions. This data can be used to resolve the 50 microsecond ambiguity inherent in 20.0 kHz single frequency transmissions.

Looney, C. H.↗
NASA NTRS1972

Electric dipole radiation at VLF in a uniform warm magneto-plasma.

Use of a linear full electromagnetic wave theory to calculate the input impedance of an electric antenna embedded in a uniform, lossless, unbounded warm magnetoplasma, which is assumed to consist of warm electrons and cold ions. In calculating the dipole radiation resistance for the thermal modes and the thermally modified whistler mode the analysis includes the finite temperature only for the electrons. In deriving the formal solution of the warm plasma dipole input impedance a full-wave analysis is used and two antenna orientations are considered, parallel and perpendicular to the static magnetic field. A general dispersion equation governing the modes of propagation is derived and a detailed analysis is made of the propagation characteristics of these modes.

Wang, T. N. C.↗
NASA NTRS1973

Time-synchronized VLF phase-tracking receiver

Coded signals transmitted at very low frequencies by National Bureau of Standards via its radio facility WWVL contain both primary time and frequency information. Synchronization of local time with WWVL signal standard requires comparison of phase differences between transmitted signal and output of traveling atomic clock such as rubidium frequency standard.

Ward, S. C.↗
NASA NTRS1972

The inversion of VLF-LF sounder data to obtain D-region electron-density distributions

The direct problem is to compute reflection coefficients for an assumed electron-density profile, using a full-wave solution. The inverse problem is treated numerically, using derivatives of the reflection matrix with respect to model parameters. A technique for the rapid computation of the derivatives is described. An algorithm for determining resolution in the profile is discussed.

Shellman, C. H.↗
NASA NTRS1972

Omega VLF timing revision 1

The report specifically discusses time dissemination techniques, including epoch determination, frequency determination, and ambiguity resolution. It also discusses operational considerations including equipment, path selection, and adjustment procedure. epoch (the actual location or timing of periodic events) is shown to be both maintainable and calibratable by the techniques described to better than 3-microsecond accuracy; and frequency (the uniformity of the time scale) to about one part in 10 to the 12th power.

Swanson, E. R.↗
NASA NTRS1973

Measurements of VLF polarization and wave normal direction on OGO-F

A major achievement of the F-24 experiment on OGO 6 was a verification of the theory of the polarization of proton whistlers. As predicted, the electron whistler was found to be right-hand polarized and the proton whistler left hand polarized. The transition from right- to left-hand polarization was found to occur very rapidly. Thus it appears that the experimental technique may allow great accuracy in the measurement of the cross-over frequency, a frequency that provides information on the ionic composition of the ionosphere.

Helliwell, R. A.↗
NASA NTRS1972

Interpretation of VLF phase data

The specific applications of very low frequency phase tracking are described. The requirements for correct interpretation of very low frequency phase data are defined. The effects of the lower ionosphere and the ground along the path of signal propagation are analyzed. The following subjects are discussed: (1) interpretation equipment, (2) representation of very low frequency waves, (3) diurnal effects and mode interference phenomena, (4) antipodal interference, and (5) overall effects resulting from solar flares, galactic X-rays, and geomagnetic parameters.

Reder, F.↗