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针对目前流星雷达测距误差大的问题,本文提出了提高流星雷达测距精度的新方法,即提高采样速率,用相关分析确定回波脉冲参考点的方法。该方法使流星雷达的测距精度提高一个数量级,测距误差降到±14m,使流星雷达不仅可以用来观测研究流星,还可用于监测飞机、火箭的飞行等,扩大流星雷达的应用。 相似文献
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L.A. Rogers 《Planetary and Space Science》2005,53(13):1341-1354
Conventional meteoroid theory assumes that the dominant mode of ablation (which we will refer to as thermal ablation) is by evaporation following intense heating during atmospheric flight. Light production results from excitation of ablated meteoroid atoms following collisions with atmospheric constituents. In this paper, we consider the question of whether sputtering may provide an alternative disintegration process of some importance. For meteoroids in the mass range from 10-3 to and covering a meteor velocity range from 11 to , we numerically modeled both thermal ablation and sputtering ablation during atmospheric flight. We considered three meteoroid models believed to be representative of asteroidal ( mass density), cometary () and porous cometary () meteoroid structures. Atmospheric profiles which considered the molecular compositions at different heights were use in the sputtering calculations. We find that while in many cases (particularly at low velocities and for relatively large meteoroid masses) sputtering contributes only a small amount of mass loss during atmospheric flight, in some cases sputtering is very important. For example, a porous meteoroid at will lose nearly 51% of its mass by sputtering, while a asteroidal meteoroid at will lose nearly 83% of its mass by sputtering. We argue that sputtering may explain the light production observed at very great heights in some Leonid meteors. We discuss methods to observationally test the predictions of these computations. A search for early gradual tails on meteor light curves prior to the commencement of intense thermal ablation possibly represents the most promising approach. The impact of this work will be most dramatic for very small meteoroids such as those observed with large aperture radars. The heights of ablation and decelerations observed using these systems may provide evidence for the importance of sputtering. 相似文献
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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
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The Marshall Space Flight Center (MSFC) Meteoroid Stream Model simulates particle ejection and subsequent evolution from comets
in order to provide meteor shower forecasts to spacecraft operators for hazard mitigation and planning purposes. The model,
previously detailed in Moser and Cooke (Earth Moon Planets 95, 141 (2004)), has recently been updated; the changes include the implementation of the RADAU integrator, an improved planetary
treatment, and the inclusion of general relativistic effects in the force function. The results of these updates are investigated
with respect to various meteoroid streams and the outcome presented. 相似文献
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Peter Brown Robert J. Weryk Daniel K. Wong James Jones 《Earth, Moon, and Planets》2008,102(1-4):209-219
The Canadian Meteor Orbit Radar is a multi-frequency backscatter radar which has been in routine operation since 1999, with
an orbit measurement capability since 2002. In total, CMOR has measured over 2 million orbits of meteoroids with masses greater
than 10 μg, while recording more than 18 million meteor echoes in total. We have applied a two stage comparative technique
for identifying meteor streams in this dataset by making use of clustering in radiants and velocities without employing orbital
element comparisons directly. From the large dataset of single station echoes, combined radiant activity maps have been constructed
by binning and then stacking each years data per degree of solar longitude. Using the single-station mapping technique described
in Jones and Jones (Mon Not R Astron Soc 367:1050–1056, 2006) we have identified probable streams from these single station
observations. Additionally, using individual radiant and velocity data from the multi-station velocity determination routines,
we have utilized a wavelet search algorithm in radiant and velocity space to construct a list of probable streams. These two
lists were then compared and only streams detected by both techniques, on multiple frequencies and in multiple years were
assigned stream status. From this analysis we have identified 45 annual minor and major streams with high reliability. 相似文献
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Peter Jenniskens 《Earth, Moon, and Planets》2008,102(1-4):505-520
The history of associating meteor showers with asteroidal-looking objects is long, dating to before the 1983 discovery that
3200 Phaethon moves among the Geminids. Only since the more recent recognition that 2003 EH1 moves among the Quadrantids are
we certain that dormant comets are associated with meteoroid streams. Since that time, many orphan streams have found parent
bodies among the newly discovered Near Earth Objects. The seven established associations pertain mostly to showers in eccentric
or highly inclined orbits. At least 35 other objects are tentatively linked to streams in less inclined orbits that are more
difficult to distinguish from those of asteroids. There is mounting evidence that the streams originated from discrete breakup
events, rather than long episodes of gradual water vapor outgassing. If all these associations can be confirmed, they represent
a significant fraction of all dormant comets that are in near-Earth orbits, suggesting that dormant comets break at least
as frequently as the lifetime of the streams. I find that most pertain to NEOs that have not yet fully decoupled from Jupiter.
The picture that is emerging is one of rapid disintegration of comets after being captured by Jupiter, and consequently, that
objects such as 3200 Phaethon most likely originated from among the most primitive asteroids in the main belt, instead. They
too decay mostly by disintegration into comet fragments and meteoroid streams. The disintegration of dormant comets is likely
the main source of our meteor showers and the main supply of dust to the zodiacal cloud.
Editorial handling: Frans Rietmeijer. 相似文献
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Peter Jenniskens 《Earth, Moon, and Planets》2008,102(1-4):5-9
The International Astronomical Union at its 2006 General Assembly in Prague has adopted a set of rules for meteor shower nomenclature,
a working list with designated names (with IAU numbers and three-letter codes), and established a Task Group for Meteor Shower Nomenclature in Commission 22 (Meteors and Interplanetary Dust) to help define which meteor showers exist from well defined groups of
meteoroids from a single parent body. 相似文献