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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

The annual variation in the global heat balance of the earth

An annual variation with a range of 31 W/sq m is found in the global net radiation balance of the earth. The net radiation flux values measured from satellites and the changes in total heat content computed from independent sets of atmospheric and oceanic data show annual variations which are consistent with each other in both phase and magnitude. The net energy gain and loss by the planet within a year is stored and released within the system primarily by the oceans.

Ellis, J. S.↗
NASA NTRS1978

On the monochromatic brightness variations of comets

The nonsteady development of the multispecies atmosphere of a long-period comet approaching the sun is modeled, and the associated monochromatic brightness variations are discussed in terms of the varying abundances of the atmospheric species. A simple homogeneous clathrate structure, 85% of which is H2O, provides the representation for the cometary nucleus. Monochromatic brightness variations of the emission bands due to OH, CN and C2 are found to follow the law proposed by Levin (1943) for small heliocentric distance where a quasi-steady approximation is valid. However, the large time-scales of residence for emitting species leads to a breakdown of Levin's law at large heliocentric distances.

Mendis, D. A.↗
NASA NTRS1978

Cometary brightness variation and nucleus structure

The Bobrovnikoff and Beyer photometric data for more than 100 comets analyzed for intrinsic brightness variations, before and after perihelion, according to some inverse power law of solar distance. The Oort and Schmidt classification of comet age is extended and applied with Marsden's new determinations of inverse semimajor axis. A physical interpretation of the data involves the quick loss of a frosting of supervolatile materials from new comets, and for all comets, the development of an insulating crust after perihelion. The orientation of the axes of rotating comets is shown to be an important factor in cometary brightness variations. A speculation is made concerning the axis of rotation of Comet Kohoutek.

Whipple, F. L.↗
NASA NTRS1977

A practical method for correcting bidirectional reflectance variations

The purpose of the investigation was to analyze angular bidirectional reflectance variations and to test the hypothesis that first order variations could be described from a consideration of shadows created by surface perturbations. The results demonstrate the validity of this approach, and while it is not suitable for calculating absolute spectral reflectance characteristics, the development of such a model was not the objective of the investigation. Instead, a model was needed which can make relative angular corrections to bidirectional reflectance measurements independent of the details of surface geometry.

Egbert, D. D.↗
NASA NTRS1977

Historical variations in the density and distribution of impacting debris in the inner solar system - Evidence from planetary imaging

The global cratering records are examined on the basis of planetary images to establish for each planet the global succession of stratigraphic units and the variations in crater densities among these global provinces. Crater density on a global scale on each of the planets is mapped to establish the range of variation of crater density of post-highland plains for Mercury, moon, and Mars. A narrow diameter-range (5-10 km) was chosen for this purpose. Crater abundance in this size range has been continuously mapped for available coverage for each of the three planets. Craters in this size range superposed on the plains usually display pristine morphology suggesting that most were formed after the plains. Evidently, most preexisting craters in this size range were erased by the plains-forming processes.

Soderblom, L. A.↗
NASA NTRS1978

Variations in the spatial distribution of 11 micron radiation from Omicron Ceti

The spatial distribution of 11-micron radiation from Omicron Ceti has been observed at various phases of its light cycle by using a stellar interferometer. Variations have been seen in the strength of thermal emission from circumstellar dust relative to the stellar continuum at 11 microns. These variations are shown to be correlated with the changes in luminosity of Omicron Ceti in such a way that dust-grain emission at 11 microns was increased more than the continuum during the period of maximum luminosity. The degree of the change in dust-grain emission implies that the maximum dust temperature is in the range of 500 to 700 K during minimum stellar luminosity.

Sutton, E. C.↗
NASA NTRS1978

Rapid space/time variations in mesospheric ozone

A 5 meter telescope was used to observe variations in the narrow emission line which is present in the nightime emission spectrum of ozone. The line was measured for several nights on two different transitions of the ozone molecule at 110.8 GHz and 142.2 GHz. Individual spectra with a time resolution of 5 minutes were taken. The narrow emission line showed considerable variation in intensity indicating that the ozone layer from which its arises has a rather detailed structure. Analysis of the line profile shows that the emission is coming from an ozone layer in the 55-75 km region of the mesosphere. This layer has a column density of 2 x 10 to the 16th power molecules/sq cm in a vertical path through the region.

Buhl, D.↗
NASA NTRS1979

Variations of the earth's magnetic field and rapid climatic cooling: A possible link through changes in global ice volume

A possible relationship between large scale changes in global ice volume, variations in the earth's magnetic field, and short term climatic cooling is investigated through a study of the geomagnetic and climatic records of the past 300,000 years. The calculations suggest that redistribution of the Earth's water mass can cause rotational instabilities which lead to geomagnetic excursions; these magnetic variations in turn may lead to short-term coolings through upper atmosphere effects. Such double coincidences of magnetic excursions and sudden coolings at times of ice volume changes have occurred at 13,500, 30,000, 110,000, and 135,000 YBP.

Rampino, M. R.↗
NASA NTRS1978

Long period time variations of ozone in the lower stratosphere

Observations of total ozone at a number of stations in the Northern Hemisphere show an increase during the period 1961-1970 followed by a decrease of ozone during the 1970's, at least at many stations in Central Europe. It is well known that total ozone is highly correlated with ozone in the lower stratosphere. Analysis of the trends of ozone based on data derived from balloon-borne ozonesondes during the period 1967-75 at four stations in Central Europe shows that most of the ozone variations occurred in the lower stratosphere with relatively little contribution from tropospheric changes or those above the ozone peak. Possible meteorological origins of these decade type variations will be discussed.

London, J.↗
NASA NTRS1979

The global distribution of long-term total ozone variations during the period 1957-1975

Total ozone observations in the international network have been used as a basis for the analysis of the mean monthly ozone distribution over the globe for the period 1957-1975. It has been found that during the period 1961-1970 the total ozone amount increased in the Northern Hemisphere by about 12 percent and that this increase seems to be significant at all latitudes. Although the data were sparse for the Southern Hemisphere, there did not appear to be any significant ozone changes during the 10 year period. Relatively large geographic variations were found in the ozone trends and it is suggested that these variations are related to large scale changes in the atmospheric circular pattern.

London, J.↗
NASA NTRS1979

Solar wind latitudinal variations deduced from Mariner 10 interplanetary H /1216 A/ observations

The Mariner 10 H (1216-A) interplanetary observations are examined by using models that consider anisotropies in the solar fluxes. It is verified that the dominant contribution to asymmetric structure in the Mariner 10 H (1216-A) data is a latitudinal variation of the solar-wind flux and of the solar wind velocity, leading to a hydrogen atom lifetime that is latitude dependent. The average lifetime at 1 AU is found to increase from the solar equator to the solar poles by about 25%. This allows interstellar hydrogen to penetrate closer to the solar poles than to the equator. A general analytic model is constructed for evaluating the neutral hydrogen density distribution in interplanetary space. This model takes into account the latitude-dependent ionization rate. When this model is applied to the Mariner 10 H (1216-A) data, it is shown to be capable of matching the observations with a statistical accuracy of 5%. The effect of this latitudinal variation on H (1216-A) sky background maps is to produce a latitudinal shift in the maximum toward the north ecliptic pole.

Witt, N.↗
NASA NTRS1979

The Relationship of Red and Photographic Infrared Spectral Data to Grain Yield Variation Within a Winter Wheat Field

Two band hand-held radiometer data from a winter wheat field, collected on 21 dates during the spring growing season, were correlated within field final grain yield. Significant linear relationships were found between various combinations of the red and photographic infrared radiance data collected and the grain yield. The spectral data explained approximately 64 percent of the within field grain yield variation. This variation in grain yield could not be explained using meteorological data as these were similar for all areas of the wheat field. Most importantly, data collected early in the spring were highly correlated with grain yield, a five week time window existed from stem elongation through antheses in which the spectral data were most highly correlated with grain yield, and manifestations of wheat canopy water stress were readily apparent in the spectral data.

Tucker, C. J.↗
NASA NTRS1980

Parametric study of variation in cargo-airplane performance related to progression from current to spanloader designs

A parametric analysis was made to investigate the relationship between current cargo airplanes and possible future designs that may differ greatly in both size and configuration. The method makes use of empirical scaling laws developed from statistical studies of data from current and advanced airplanes and, in addition, accounts for payload density, effects of span distributed load, and variations in tail area ratio. The method is believed to be particularly useful for exploratory studies of design and technology options for large airplanes. The analysis predicts somewhat more favorable variations of the ratios of payload to gross weight and block fuel to payload as the airplane size is increased than has been generally understood from interpretations of the cube-square law. In terms of these same ratios, large all wing (spanloader) designs show an advantage over wing-fuselage designs.

Toll, T. A.↗
NASA NTRS1979

Solar-induced variations of environment affecting manned space flight and spacecraft operations

Estimates of short and long term solar activity are required for calculating variations in the environment with regard to spacecraft charging, radiation effects, and orbital lifetime. Correlations appear to exist between the time of solar activity and the time of operational anomalies due to electrical discharges when the dielectric surfaces of geosynchronous spacecraft are charged by interaction with the ambient plasma to levels above breakdown voltage. An ability to predict the solar induced variation variability of the plasmas could permit refinement of design criteria. The influence of the radiation on spacecraft materials, systems, and manned operations is summarized. Solar radition effects on the orbital altitude atmospheric density environment and spacecraft lifetimes are also considered.

Johnson, W. G.↗
NASA NTRS1980

The influence of NO and ClO variations at twilight on the interpretation of solar occultation measurements

The influence of short lived photochemically produced species on solar occultation measurements of ClO and NO was examined. Time varying altitude profiles of ClO and NO were calculated with a time dependent photochemical model to simulate the distribution of these species during a solar occultation measurement. These distributions were subsequently used to calculate simulated radiances for various tangent paths from which mixing ratios were inferred with a conventional technique that assumes spherical symmetry. These results show that neglecting the variation of ClO in the retrieval process produces less than a 10 percent error between the true and inverted profile for both sunrise and sunset above 18 km. For NO, errors are less than 10 percent for tangent altitudes above about 35 km for sunrise and sunset; at lower altitudes, the error increases, approaching 100 percent at altitudes near 25 km. the results also show that average inhomogeneity factors, which measure the concentration variation along the tangent path and which can be calculated from a photochemical model, can indicate which species require more careful data analysis.

Boughner, R.↗
NASA NTRS1980

The rate of mass loss and variations in the wind from the Be star delta Centauri

Copernicus ultraviolet scans of the Be star delta Centauri obtained in 1976 and 1979, show a significant variation in the Si III lambda 1206 profile, The strong asymmetry that was present in 1976 had disappeared by 1979. The Si IV lambda 1400 doublet was also asymmetric in 1976, but was not observed in 1979. A quantitative fit of the line shapes to theoretical wind profiles shows that the mass-loss rate in 1976 was 2 x 10 to the minus 8th power/yr, and that the rate of mass loss in Si III was at least one order of magnitude less in 1979. It is not possible to determine whether the variation represented an overall change in the lass-loss rate, or whether it was due to a change in the ionization balance. The profile fitting procedure resulted in the adoption of assumed underlying photospheric Si III and Si IV profiles, and the equivalent widths measured from these profiles are most consistent with T sub eff between 30,000 and 35,000 K, somewhat hotter than implied by the spectral classification normally assigned to this star. The ultraviolet photospheric line widths, coupled wit published theoretical analyses of rotational gravitational darkening, imply an intrinsic equatorial velocity of about 310 km/sec and an angle of inclination of the rotational axis to the line of sight of i is less than or equal to 44 deg.

Snow, T. P., Jr.↗
NASA NTRS1980

The upper atmosphere of Uranus - Mean temperature and temperature variations

The number-density, pressure, and temperature profiles of the Uranian atmosphere in the pressure interval from 0.3 to 30 dynes/sq cm are derived from observations of the occultation of SAO 158687 by Uranus on 1977 March 10, observations made from the Kuiper Airborne Observatory and the Cape Town station of the South African Astronomical Observatory. The mean temperature is found to be about 95 K, but peak-to-peak variations from 10 K to 20 K or more exist on a scale of 150 km or 3 scale heights. The existence of a thermal inversion is established, but the inversion is much weaker than the analogous inversion on Neptune. The mean temperature can be explained by solar heating in the 3.3 micron methane band with a methane mixing ratio of 4 x 10 to the -6th combined with the cooling effect of ethane with a mixing ratio of not greater than 4 x 10 to the -6th. The temperature variations are probably due to a photochemical process that has formed a Chapman layer.

Dunham, E.↗