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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 91 records · Page 5
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NASA NTRS1972

Lunar dust motion.

Surveyor 7 photographed a bright glow along the western lunar horizon one hour after local sunset. This horizon glow must result from the forward scattering of sunlight by a swarm of dust grains extending 3 to 30 centimeters above the local horizon with a column density of 5 grains/sq cm. The observable glow is evoked by grains approximately 6 microns in radius. An annual churning rate of .001 g/sq cm is implied. A model is presented for dust cloud production in terms of electrostatic levitation of lunar surface fines.

Criswell, D. R.↗
NASA NTRS1973

The diurnal wind variation in the lowest 1500 ft in central Oklahoma - June 1966-May 1967.

A one-year accumulation of wind data from a television tower in northern Oklahoma City has been analyzed on a diurnal basis. The annual mean speeds below the third level at 296 ft are lowest at night and highest during the day, and conversely the speeds up to the seventh level at 1458 ft are lowest during the day and highest at night. Generally, speed changes occur in short time periods shortly after sunrise and near sunset. Resultant wind directions veer most with height from 1700 to 1000 CST and least during midday. At all levels winds veer with time between 2100 and approximately 1100 CST and then back with time during the remaining hours.

Crawford, K. C.↗
NASA NTRS1973

Surveyor observations of lunar horizon-glow.

Each of the Surveyor 7, 6, and 5 spacecraft observed a line of light along its western lunar horizont following local sunset. This horizon-glow (HG) is sunlight, which is forward scattered by dust grains present in a tenuous cloud formed temporarily (less than 3 hrs duration) just above sharp sunlight/shadow boundaries in the terminator zone. Electrically charged grains are levitated into the cloud by intense electrostatic fields (above 500 volts per centimeter) extending across the sunlight/shadow boundaries. Detailed analysis of the HG absolute luminance, temporal decay, and morphology confirm the cloud-model. This electrostatic mechanism ejects 10 million more particles per unit time into the cloud than could micro-meteorites. Electrostatic transport is probably the dominant local transport mechanism of lunar surface fines.

Rennilson, J. J.↗
NASA NTRS1973

Horizon-glow and the motion of lunar dust

Surveyor-7 photographed a bright glow along the western lunar horizon one hour after local sunset. This horizon-glow (HG) must result from the forward scattering of sunlight by electrically charged dust grains which are electrostatically levitated 3 to 30 cm above rocks or surface irregularities located in the lunar terminator zone. Column densities the order of 50 grains/sq cm are produced. The mechanism by which the electrostatic field is generated is described, and the amount of surface material annually churned by this process is estimated.

Criswell, D. R.↗
NASA NTRS1974

Exospheric temperature and composition from satellite beacon measurements

Routine measurements of the slab thickness of the ionosphere, from 1965 to 1971, are used to infer the changes in neutral temperature and ion composition at a mean latitude of 40 S. Values of neutral temperature at solar maximum are 5 to 10% above Northern Hemisphere backscatter results. The diurnal and seasonal changes agree closely with satellite drag and backscatter measurements, except that the maximum temperature occurs after sunset in winter. Winter night-time values of the O(+)/H(+) transition height were 500 km in 1965-1966, 800 km in 1968-1969, and 700 km in 1971. Changes in the transition height lag about six months behind the changes in solar flux. Diurnal variations have a minimum just before sunrise and a maximum 1 to 3 hr after noon. On winter nights the transition height descends to the level set by chemical equilibrium. On summer nights the transition height is always above this level, giving a continual production of H(+) which serves as an additional source for maintaining the night-time ionosphere in the winter hemisphere.

Titheridge, J. E.↗
NASA NTRS1973

Lunar ion energy spectra and surface potential

The acceleration model for lunar ions and the resulting ionosphere dynamics are reviewed briefly. An application is made to lunar atmosphere trapped in the surface fines, and the enhancement in the Ar-40/Ar-36 ratio in samples from the Apennine Front compared to the adjacent mare is calculated to be about 2.0. The predicted lunar ion energy spectra is shown and found to agree well with Suprathermal Ion Detector measurements; from this spectra, the neutral atmosphere scale height can be studied and the neutral atmosphere number density is found to be 100,000 to 300,000 per cu cm at the sunrise and sunset terminators. The lunar surface potential is calculated and is found to be several volts positive over much of the sunlit face of the moon but to go tens of volts negative at the terminator.

Manka, R. H.↗
NASA NTRS1974

Global temperature distributions from OGO-6 6300 A airglow measurements

The OGO-6 6300 A airglow temperature measurements have been used to develop models of the global temperature distributions under solstice and equinox conditions for the altitude region from 240 to 300 km and for times ranging from dawn in this altitude region to shortly after sunset. The distributions are compared with models derived from satellite orbital decay and incoherent scatter sounding. The seasonal variation of the temperature as a function of latitude is shown to be very different from that derived from static diffusion models with constant boundary conditions.

Blamont, J. E.↗
NASA NTRS1974

Preliminary infrared radiometry of the night side of Mercury from Mariner 10

The infrared radiometer on Mariner 10 measured the thermal emission from the planet with a spatial resolution element as small as 40 kilometers in a broad wavelength band centered at 45 micrometers. The minimum brightness temperature (near local midnight) in these near-equatorial scans was 100 K. Along the track observed, the temperature declined steadily from local sunset to near midnight, behaving as would be expected for a homogeneous, porous material with a thermal inertia only slightly larger than that of the moon. From near midnight to dawn, however, the temperature fluctuated over a range of about 10 K.

Chase, S. C.↗
NASA NTRS1974

Surveyor observations of lunar horizon-glow

Each of the Surveyor 7, 6, and 5 spacecraft observed a line of light along its western lunar horizon following local sunset. It has been suggested that this horizon-glow (HG) is sunlight, which is forward-scattered by dust grains present in a tenuous cloud formed temporarily just above sharp sunlight/shadow boundaries in the terminator zone. Electrically charged grains could be levitated into the cloud by intense electrostatic fields extending across the sunlight/shadow boundaries. Detailed analysis of the HG absolute luminance, temporal decay, and morphology confirm the cloud model. The levitation mechanism must eject 10,000,000 more particles per unit time into the cloud than could micrometeorites. Electrostatic transport is probably the dominant local transport mechanism of lunar surface fines.

Rennilson, J. J.↗
NASA NTRS1975

The investigation of O and N2 densities from the OSO-7 extreme UV data

The results of solar radiation observations in the extreme ultra-violet spectrum from 200 A to 600 A made by the OSO-7 Satellite were studied. The results of the influence of attenuation by the atmosphere in the 250 to 500 km altitude range are presented. Using published molecular absorption cross-sections at 304 A and 256 A, the Jaccia atmospheric model is validated, and shows that a mean exospheric of 1050 K is appropriate for the sunset data.

Source record↗
NASA NTRS1974

Thermal moonquakes

Review of the results of a study of the characteristics of thermal moonquakes and of their role in the erosion of the lunar surface. Thermal moonquake activity starts abruptly about 2 days after lunar sunrise and decreases rapidly after sunset. Two possible source mechanisms for thermal moonquakes are suggested: fracturing or movement of rocks along zones of weakness and slumping of lunar soil on slopes triggered by thermal stresses.

Duennebier, F.↗
NASA NTRS1975

Mission analysis for satellite measurements of stratospheric constituents by solar occultation

Orbital characteristics and launch vehicle requirements for a solar occultation experiment measuring atmospheric constituents, such as aerosols or ozone, during the Nimbus-G and Applications Explorer Missions are analyzed. The experiment to be flown is basically a sun photometer which measures the spectral attenuation of solar radiation by the earth's atmosphere during spacecraft sunrise and sunset, yielding two aerosol and/or ozone stratospheric profiles per orbit. The tangent latitudes and longitudes as well as frequency of these measurements are analyzed for various spacecraft orbits to define maximum geographical coverage capability. Results indicate that a 50 deg inclined orbit for Applications Explorer provides latitude coverage from approximately 70 deg north to 70 deg south every 2-1/2 weeks. A high-moon, sun-synchronous orbit with an inclination of 99 deg for Nimbus-G will provide for coverage of occultation measurements at high latitudes near the polar regions (i.e., 64 to 80 deg north and south). The solar pointing requirements of the experiment in terms of yaw and pitch angles are also defined.

Harrison, E. F.↗
NASA NTRS1975

Determination of nitric oxide concentrations from sunrise E-region electron density measurements

Midlatitude sunrise electron density profiles have been analyzed in order to determine nitric oxide concentrations in the range 100-160 km. In general, the determinations are restricted to heights for which the ionization of nitric oxide by direct solar Lyman-alpha radiation is the main contribution to the growth of the E region. The concentrations obtained are larger, by factors of approximately 3 to 4, than those obtained from the midlatitude airglow measurements of other workers. Concentrations have been obtained from one sunset measurement and these are significantly lower than the sunrise values. The results also give a clear indication of increasing nitric oxide concentrations above 120 km with increasing solar activity.

Monro, P. E.↗
NASA NTRS1975

Observations of OI 7774 emission excited by conjugate photoelectrons

Observations and computer calculations of O I 7774 A airglow emissions excited by conjugate photoelectrons have been carried out. The observations were made at McDonald Observatory, Texas using a 2 m grille spectrometer from December 1972 to June 1973. The zenithal emission intensity during conjugate photoelectron precipitation was fairly constant at 2-4 R until conjugate sunset, after which it diminished steadily and ceased near a conjugate solar zenith angle of 105 (plus or minus 3) deg. A predawn enhancement in both O I 7774 A and forbidden O I 6300 A was observed to commence near 102 deg. The computations utilize the two-stream technique of Nagy and Banks (1970) to obtain the escaping photoelectron flux and the local excitation rates of the oxygen emissions. Good agreement with the observations is obtained for the dependence of the emission rate on conjugate solar zenith angle.

Christensen, A. B.↗
NASA NTRS1976

Apollo 14 and 16 Active Seismic Experiments, and Apollo 17 Lunar Seismic Profiling

Seismic refraction experiments were conducted on the moon by Apollo astronauts during missions 14, 16, and 17. Seismic velocities of 104, 108, 92, 114 and 100 m/sec were inferred for the lunar regolith at the Apollo 12, 14, 15, 16, and 17 landing sites, respectively. These data indicate that fragmentation and comminution caused by meteoroid impacts has produced a layer of remarkably uniform seismic properties moonwide. Brecciation and high porosity are the probable causes of the very low velocities observed in the lunar regolith. Apollo 17 seismic data revealed that the seismic velocity increases very rapidly with depth to 4.7 km/sec at a depth of 1.4 km. Such a large velocity change is suggestive of compositional and textural changes and is compatible with a model of fractured basaltic flows overlying anorthositic breccias. 'Thermal' moonquakes were also detected at the Apollo 17 site, becoming increasingly frequent after sunrise and reaching a maximum at sunset. The source of these quakes could possibly be landsliding.

Source record↗
NASA NTRS1975

Energetic lunar nighttime ion events

The suprathermal ion detector experiment regularly observes ion events normally ranging from 250 eV/q to 1000 eV/q all through the lunar night. These ion events occur most often 2 to 3 days prior to the sunrise terminator. There is also a secondary activity peak 3 to 4 days after local sunset on the moon. The events are normally of 4 hr or less in duration, and the integral flux is 1 million ions per sq cm/sec/sr. This article discussed the character of these events and presents preliminary findings of a detailed study on this subject.

Schneider, H. E.↗
NASA NTRS1976

Sources of lunar limb compressions - Topographic correlations

Apollo 15 and 16 subsatellite observations of lunar limb compressions in the solar wind have been studied statistically by correlating occurrence rates for the compressions with seven topographic parameters derived from Apollo laser altimetry, with the use of a 5-deg x 5-deg selenographic grid. Maximum, rms, and average sunset-facing slopes are significantly correlated with occurrence rates in the source regions, but no correlation with elevation differences is found. Variance percentages suggest that a slope-related source mechanism generates about 6-8% of the limb compressions originating in source areas covered by the laser altimetry. These results confirm the preliminary conclusions of an earlier statistical study, based on Explorer 35 limb-compression observations, which used a coarser 15-deg x 15-deg grid

Srnka, L. J.↗
NASA NTRS1976

The O I /5577-A wavelength/ airglow - Observations and excitation mechanisms

Analysis of the O I /5577-A wavelength/ airglow observations conducted on board the Atmosphere Explorer C satellite yields the following results when combined with simultaneous measurements of ion and neutral composition. A volume emission rate profile derived after sunset requires the production of an O(1S) atom in 8% of the O2(+) recombinations. Photoelectric impact on atomic oxygen and the dissociative recombination of O2(+) are important sources of O(1S) in the dayglow; however, the airglow measurements require a large additional production of O(1S) below 200 km in addition to these. The reaction N + O2(+) yielding NO(+) + O(1S) can provide the missing O(1S) source if the rate coefficient is near 2.5 times 10 to the minus 11th cu cm per sec.

Frederick, J. E.↗