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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Dust Production of Comet 21P/Giacobini Zinner Using Broadband Photometry

Comet 21P/Giacobini-Zinner is a Jupiter family comet that was discovered in December of 1900 by the French astronomer Michel Giacobini, and rediscovered two orbits later by German astronomer Ernst Zinner in 1913. 21P is approximately 2 km in diameter, and is the parent of the Draconids, a meteor shower known to undergo dramatic outbursts. In 1933 and 1946, up to 10,000 meteors per hour were reported for the Draconids; and 2011 saw a minor Draconid outburst. As meteor stream modeling/ forecasting is a primary focus for the NASA Meteoroid Environment Office, it was decided to monitor 21P for three purposes: firstly to find the apparent and absolute magnitude with respect to heliocentric distance; second to calculate Af(rho), a quantity that describes the dust production rate and is used in models to predict the activity of the Draconids; thirdly to detect possible increases in cometary activity, which could correspond to future Draconid meteor outbursts. Giacobini-Zinner is unique in several ways. It was the first comet to have measurements made in situ. Comet 21P was visited by ICE (International Cometary Explorer) in 1985 to study the interaction of the cometary atmosphere with the flowing solar-wind plasma. It is a carbon-depleted comet, and most studies show that it peaks in gas and dust production pre-perihelion, specifically in two very studied passages; 1985 and 1998. A prior study was conducted by Pittichova et al (2008) for 21P during its 2004-2006 close approach to the Sun. Apparent and absolute magnitudes were measured at various heliocentric distances as well as the dust production. At 2.32 AU from the Sun, 21P exhibited an apparent magnitude of 17.05 and Af of 83 cm, and an apparent magnitude of 15.91/Af(rho) of 130.66 cm at 1.76 AU. Another such study performed by Lara et al.on 21P s 1998 apparition found values of Af(rho) of 1010 cm when 1.05 AU from the Sun, two weeks before perihelion, and 669 cm at perihelion, when 1.03 AU from the Sun

Blaauw, Rhiannon↗
NASA NTRS2016

Determination of the Meteor Limiting Magnitude

The limiting meteor magnitude of a meteor camera system will depend on the camera hardware and software, sky conditions, and the location of the meteor radiant. Some of these factors are constants for a given meteor camera system, but many change between meteor shower or sporadic source and on both long and short timescales. Since the limiting meteor magnitude ultimately gets used to calculate the limiting meteor mass for a given data set, it is important to have an understanding of these factors and to monitor how they change throughout the night, as a 0.5 magnitude uncertainty in limiting magnitude translates to a uncertainty in limiting mass by a factor of two.

Kingery, A.↗
NASA NTRS2003

Practical Meteor Stream Forecasting

Inspired by the recent Leonid meteor storms, researchers have made great strides in our ability to predict enhanced meteor activity. However, the necessary calibration of the meteor stream models with Earth-based ZHRs (Zenith Hourly Rates) has placed emphasis on the terran observer and meteor activity predictions are published in such a manner to reflect this emphasis. As a consequence, many predictions are often unusable by the satellite community, which has the most at stake and the greatest interest in meteor forecasting. This paper suggests that stream modelers need to pay more attention to the needs of this community and publish not just durations and times of maxima for Earth, but everything needed to characterize the meteor stream in and out of the plane of the ecliptic, which, at a minimum, consists of the location of maximum stream density (ZHR) and the functional form of the density decay with distance from this point. It is also suggested that some of the terminology associated with meteor showers may need to be more strictly defined in order to eliminate the perception of crying wolf by meteor scientists. An outburst is especially problematic, as it usually denotes an enhancement by a factor of 2 or more to researchers, but conveys the notion of a sky filled with meteors to satellite operators and the public. Experience has also taught that predicted ZHRs often lead to public disappointment, as these values vastly overestimate what is seen.

Cooke, William J.↗
NASA NTRS2011

Numerical Modeling of Cometary Meteoroid Streams Encountering Mars and Venus

We have simulated numerically the existence of meteoroid streams that encounter the orbits of Mars and Venus, potentially producing meteor showers at those planets. We find that 17 known comets can produce such showers, the intensity of which can be determined through observations. Six of these streams contain dense dust trails capable of producing meteor outbursts.

Christou, A. A.↗
NASA NTRS2001

In Situ Measurements of Meteoric Ions

Metal ions found in the atmosphere above 60 km are the result of incoming meteoroid atmospheric ablation. Layers of metal ions are detected by sounding rocket in situ mass spectrometric sampling in the 80 to 130 km region, which coincides with the altitude region where meteors are observed. Enhancements of metal ion concentrations occur during meteor showers. Even outside of shower periods, the metal ion altitude profiles vary from measurement to measurement. Double layers are frequent at middle latitudes. More than 40 different meteoric atomic and molecular ions, including isotopes, have been detected. Atmospheric metal ions on average have an abundance that matches chrondritic material, the same composition as the early solar system. However there are frequently local departures from this composition due to differential ablation, species dependent chemistry and mass dependent ion transport. Metal ions react with atmospheric O2, O, O3, H2O and H2O2 to form oxygenated and hydrogenated ionic compounds. Metal atomic ions at high altitudes have long lifetimes. As a result, these ions, in the presence of Earth's magnetic field, are transported over long distances by upper atmospheric winds and ionospheric electric fields. Satellite measurements have detected metal ions as high as, approximately 1000 km and have revealed circulation of the ions on a global scale.

Grebowsky, Joseph M.↗
NASA NTRS1982

Chemistry of cometary meteoroids from video-tape records of meteor spectra

The chemistry of the cometary meteoroids was studied by closed circuit television observing systems. Vidicon cameras produce basic data on standard video tape and enable the recording of the spectra of faint shower meteors, consequently the chemical study is extended to smaller particles and we have a larger data bank than is available from the more conventional method of recording meteor spectra by photography. The two main problems in using video tape meteor spectrum records are: (1) the video tape recording has a much lower resolution than the photographic technique; (2) video tape is relatively new type of data storage in astronomy and the methods of quantitative photometry have not yet been fully developed in the various fields where video tape is used. The use of the most detailed photographic meteor spectra to calibrate the video tape records and to make positive identification of the more prominent chemical elements appearing in the spectra may solve the low resolution problem. Progress in the development of standard photometric techniques for the analysis of video tape records of meteor spectra is reported.

Millman, P. M.↗
NASA NTRS1999

Johnson Space Center's Leonids Optical Observations

The 1998 Leonids Meteor Shower was videoed by NASA Johnson Space Center (JSC) personnel at Houston, Texas, and Cloudcroft, New Mexico. The videos were screened and the Leonids Meteors in the videos were analyzed. The outcome of this effort was tables of counts per hour over the viewing period and a comparison to the Leonids Meteors Mass Distribution model used for risk assessment calculations associated with space shuttle missions. The comparison exhibited a difference between the observed data and the model.

Pawlowski, James F.↗
NASA NTRSDate not supplied

Workshop Goals and MEO Overview

To provide an overview of current meteor instrumentation, meteoroid models, and meteor shower forecasting techniques.§Identify knowledge gaps and areas of focus for the hazardousmeteoroid environment (0.1 to 1 cm). Foster collaborations and discussions among North American meteor researchers.

MEO↗
NASA NTRS2000

The Leonid Meteors and Space Shuttle Risk Assessment

The November 1999 Leonid meteor shower was videotaped on the grounds of the NASA Johnson Space Center (JSC) and at the JSC Observatory in Cloudcroft, New Mexico. The videotapes were analyzed using a meteor analysis system developed at JSC. The results of the analysis were compared to the Leonid Meteors Mass Distribution Model derived at JSC and used for micrometeoroid and orbital debris risk assessment performed before each Space Shuttle mission. The observed data compared favorably to the model in the .001 to 0.2 gram range but diverged from the model for the smaller masses. We attribute the divergence to optical equipment limitations. These 1999 results will be compared with the 1998 results which were presented at the April 1999 Leonid Multi-Instrument Aircraft Campaign (MAC) Workshop.

Pawlowski, James F.↗
NASA NTRS2019

The Search for the Gamma Lyrid Progenitor

On 5 February 2015, a previously unknown meteor shower, the γ Lyrids were observed for the first time. Because of the Sun-Earth-Moon viewing geometry, however, stream members were observed almost exclusively by the Canadian Meteor Orbit Radar (CMOR). The γ Lyrids did not appear again until 2018, and that outburst was stronger than in 2015. This study analyzed the 2015 and 2018 CMOR data in order to determine the orbital parameters of the stream in an attempt to determine the γ Lyrid parent body. Of primary importance is to determine if the γ Lyrids will recur in a predictable manner. Two bodies, with dramatically different orbital parameters and evolutionary behaviors, emerged as the leading candidates: 2003 EH1 and 1854 R1.

Grazier, Kevin R.↗
NASA NTRS2005

From H.G. Wells to Unmanned Planetary Exploration

The possibility of planetary exploration has been a dream of the human race since Galileo discovered the moons of Jupiter in 1610. Visual sightings of bodies entering Earth s atmosphere have been made by Earth s inhabitants over the centuries. Over time, the many meteor showers (Leonid, Perseid) have provided dramatic evidence of the intense heat generated by a body entering Earth s atmosphere at hypervelocity speeds. More recently (in 1908), few viewed the Tunguska meteor that impacted in Siberia, but the destructive power on the countryside was awesome.

Boyd, John W.↗
NASA NTRS2017

Meteoroid Bulk Density and Ceplecha Types

The determination of asteroid bulk density is an important aspect of Near Earth Object (NEO) characterization. A fraction of meteoroids originate from asteroids (including some NEOs), thus in lieu of mutual perturbations, satellites, or expensive spacecraft missions, a study of meteoroid bulk densities can potentially provide useful insights into the densities of NEOs and PHOs (Potentially Hazardous Objects). Meteoroid bulk density is still inherently difficult to measure, and is most often determined by modeling the ablation of the meteoroid. One approach towards determining a meteoroid density distribution entails using a more easily measured proxy for the densities, then calibrating the proxy with known densities from meteorite falls, ablation modelling, and other sources. An obvious proxy choice is the Ceplecha type, KB (Ceplecha, 1958), which is thought to indicate the strength of a meteoroid and often correlated to different bulk densities in literature. KB is calculated using the air density at the beginning height of the meteor, the initial velocity, and the zenith angle of the radiant; quantities more readily determined than meteoroid bulk density itself. Numerical values of K(sub B) are sorted into groups (A, B, C, etc.), which have been matched to meteorite falls or meteor showers with known composition such as the porous Draconids. An extensive survey was conducted to establish the strength of the relationship between bulk density and K(sub B), specifically looking at those that additionally determined K(sub B) for the meteors. In examining the modeling of high-resolution meteor data from Kikwaya et al. (2011), the correlation between K(sub B) and bulk density was not as strong as hoped. However, a distinct split by dynamical type was seen with Jovian Tisserand parameter (T(sub J)), with meteoroids from Halley Type comets (T(sub J) < 2) exhibiting much lower bulk densities than those originating from Jupiter Family comets and asteroids (T(sub J) > 2). Therefore, this work indicates that the dynamical classification of a meteoroid is a better indicator of the density than the strength proxy, a somewhat surprising result.

Blaauw, R. C.↗
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 NTRS1990

Ca(+) emission in the sunlit ionosphere

In the course of a program of twilight airglow observations, the resonance fluorescence emissions from calcium ions were measured. In particular, twilight sequences were obtained during the period of December 19-22, 1987, which coincided with the Ursids meteorite shower. During this meteorite event the intensities of the Ca(+) emission lines at 3934A increased to the point that the surface brightness profiles could be inverted to volume emission rate profiles. These profiles show evidence for strong spatial redistribution of the Ca(+) over the course of three days. Observations of these emissions during meteor shower periods could provide a valuable tracer for the processes responsible for the transport of ions in the D, E, and F region, allowing the full altitude and latitude extent of the distribution to be determined.

Torr, Marsha R.↗
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 NTRSDate not supplied

Realistic gravitational focusing of meteoroid streams

A meteor shower can be modeled, to first order, as a parallel stream of particles encountering the Earth. Gravity bends the trajectories of these particles inward, producing an increase in flux both near the planet and along the anti-radiant line. This effect is known as gravitational focusing, and the interception of a portion of meteoroid trajectories by the Earth or another massive body is known as planetary shielding. For a perfectly parallel meteoroid stream, gravitational focusing produces a flux singularity along the anti-radiant line, near which intense enhancements in flux occur. In reality, meteoroids will exhibit some dispersion in their motion that removes this singularity. We present a modified analytic treatment of gravitational focusing and planetary shielding that takes this dispersion into account and discuss its ramifications for several problems in meteor astronomy.

Althea Valkyrie Moorhead↗
DOE OSTI2026

Steady Spills, Stronger Signals: Machine Learning for Slow Spill Analysis

Particle accelerator experiments rely on stable, consistent proton beams to maximize scientific discovery. This presentation introduces beam spills, duty factor, and beam stability using a meteor shower analogy before exploring how feedback control and machine learning, including recurrent neural networks (RNNs), can analyze spill data, identify patterns, and predict beam behavior. Together, these approaches support beam optimization and improve our understanding of accelerator performance for experiments such as Mu2e.

Prescott, Matthew J. [Fermilab]↗