Re: Can someone ID this object for me?

From: George Roberts (gr@gr5.org)
Date: Tue Nov 06 2012 - 21:56:47 UTC

  • Next message: Brad Young: "BY C 110712"

    I'm pretty sure the ISS was just a bit below the horizon as seen from 
    Seattle.  About 1 degree below the horizon.  And in the same general 
    direction as the sun.  So I don't think it was the ISS.
    
    >across the horizon from NNW to SSW
    That part matches
    
    >with about a peak of 40deg inclination (at most)
    You mean altitude, right?  We usually measure positions of satellites using 
    alt/azi where azimuth is compass heading and azimuth is degree from horizon 
    from 0 to 90 (but in this case ISS should have been -1 degree).
    
    If you mean it was 1 degree from the horizon then maybe you did see it. 
    Whereas 40 degrees altitude would be very high - about half way between 
    horizon and straight up.
    
    FYI, Inclination is an orbital term that refers to the tilt of the orbit and 
    by definition is also the farthest latitude that the orbit passes over.  So 
    a satellite with an inclination of 40 degrees would never get straight 
    overhead if you lived in seattle (latitude 47) but would still be visible to 
    the south.
    
    So if it isn't the ISS then it's going to be hard to find.  If I put even a 
    10 degree patch of sky into any satellite searching software with a 5 minute 
    window I'm going to get a dozen satellites passing through that tiny piece 
    of sky.  But if you give me a broad swath of sky as you did there will be 
    many thousands of matching satellites.  Too many to look through.  So no one 
    is likely to reply to this email.  Sorry!
    
    - George Roberts
    http://gr5.org
    -----Original Message----- 
    From: Kevin Grey
    Sent: Tuesday, November 06, 2012 1:24 PM
    To: SeeSat-L@satobs.org
    Subject: Can someone ID this object for me?
    
    Hello,
    
    I was outside walking with a coworker last night.  We saw what appeared to
    be an aircraft travelling across the horizon from NNW to SSW with about a
    peak of 40deg inclination (at most). It was just after sunset and there
    were some high altitude clouds (thin with big shadows, I believe) that did
    not appear to affect the magnitude of the object.  Coworker thinks I am
    crazy for stating its likely ISS, as opposed to an airplane.
    
    I loaded up an ISS tracking app on my phone and sure enough, it showed ISS
    passing with a trajectory consistent with what we had observed but when I
    login to Heavens-Above, it does not list an ISS pass for my location at
    that time.  I suspect that the only reason it was visible was because of
    its trajectory perpendicular to the setting Sun and my geographic location
    and that Heavens-Above may exclude passes below a certain inclination.
    
    Can someone identify this object for me?
    
    Date/Time of End of Pass:   11/05/2012 17:32 Pacific Time == 11/06/2012
    01:32 UTC
    Location: 47.644704, -122.139079
    Object trajectory: Travelled from NNW to SSW with peak inclination of 40
    degrees (probably lower)
    
    ~~K
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