共查询到20条相似文献，搜索用时 8 毫秒
1.
V. A. Leonov 《Solar System Research》2010,44(2):122-135
Massive television observations of meteors aimed at verifying the existing and finding new meteor streams create the task
of the reliable preliminary determination of the detected meteor membership in a particular known stream. The mostly widely
used method of meteor identification is connected with the estimation of the distance between the great circle of the meteor
and the point of the examined radiant. Often observers perform this estimation without checking the possibility that the same
meteor belongs to another stream. When several streams occur simultaneously, many meteors can be members of two or more streams.
When the determination of the meteor membership is done in a subjective way, it may lead to an overestimation of strong streams’
and an underestimation of weak streams’ activity. In this work, we describe a method and algorithm for the determination of
the meteor membership in known streams which were tested using real television observations and were successfully used at
INASAN. This algorithm is almost completely automatic and allows for the obtainment of additional information regarding meteor
streams. We also show some results of the processing of 2254 meteors observations obtained with the FAVOR camera from July
31, 2006 to October 21, 2006 using the proposed method. The work is part of the program for the creation of the Verified Catalogue
of Meteor Streams. 相似文献
2.
Radio meteor observations by Ham-band beacon or FM radio broadcasts using “Ham-band Radio meteor Observation Fast Fourier
Transform” (HROFFT) an automatic operating software have been performed widely in recent days. Previously, counting of meteor
echoes on the spectrograms of radio meteor observation was performed manually by observers. In the present paper, we introduce
an automatic meteor echo counting software application. Although output images of the HROFFT contain both the features of
meteor echoes and those of various types of noises, a newly developed image processing technique has been applied, resulting
in software that enables a useful auto-counting tool. There exists a slight error in the processing on spectrograms when the
observation site is affected by many disturbing noises. Nevertheless, comparison between software and manual counting revealed
an agreement of almost 90%. Therefore, we can easily obtain a dataset of detection time, duration time, signal strength, and
Doppler shift of each meteor echo from the HROFFT spectrograms. Using this software, statistical analyses of meteor activities
is based on the results obtained at many Ham-band Radio meteor Observation (HRO) sites throughout the world, resulting in
a very useful “standard” for monitoring meteor stream activities in real time. 相似文献
3.
Josep M. Trigo-Rodriguez José M. Madiedo Peter S. Gural Alberto J. Castro-Tirado Jordi Llorca Juan Fabregat Standa Vítek Pep Pujols 《Earth, Moon, and Planets》2008,102(1-4):231-240
By using high-resolution, low-scan-rate, all-sky CCD cameras, the SPanish Meteor Network (SPMN) is currently monitoring meteor
and fireball activity on a year round basis. Here are presented just a sampling of the accurate trajectory, radiant and orbital
data obtained for meteors imaged simultaneously from two SPMN stations during the continuous 2006–2007 coverage of meteor
and fireball monitoring. Typical astrometric uncertainty is 1–2 arc min, while velocity determination errors are of the order
of 0.1–0.5 km/s, which is dependent on the distance of each event to the station and its particular viewing geometry. The
cameras have demonstrated excellent performance for detecting meteor outbursts. The recent development of automatic detection
software is also providing real-time information on the global meteor activity. Finally, some examples of the all-sky CCD
cameras applications for detecting unexpected meteor activity are given. 相似文献
4.
J. D. Mathews S. J. Briczinski D. D. Meisel C. J. Heinselman 《Earth, Moon, and Planets》2008,102(1-4):365-372
Radio science and meteor physics issues regarding meteor “head-echo” observations with high power, large aperture (HPLA) radars,
include the frequency and latitude dependency of the observed meteor altitude, speed, and deceleration distributions. We address
these issues via the first ever use and analysis of meteor observations from the Poker Flat AMISR (PFISR: 449.3 MHz), Sondrestrom
(SRF: 1,290 MHz), and Arecibo (AO: 430 MHz) radars. The PFISR and SRF radars are located near the Arctic Circle while AO is
in the tropics. The meteors observed at each radar were detected and analyzed using the same automated FFT periodic micrometeor
searching algorithm. Meteor parameters (event altitude, velocity, and deceleration distributions) from all three facilities
are compared revealing a clearly defined altitude “ceiling effect” in the 1,290 MHz results relative to the 430/449.3 MHz
results. This effect is even more striking in that the Arecibo and PFISR distributions are similar even though the two radars
are over 2,000 times different in sensitivity and at very different latitudes, thus providing the first statistical evidence
that HPLA meteor radar observations are dominated by the incident wavelength, regardless of the other radar parameters. We
also offer insights into the meteoroid fragmentation and “terminal” process. 相似文献
5.
Štefan Gajdoš 《Earth, Moon, and Planets》2008,102(1-4):117-123
A new meteroid stream—October Ursa Majorids—was announced by Japanese observers on Oct. 14–16, 2006 (Uehara et al. 2006).
Its weak manifestation was detected among coincidental major meteor showers (N/S Taurids, Orionids), as its meteors radiated
from a higher placed radiant on the northern sky. We have tried to find out previous displays of the stream throughout available
meteor orbits databases, and among ancient celestial phenomena records. Although we got no obvious identification, there are
some indications that it could be a meteor shower of cometary origin with weak/irregular activity, mostly overlayed by regular
coincidental meteor showers. With a procedure based on D-criterion (Southworth and Hawkins 1963) we found a few records in IAU MDC database of meteor photographic orbits which fulfill
common similarity limits, for October Ursae Majorids. However, their real association cannot be established, yet. With respect
to the mean orbit of this stream, we suggest for its parent body a long-period comet. 相似文献
6.
Pavlo Kozak 《Earth, Moon, and Planets》2008,102(1-4):277-283
Software named “Falling Star” has been developed for digital processing of double-station TV meteor observations. It was designed
for measurement and calculation of both kinematic and photometric parameters of faint meteors observed with any video system.
Data from video recordings are first digitized as standard AVI files, and then converted into the software’s TVS (TV sequence)
format. Additional astronomical information like date, time of observations, geographic position of point of the observation
and horizontal coordinates of TV camera optical axis orientation are added to the files. These parameters allow the right
ascension and declination of the optical center of camera for the moment of meteor flight to be calculated. “Falling Star”
includes a range of automated procedures for the identification of frame stars with star catalogues, search of movable meteor-like
objects inside frame, calculation of equatorial coordinates and photometry. Finally, meteor trajectory parameters, orbital
elements and brightness curves are calculated. Errors of calculations are determined using Monte-Carlo method. 相似文献
7.
The correlation of sporadic meteor rates from radar observations in January, August, and December non-show-er periods in 1958–2000,
and relevant solar activity represented by the solar relative number, R, is investigated. Similar analysis of the December
sporadic period was already presented by Simek 1999, and Pecina. Complete analysis indicates high correlation of both phenomena
with sporadic meteor counts curve following that of solar activity after 1.5–2 years in the mean eleven year solar cycle with
the correlation index exceeding 70%. This result supports the large volume of observing material of the Ondřejov meteor radar
in the above mentioned span covering almost four solar cycles.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Joseph A. Nuth III John L. Lowrance George R. Carruthers 《Earth, Moon, and Planets》2008,102(1-4):495-504
The prime measurement objective of the Near Earth Object Chemical Analysis Mission (NEOCAM) is to obtain the ultraviolet spectra
of meteors entering the terrestrial atmosphere from ∼125 to 300 nm in meteor showers. All of the spectra will be collected
using a slitless ultraviolet spectrometer in Earth orbit. Analysis of these spectra will reveal the degree of chemical diversity
in the meteors, as observed in a single meteor shower. Such meteors are traceable to a specific parent body and we know exactly
when the meteoroids in a particular shower were released from that parent body (Asher, in: Arlt (ed.) Proc. International
Meteor Conference, 2000; Lyytinen and van Flandern, Earth Moon Planets 82–83:149–166, 2000). By observing multiple apparitions
of meteor showers we can therefore obtain quasi-stratigraphic information on an individual comet or asteroid. We might also
be able to measure systematic effects of chemical weathering in meteoroids from specific parent bodies by looking for correlations
in the depletions of the more volatile elements as a function of space exposure (Borovička et al., Icarus 174:15–30, 2005).
By observing the relation between meteor entry characteristics (such as the rate of deceleration or breakup) and chemistry
we can determine if our meteorite collection is deficient in the most volatile-rich samples. Finally, we can obtain a direct
measurement of metal deposition into the terrestrial stratosphere that may act to catalyze atmospheric chemical reactions. 相似文献
9.
Asta Pellinen-Wannberg Edmond Murad Gudmund Wannberg Assar Westman 《Earth, Moon, and Planets》2004,95(1-4):627-632
High Power Large Aperture (HPLA) radars generally observe very high meteor velocities averaging over 50 km s−1. There are only a few events recorded around 30 km s−1, while meteors at 20 km s−1 or slower are very rare. This is a clear and debated contradiction to specular meteor radar results. A high plasma density
condition contributes, but the dominating phenomenon is the hyperthermal ionization mechanism due to chemical dynamics of
the ionization process. The observed high velocities can be explained in terms of high hyperthermal ionization cross-sections
for collisions between ablated meteoroid metal atoms such as Na and/or Fe and atmospheric species. 相似文献
10.
L. M. G. Poole 《Astrophysics and Space Science》1995,230(1-2):471-478
Recent meteor research in South Africa, arising largely from the development of forward and back scatter observing systems, is briefly reviewed. The main areas of investigation have been the use of single station radars to deduce meteor radiant structures, the study of upper atmospheric wind patterns, and research into the factors which influence the performance of meteor burst communication systems. 相似文献
11.
Devulapalli Venkata Phani Kumar Kammadhanam Chenna Reddy Ganji Yellaiah 《Astrophysics and Space Science》2006,306(4):235-239
Observations carried out during Leonid meteor shower 2003, by using Indian MST radar (13.46^N, 79.18^E; dip 12.5^N) are used
to determine the number density of meteoroids through the cross section of the meteor streams. Cross sections are calculated
for a number of classes of echo duration (particle size). They are also used to determine the relative flux of the shower
in particle size ranges producing radar meteor echoes having durations <0.4 s, 0.4–1 s and >1 s. Mean activity profiles along
the Earth's passage through the stream show a systematic change of the peak activity and the width of the stream depending
on the distribution of echo durations across the stream. The patterns of mass distribution index s are presented and discussed. 相似文献
12.
Wayne N. Edwards Peter G. Brown Robert J. Weryk Douglas O. ReVelle 《Earth, Moon, and Planets》2008,102(1-4):221-229
Recent observations using the newly installed Elginfield infrasound array in coordination with the Southern Ontario all-sky
meteor camera network and Canadian Meteor Orbit Radar (CMOR) has shown that the number of meteors producing infrasound at
the Earth’s surface is more frequent than previously thought. These data show the flux of meteoroids capable of producing
infrasound at the ground is at least 1/month and is limited to meteors with peak visual brightness above −2. Comparisons to
current meteor infrasound theory show excellent agreement with amplitude and period predictions for weakly non-linear shock
waves using a realistic vertically inhomogeneous atmosphere. Similar predictions show isothermal assumptions underestimate
the amplitude by orders of magnitude. 相似文献
13.
Apostolos A. Christou Jeremie Vaubaillon Paul Withers 《Earth, Moon, and Planets》2008,102(1-4):125-131
We have simulated the formation and evolution of comet 1P/Halley’s meteoroid stream by ejecting particles from the nucleus
5000 years ago and propagating them forward to the present. Our aim is to determine the existence and characteristics of associated
meteor showers at Mars and Venus and compare them with 1P/Halley’s two known showers at the Earth. We find that one shower
should be present at Venus and two at Mars. The number of meteors in those atmospheres would, in general, be less than that
at the Earth. The descending node branch of the Halley stream at Mars exhibits a clumpy structure. We identified at least
one of these clumps as particles trapped in the 7:1 mean motion resonance with Jupiter, potentially capable of producing meteor
ourbursts of ZHR∼1000 roughly once per century. 相似文献
14.
Lars P. Dyrud Kelly Denney Julio Urbina Diego Janches Erhan Kudeki Steve Franke 《Earth, Moon, and Planets》2004,95(1-4):89-100
In this paper, we use radar observations from a 50 MHz radar stationed near Salinas, Puerto Rico, to study the variability
of specular as well as non-specular meteor trails in the E-region ionosphere. The observations were made from 18:00 to 08:00 h
AST over various days in 1998 and 1999 during the Coqui II Campaign [Urbina et al., 2000, Geophys. Rev. Lett. 27, 2853–2856]. The radar system had two sub-arrays, both produced beams pointed to the north in the magnetic meridian plane,
perpendicular to the magnetic field, at an elevation angle of approximately 41 degrees.
The Coqui II radar is sensitive to at least two types of echoes from meteor trails: (1) Specular reflections from trails oriented
perpendicular to the radar beam, and (2) scattering, or, non-specular reflections, from trails deposited with arbitrary orientations.
We examine and compare the diurnal and seasonal variability of echoes from specular and non-specular returns observed with
the Coqui II radar. We also compare these results with meteor head echo observations made with the Arecibo 430 MHz radar.
We use common region observations of these three types of meteor echoes to show that the diurnal and seasonal variability
of specular trails, non-specular trails, and head echoes are not equivalent. The implications of these results on global meteor
mass flux estimates obtained from specular meteor observations remains to be examined. 相似文献
15.
A recently observed broad 3.4 μm spectral ‘fingerprint’ in a persistent Leonid meteor train at a height of 83km is likely
to be due to emission of surrounding mesospheric bacteria heated by the passage of an incandescent fireball.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
We deal with theoretical meteoroid streams the parent bodies of which are two Halley-type comets in orbits situated at a relatively
large distance from the orbit of Earth: 126P/1996 P1 and 161P/2004 V2. For two perihelion passages of each comet in the far
past, we model the theoretical stream and follow its dynamical evolution until the present. We predict the characteristics
of potential meteor showers according to the dynamical properties of theoretical particles currently approaching the orbit
of the Earth. Our dynamical study reveals that the comet 161P/2004 V2 could have an associated Earth-observable meteor shower,
although no significant number of theoretical particles are identified with real, photographic, video, or radar meteors. However,
the mean radiant of the shower is predicted on the southern sky (its declination is about −23°) where a relatively low number
of real meteors has been detected and, therefore, recorded in the databases used. The shower of 161P has a compact radiant
area and a relatively large geocentric velocity of ∼53 km s−1. A significant fraction of particles assumed to be released from comet 126P also cross the Earth’s orbit and, eventually,
could be observed as meteors. However, their radiant area is largely dispersed (declination of radiants spans from about +60°
to the south pole) and, therefore, mixed with the sporadic meteor background. An identification with real meteors is practically
impossible. 相似文献
17.
We present the results of a study of meteoroid bulk densities determined from meteor head echoes observed by radar. Meteor
observations were made using the Advanced Research Projects Agency Long-Range Tracking And Instrumentation Radar (ALTAIR).
ALTAIR is particularly well suited to the detection of meteor head echoes, being capable of detecting upwards of 1000 meteor
head echoes per hour. Data were collected for 19 beam pointings and are comprised of approximately 70 min. of VHF observations.
During these observations the ALTAIR beam was directed largely at the north apex sporadic source. Densities are calculated
using the classical physical theory of meteors. Meteoroid masses are determined by applying a full wave scattering theory
to the observed radar cross-section. Observed meteoroids are predominantly in the 10−10 to 10−6 kg mass range. We find that the vast majority of meteoroid densities are consistent with low density, highly porous objects
as would be expected from cometary sources. The median calculated bulk density was found to be 900 kg/m3. The orbital distribution of this population of meteoroids was found to be highly inclined. 相似文献
18.
The IAU Meteor Data Center in Lund has acted as a central depository for meteor orbits obtained by photographic, video and
radar techniques. The database of precisely reduced photographic meteors contains data on 4581 meteor orbits obtained by 17
different stations or groups in the period 1936–1996. The orbital and geophysical data are available in two separate files
as well as in an alternative file with the merged data. In various studies of meteoroid streams as well as in studies of the
sporadic meteor background, it is often necessary to utilize both the orbital and the geophysical data files. Since the database
is a compilation of partial, not perfectly compatible catalogues from many observing stations, the merging of parameters from
one data set to another may sometimes present problems. The present contribution is a note on some problems encountered in
the merging procedure. Moreover, it is evident that the database includes a small amount of erroneous data – either in the
observations or in the subsequent data reductions. The latter error is not surprising in view of the lack of modern computers
at several stations in the past. A final, corrected version of the IAU MDC Lund photographic meteor orbits (eq. 2000.0) can
now be requested through the homepage of the Astronomical Institute, Slovak Academy of Sciences (http://www.astro.sk/~ne/IAUMDC/Ph2003/database.html). 相似文献
19.
Meteor44 is a software system developed at MSFC for the calibration and analysis of video meteor data. The photometric range
of the (8 bit) video data is extended from a visual magnitude range of from 8 to 3 to from 8 to −8 for both meteors and stellar
images using saturation compensation. Camera and lens specific saturation compensation coefficients are derived from artificial
variable star laboratory measurements. Saturation compensation significantly increases the number of meteors with measured
intensity and improves the estimation of meteoroid mass distribution. Astrometry is automated to determine each image's plate
coefficient using appropriate star catalogs. The images are simultaneously intensity calibrated from the contained stars to
determine the photon sensitivity and the saturation level referenced above the atmosphere. The camera's spectral response
is used to compensate for stellar color index and typical meteor spectra in order to report meteor light curves in traditional
visual magnitude units. Recent efforts include improved camera calibration procedures and long focal length "streak" meteor
photometry. Meteor44 has been used to analyze data from the 2001, 2002 and 2003 MSFC Leonid observational campaigns as well
as several lesser showers. 相似文献
20.
In our work, the method that can help to predict the existence of distant objects in the Solar system is demonstrated. This
method is connected with statistical properties of a heliocentric orbital complex of meteoroids with high eccentricities.
Heliocentric meteoroid orbits with high eccentricities are escape routes for dust material from distant parental objects with
near-circular orbits to Earth-crossing orbits. Ground-based meteor observations yield trajectory information from which we
can derive their place of possible origin: comets, asteroids, and other objects (e.g. Kuiper Objects) in the Solar system
or even interstellar space. Statistical distributions of radius vectors of nodes, and other parameters of orbits of meteoroids
contain key information about position of greater bodies. We analyze meteor orbits with high eccentricities that were registered
in 1975–1976 in Kharkiv (Ukraine). The orbital data of the Kharkiv electronic catalogue are received from observations of
radiometeors with masses 10−6−10−3 g. 相似文献