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| Titel |
Observations of meteor-head echoes using the Jicamarca 50MHz radar in interferometer mode |
| VerfasserIn |
J. L. Chau, R. F. Woodman |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 4, no. 2 ; Nr. 4, no. 2 (2004-03-24), S.511-521 |
| Datensatznummer |
250001608
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| Publikation (Nr.) |
 copernicus.org/acp-4-511-2004.pdf |
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| Zusammenfassung |
| We present results of recent observations of meteor-head echoes obtained with the high-power large-aperture Jicamarca 50MHz radar
(11.95°S, 76.87°W) in an interferometric mode.
The large power-aperture of the system allows us to record more
than 3000 meteors per hour in the small volume subtended by the
1° antenna beam, albeit when the cluttering equatorial
electrojet (EEJ) echoes are not present or are very weak. The
interferometry arrangement allows the determination of the radiant
(trajectory) and speed of each meteor. It is found that the
radiant distribution of all detected meteors is concentrated in
relative small angles centered around the Earth's Apex as it
transits over the Jicamarca sky, i.e. around the corresponding
Earth heading for the particular observational day and time, for
all seasons observed so far. The dispersion around the Apex is
~18° in a direction transverse to the Ecliptic plane
and only 8.5° in heliocentric longitude in the Ecliptic
plane both in the Earth inertial frame of reference. No
appreciable interannual variability has been observed. Moreover,
no population related to the optical (larger meteors) Leonid
showers of 1998-2002 is found, in agreement with other large
power-aperture radar observations.
A novel cross-correlation detection technique (adaptive
match-filtering) is used in combination with a 13 baud Barker
phase-code. The technique allows us to get good range resolution
(0.75km) without any sensitivity deterioration for the same
average power, compared to the non-coded long pulse scheme used at
other radars. The matching Doppler shift provides an estimation of
the velocity within a pulse with the same accuracy as if a
non-coded pulse of the same length had been used. The velocity
distribution of the meteors is relatively narrow and centered
around 60kms-1. Therefore most of the meteors have an
almost circular retrograde orbit around the Sun. Less than 8% of
the velocities correspond to interstellar orbits, i.e. with
velocities larger than the solar escape velocity
(72kms-1). Other statistical distributions of interest
are also presented. |
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