Astronomy & Astrophysics 507, 1015–1022 (2009)
DOI: 10.1051/0004-6361:200912639
Meteosat observation of the atmospheric entry of 2008 TC3
over Sudan and the associated dust cloud
J. Borovicka1 and Z. Charvat2
1Astronomical Institute of the
Academy of
Sciences, Fricova 298, 25165 Ondrejov Observatory, Czech Republic
2Czech Hydrometeorological Institute, Satellite
Department, Na Sabatce 17, 14306 Praha 4, Czech Republic
Abstract.
We analyzed serendipitous observations by the Meteosat 8 weather
satellite of the fireball caused by the entry of the small asteroid (or
large meteoroid) 2008 TC3 over northern Sudan on October 7,
2008.
Meteosat 8 scans the Earth in 5 min cycles. The fireball was captured
in
the 2:45 UT images in four visible-near infrared channels (0.6–1.6
μm) at a height of 45 km, and in eight mid infrared channels
(3.9–13.4 μm) at a height of 33 km. The latter channels also detected
at least two dust clouds deposited in the atmosphere at the heights of
about 44 and 36 km. The dust deposition was a result of severe
atmospheric fragmentation of the asteroid, accompanied by fireball
flares, which could be detected in the light scattered by the Earth's
surface. The fireball brightness was measured at two random heights, 45
and 37.5 km, where it reached –18.8 and –19.7 mag, respectively. The
peak brightness was probably higher than –20 mag. The color temperature
of the fireball at 45 km was 3650 ± 100 K. Infrared spectra of
the fresh dust clouds were dominated by the 10 μm Si-O band caused by
recondensed amorphous silicates. Five minutes later, the dust clouds
were detected in absorption of thermal radiation of the Earth. At that
time, the silicates were largely crystalline, suggesting silicate smoke
temperatures exceeding 1000 K. The total mass of the silicate smoke was
estimated to be 3100 ± 600 kg. More mass was probably contained
in larger, micron sized, and colder dust particles resulting from
incomplete sublimation of the asteroidal material and detected later by
Meteosat 8 and 9 in scattered sunlight. Based on the heights of
asteroid
fragmentations, we guess that the bulk porosity of 2008 TC3
was of the
order of 50%, i.e. higher than the porosity of the recovered meteorite
Almahata Sitta.
Keywords: meteors, meteoroids – minor planets,
asteroids
– Earth – infrared: solar system
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