Re: ISS magnitude surge

From: Markus Mehring (m.m@gmx.de)
Date: Sat Dec 15 2001 - 10:34:17 EST

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    On Fri, 14 Dec 2001 19:00:14 -0500, you (Daniel Deak
    <dan.deak@sympatico.ca>) wrote:
    
    >James wrote:
    >> Early this evening I observed an unbelievably bright surge in magnitude of
    >> the ISS - 30 seconds before entering the Earth's shadow.
    >I've observed many passes this week and this phenomenon was seen all times the
    >ISS stack was low to the northeast right after sunset and just before shadow
    >entry. Magnitude easily reached -5 or better.
    
    I've had a few good W->E zenith passes over the last few days, which at
    this time makes for a really colorful show. With the Shuttle/ISS stack
    rising in the West through the darkening sky, brightness is rather low in
    the order of mag 0 (not surprisingly), and the color is usually a really
    strong orange tint. This is quite probably due to the sunlight shining
    through the solar panels and thus illuminating them (which to me is a
    rather unique satobs feature), while the rest of the station remains at a
    rather unfavorable phase angle. The Shuttle with its black belly covering
    most of the station for a while definitely takes away some of the reflected
    light. Then, with the stack rising in the sky, the improving phase-angle
    makes the brightness increase, while the orange tint vanishes slowly
    because we're looking more and more edge-on onto the solar panels. The
    first real surge in brightness appears as soon as the angle allows us to
    look onto the brightly lit upper side of the Shuttle, including the white
    payload bay. At this point, I guess the brightness is at -3 easily, and the
    color is of course an extreme, almost blue-ish, white. Brightness keeps
    rising slowly, with the improving phase-angle, and sometimes there is this
    second surge in brightness when the solar panels produce a bit of a flare
    shortly before shadow entry.
    I think that's quite a show indeed. :)
    
    
    CU!	Markus
    
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