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Fw: RE: 2008 TC3

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  • Aleksandar Cikota
    Hi, I m forwarding an e-mail from Peter Brown who is reporting about one definite airwave detection from the impact at the Kenyian Infrasonic Array. He send
    Message 1 of 1 , Oct 7, 2008
      Hi,

      I'm forwarding an e-mail from Peter Brown who is reporting about one
      definite airwave detection from the impact at the Kenyian Infrasonic Array.
      He send also an attached map which you can see here:
      http://www.minorplanets.org/OLS/images/map-prelim.jpg

      Thanks to Peter Brown!


      Best regards,
      Aleksanadar Cikota
      J75 La Sagra Sky Survey

      -----------------------------------------
      Aleksandar Cikota
      (University of Zurich)
      e-mail: alexci@...
      acikota@...
      SkyPe: Aleksandar_Cikota
      MSN: Aleksandar_Cikota@...


      -------Original Message-------

      From: Pbrown
      Date: 10/07/08 19:42:17
      To: 'Aleksandar Cikota'
      Subject: RE: 2008 TC3

      A very preliminary examination of several infrasound stations proximal to
      the predicted impact point for the NEO 2008 TC3 has yielded one definite
      airwave detection from the impact. The airwave was detected at the Kenyian
      Infrasonic Array, (IMS station IS32), beginning near 05:10 UT on Oct 7, 2008
      and lasting for several minutes. The signal correlation was highest at very
      low frequencies � the dominant period of the waveform was 5-6 seconds. The
      backazimuth of the signal over the entire 7 element array is shown in the
      attached map � it clearly points to within a few degrees of the expected
      arrival direction. Moreover, assuming a stratospheric mean signal speed of 0
      28 km/s, the arrival time corresponds to an origin time near 02:43 UT, which
      is consistent with the expected impact time near 02:45:40 UT given expected
      variations in stratospheric arrival speeds. The dominant period of 5-6
      seconds corresponds to an estimated energy (using the AFTAC period at
      maximum amplitude relationship from ReVelle, 1997) of 1.1 � 2.1 kilotons of
      TNT. The five other closest infrasound stations were briefly examined for
      obvious signals and showed none � more detailed signal processing of these
      additional data are ongoing in the search for additional signals.

      ------------------------
      Dr. Peter Brown
      Canada Research Chair in Meteor Science
      Acting Director - Centre for Planetary Science and Exploration (CPSX)
      Associate Professor
      Department of Physics and Astronomy
      University of Western Ontario
      London, ON N6A 3K7
      CANADA
      519-661-2111 x86458
      http://aquarid.physics.uwo.ca/~pbrown



      From: Aleksandar Cikota [mailto:alexci@...]
      Sent: Tuesday, October 07, 2008 1:41 PM
      To: Wayne Edwards
      Cc: pbrown@...
      Subject: 2008 TC3

      Hi Wayane and Peter,

      I'm sure you heard about 2008 TC3 - the small 2-3m asteroid which was
      discovered on 2008 Oct. 6 by the Mt. Lemmon Survey in Arizona. The
      atmospheric impact over northern Sudan was expected today morning - 2008 Oct
      07 0246 UTC, but there is no official report that it entered the atmosphere
      yet.
      The predicted time and location of the impact should be precise, we and many
      other astronomers observed the asteroid until it entered the Earth's shadow.

      I wanted to aks, did some of your infrasound stations detected somethig at
      this time?

      Here are the predicted informations for the entery:

      Object: 2008 TC3 (discovered Oct. 6 at Mt. Lemmon by the Catalina Sky
      Survey) H=31.2
      Impact time: 2454746.61578 JD = 2008-10-07 02:46 UT = 19:46 PT = 22:46 EDT
      Long., Lat. (deg) = 31.697 20.855 (Northern Sudan)
      V_imp = 12.82 km/s Atmospheric impact velocity
      Zenith Angle= 70.86 (Shallow, near-grazing impact)

      Thank You!

      Best regards,
      Aleksandar Cikota
      J75 La Sagra Sky Survey


      P.S. A nice image of the asteorid entering the Earth's shadow:
      http://www.minorplanets.org/OLS/2008_TC3/


      -----------------------------------------
      Aleksandar Cikota
      (University of Zurich)
      e-mail: alexci@...
      acikota@...
      SkyPe: Aleksandar_Cikota
      MSN: Aleksandar_Cikota@...






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