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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 163 records · Page 9
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NASA NTRS1980

Exploring the veiled planet

An overview of data obtained from various experiments which characterize geological features and atmospheric properties of Venus is presented. Data from the two Pioneer sounder probes (one located at Venus's equator and the other near the north pole) exhibit a reversal in the equator-to-pole temperature patterns at 60 km altitude which suggests that two circulation cells exist within the atmospheric region. However, the atmospheric temperature and pressure beneath the clouds are found to be nearly identical everywhere on Venus and both temperature and pressure conditions at the surface are lower than first expected. The identification of sulphur dioxide clouds which appear to coincide with Venus's characteristic global patterns of C- and Y-shaped dark markings support the hypothesis of a regular pattern of planet spanning breaks in the upper cloud layer. Explanations of a Venus sulphur cycle and of observed magnetic field structures are suggested

Source record↗
NASA NTRS1980

Microwave properties of solid CO2

Measurements over the range of 2.2 to 12.0 GHz show that CO2 snow is a slightly lossy dielectric whose constant varies with density following the Rayleigh formula to 1.27 g/cu cm. It is independent of frequency and does not vary with temperature in the 113 to 183 K range; frequency independence and agreement with the Rayleigh fit are obtained from measurements on dry block ice. The dielectric constant of solid CO2 in block form is lower than that of solid water ice or solid rock; in powder form, the constant for CO2 is also lower than that of H2O (snow) or soils. These measurements may be useful in limiting the interpretations of the Viking radio reflection experiment; a radio value of 3.0 for the dielectric constant near the North Pole would be strong evidence against the presence of cm thicknesses of CO2 in that region.

Simpson, R. A.↗
NASA NTRS1982

Ultraviolet spectroscopy of the Jovian and Saturnian auroras

The results of a series of IUE observations of the north polar aurora obtained during a substantial fraction of one complete rotation of Jupiter are presented. From these data a spectrum of the aurora with high signal to noise ratio, and a resolution of about 8 A was obtained, making possible the identification of many H2 Lyman and Werner bands. The spectrum is of sufficient quality to provide reliable quantative data for a comparison with the model atmosphere calculations. The lack of an observable absorption signature makes it possible to set an upper limit on the column density of CH4 and C2H6 above the auroral emissions and hence an upper limit on the primary particle energies. A comparison of this spectrum with a laboratory spectrum of discharge excited H2 shows a remarkable similarity. The results of several IUE observations of the full disk of Saturn are also examined. The exposures were of approximately 2 hours each, and the H2 Lyman and Werner bands were observed near the north pole in two of them.

Durrance, S. T.↗
NASA NTRS1982

On the origin and spatial extent of high-latitude F region irregularities

Evidence for the direct production of macroscale irregularities by structured, soft electron fluxes is employed to form the basis for a model for the transport and decay of such structures and the role of plasma instabilities in the production of smaller irregularities. Large scale structures were defined with wavelengths of at least 10 km, intermediate between 0.0-10 km, and short less than 10 m. Data were gathered by means of a rocket flight into the auroral oval and radar scans of 10-350 km altitudes for electron density contours. The radar data indicated that the large-scale structure in the F region plasma was in the main due to electron precipitation. The instability of the structures caused the emergence of smaller scale irregularities in a dynamic balance of instability growth and damping. Additional productive sources which allow the greater than 100 km structures to pass over the North Pole intact are discussed.

Kelley, M. C.↗
NASA NTRS1982

Stratigraphic relationships within Martian polar cap deposits

It is found that layered ice and dust deposits accumulate on the smooth and banded terrains of the north and south polar cap deposits of Mars, while erosion exposes these layers on the equator-facing slopes of layered terrain. The stripping of layers occurs in areas of strong and multidirectional wind, forming striped terrain. Also noted is the production of steep scarps with crescentic planform by local wind scour, in frequent association with dune fields positioned immediately downwind. Unconformities, which are common within layered deposits in areas of complex topography at the north pole, indicate that deposition episodes of 5-10 layers alternate with the slight erosion of pole-facing trough walls. It is suggested that poles may migrate poleward, replacing the relief increase by depositional infilling when they near the poles.

Howard, A. D.↗
NASA NTRS1983

To Uranus and beyond

Known characteristics of the planet Uranus are reviewed, together with a status report on the Voyager spacecraft. Uranus was discovered in 1781, and has been found to have a north pole that is pointed directly at the sun. Data is still needed on the Uranus atmosphere, its possible magnetic field, and its rotation frequency. Five moons have been sighted, accompanied by nine rings. The Voyager 2 spacecraft will encounter Uranus in December 1986 at a 14.7 km/sec velocity, imposing limitations on the observation sequence. The spacecraft carries 11 scientific packages, including a camera, and will pass within 50,000 km of the moon Miranda and 107,000 km of Uranus. Radio signals will be broadcast through the rings, which will be imaged by a UV spectrometer. Voyager 2 will then continue on to a Neptune encounter in 1989 before moving toward interstellar space.

Kerridge, S. J.↗
NASA NTRS1984

IUE observations of longitudinal and temporal variations in the Jovian auroral emission

The IUE's short wavelength spectrograph has been used to monitor the auroral emissions from Jupiter's northern hemisphere, yielding eight observations between January 1981 and January 1982 of H I Lyman-alpha and the H2 Lyman and Werner bands. Attention is given to an apparent periodic emission flux fluctuation, through detailed modeling of the emission geometry. Two possible auroral zones are defined at the north pole by mapping the magnetic field lines from the Io torus and the magnetotail onto the planet's atmosphere. The observed variation in flux with central meridian longitude is not consistent with a uniform brightness as a function of magnetic longitude in either auroral zone. The data can be fitted by confining the emissions to the region of the northern torus auroral zone, in qualitative agreement with the magnetic anomaly model. A similar emission from the magnetotail auroral zone cannot be ruled out.

Skinner, T. E.↗
NASA NTRS1984

Brominated organic species in the arctic atmosphere

Measurements are reported of four gas-phase, brominated organic species found in the Arctic atmosphere during March and April 1983. Volume mixing ratios for CH3Br, CH2BrCH2Br, CHBr3, and CH2Br2 were determined by gas chromatography/mass spectrometry analysis from samples taken Arctic wide, including at the geographic North Pole and during a tropopause folding event over Baffin Bay near Thule, Greenland. Methyl bromide mixing ratios were reasonably constant at 11 plus or minus 4 pptv, while the other three brominated organics showed a high degree of variability. Bromoform (2 to 46 pptv) was found to be the dominant contributor to gaseous organic bromine to the Arctic troposphere at 38 plus or minus 10 percent followed by CH2Br2 (3 to 60 pptv) at 29 plus or minus 6 percent. Both CH3Br and CH2BrCH2Br (1 to 37 pptv) reservoirs contained less than 20 percent of the organically bound bromine. Stratospheric samples, taken during a tropopause folding event, showed mixing ratios for all four species at levels high enough to support a stratospheric total volume mixing ratio of 249 pptv Br (888 ngBr/SCM).

Berg, W. W.↗
NASA NTRS1985

Speckle interferometry of asteroids. II - 532 Herculina

Speckle interferometry of 532 Herculina performed on January 17 and 18, 1982, yields triaxial ellipsoid dimensions of (263 + or - 14) x (218 + or - 12) x (215 + or - 12) km, and a north pole for the asteroid within 7 deg of RA = 7h47min and DEC = -39 deg (ecliptic coordinates lambda = 132 deg beta = -59 deg). In addition, a 'spot' some 75 percent brighter than the rest of the asteroid is inferred from both speckle observations and Herculina's lightcurve history. This bright complex, centered at asterocentric latitude -35 deg, longitude 145-165 deg, extends over a diameter of 55 deg (115 km) of the asteroid's surface. No evidence for a satellite is found from the speckle observations, which leads to an upper limit of 50 km for the diameter of any satellite with an albedo the same as or higher than Herculina.

Drummond, J. D.↗
NASA NTRS1985

Mean zonal winds and planetary waves induced by internal gravity wave packets

The generation of mean zonal winds and planetary waves induced by internal gravity wave packets are investigated by numerical experiments. The numerical model is a 3-dimensional primitive equation model on the equatorial beta-plane with boundaries at the equator and North Pole. Because of equatorial boundary conditions, equatorial symmetric modes only are included in the model. Internal gravity wave packets are produced by thermal heating at the bottom boundary. Because of restriction of grid size, convective instability is parameterized by time-independent vertical and horizontal eddy viscosity. Other dissipation mechanisms (e.g., Newtonian cooling, ion drag, molecular viscosity etc.) are also included in the model.

Takahashi, M.↗
NASA NTRS1985

Decomposition of CO2 molecules due to auroral X-rays

It has been reported by SEKIHARA (1981), that the circumpolar measurement from a commercial airliner reported by PRATT and FALCONER (1979) was subjected to a strong influence of a geomagnetic storm, specifically at the beginning stage through the North Pole. The main point of interest was the increase of CO concentration by the order of 10 ppb that took place simultaneously with a temperature decrease of several degrees, which was regarded as a result of enhanced cooling to space due to CO2 decomposition. Later inspection of the original magnetogram of eleven auroral zone stations revealed that the observation started 13 hours after the main phase of a geomagnetic storm, which lasted for 22 hours. A quantitative estimation is made of CO2 decomposition due to auroral X-rays that should take place during the degradation of photoelectrons injected into the lower stratospheres.

Sekihara, K.↗
NASA NTRS1988

A study of Upgren 1

Upgren and Rubin (1965) have suggested that a small group of bright F stars, in the direction of the galactic north pole, may be the remnant of an old cluster. The multichannel astrometric photometer (MAP) has been used to determine the parallaxes of six of the candidate stars with an average precision of 1.1 thousandths of an arcsecond (1.1 mas). The derived distances are, as suggested, similar, and an unusual space density of F stars seems indicated. However, the derived space velocities indicate that the proposed cluster is composed of members of two dynamically different groups.

Gatewood, George↗
NASA NTRS1987

The thermal properties of Martian surface materials at high lattitudes: Possible evidence for permafrost

Evidence is presented from analysis of Viking thermal mapping results that suggests a transition to high thermal inertial material at a depth of approx. 12 cm at +75 deg latitude. This was interpreted as reflecting the transition from ice poor soil to hard frozen permafrost. It was pointed out that such a transition would be expected on the basis of theoretical models of hard frozen permafrost distribution. Although permafrost is not the only plausible martian surface material with high thermal inertia, polar thermal mapping may turn out to be a powerful tool for determining the distribution of permafrost deposits and understanding their behavior. At this point, the circumstantial case for permafrost deposits in the north pole region of Mars is very strong.

Paige, D. A.↗
NASA NTRS1988

Search for Mars lander/rover/sample-return sites: A status review

Ten Mars sites were studied in the USA for four years. The sites are the Chasma Boreale (North Pole), Planum Australe (South Pole), Olympus Rupes, Mangala Valles, Memnonia Sulci, Candor Chasma, Kasel Valles, Nilosyrtis Mensae, Elysium Montes, and Apollinaris Patera. Seven sites are being studied by the USSR; their prime sites are located at the east mouth of Kasel Valles and near Uranius Patera. Thirteen geological maps of the first six USA sites are compiled and in review. Maps of the Mangala East and West sites at 1:1/2 million scale and a 1:2 million scale map show evidence of three episodes of small-channel formation interspersed with episodes of volcanism and tectonism that span the period from 3.5 to 0.6 b.y. ago. The tectonic and geological history of Mars, both ancient and modern, can be elucidated by sampling volcanic and fluvial geologic units at equatorial sites and layered deposits at polar sites. The evidence appears clear for multiple episodes of fluvial channeling, including some that are quite recent; this evidence contrasts with the theses of Baker and Partridge (1986) and many others that all channels are ancient. Verification of this hypothesis by Mars Observer will be an important step forward in the perception of the history of Mars.

Masursky, Harold↗
NASA NTRS1989

Kilometric radiation power flux dependence on area of discrete aurora

Kilometer wavelength radiation, measured from distant positions over the North Pole and over the Earth's equator, was compared to the area of discrete aurora imaged by several low-altitude spacecraft. Through correlative studies of auroral kilometric radiation (AKR) with about two thousand auroral images, a stereoscopic view of the average auroral acceleration region was obtained. A major result is that the total AKR power increases as the area of the discrete auroral oval increases. The implications are that the regions of parallel potentials or the auroral plasma cavities, in which AKR is generated, must possess the following attributes: (1) they are shallow in altitude and their radial position depends on wavelength, (2) they thread flux tubes of small cross section, (3) the generation mechanism in them reaches a saturation limit rapidly, and (4) their distribution over the discrete auroral oval is nearly uniform. The above statistical results are true for large samples collected over a long period of time (about six months). In the short term, AKR frequently exhibits temporal variations with scales as short as three minutes (the resolution of the averaged data used). These fluctuations are explainable by rapid quenchings as well as fast starts of the electron cyclotron maser mechanism. There were times when AKR was present at substantial power levels while optical emissions were below instrument thresholds. A recent theoretical result may account for this set of observations by predicting that suprathermal electrons, of energies as low as several hundred eV, can generate second harmonic AKR. The indirect observations of second harmonic AKR require that these electrons have mirror points high above the atmosphere so as to minimize auroral light emissions. The results provide evidence supporting the electron cyclotron maser mechanism.

Saflekos, N. A.↗
NASA NTRS1988

Stratospheric NO2 over Antarctica as measured by the Solar Mesosphere Explorer during austral spring, 1986

This paper presents the results of polar NO2 measurements carried out by the SME satellite during the fall and spring of 1985 and 1986 and compares the results with observations at the north pole and the results of model calculations. During the austral spring, a polar low was observed in stratospheric NO2 densities measured between 24 and 40 km, consistent with the predictions of standard photochemical theory. The geographic extent of the area of low NO2 densities was found to decrease as the hours of sunlight increased, in marked contrast to the behavior of the Antarctic ozone hole during the same period. A comparison of measurements with model calculations for NO2 imply that much of the odd nitrogen is converted to HNO3 during the polar night. Data also suggest no evidence that changes in high-altitude odd nitrogen are influencing the ozone below, or that the 'ozone hole' penetrates above 24 km to affect odd nitrogen there.

Thomas, Ronald J.↗
NASA NTRS1989

Phoebe: A preliminary control network and rotational elements

A preliminary control network for the Saturnian satellite Phoebe was determined based upon 6 distinct albedo features mapped on 16 Voyager 2 images. Using an existing map and an analytical triangulation program which minimized the measurement error, the north pole of Phoebe was calculated to be alpha sub 0 = 355.0 deg + or - 9.6 deg, delta sub 0 = 68.7 deg + or - 7.9 deg, where alpha sub 0, delta sub 0 are standard equatorial coordinates with equinox J2000 at epoch J2000. The prime meridian of Phoebe was computed to be W = 304.7 deg + 930.833872d, where d is the interval in days from JD 2451545.0 TDB.

Colvin, Tim R.↗