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Meteor captured in Kiruna (Sweden) on October 06 2007 at 01:54:42 UTC crossing the entire field of view.
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We have optically recorded faint meteors using a large aperture LLLTV (low light level television) system based on second generation image intensifiers. These data consist of 42 two-station meteors of which 13 were captured during an observing campaign near London, Ontario (Canada) in May 2004, and 29 during a campaign near Kiruna (Sweden) in Octob...
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... of the meteors, as seen from both sites, either started in the field of view but ended outside, or started outside and ended in the field of view of one camera ( Figs. 1 and 2). Some com- pletely crossed the field of view (Fig. 3). Some even crossed the entire field of view in just one frame, making it virtually impos- sible to get an astrometric solution. All these meteors failed to satisfy our two criteria and were eliminated. Among the 13 mete- ors seen simultaneously on both sites in the first observing run, only four satisfied the conditions of starting and ...
Citations
... Additionally, potential damage to satellites and spacecraft caused by impacts is strongly affected by whether the particle is a porous dust aggregate or a monolithic body (Drolshagen and Moorhead, 2019). For meteors, bulk density is difficult to determine due to complicating effects such as fragmentation, variations in ablation behaviour and shape, as well as differences in structure and chemical composition (Kikwaya et al., 2009). With these caveats in mind, attempts have been made in the past to estimate bulk densities of various meteor populations including meteor showers and comet nuclei. ...
... Thus, the study of meteoroid flight through the atmosphere can provide constraints on the strength and bulk density of the bolides that give rise to some of the meteorites. Unlike the meteorites, which may be measured directly in the laboratory, the flight of meteoroids in the atmosphere permit only indirect inference of physical properties based on the observed ablation behavior (e.g., Ceplecha et al., 1998;Kikwaya et al., 2009;Kikwaya et al., 2011). This drawback is counterbalanced by the wider range of material probed using the atmosphere as the "detector," since many weak or fast meteoroids do not survive to reach the ground. ...
The physical properties of the stone meteorites provide important clues to understanding the formation and physical evolution of material in the Solar protoplanetary disk as well providing indications of the properties of their asteroidal parent bodies. Knowledge of these properties is essential for modeling a number of Solar System processes, such as bolides in planetary atmospheres, the thermal inertia of atmosphereless solid body surfaces, and the internal physical and thermal evolution of asteroids and rock-rich icy bodies. In addition, insight into the physical properties of the asteroids is important for the design of robotic and crewed reconnaissance, lander, and sample return spacecraft missions to the asteroids. One key property is meteorite porosity, which ranges from 0% to more than 40%, similar to the range of porosities seen in asteroids. Porosity affects many of the other physical properties including thermal conductivity, speed of sound, deformation under stress, strength, and response to impact. As a result of the porosity, the properties of most stone meteorites differ significantly from those of compact terrestrial rocks, whose physical properties have been used in many models of asteroid behavior. A few physical properties, such as grain density, magnetic susceptibility, and heat capacity are not functions of porosity. Taken together, the grain density and the magnetic susceptibility can be used to classify unweathered or minimally weathered ordinary chondrites. This provides a rapid screening technique to identify heterogeneous samples, classify new samples, and identify misclassified meteorites or interlopers in strewn fields.
... The idea of very short baseline trajectory estimation was made apparent to this author after a serendipitous collection of a meteor from closely spaced video cameras measuring the diameter of the asteroid Metis (Degenhardt and Gural 2010). This concept was also independently evaluated and processed for 5 km spaced zenith pointing cameras at the University of Western Ontario (Kikwaya et al. 2009). The simulation herein bears this out, as it shows that as long as the observed elevation angle of a meteor is above 35°, the sites could be as close as 1 km apart for the multiparameter fit to function as well as seen in Fig. 10. ...
A new approach has been formulated to solve for the straight line
trajectory of a meteor through the atmosphere when given multiple camera
views of the meteor's luminous track. Using a motion propagation model
in 3-D space plus time, and iteratively solving for all free model
parameters simultaneously, one can obtain a fully coupled solution to
the apparent radiant direction, 3-D begin position, atmospheric entry
speed, deceleration terms, and timing offsets when using data from
unsynchronized video cameras. A Monte Carlo component adds empirical
error estimation for each of the key model parameters computed. This
multiparameter fitting method extends the allowable collection
geometries for meteor trajectory estimation to lower convergence angles
between camera-meteor-camera lines of sight and smaller site separation
distances.
... The deceleration profile (Eqs. (5)), combined with the calibrated meteor light curves (stored in the folder ''gefdat''), can be used to calculate the meteoroid mass, density, ablation coefficient, and fragmentation properties (e.g., McKinley, 1961;Murray et al., 2000;Campbell et al., 2000;Kikwaya et al., 2009). These are a topic of future study, because the derivation of those parameters is model dependent and outside the scope of this work. ...
Meteoroids pose one of the largest risks to spacecraft outside of low Earth orbit. To correctly predict the rate at which meteoroids impact and damage spacecraft, environment models must describe the mass, directionality, velocity, and density distributions of meteoroids. NASA’s Meteoroid Engineering Model (MEM) is one such model; MEM 3 is an updated version of the code that better captures the correlation between directionality and velocity and incorporates a bulk density distribution. This paper describes MEM 3 and compares its predictions with the rate of large particle impacts seen on the Long Duration Exposure Facility and the Pegasus II and III satellites.
The bulk density of a meteoroid affects its dynamics in space, its ablation in the atmosphere, and the damage it does to spacecraft and lunar or planetary surfaces. Meteoroid bulk densities are also notoriously difficult to measure, and we are typically forced to assume a density or attempt to measure it via a proxy. In this paper, we construct a density distribution for sporadic meteoroids based on existing density measurements. We considered two possible proxies for density: the KB parameter introduced by Ceplecha and Tisserand parameter, TJ. Although KB is frequently cited as a proxy for meteoroid material properties, we find that it is poorly correlated with ablation-model-derived densities. We therefore follow the example of Kikwaya et al. in associating density with the Tisserand parameter. We fit two density distributions to meteoroids originating from Halley-type comets (TJ < 2) and those originating from all other parent bodies (TJ > 2); the resulting two-population density distribution is the most detailed sporadic meteoroid density distribution justified by the available data. Finally, we discuss the implications for meteoroid environment models and spacecraft risk assessments. We find that correcting for density increases the fraction of meteoroid-induced spacecraft damage produced by the helion/antihelion source. Published by Oxford University Press on behalf of The Royal Astronomical Society 2017.
More than 7000 two-station meteors observed with two different video systems, both part of the Canadian Automated Meteor Observatory, have been analysed. The more sensitive (limiting magnitude +6.5) influx system shows a significant population of slow meteors with begin heights under 86 km, while the less sensitive (limiting magnitude +4) tracking system shows many more fast meteors ablating at high altitudes. The low, slow population has asteroidal orbits with low inclinations and moderate eccentricities, and radiants which are not, in general, associated with the sporadic sources. In spite of their low begin heights, which imply that they are strong and refractory, the meteors have early peaked light curves which are not predicted by classical ablation theory for non-fragmenting objects.
Simultaneous radar and video measurements were made using the Canadian Meteor Orbit Radar (CMOR) and several Gen-III image-intensified CCD cameras to observationally validate metric instrument errors determined through Monte Carlo modelling. We find that our radar interferometry accuracy is ∼0.8°∼0.8° using multiple independent techniques validated with video data. Our average radar–video radiant difference is 3.4°, suggesting that radiant errors for CMOR are dominated by errors in time-of-flight lag time determinations. Our video speeds were found to be consistently lower for slower speed meteors, with our modelled video speed errors following the relation log10δv=−1.64+0.02v. Our modelled video radiant errors had error distributions of 0.73°±0.51°. Errors in the fiducial picks for video meteors were found to be anisotropic, with errors along the meteor trail being larger than those perpendicular to the trail, primarily affecting the fit speed. We also find that the majority of our radar detections occur near the end of the observed video height interval. Our average video speeds are higher than our radar speeds, consistent with decelerations and specular reflections occurring preferentially near the end of trails. Range comparisons show our radar determined specular ranges to be systematically +0.32 km farther in range, although this is smaller than the statistical spread. We find 7%±3% of our video events are simultaneously detected by our radar system. This is above the expected 2%–5% range determined through modelling, suggesting our observations are biased towards larger, non-fragmenting meteoroids.
Aims: Here we report on precise metric and photometric
observations of 107 optical meteors, which were simultaneously recorded
at multiple stations using three different intensified video camera
systems. The purpose is to estimate bulk meteoroid density, link small
meteoroids to their parent bodies based on dynamical and physical
density values expected for different small body populations, to better
understand and explain the dynamical evolution of meteoroids after
release from their parent bodies. Methods: The video systems used
had image sizes ranging from 640 × 480 to 1360 × 1036
pixels, with pixel scales from 0.01° per pixel to 0.05° per
pixel, and limiting meteor magnitudes ranging from Mv = +2.5
to +6.0. We find that 78% of our sample show noticeable deceleration,
allowing more robust constraints to be placed on density estimates. The
density of each meteoroid is estimated by simultaneously fitting the
observed deceleration and lightcurve using a model based on thermal
fragmentation, conservation of energy and momentum. The entire phase
space of the model free parameters is explored for each event to find
ranges of parameters which fit the observations within the measurement
uncertainty. Results: (a) We have analysed our data by first
associating each of our events with one of the five meteoroid classes.
The average density of meteoroids whose orbits are asteroidal and
chondritic (AC) is 4200 kg m-3 suggesting an asteroidal
parentage, possibly related to the high-iron content population.
Meteoroids with orbits belonging to Jupiter family comets (JFCs) have an
average density of 3100 ± 300 kg m-3. This high
density is found for all meteoroids with JFC-like orbits and supports
the notion that the refractory material reported from the Stardust
measurements of 81P/Wild 2 dust is common among the broader JFC
population. This high density is also the average bulk density for the 4
meteoroids with orbits belonging to the Ecliptic shower-type class (ES)
also related to JFCs. Both categories we suggest are chondritic based on
their high bulk density. Meteoroids of HT (Halley type) orbits have a
minimum bulk density value of 360+400-100 kg
m-3 and a maximum value of 1510+400-900
kg m-3. This is consistent with many previous works which
suggest bulk cometary meteoroid density is low. SA
(Sun-approaching)-type meteoroids show a density spread from 1000 kg
m-3 to 4000 kg m-3, reflecting multiple origins.
(b) We found two different meteor showers in our sample: Perseids (10
meteoroids, ~11% of our sample) with an average bulk density of 620 kg
m-3 and Northern Iota Aquariids (4 meteoroids) with an
average bulk density of 3200 kg m-3, consistent with the
notion that the NIA derive from 2P/Encke.
We report high-resolution multi-station observations of meteors by the Canadian Automated Meteor Observatory recorded from 2009 June to 2010 August. Our survey has a limiting detection magnitude of +5 mag in R band, equivalent to a limiting meteoroid mass of ~2 × 10–7 kg. The high metric trajectory accuracy (of the order of 30 m perpendicular to the solution and 200 m along track) allows us to determine velocities with average uncertainty of <1.5% in speed and ~04 in the radiant direction. A total of 1739 meteors had measured orbits. The data have been searched for meteors in hyperbolic orbits, which are potentially of interstellar origin. We found 22 potential hyperbolic meteors among our sample, with only two of them having a speed at least 3σ above the hyperbolic limit. For our one-year survey we find no clear evidence of interstellar meteoroids at millimeter sizes in a weighted time-area product of ~104 km2 hr. Backward integrations performed for these 22 potentially hyperbolic meteors to check for close encounters with planets show no considerable changes in their orbits. Detailed examination leads us to conclude that our few identified events are most likely the result of measurement error. We find an upper limit of f
ISP < 2 × 10–4 km–2 hr–1 for the flux of interstellar meteoroids at Earth with a limiting mass of m > 2 × 10–7 kg.
