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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Bi-telescopic, deep, simultaneous meteor observations

A statistical summary is presented of 10 hours of observing sporadic meteors and two meteor showers using the Experimental Test System of the Lincoln Laboratory. The observatory is briefly described along with the real-time and post-processing hardware, the analysis, and the data reduction. The principal observational results are given for the sporadic meteor zenithal hourly rates. The unique properties of the observatory include twin telescopes to allow the discrimination of meteors by parallax, deep limiting magnitude, good time resolution, and sophisticated real-time and post-observing video processing.

Taff, L. G.↗
NASA NTRS1987

The archiving of meteor research information

The results obtained over the past years under GLOBMET are not reviewed but some of the problems the solution of which will guide further development of meteor investigation and international cooperation in this field for the near term are discussed. The main attention is paid to problems which the meteor community itself can solve, or at least expedite. Most of them are more or less connected with the problem of information archiving. Information archiving deals with methods and techniques of solving two closely connected groups of problems. The first is the analysis of data and information as an integral part of meteor research and deals with the solution of certain methodological problems. The second deals with gathering data and information for the designing of models of the atmosphere and/or meteor complex and its utilization. These problem solutions are discussed.

Nechitailenko, V. A.↗
NASA NTRS1987

On the meteor trail spectra

Meteor radiation appears as a result of collisions between meteoroid atoms and air molecules. Depending on duration, this radiation is usually divided into the following types: radiation of the meteor head; radiation of a coma surrounding or immediately following the meteor head; radiation of a trail formed as a result of fragments lagging behind or by the afterglow; and radiation of a meteor train forming from a tail as a result of various chemical and dynamical processes. To investigate physical processes caused by each of the above types, it is necessary to obtain the corresponding experimental data. The physical processes of the radiation and the measurement of the experimental data is discussed.

Ovezgeldyev, O. G.↗
NASA NTRS1987

Meteor matter interaction with the Earth's atmosphere and the ionospheric E-region structure

The exploration of the ionospheric E region is a pressing problem, both in the applied and fundamental studies. Results are presented of an investigation: (1) to estimate the meteor ionization contribution to the night time E layer and influx; (2) to study the phenomenon of intensive sporadic layer formation following cessation of meteor stream activity; and (3) to access the role of metallic ions of meteor origin in the diurnal and seasonal variations in the occurrence probabilities of midlatitude E sub s. The contribution was evaluated of meteor matter, Lyman radiation and corpuscular particles to the electron concentration of the night E region. Results are discussed.

Alimov, O.↗
NASA NTRS1987

Density variations of meteor flux along the Earth's orbit

No model of distribution of meteor substance is known to explain the observed diurnal and annual variations of meteor rates, if that distribution is assumed to be constant during the year. Differences between the results of observations and the prediction of diurnal variation rates leads to the conclusion that the density of the orbits of meteor bodies changes with the motion of the Earth along its orbit. The distributions of the flux density over the celestial sphere are obtained by the method described previously by Svetashkova, 1984. The results indicate that the known seasonal and latitudinal variations of atmospheric conditions does not appear to significantly affect the value of the mean flux density of meteor bodies and the matter influx onto the Earth.

Svetashkova, N. T.↗
NASA NTRS1987

Monte Carlo modeling and meteor showers

Prediction of short lived increases in the cosmic dust influx, the concentration in lower thermosphere of atoms and ions of meteor origin and the determination of the frequency of micrometeor impacts on spacecraft are all of scientific and practical interest and all require adequate models of meteor showers at an early stage of their existence. A Monte Carlo model of meteor matter ejection from a parent body at any point of space was worked out by other researchers. This scheme is described. According to the scheme, the formation of ten well known meteor streams was simulated and the possibility of genetic affinity of each of them with the most probable parent comet was analyzed. Some of the results are presented.

Kulikova, N. V.↗
NASA NTRS1987

The Cyclone meteor radar system for routine wind measurements in the lower thermosphere

A new meteor wind radar system called Cyclone was devised to extend and update the meteor radar network and for unattended operation. The Cyclone meteor radar system obtains information from four directions simultaneously. To automate data processing a special digital device was developed. An algorithm used to determine the Doppler shifts was adopted, which makes it possible to eliminate selectivity with respect to slow velocity meteor drifts. The operation of the Cyclone system is described.

Lysenko, I. A.↗
NASA NTRS1989

The meteor radar as a tool for upper atmosphere research

Meteor radar provide measurements of the upper mesosphere and lower thermosphere neutral wind field by using the reflection of electromagnetic waves from meteor trails. These radars are relatively inexpensive and provide an excellent means of monitoring the mean winds and tides in the 80 to 100 km region. Recently new techniques were developed to detect meteor echoes from other ground based radar systems operating in the HF/VHF frequency range. The meteor echo information augments the data that are routinely collected by these radars. These new techniques are discussed.

Avery, S. K.↗
NASA NTRS1989

Radar scattering mechanisms within the meteor crater ejecta blanket: Geologic implications and relevance to Venus

Simple impact craters are known to occur on all of the terrestrial planets and the morphologic expression of their ejecta blankets is a reliable indicator of their relative ages on the Moon, Mars, Mercury, and most recently for Venus. It will be crucial for the interpretation of the geology of Venus to develop a reliable means of distinguishing smaller impact landforms from volcanic collapse and explosion craters, and further to use the observed SAR characteristics of crater ejecta blankets (CEB) as a means of relative age estimation. With these concepts in mind, a study was initiated of the quantitative SAR textural characteristics of the ejecta blanket preserved at Meteor Crater, Arizona, the well studied 1.2 km diameter simple crater that formed approx. 49,000 years ago from the impact of an octahedrite bolide. While Meteor Crater was formed as the result of an impact into wind and water lain sediments and has undergone recognizable water and wind related erosion, it nonetheless represents the only well studied simple impact crater on Earth with a reasonably preserved CEB. Whether the scattering behavior of the CEB can provide an independent perspective on its preservation state and style of erosion is explored. Finally, airborne laser altimeter profiles of the microtopography of the Meteor Crater CEB were used to further quantify the subradar pizel scale topographic slopes and RMS height variations for comparisons with the scattering mechanisms computed from SAR polarimetry. A preliminary assessment was summarized of the L-band radar scattering mechanisms within the Meteor Crater CEB as derived from a NASA/JPL DC-8 SAR Polarimetry dataset acquired in 1988, and the dominant scattering behavior was compared with microtopographic data (laser altimeter profiles and 1:10,000 scale topographic maps).

Garvin, J. B.↗
NASA NTRS1992

About distribution and origin of the peculiar group of sporadic meteors

A particular group of sporadic meteors are picked out from analysis of meteor catalogs derived from results of radar observations in Mogadisho and Kharkov. The semi-major axes are equal or more than 1.73 AU and inclinations of orbits are equal or more than 90 degrees for these meteors. The distributions of radiants, velocities, and elements of orbits were derived. The probable source of meteor bodies of this peculiar group is the long-period comets, in particular, the comets of the Kreutz's group.

Andreev, V. V.↗
NASA NTRS1992

On associations of Apollo asteroids with meteor streams

Potential associations of Apollo asteroids with meteor streams are searched on the basis of the orbital parameters comparison. From all Apollo asteroids discovered through 1991 June those are only selected for further analysis whose orbits approach to less than 0.1 AU to the Earth's orbit. Their orbits are compared with precise photographic orbits of individual meteors from the Meteor Data Center in Lund. Results on the associations of asteroids with meteor streams are presented and discussed.

Porubcan, V.↗
NASA NTRS1992

Visual data of minor meteor showers limits of the method

Visual meteor observations are carried out on a regular basis by many experienced observers worldwide, thus supplying information about activity of meteor showers. The limits of the method are determined by the accuracy of the detection of the meteor trail. This study shows that visual meteor observations provide reliable data for an observable hourly rate of greater than or equal to 3.

Rendtel, Jurgen↗
NASA NTRS1961

Interplanetary Dust Particles of Micron Size Probably Associated with the Leonid Meteor Stream

An interplanetary dust particle event, coincident with the Leonid meteor shower and lasting approximately 70 hours, was recorded by a sensor on the Vanguard III satellite. During this interval the satellite's microphone system registered impacts of approximately 2800 dust particles with momenta exceeding 10(exp -2) dyne-second. The impact rate varied by as much as two orders of magnitude within a few hours. The microphone system was almost omnidirectional, so the radiants of the dust particles cannot be defined. Association of these dust particles with the Leonid meteor stream is suggested by the coincidence in time and by the location of the satellite. Vanguard III traversed five major meteor streams, but the impact rates significantly exceeded the background rate only during this one interval. This is the first case in which a significant increase in the directly measured impact rate of dust particles possibly can be associated with a major meteor stream.

Alexander, W. M.↗
NASA NTRS1999

Martian Meteor Ionization Layers

Small interplanetary grains bombard Mars, like all the solar system planets, and, like all the planets with atmospheres, meteoric ion and atom layers form in the upper atmosphere. We have developed a comprehensive one-dimensional model of the Martian meteoric ionization layer including a full chemical scheme. A persistent layer of magnesium ions should exist around an altitude of 70 km. Unlike the terrestrial case, where the metallic ions are formed via charge-exchange with the ambient ions, Mg(+) in the Martian atmosphere is produced by photoionization. Nevertheless, the predicted metal layer peak densities for Earth and Mars are similar. Diffusion solutions, such as those presented here, should be a good approximation of the metallic ions in regions where the magnetic field is negligible and may provide a significant contribution to the nightside ionosphere. The low ultraviolet absorption of the Martian atmosphere may make Mars an excellent laboratory in which to study meteoric ablation. Resonance lines not seen in the spectra of terrestrial meteors may be visible to a surface observatory in the Martian highlands.

Grebowsky, J. M.↗
NASA NTRS2000

The First Confirmed Videorecordings of Lunar Meteor Impacts

North American observers recorded at least six meteors striking the Moon's surface during the Leonid meteor shower on 1999 Nov. 18. Each meteor produced a flash that was recorded from at least two separate locations, marking the first confirmed lunar meteor impacts.

Dunham, D. W.↗
NASA NTRS2000

Characteristics of Fe Ablation Trials Observed During the 1998 Leonid Meteor Shower

Eighteen Fe ablation trails were observed during the 17/18 Nov 1998 Leonid meteor shower with an airborne Fe lidar aboard the National Simulation Facility/National Center for Atmospheric Research (NSF/NCAR) Electra aircraft over Okinawa. The average altitude of the 18 trails from the high velocity (72 km/s) Leonid meteors, 95.67 +/- 0.93 km, is approximately 6.7 km higher than previously observed for slower (approx. 30 km/s) sporadic meteors. This height difference is consistent with the assumption that meteors ablate when the kinetic energy imparted to the atmosphere reaches a critical threshold. The average age of the Fe trails, determined by a diffusion model, is 10.1 min. The youngest ages were observed below 92 km and above 98 km where chemistry and diffusion dominate, respectively. The average abundance of the trails is ten percent of the abundance of the background Fe layer. Observations suggest that the 1998 Leonid shower did not have a significant impact on the abundance of the background Fe layer.

Chu, Xin-Zhao↗
NASA NTRS2000

Jet-Like Structures and Wake in Mg I (518 nm) Images of 1999 Leonid Storm Meteors

Small meteoric fragments are ejected at significant transverse velocities from some (up to approx. 8%) fast Leonid meteors. We reach this conclusion using low light intensified image measurements obtained during the 1999 Leonid Multi-Instrument Aircraft Campaign. High spatial resolution, narrow band image measurements of the Mg I emission at 518 nm have been used to clearly identify jet-like features in the meteor head that are the same as first observed in white light. We postulate that these unusual structures are caused by tiny meteoroid fragments (containing metallic grains) being rapidly ejected away from the core meteoroid as the constituent glue evaporates. Marked curvature observed in the jet-like filaments suggest that the parent meteoroids are spinning and as the whirling fragments are knocked away by the impinging air molecules, or by grain-grain collisions in the fragment ensemble, they ablate quickly generating an extended area of structured luminosity up to about 1-2 km from the meteoroid center. Fragments with smaller transverse velocity components are thought to be responsible for the associated beading evident in the wake of these unusual Leonid meteors.

Taylor, M. J.↗
NASA NTRS2002

Major Element Analysis of the Target Rocks at Meteor Crater, Arizona

We collected approximately 400 rock chips in continuous vertical profile at Meteor Crater, Arizona, representing, from bottom to top, the Coconino, Toroweap, Kaibab, and Moenkopi Formations to support ongoing compositional analyses of the impact melts and their stratigraphic source depth(s) and other studies at Meteor Crater that depend on the composition of the target rocks. These rock chips were subsequently pooled into 23 samples for compositional analysis by XRF (x ray fluorescence) methods, each sample reflecting a specific stratigraphic "subsection" approximately 5-10 in thick. We determined the modal abundance of quartz, dolomite, and calcite for the entire Kaibab Formation at vertical resolutions of 1-2 meters. The Coconino Formation composes the lower half of the crater cavity. It is an exceptionally pure sandstone. The Toroweap is only two inches thick and compositionally similar to Coconino, therefore, it is not a good compositional marker horizon. The Kaibab Formation is approximately 80 in thick. XRD (x ray diffraction) studies show that the Kaibab Formation is dominated by dolomite and quartz, albeit in highly variable proportions; calcite is a minor phase at best. The Kaibab at Meteor Crater is therefore a sandy dolomite rather than a limestone, consistent with pronounced facies changes in the Permian of SE Arizona over short vertical and horizontal distances. The Moenkopi forms the 12 in thick cap rock and has the highest Al2O3 and FeO concentrations of all target rocks. With several examples, we illustrate how this systematic compositional and modal characterization of the target ideologies may contribute to an understanding of Meteor Crater, such as the depth of its melt zone, and to impact cratering in general, such as the liberation of CO2 from shocked carbonates.

See, Thomas H.↗