Re: geosat occultation

From: John Locker (
Date: Wed Oct 03 2007 - 16:31:20 EDT

  • Next message: Mike McCants: "Re: geosat occultation"

    Hi Bob.....
    Have seen this happen a number of times over here in the UK where we have 
    views of five and seven geo-satellite "constellations "
    In this animation from four years ago you can see two of the five Eutelsat 
    Hotbirds converge ........the most northerly pair.
    As I understand it , the control box within which the birds operate is an 
    imaginery cube  about 120 km on each side.
    ----- Original Message ----- 
    From: "Bob Hampton" <>
    To: <>
    Sent: Wednesday, October 03, 2007 6:24 PM
    Subject: geosat occultation
    Monday night (Tue AM, 10/02/2007 about 04:00 UTC) I was watching
    a group of three geosats I often observe.  They are all 3 visible at once
    at 125X (FOV = 0.4 degree), very bright in the 13" scope, easy targets
    now in the 4.5" at 45X.  I find them at 192 degrees AZ, 47 degrees EL,
    from my location here, (35.9465N, 82.2147W, 2,965 ft.), but my
    pedestal has leaned and I've not yet fixed it (my next project!), so my
    numbers may be off by 2 or 3 degrees (crude check sez 1.5 in az).
    One sat, I'll call it "A", is usually the brightest.  "Following"
    sat A, about 10 to 11 arcminutes to it's west are satellites "B" and "C".
    B and C are always within about 1 arcminute of each other, and I
    noticed a while back that they change position relative to each other.
    But then I saw something I've never seen before.  As I watched for
    about 30 minutes B and C converged until they became a single point of
    light that I could not split at 350X!  They became one at 04:04 and then
    visibly separate again at 04:12 UTC, so I'm thinking closest approach
    was around 04:08. Something else I hadn't noticed before is that sat B
    has a slightly more golden color, C is slightly more blue, this became
    apparent to me when they got real close to each other.
    I didn't realize they could get so close to each other!  I wonder how
    close they were and how close, in geosat terms, is close?  I'm
    guessing the same entity owns both sat B and sat C?
    Last night I began watching them at about 00:00 UTC 10/03/07, sat A
    was very obvious but B and C were not visible at all.  Over the next hour
    B and C slowly brightened into view (something else I've never seen
    before), while A maintained it's brightness but didn't seem to brighten
    any.  I was hoping to watch until about 04:00 to see if the "occultation"
    would occur again, suspecting that it might happen 4 minutes earlier,
    or at about 04:00 UTC, but by 22:30 I was clouded out.
    Bob Hampton
    35.9465N, 82.2147W, 2,965 ft.
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