RE: {Spam?} Lacrosse 4 _USA-152) (26473 2000-047-A) telescopic OBS

From: Ted Molczan (ssl3molcz@rogers.com)
Date: Mon Aug 02 2010 - 19:04:20 UTC

  • Next message: Allen Thomson: "RE: {Spam?} Lacrosse 4 _USA-152) (26473 2000-047-A) telescopic OBS"

    Ralf Vandebergh wrote:
    
    > Here are some observations of Lacrosse 4 spacecraft from last evening
    > during a 74 culm NW pass:
    > 
    > http://img535.imageshack.us/img535/1997/lacrosse410010823342931.jpg
    > 
    > The drop-shape is a typical behave of a Lacrosse satellite seen from
    > a certain angle. Here is an older image from a professional telescope
    > of the Lacrosse 1:
    > 
    > http://www.fas.org/spp/military/program/track/lacr1_2.jpg
    
    Three years ago, Allen Thomson alerted the list to more recent professional imagery, by Russia's
    Altay Optical-Laser Center:
    
    http://satobs.org/seesat/Jun-2007/0275.html
    
    Images of Lacrosse 2 and other satellites are on slide 14 of the following presentation at the site
    in Allen's post:
    
    http://www.niipp-moskva.ru/ppt/booklet_IPIE_int.ppt
    
    Allen's translation revealed that the scale is the short white bar within the caption on the left
    edge of the image on slide 14; the length of that bar is 1 arc sec. 
    
    I will take a stab at calculating the size of what appears to be the satellite's dominant feature: a
    dish antenna (corrections/improvements welcome!):
    
    The scale bar appears to be about 22 pixels long, and the dish of the middle Lacrosse image is about
    34 pixels wide; therefore, 1*34/22 = 1.5 arc sec for the dish.
    
    On the pass on which that image was taken, Lacrosse's closest range was 816 km, which would result
    in ~4 m per arc sec, which makes the dish at least 1.5 x 4 m = 6 m wide. Of course, the image range
    could have been somewhat further, up to perhaps 1000 km, in which case, 1 arc sec = 4.9 m, which
    would make the dish about 7.4 m.
    
    The plane of the dish appears not to be perpendicular to the observer, so perhaps its real diameter
    is somewhat greater, but not by much (I guess).
    
    Further reading: Allen's source book on the Altay Optical-Laser Center
    
    http://www.fas.org/spp/military/program/track/altay.pdf
    
    Ted Molczan
    
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