Engineering topics

Harvey, G. A.

Publications and source records attributed to Harvey, G. A..

33 records · Page 2

NASA NTRS1974

Strongly differentiated material in high-inclination and retrograde orbits

Two definitive spectra of strongly differentiated meteors are discussed. The meteors entered the earth's atmosphere at velocities greater than 40 km/sec from high-inclination and retrograde orbits. Both were magnesium-calcium particles, and their spectra show them to be highly deficient in iron and sodium. The moon and the asteroids have been discussed as sources of such calcium-rich achondrites, but these sources give low or intermediate geocentric velocities. Long-period comets and meteoroids of probable cometary origin are the only objects now known to have orbits similar to the orbits of these two meteors.

Harvey, G. A.↗

NASA NTRS1973

Note on the 1972 Giacobinid meteor shower.

It is shown that the 1972 Giacobinid meteor shower was extremely weak with a peak activity of two to three visual meteors per hour. Only two meteor spectra were obtained from the 17 slitless spectrograph systems operated by the Langley Research Center. The largely unexpected, essentially null results of the 1972 Giacobinid meteor shower observations are indicative of the present limited understanding and predictability of cosmic dust storms.

Harvey, G. A.↗

NASA NTRS1973

Elemental abundance determinations for meteors by spectroscopy.

Relative elemental abundance determinations for meteors by spectroscopy are discussed. Relative abundances of spectroscopically accessible elements of four major shower meteors and one sporadic meteor are presented. A sporadic meteor with dominant sodium radiation and an iron-deficient sporadic meteor are analyzed. Empirical and theoretical tests for self-absorption in optical meteor plasmas have been conducted. Both ionization and incomplete dissociation are found to severely deplete certain neutral atoms from meteor plasmas.

Harvey, G. A.↗

NASA NTRS1973

Apparatus for photographing meteors

Apparatus for photographing meteors in a selected area of the sky is described. A photomultiplier is pointed in the direction of the area. When a meteor passes through the area the signal output of the photomultiplier increases. Means are provided that activate a camera, pointed at the area, in response to an increased signal from the photomultiplier. Hence, the camera photographs the selected are only while meteors are likely to be passing through the area.

Harvey, G. A.↗

NASA NTRS1973

Spectral analysis of four meteors

Four meteor spectra are analyzed for chemical composition and radiative processes. The chemical compositions of the Taurid, Geminid, and Perseid meteors were found to be similar to that of a typical stony meteorite. The chemical composition of the sporadic meteor was found to be similar to that of a nickel iron meteorite. The radiation from optical meteors was found to be similar to that of a low temperature gas, except that strong, anomalous ionic radiation is superposed on the neutral radiation in bright, fast meteors.

Harvey, G. A.↗

NASA NTRS1973

NASA-LRC faint meteor spectra

A brief description is given of the instrumentation, the facilities, and the patrol technique used by the NASA faint meteor spectra patrol. A classification of 500 meteor spectra obtained in the first 2-1/2 years of the patrol is reported. The general characteristics of typical spectra are discussed and preliminary conclusions drawn. Examples of unusual spectra are briefly described.

Harvey, G. A.↗

NASA NTRS1971

The NASA LRC Faint Meteor Spectra Patrol

Composition and mass data analysis of meteoroids in 1 milligram to 1 gram range using NASA LRC Faint Meteor Spectra Patrol data

Harvey, G. A.↗

NASA NTRS1971

The calcium H- and K-line anomaly in meteor spectra

Calcium H and K line anomaly in faint meteor spectra, discussing brightness correlation with aerodynamic flow and resonant charge exchange with ionized nitrogen

Harvey, G. A.↗

NASA NTRS1971