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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

The Structure and Dynamics of Titan's Middle Atmosphere

Titan's middle atmosphere is characterized by cyclostrophic winds and strong seasonal modulation. Cassini CIRS observations, obtained in northern winter, indicate that the stratosphere near l mbar is warmest at low latitudes, with the South Pole a few degrees colder and the North Pole approximately 20 K colder. Associated with the cold northern temperatures are strong circumpolar winds with speeds as high as 190 m/s. Within this vortex, the mixing ratios of several organic gases are enhanced relative to those at low latitudes. Comparison with Voyager thermal infrared measurements, obtained 25 years ago in northern spring, suggests that the enhancement currently observed will increase as the winter progresses. The stratopause height, increases from 0.1 mbar near the equator to 0.01 mbar near the North Pole, where it is the warmest part of the atmosphere, greater than 200 K. This implies subsidence at the pole, which is consistent with the enhanced organics observed. Condensate features, several still not identified, are also apparent in the infrared spectra at high northern latitudes. In many ways, the winter vortex observed on Titan, with cyclostrophic winds, resembles the polar winter vortices on the Earth, where the mean winds are geostrophic.

Flasar, F. M.↗
NASA NTRS1973

S-band radio occultation measurements of the atmosphere and topography of Mars with Mariner 9: Extended mission coverage of polar and intermediate latitudes

Radio occultation measurements from Mariner 9 orbits around Mars show that the radius of Mars changes by only about 2 km from a latitude of 65 deg to the north pole, that the north polar area is about average in elevation, and that polar temperature profiles are indicative of the possibility that the remnant north polar cap may be at least partially composed of water ice. It is also found that Mars, in addition to being asymmetrical equatorially, is also significantly asymmetrical in the north and south direction with the Southern Hemisphere lying 3 to 4 km higher. Temperature gradients in the clear Martian atmosphere of only about one-half of the adiabatic gradients of 5 deg K/km suggest the importance of dynamical processes.

Kliore, A. J.↗
NASA NTRS1985

Experiments on the Assimilation of Patches of Data Using a Barotropic Model

Experiments were performed to examine the impact of adopting various procedures in the assimilation of patches of data during the progress of a numerical forecast. A barotropic model described by Takacs and Balgovind, 1983 is used for the experiments. The model is global and its discretization is similar to the GLA Fourth Order GCM. The effect of orography is included in the model. The experiments are of an identical twin kind. The nature run starts from global fields of wind (u and v) and height (h) at 300 mb. They are real data of January, 1979 OOZ which were interpolated from the adjacent sigma levels of the GLA GCM and then balanced by the bounded derivative method. From this initial state a 6 day forecast is performed. At intervals of 3 hours this information is saved over sectors of 60 width in longitude, from the south pole to the north pole, to simulate data coverage and observational frequency of a polar orbiting satellite.

Semazzi, F. H. M.↗
NASA NTRS1992

Mercury radar imaging - Evidence for polar ice

The first unambiguous full-disk radar mapping of Mercury at 3.5-centimeter wavelength, with the Goldstone 70-meter antenna transmitting and 26 antennas of the Very Large Array receiving, has provided evidence for the presence of polar ice. The radar experiments, conducted on 8 and 23 August 1991, were designed to image the half of Mercury not photographed by Mariner 10. The orbital geometry allowed viewing beyond the north pole of Mercury; a highly reflective region was clearly visible on the north pole during both experiments. This polar region has areas in which the circular polarization ratio was 1.0 to 1.4; values less than about 0.1 are typical for terrestrial planets. Such high values of this ratio have hitherto been observed in radar observations only from icy regions of Mars and icy outer planet satellites.

Slade, Martin A.↗
NASA NTRS2000

Shape and Topography of Mars

Observations by the Mars Orbiter Laser Altimeter (MOLA) on the Mars Global Surveyor (MGS) spacecraft are showing a new planet in its range of topography and in the detail of the geological features. MGS arrived at Mars in Sept 1997 and since Feb. 28, 1999 the laser altimeter has operated continuously. By the end of April 2000 MOLA had acquired over 350 million measurements of the planet's shape and topography. These observations show a strong down-hill topographic gradient from the south pole to the north pole with an extremely low and flat basin encompassing most of the northern hemisphere. Large outflow channels are seen in the Chyrse region that strongly suggest considerable quantities of water once flowed into the lower northern hemisphere from the south. The northern icecap, which rises to a height of three kilometers above the surrounding terrain, is shown to be largely composed of water ice and at the center of a large basin. The southern hemisphere is about five kilometers higher than the low northern plains and dominated by the Hellas impact basin whose ejecta is the major contributor to the topography of the hemisphere and the crustal dichotomy. The south polar icecap, which is part of a much larger region of layered terrain composed of water ice and dust, reaches an elevation of nearly five kilometers and except for the large Tharsis volcanoes is the highest part of the planet.

Smith, David E.↗
NASA NTRS2019

Coronagraphic Observations of the Lunar Sodium Exosphere January-June, 2017

In order to observe the lunar sodium exosphere out to one-half degree around the Moon, we designed, built and installed a small robotically controlled coronagraph at the Winer Observatory in Sonoita, Arizona. Observations are obtained remotely every available clear night from our home base at Goddard Space Flight Center or from Prescott, Arizona. We employ an Andover temperature-controlled 1.5-angstrom-wide narrow-band filter centered on the sodium D2 line, and a similar 1.5-angstrom filter centered blueward of the D2 line by 3 angstroms for continuum observations. Our data encompass lunations in 2015, 2016, and 2017, thus we have a long baseline of sodium exospheric calibrated images. During the course of three years we have refined the observational sequence in many respects. Therefore this paper only presents the results of the spring, 2017, observing season. We present limb profiles from the south pole to the north pole for many lunar phases. Our data do not fit any power of cosine model as a function of lunar phase or with latitude. The extended Na exosphere has a characteristic temperature of about 2250–6750 degrees Kelvin, indicative of a partially escaping exosphere. The hot escaping component may be indicative of a mixture of impact vaporization and a sputtered component.

Moon↗
NASA NTRS2019

Coronagraphic Observations of the Lunar Sodium Exosphere January-June, 2017

In order to observe the lunar sodium exosphere out to one-half degree around the Moon, we designed, built and installed a small robotically controlled coronagraph at the Winer Observatory in Sonoita, Arizona. Observations are obtained remotely every available clear night from our home base at Goddard Space Flight Centeror from Prescott, Arizona. We employ an Andover temperature-controlled 1.5 Å wide narrow-band filter centered on the sodium D2line, and a similar 1.5 Å filter centered blueward of the D2line by 3Åfor continuum observations. Our data encompass lunations in 2015, 2016, and 2017, thus we have a long baseline of sodium exospheric calibrated images. During the course of three years we have refined the observational sequence in many respects. Therefore this paper only presents the results of the spring, 2017, observing season. We present limb profiles from the south pole to the north pole for many lunar phases.Our data do not fit any power of cosine model as a function of lunar phase or with latitude. The extended Na exosphere has a characteristic temperature of about 2250 -6750 K, indicative of a partially escaping exosphere. The hot escaping component may be indicative of a mixture of impact vaporization and a sputtered component.

Lunar exosphere composition↗
NASA NTRS2017

Illumination Conditions at the Lunar Poles: Implications for Future Exploration

We produced 400 x 400 km Digital Terrain Models (DTMs) of the lunar poles from Lunar Orbiter Laser Altimeter (LOLA) ranging measurements. To achieve consistent, high-resolution DTMs of 20 m/pixel the individual ranging profiles were adjusted to remove small track-to-track o sets. We used these LOLADTMs to simulate illumination conditions at surface level for 50 x 50 km regions centered on the poles. Illumination was derived in one-hour increments from 01 January, 2017 to 01 January, 2037 to cover the lunar precessional cycle of 18.6 years and to determine illumination conditions over several future mission cycles. We identified three regions receiving high levels of illumination at each pole, e.g. the equator-facing crater rims of Hinshelwood, Peary and Whipple for the north pole and the rim of Shackleton crater, and two locations on a ridge between Shackleton and de Gerlache crater for the south pole. Their average illumination levels range from 69.5% to 82.9%, with the highest illumination levels found at the north pole on the rim of Whipple crater. A more detailed study was carried out for these sites as targets for a lander and/or rover equipped with solar arrays. For this purpose we assumed a lander with a structural height of two meters above the ground (height of the solar panels). Here average illumination levels range from 77.1% to 88.0%, with the maximum found at the ridge between Shackleton and de Gerlache crater on the south pole. Distances, sizes and slopes of nearby Permanently Shadowed Regions (PSRs) as a prime science target were also assessed in this case.

LOLA↗
NASA NTRS2019

Mission Design for the Lunar Pallet Lander

Due to lighting conditions, the program decided to only fly to the north pole in June 2022 and south pole in December 2022. Starting with the June 2022 landing sites at the north pole, a trajectory scan was run for one landing per day for the latitudes from 85 up to 88 degrees at 0.5 degree increments. Each landing site was at lunar dawn, which determined the landing site’s longitude as described in the previous section. The results of the June 2022 scan showed that LPL had the capability to reach a landing site at least once per day for the region examined as see in in Figure 12. There appears to be a correlation between the landing site’s altitude and the propellant remaining above the lander’s FPR, Figure 13. This is most likely due to the >10 km altitude constraint at SRM burnout. This constraint was applied to keep the lander high above the lunar terrain to avoid mountains, but can be relaxed when the full terrain data is added. Figure 12. June 2022 Nominal Usable Propellant Remaining vs Landing Date/time Similarly, the December 2022 landing sites were run showing that LPL was also capable of reaching a landing site at the Moon at least once per day. Figure 14 shows the results of the December scan, however, there were 3 landing sites that LPL could not reach. Two were very low in altitude (-5 and -4 km in altitude), which looking at the altitude trends in Figure 15, indicates that these sites may not be feasible with the current mission design. It may be possible to achieve the low altitude landing sites by lowering the SRM burnout altitude constraint, but that requires detailed terrain modeling, planned for a future phase of the analysis. The third non-reachable landing site is most likely due to an optimization error, as its altitude was high enough, at -2 km, that it should not have been a problem for the lander to arrive there. More analysis is required to verify this observation.

Craig, Scott↗
NASA NTRS2011

High Resolution Camera for Mapping Titan Surface

Titan, Saturn's largest moon, has a dense atmosphere and is the only object besides Earth to have stable liquids at its surface. The Cassini/Huygens mission has revealed the extraordinary breadth of geological processes shaping its surface. Further study requires high resolution imaging of the surface, which is restrained by light absorption by methane and scattering from aerosols. The Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft has demonstrated that Titan's surface can be observed within several windows in the near infrared, allowing us to process several regions in order to create a geological map and to determine the morphology. Specular reflections monitored on the lakes of the North Pole show little scattering at 5 microns, which, combined with the present study of Titan's northern pole area, refutes the paradigm that only radar can achieve high resolution mapping of the surface. The present data allowed us to monitor the evolution of lakes, to identify additional lakes at the Northern Pole, to examine Titan's hypothesis of non-synchronous rotation and to analyze the albedo of the North Pole surface. Future missions to Titan could carry a camera with 5 micron detectors and a carbon fiber radiator for weight reduction.

Cassini↗
NASA NTRS2010

Lunar Pole Illumination and Communications Statistics Computed from GSSR Elevation Data

The Goldstone Solar System RADAR (GSSR) group at JPL produced a Digital Elevation Model (DEM) of the lunar south pole using data obtained in 2006. This model has 40-meter horizontal resolution and about 5-meter relative vertical accuracy. This paper uses that Digital Elevation Model to compute average solar illumination and Earth visibility near the lunar south pole. This data quantifies solar power and Earth communications resources at proposed lunar base locations. The elevation data were converted into local terrain horizon masks, then converted into selenographic latitude and longitude coordinates. The horizon masks were compared to latitude, longitude regions bounding the maximum Sun and Earth motions relative to the moon. Proposed lunar south pole base sites were examined in detail, with the best site showing multi-year averages of solar power availability of 92% and Direct-To-Earth (DTE) communication availability of about 50%. Results are compared with a theoretical model, and with actual sun and Earth visibility averaged over the years 2009 to 2028. Results for the lunar North pole were computed using the GSSR DEM of the lunar North pole produced in 1997. The paper also explores using a heliostat to reduce the photovoltaic power system mass and complexity.

Lunar base↗
NASA NTRS1985

Discrimination of a major stratospheric warming event in February-March 1984 from earlier minor warmings

As part of its responsibility for stratospheric monitoring, the Climate Analysis Center derives time trends of various dynamic parameters from NMC stratospheric analyses. Selected figures from this stratospheric monitoring data base are published in Climate Diagnostics Bulletin in March and October, after each hemispheric winter. During the Northern Hemisphere winter of December 1983-February 1984 several warming events may be seen in the plot of 60 deg. N zonal mean temperatures for 10 mb. Minor warmings may be noted in early December, late December, mid January and early February. A major warming with the 60 deg. N zonal mean temperatures reaching -40C is observed in late February, associated with a circulation reversal. In all of the minor warming episodes, there is a polarward movement of the Aleutian anticyclone; however, at 10 mb the North Pole remains in the cyclonic circulation of the stratospheric vortex which is not displaced far from its usual position. In the case of the later February major warming, the 10 mb circulation pattern over the North Pole is anticyclonic, and the cyclonic circulation has moved to the south and east with a considerable elongation. Cross sections of heat transport and momentum transport are not dramatically different for the minor and major warming episodes.

Johnson, K. W.↗
NASA NTRS1989

Observations and statistical simulations of a proposed solar cycle/QBO/weather relationship

The 10.7-cm solar flux is observed to be highly correlated with North Pole stratospheric temperatures when partitioned according to the phase of the equatorial stratospheric winds (the quasi-biennial oscillation, or QBO). Calculations show that temperatures over most of the Northern Hemisphere are highly correlated or anticorrelated with North Pole temperatures. The observed spatial pattern of solar-cycle correlations at high latitudes is shown to be not unique to the solar cycle.

Baldwin, Mark P.↗
NASA NTRS1984

Comparison of the Jovian north and south pole aurorae using the IUE observatory

New results on the spatial and temporal variability of the auroral emissions from Jupiter have been obtained from three IUE observations of the south pole made during the period July 1983 to March 1984. The current observations, together with previous IUE studies of the north pole aurora, provide convincing evidence for persistent longitudinal asymmetries in the Jovian auroral emissions. The strongest emissions appear to originate from regions centered near lambda-III of about 0 deg at the south pole and lambda-III of about 185 deg at the north pole. Differences in surface magnetic field strength seem inadequate to explain the extent to which particles precipitating along field lines into a given longitude sector in one hemisphere are inhibited from precipitating along the same field lines into the opposite hemisphere. Thus, the IUE auroral results present a challenge to existing models of auroral production.

Skinner, T. E.↗
NASA NTRS1982

Documentation for the machine-readable version of A Finding List of Stars of Spectral Type F2 and Earlier in a North Galactic Pole Region

The machine-readable data set is the result of an objective-prism survey made with an 80 cm/120 cm Schmidt telescope. The F2 and earlier stars were isolated from later type objects by using the MK classification criteria. The catalog contains 601 stars and includes cross identifications to the BD and HD catalogs, coordinates, photographic magnitudes and spectral types. A separate file contains the remarks from the original data tables merged with those following the data. The machine-readable files are described.

Warren, W. H., Jr.↗
NASA NTRS1992

The ionization conditions in the Milky Way halo - Infalling gas toward the North Galactic Pole

Observations of gas in the Milky Way halo are studied with an eye toward the theoretical predictions of the Galactic Fountain model for the production of halo gas. Data are shown that indicate significant variations in the ionization conditions in infalling halo gas in the northern galactic hemisphere. Understanding the nature of Milky Way halo gas plays a critical role in interpreting QSO absorption lines in the investigation of galaxies at high redshift.

Danly, Laura↗
NASA NTRS1994

Groups of galaxies in the ROSAT north ecliptic pole survey

The X-ray properties of groups of galaxies are presented. Their distribution of luminosity and temperature appears to be associated with the extrapolation of these distributions from rich clusters of galaxies. The properties of the ensemble of groups of galaxies are almost totally unknown. Only a few X-ray observations of groups that were selected by optical methods were published so far. A sample of eight groups with 'z' inferior to 0.04, of which three have 'z' inferior to 0.03 was investigated. The temperature and the luminosity functions at one point were determined.

Henry, J. Patrick↗