A bright GeoSat

From: Brian Hunter (bkh@chem.queensu.ca)
Date: Thu Jul 06 2000 - 12:06:38 PDT

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    I was observing in the region of the geostationary belt on July 5, 2000 at
    5:36 UT when I picked up Brasilsat B3 (98006A, 25152). It was unusually
    bright, between 7.5 and 8th magnitude.  As a quick check, I was able to see
    it my 10 x 40 binoculars.  M11 made a handy reference for the position.  I
    had observed Brasilsat B1 and B2 earlier the same night and bother were the
    more normal 12th magnitude or so.  I believe all three are HS376W spin
    stabilized spacecraft.
    I suspect I understand the brightness of B3 but maybe one of the geometry
    gurus (Rob?) can do the calculations more carefully than I can.
    The position of the satellite was  RA 18hr 51min DEC -6 deg 47' and the sun
    was at RA 6hr 59 min DEC 22deg 45'.  This puts them almost exactly 180
    degrees apart in RA.  Putting it another way, the satellite was at AZ 188
    EL 39 degrees and the time was about half an hour after solar midnight so
    the sun was at about AZ 8  -18 EL degrees.  All of this puts me close to the
    Sun-Satellite line and about 20 degrees below it and I suspect all I saw was
    a favourable set of reflections off the solar cells on the cylindrical
    I have occasionally seen other geosats appear brighter that others but this
    was much more obvious.  Any other ideas on the cause?  Is there something
    unusual about this object?  I tried to find it last night to see if the
    brightness is strongly time dependant but the clouds did not cooperate and I
    could not see it at all.
    Brian K. Hunter,                              Department of Chemistry
    Professor                                        Queen's University
    bkh@chem.queensu.ca                 Kingston, Ontario
    (613)-533-2620                               Canada   K7L 3N6
    44 14'  N         76 30' W
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