BS-3A / YURI 3A Flashes

Brian Hunter (bkh@chem.QueensU.CA)
Wed, 24 Feb 1999 15:21:37 -0500

I made two detailed observations of BS-3A ( YURI 3A / 20771 / 90 077A ) over
the weekend.
I observed on 1999 02 21 from 01:29 to 02:40 UT and timed 49 intervals over
4303.8 seconds giving a period of 87.83 seconds.  I missed only two of these
flashes when I tried to see them naked eye.  There is a significant range in
brightness with the faintest being about 8th magnitude and the brightest
about 4th.  The bright ones are very hard to judge through a 25cm reflector.
I normally  cannot see the satellite but occasionally there is a brightening
to about 10th magnitude between the flashes.  Strangely, this ocurrs 3/4 of
the way between the flashes, not in the middle.  Furthermore, this extra
brightening always preceeds a fainter than usual flash.

The second set of observations was made on 1999 02 22 from 02:13 to 05:28
UT.  Knowing the period from the night before, I did not try to observe all
of the flashes but instead left an 11 cm reflector pointed at the satellite
position and made occasional observations while looking for other things.
I then fitted the data to a period close to the evening before and obtained
a value of 87.84 seconds based on 133 intervals.  I followed the flashes
until they began to fade  The fading pattern is clearly: bright, faint,
fainter.  By the time I quit, the third of the three was lost first, then
the second, and the bright ones were almost invisible.

I suspect that the object is actually precessing slowly rather than being in
a simple spin.  This would lead to the angle of the reflecting solar
panel(s) changing slightly.  I am puzzled by the timing of the extra
brightning in the middle.  I assume that the AS3000 spacecraft has the solar
panels protuding from the centres of the faces of a roughly cubic box so
that the flashes cannot originate from the side panels of the satellite
itself.  I have to wonder if I am picking up a reflection from an antenna
oriented at an acute angle to both the satellite structure and the solar
panel.

Cheers,

Brian

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