Latest Iridiums

Matson, Robert (ROBERT.D.MATSON@cpmx.saic.com)
Mon, 9 Nov 1998 11:34:47 -0800

Hi All,

Had quite a nice sighting of the newest 5 Iridiums last night from
Long Beach, CA.  My TLEs from OIG were 3 days old, but I figured
they'd be good enough for acquisition.  Using IRIDFLAR, 3 of the
5 were predicted to flare up quite nicely (-1) assuming enough
time had elapsed for the satellites to properly orient themselves.
Well, all I can say is that these satellites must lock into their
correct orientations very soon after deployment.  I saw 5 flares
to magnitude -2, one after another!  It was beautiful.  The first
4 were evenly spaced; the 5th came fairly close to the 4th, such
that both were flaring at the same time.  I wish I'd had a video
camera!

In related news, I've had time to reduce all the Iridium 11 data,
and unfortunately the observations indicate that the spin axis
is not yet stable, preventing accurate prediction of future
bright flashes.  My advice:  if you've got a sunlit pass of IR11,
it's worth a look.  I've observed -1 magnitude or brighter flashes
every single time I've looked for it.  For north-bound passes it
doesn't seem to matter if it is in the west or the east in the
evening -- the flashes are still bright.  From latitudes in the
mid-30s, the brightest flashes generally occur when the
satellite is approaching culmination (i.e., just south of due
east or due west).

I'll be reducing the Iridium 14 data next.  --Rob