Re: Light Curve from Satellite Trail

From: John Locker (john@satcom.freeserve.co.uk)
Date: Thu Jan 10 2008 - 21:37:34 UTC

  • Next message: Björn Gimle at ComHem: "Re: Light Curve from Satellite Trail"

    I agree to some extent Björn , especially in the case of structures like ISS 
    where we see obvious shadowing from the large solar arrays....but that 
    shadowing is only noticed when we look at images taken at high 
    magnification.From the ground the naked eye observer wouldnt really be aware 
    .
    
    L5 and possibly 3 and 4 seem to have  a more "on / off" ability to change 
    brightness.
    
    In some reports it is muted that MISTY used some sort of inflatable device 
    to cloak itself....I think that highly unlikely....but rather it used a 
    simply mechanical system and so too  Lacrosse . Perhaps light absorbing , 
    non reflective panels which encase the outer structure when required. Of 
    course if that was the case , why not leave the panels in situ all the time 
    to stop the satellite reflecting at all.
    
    All very confusing.
    
    As an aside , I imaged Lacrosse 2 this evening during a 64 degree pass , no 
    flaring or disappearing trick was observed.
    
    John
    
    ----- Original Message ----- 
    From: "Björn Gimle @GlocalNet" <bg_26934@glocalnet.net>
    To: <SeeSat-L@satobs.org>
    Sent: Thursday, January 10, 2008 6:41 PM
    Subject: Re: Light Curve from Satellite Trail
    
    
    > Without knowing the exact layout, IMHO any satellite with a large
    > antenna/panel monted on some boom outside the spacecraft
    > can get into an attitude where we see the dark backside of
    > the panel, and/or the panel shadows the satellite.
    >
    > Likewise, more or less box-shaped satellites can in some
    > attitudes display only shadowed surfaces to the observers,
    > and there may be no large protrusions that cast even
    > secondary light onto these surfaces.
    >
    > Just my 5c
    >
    > /Björn
    >
    > ----- Original Message ----- 
    > From: "John Locker" <john@satcom.freeserve.co.uk>
    > To: <SeeSat-L@satobs.org>
    > Sent: Thursday, January 10, 2008 6:05 PM
    > Subject: Re: Light Curve from Satellite Trail
    >
    >
    >> On that page , Phil says...
    >>
    >>
    >> "A sudden brightening, then a drop of 5 magnitudes then a final flare."
    >>
    >> Which is more or less how I observed L 5 when I took a series of images 
    >> at the end of last May
    >>
    >> http://mysite.wanadoo-members.co.uk/satcom_transits/Lstrip.jpg
    >>
    >> The flare as it returned was quite distinct , before it faded again
    >>
    >> To me this says  one of two things...either L5 rotates to make itself 
    >> "invisible" ...or it has a mechanical device that shields it.
    >> Question is , why only go into stealth mode for short periods ?
    >>
    >> John
    
    
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