Superbird A addendum

Matson, Robert (
Tue, 14 Jul 1998 13:34:55 -0700

Hi All,

For Superbird A newcomers, I want to add that the information I
posted for July 14th flashes is equally valid the night of the
15th.  Just add about 2 minutes to the times I posted yesterday.
In fact, for each subsequent night you can continue to add two
minutes.  Once someone has reacquired the flashes and posts the
time that the peak flashes were observed, I can make much more
accurate predictions for future nights.

Peak flashes are about magnitude 3.  I'll describe what you can
expect to see by way of example.  Let's say that the peak
flashes ultimately occur at 2:45 UTC.  If so, starting around
2:41, dim flashes should be visible about once every 23.24
seconds.  Call the source of these flashes solar array #1.
By 2:43 these flashes will have brightened considerably to
around 4th magnitude.  But 11.62 seconds after each of these
flashes, you'll begin to see dim, second flashes.  These are
from solar array #2.  Like the flashes from array #1, these
will continue to get brighter.  Eventually the flashes from
array #1 will top out at about 3rd magnitude, with array #2
also peaking at 3rd magnitude thirty seconds to a minute later.

At the peak time (2:45 in the example), flashes are equally
bright from either array.  But within a minute, the flashes
from array #1 will start to get noticeably dimmer than those
from #2.  By around 2:48, only flashes from array #2 will be
visible.  In prior messages on Seesat, we've referred to this
change-over as a "phase shift", but really it's just a
consequence of the two arrays pointing in nearly opposite
directions.  The optimum alignment of one array just happens
to precede the other by a minute or two.

For anyone who has yet to observe a near-geosynchronous-
altitude satellite, this is the one to see!  None are brighter
that can also be predicted reliably.  --Rob