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Engineering topics

Mcelroy, M. B.

Publications and source records attributed to Mcelroy, M. B..

72 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

The atmosphere and ionosphere of Io

Models for Jupiter's innermost Galilean satellite's atmosphere, ionosphere, and sodium airglow are developed on the basis of recent observational data. The sodium emission detected by Brown (1973) is seen to require a collisional excitation process in Io's atmosphere, while the extended sodium emission measured by Trafton et al. (1974) may require scattering of the planetary radiation by an extended sodium cloud. The sodium is presumably present in bound form on Io's surface, and may be released by a sputtering mechanism proposed by Matson et al. (1974). The ionosphere detected by a radio occultation experiment on Pioneer 10 could be attributed to photoionization of atmospheric sodium, provided Io's atmosphere could sustain significant upward motions during daytime and downward motions during nighttime. The incomplete hydrogen torus observed by Judge and Carlson (1974) in the vicinity of Io appears to require a large supply of hydrogen from the satellite's atmosphere. Implications of the hydrogen torus for the energy and mass balance of Jupiter's magnetosphere are discussed.

Mcelroy, M. B.↗
NASA NTRS1975

Freon consumption - Implications for atmospheric ozone

Freons are a potential source of stratospheric chlorine and may indirectly cause serious reductions in the concentration of ozone. The reduction could be as large as 3 percent by 1980, or 16 percent by 2000, if Freon consumption were to grow at 10 percent per year. Even if Freon use were terminated as early as 1990, it could leave a significant effect which might endure for several hundred years.

Wofsy, S. C.↗
NASA NTRS1975

Engineering models of the Mars atmosphere

Engineering models of the Mars atmosphere are presented for use in spacecraft design and mission planning. The models are developed from (1) data measured by the U.S. Mariner 4, 6, 7, and 9 and USSR Mars 2 and 3 spacecraft, (2) earth-based measurements, and (3) theory which best satisfies the observations. The models include a nominal model for a clear atmosphere, a model for a dusty atmosphere, and models that encompass reasonable extremes of exospheric temperature. In addition to the basic engineering models, other atmospheric characteristics affecting the models are discussed including clouds, ionosphere and atmospheric dynamics.

Noll, R. B.↗
NASA NTRS1974

Mercury's atmosphere from Mariner 10 - Preliminary results

Analysis of data obtained by the ultraviolet experiment on Mariner 10 indicates that Mercury is surrounded by a thin atmosphere consisting in part of helium. The partial pressure of helium at the terminator is about 5 trillionths of a millibar. The total surface pressure of the atmosphere is less than about 2 billionths of a millibar. Upper limits are set for the abundance of various gases, including hydrogen, oxygen, carbon, argon, neon, and xenon. The wavelength dependence of Mercury's surface albedo is similar to that of the moon over a broad range of wavelengths from 500 to 1600 A. Strong signals were recorded by the airglow instrument as Mariner 10 passed through the cavity behind Mercury. They are as yet unexplained but may provide information on the properties of the local plasma.

Broadfoot, A. L.↗
NASA NTRS1974

Jupiter's ionosphere - Prospects for Pioneer 10

Model Jovian ionospheres are constructed for comparison with Pioneer 10 results. Electron density maxima are predicted at a level approximately 220 kilometers above an assumed reference height where the hydrogen density is 10 to the 16-th power molecules per cubic centimeter. It may be possible to use observations of the electron density to locate the turbopause. Attention is drawn to a possible strong source of ionized sodium from Io which might lead to large electron densities at low altitudes.

Atreya, S. K.↗
NASA NTRS1974

Ultraviolet observations of Venus from Mariner 10 - Preliminary results

An objective grating spectrometer on Mariner 10 has measured airglow in the wavelength range 200 to 1700 angstroms. The data reveal the presence of significant concentrations of hydrogen, helium, carbon, and oxygen atoms in the upper atmosphere of Venus. A preliminary analysis of the hydrogen data indicates an exospheric temperature of 400 K. There is evidence for intense airglow emission at wavelengths longward of 1350 angstroms; the nature of this emission is unclear, but the radiation is spatially extensive and detectable on both day and night sides of the planet.

Broadfoot, A. L.↗
NASA NTRS1973

Engineering models of the Venus atmosphere.

Engineering models of the Venus atmosphere are presented for use in spacecraft design and mission planning. The models are developed from (1) data measured by the U.S. Mariner 5 and USSR Venera spacecraft, (2) earth-based measurements, and (3) theory which best satisfies the observations. The models include a most probable model and models for extremes of molecular mass and solar activity. In addition to the basic engineering models, other atmospheric characteristics and parameters affecting the models are discussed including planetary radius, atmospheric composition and clouds.

Noll, R. B.↗
NASA NTRS1972

Stability of the Martian atmosphere

A detailed chemical dynamic model is presented for a moist Martian atmosphere. Recombination of CO2 is catalyzed by trace amount of H2O. The abundances of CO and O2 should vary in response to changes in atmospheric H2O and atmospheric mixing.

Mcelroy, M. B.↗
NASA NTRS1972

Entry science experiments for Viking 1975.

A review is given of our present knowledge of the Martian atmosphere with special emphasis on the results obtained by the Mariner 4, 6 and 7 fly-bys. The Viking Project offers the first opportunity for in situ measurements which should resolve many questions left open by previous work. A description is given of the neutral gas mass spectrometer and retarding potential analyzer experiments to be performed as the lander enters the upper atmosphere and the experiments planned for determining atmospheric structure as the lander approaches the surface of the planet.

Nier, A. O.↗
NASA NTRS1968

The Atmospheres of Venus and Mars.

Collection of papers on atmospheres of Venus and Mars covering atmospheric models, light scattering, radio occultation experiments, etc

Brandt, J. C.↗