Re: Video of secret satellites: X-37B, USA186 (Keyhole), Lacrosse3

From: Thierry Legault (legault@club-internet.fr)
Date: Thu Jun 16 2011 - 18:53:54 UTC

  • Next message: Brad Young: "BY Obs Jun 17"

    hi Allen, sampling is 0.16 arcsec per pixel, this 
    means that 6 pixels cover 1 arcsec.
    
    On the image, USA-186 spans about 50 pixels, at 
    316 km this corresponds to about 13 metres. 
    Calsky gives 18 metres for the length of USA-186 
    (GlobalSecurity gives a length of 13 metres for 
    KH-12 series), but we do not know its orientation 
    in the image. The calculation gives a plausible result.
    
    The solar array of Lacrosse3 covers about 30 
    pixels (5 arcsec), at a distance of 661 km this 
    corresponds to a length of 16 meters or 52 feet. 
    GlobalSecurity indicates a length of 100 feet for 
    the solar array, therefore the hypothesis is that 
    the array is inclined by 60° towards the line of sight.
    
    X-37B covers about 30 pixels on the main axis, at 
    341 km this corresponds to a bit more than 8 
    metres, for a length announced at 8.4 metres, 
    very close considering the uncertainties of the 
    calculations (diffraction tends to spread objects 
    and make their edge fuzzy, this is the reason why 
    I wouldn't try to make the same calculations 
    about the width of satellites, it's too small).
    
    regards
    
    At 20:09 16/06/2011, Allen Thomson wrote:
    
    > >  Scale (1 arcsec) is indicated on the images.
    >
    >
    >Thanks much for these images.
    >
    >I've been working with the scale bars and ranges 
    >to try to measure the size of
    >the objects shown, but due to the bars' smallness have some uncertainty about
    >the measurements.  Could you tell us your 
    >estimates of the satellites' physical
    >size as derived from the images, i.e., x meters long and y meters wide?
    
    Thierry Legault
    www.astrophoto.fr
    
    
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