Re: Lacrosse 5 "disappearance trick" captured

From: Marco Langbroek (marco.langbroek@wanadoo.nl)
Date: Sat Jul 29 2006 - 08:27:12 EDT

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    Philip Masding wrote:
    
    > Now if I use YVV and 33 degrees for Marco's disappearence trick pass I 
    > see that around the time the satellite disappeared the SAR panel may 
    > have gone into the shadow of the solar panel. 
    [snip]
    > This assumes the Solar panel is on the sunward side of the SAR which would be a good idea I guess if you want to get the most power out of the solar panel. 
    
    Phil,
    
    Given that the other Lacrosses do not show this effect, this then could indicate 
    the relative arrangement of solar-panel and SAR-panel on Lacrosse 5 is 
    differrent from its predecessors?
    
    It would also seem to indicate that most of what we see in brightness, is due to 
    the SAR panel, not the sat main body? Is that feasible for a specular surface 
    and an object this size? (this is the point on which I feel doubt).
    
    (of course, there's still the old discussion point here about a wire dish versus 
    a planar SAR array. In view of your work on the Lacrosse flares, I favour the 
    planar array).
    
    
    > Marco have you any idea what your limiting magnitude is for the moving 
    > satellite is? I suppose it is fainter than the cut off for the stars 
    > which you are tracking.
    
    This highly depends on the observing conditions and spectral colour of the sat 
    (reddish objects appear fainter/slightly out of focus on the images; fogged 
    images due to some haze in my urban environment clearly have worse trail 
    limiting magnitudes due to worse contrast).
    
    But my estimates are that in general for a "measurable" trail the cut-off is at 
    mag. +3.0, for a marginally visible (on the image) trail at mag. +3.5. I think 
    that on the 26 July image where Lacrosse 5 becomes invisible its brightness is 
    at least 2 mag. down from its initial mag +1.5 brightness.
    
    > Also if the YVV/33 degree theory is correct Marco has a chance to 
    > observe flares in the next few days
    
    Weather prospects are not good here for the coming week, but if I have any 
    chance I'll try to observe them!
    
    > This is a fascinating mystery!
    
    It is!
    
    - Marco  :-)
    
    -----
    Dr Marco Langbroek  -  SatTrackCam Leiden, Cospar 4353
    Leiden, the Netherlands. 52.15412 N,  4.49081 E (WGS84), +0 m ASL
    
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