Engineering topics

Wallace, L.

Publications and source records attributed to Wallace, L..

16 records

NASA NTRS1979

High-resolution spectra of Jupiter in the 744-980 inverse centimeter spectral range

Spectra of the central 5 in region of Jupiter in the 744 to 980 kayser spectral range are presented at 0.05 and 0.28 kayser resolution. The gases (N-14)H3, (N-15)H3, and PH3 are observed in absorption, and C2H2 and C2H6 observed in emission. A synthetic spectrum which included the opacity from the H2, (N-14)H3, (N-15)H3, and PH3 is compared with observations. It is concluded that: (1) the (N-14)H3 line profiles are best fitted with a NH3 density in the troposphere which is 0.5 times the saturated vapor pressure density and an opaque cloud at the 0.56 bar pressure level, (2) the best fit (N-15)H3/(N-14)H3 ratio is 0.006, (3) the PH3/H2 abundance ratios of NH3 and PH3 must be highly subsaturated above the tropopause or the temperature inversion is cooler than model predictions.

Tokunaga, A. T.↗

NASA NTRS1978

Monte Carlo modeling of exospheric bodies - Mercury

In order to study the interaction with the surface, a Monte Carlo program is developed to determine the distribution with altitude as well as the global distribution of density at the surface in a single operation. The analysis presented shows that the appropriate source distribution should be Maxwell-Boltzmann flux if the particles in the distribution are to be treated as components of flux. Monte Carlo calculations with a Maxwell-Boltzmann flux source are compared with Mariner 10 UV spectrometer data. Results indicate that the presently operating models are not capable of fitting the observed Mercury exosphere. It is suggested that an atmosphere calculated with a barometric source distribution is suitable for more realistic future exospheric models.

Smith, G. R.↗

NASA NTRS1974

A simple interpretation of the 'rolling motions'

The rolling motion phenomenon is interpreted as an apparent motion in the observations. It is caused by (1) the combined effect of the differential rotation and the bending of the galactic plane for the spiral arms beyond the solar circle, or (2) the displacement of the spiral arms from the central galactic plane for those within the solar circle.

Yuan, C.↗

NASA NTRS1973

The 'rolling motion' phenomenon in galactic spiral arms

The 'rolling motion' in the spiral arms in the outer parts of the Galaxy are interpreted as only apparent motions caused by the combined effect of the bending of the galactic plane and the differential rotation. Theoretical contour maps (latitude vs velocity) are plotted in a number of directions on both sides of the Galaxy for direct comparison with observations. The velocity and density fields used in the calculations are based on a linear analysis of the three-dimensional gas motions in response to the spiral density-wave potential studied by Lin, Shu, and Yuan and by Vandervoort (1970). It is found that the combined effect under consideration is sufficient to cause an apparent rolling motion in a spiral arm.

Yuan, C.↗

NASA NTRS1972

Ultraviolet photometry from the orbiting astronomical observatory. III - Observations of Venus, Mars, Jupiter, and Saturn longward of 2000 A.

A number of high-quality spectra of Mars, Jupiter, the combined disk and rings of Saturn, as well as lower-quality spectra of Venus, have been obtained with an objective-grating spectrometer of the Wisconsin Experiment Package of OAO-2. An intercomparison of the Mars, Jupiter, and Saturn spectra has failed to disclose any discrete planetary absorptions. Continuous albedos have been derived for the four planets by using OAO-2 observations of G-type stars for wavelengths greater than 2700 A. The geometric albedo of Mars shows a steady increase below 3500 A which appears to be due to Rayleigh scattering combined with a decreasing surface reflectivity. The albedos of Venus, Jupiter, and Saturn show a maximum in reflectivity in the region of 2500 A.-

Wallace, L.↗

NASA NTRS1972

Observations of Venus, Mars, Jupiter and Saturn longward of 2000 A

A number of high quality spectra of Mars, Jupiter, the combined disk and rings of Saturn, as well as lower quality spectra of Venus, have been obtained with an objective grating spectrometer of the Wisconsin experiment package on OAO-2. An intercomparison of the Mars, Jupiter and Saturn spectra has failed to disclose any discrete planetary absorptions. Continuous albedos have been derived for the four planets by using OAO-2 observations of G-type stars for wavelengths greater than 2700 A and a new photoelectric solar spectrum for wavelengths smaller than 2700 A. The geometric albedo of Mars shows a steady increase below 3500 A which appears to be due to Rayleigh scattering combined with a decreasing surface reflectivity. The albedos of Venus, Jupiter and Saturn show a maximum in reflectivity in the region of 2500 A.

Wallace, L.↗

NASA NTRS1970