Re: very close encounter between two satellites

From: Björn Gimle (
Date: Thu Jun 12 2008 - 09:33:58 UTC

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    Hi Ed,
    the object was 66040B, a Thor-Agena B rocket for Nimbus 2.
    As it passed USA 186, it was at 1113 km height, vs 758 km for USA 186.
    You see the moment of passing (03:08:53) and 
    speed diff from timetags and tick marks in 030853.bmp.
    I zoomed to a 8' field and found the 
    predicted track separation = 1'59" (sic).
    Ed080611.bmp was the initial search for "all" 
    objects closer than 3333 km in a wide field.
    HD189037.bmp is a better approach - in the 
    same field, but only the objects within 4 deg from
    HD189037 on the tracks at az=42 deg. 
    The "HD" search found (within 5555 km range):
    Cat # Satellite Name
    ----- --------------
    31380 FENGYUN 1C DEB
    27600 MICRO LABSAT
    10412 COSMOS 839 DEB
    28888 USA 186
    02174 THOR AGENA B R/B
    30353 FENGYUN 1C DEB
    21819 INTERCOSMOS 25
    ----- Original Message ----- 
    From: "Ed Cannon" <>
    To: <>
    Sent: Wednesday, June 11, 2008 9:32 PM
    Subject: very close encounter between two satellites
    > Last night USA 186 (05-042A, 28888) caught up to and
    > passed another object going the same direction.  With
    > my binoculars I could not see any separation between
    > them at the moment they passed.  I don't have the data
    > and don't know what the other object was, but this
    > occurred on the first pass, with both of them low in
    > our northeast around 3:07-08 UTC.  We were at BCRC.
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