Re: ISS Magnitude After Solar Panel Installation?

From: Russell (
Date: Fri Dec 01 2000 - 14:41:53 PST

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    At 07:17 01/12/00 -0500, Penny Fischer wrote:
    >Hi Satters,
    >I have not seen predictions yet on the estimated brightness of the ISS
    after the solar
    >panel deployment this Sunday.  I only heard it's going to be the brightest
    >orbiting body.  Anyone have any idea how bright it will get?
    There have been numerous reports on how the brightness of the ISS will
    increase markedly after the addition of the huge solar panels during the
    present shuttle mission.  
    It should be pointed out, as many will already be aware, that ISS is
    one of the brightest objects in the sky, even before the installation
    of these massive 'wings'. It is frequently observed as brighter than
    first magnitude, sometimes even in the range of negative magnitudes.
    The solar panels are designed to convert the sunlight falling on them
    into electrical current to power the operation of the ISS.  They therefore
    absorb the vast majority of the incident sunlight and reflect very little.
    This is why they appear black, or at least very dark in photographs.
    Furthermore, the panels will be aligned with the Sun so they present the
    maximum area towards the incoming radiation. Any reflection is therefore
    likely to be directly back towards the Sun and not downwards toward to
    observer on the surface of the Earth.
    There is even the possibility that the brightness of ISS might be 
    diminished, since these panels will cast vast shadows, intercepting some
    of the sunlight that might have gone on to reflect off the (cylindrical)
    modules that are already part of ISS.  Just what effect this 'shadowing'
    has remains to be seen, but I for one do not anticipate a major jump in
    the brilliance of ISS after this mission is completed.
    It may however be easier to spot a distinct 'shape' under even moderate
    Best wishes,  Russell Eberst
    Station 2420:  Latitude 55.9486N, Longitude 3.1383W, height 150ft = 46m.
    181105 Observations
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