Simultaneous meteor echo observations by large aperture VHF and
UHF radars
We report simultaneous meteor echo observations using the Arecibo
430-MHz and 46.8-MHz radars. Using identical data taking and meteor
selection criteria, 1868 and 367 meteors were found in the 430-MHz and
47-MHz beam respectively, while 145 were found in both beams during
the 7 hours of observation. The smaller number of meteors detected by
the VHF system and its wide beam width show that UHF meteors are far
smaller than the VHF meteors. Of the 367 VHF echoes, there are only
10 trail echoes while the rest are head echoes. The small percentage
of trail echoes was quite contrary to expectation. We estimate that
VHF head echoes have a typical effective scattering cross section of
10-3 m2 although the spread of cross section for
all the echoes was very large. The fact that there are only very few
trail echoes observed leads us to suggest that the ratio of head echo
power to the trail echo power increases with decreasing meteor size.
Comparison of VHF and UHF echo characteristics suggests that the VHF
head echoes are likely not very aspect sensitive. Of the 145 metoers
observed by both radars, the powers received by the two systems were
not correlated. Although antenna pattern difference may partially
account for the lack of correlation, it is possible that UHF and VHF
echoes are enhanced by different mechanisms.
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