Iridium 27 'strobe' confirmed

Craig Cholar (3432P@VM1.CC.NPS.NAVY.MIL)
Fri, 02 Jan 98 18:52:56 PST

I just saw an evening SW -> W -> NW pass of Iridium 27 (24947 97-57D) and
witnessed the multiple flashes that were recently described by Jari
(finn@main.jetnet.ab.ca).  I didn't expect to see anything, frankly,
but went outside in mostly cloudy skies to see what I could in between
the clouds.  A gap appeared in the right place, and I was rewarded with
6 flashes, each separated by about 5 seconds, before it went behind some
clouds.  It briefly reappeared about 30 seconds later, and saw another
sharp flash, but a bit dimmer.  The brightest flashes were about -2.
The flashes were very short, lasting a fraction of a second, and
are nothing like the relatively long duration flares we've seeing.

Iridium 27 is non-operational, and is probably tumbling for it to be
able to flash like that.  Thanks, Jari, for the report.  I haven't
been looking at the dead Iridiums lately, but I will now!  The other
Iridiums in non-operational orbits are 24842 and 24873.  My notes
indicate that 24967 is also dead, but it appears to be in a useful
orbit based on perigee and apogee, so I may be mistaken.

Quicksat output:

***  1998 Jan   3  Sat morning  *** Times are UTC ***

 H  M  S  Tim Al Azi C Dir  Mag Dys F  Hgt Shd  Rng     EW Phs  R A   Dec
02 48 34   .0 43 278 C  92 20.8   1 5  566 310  796 km 1.3 113 2147  28.9
                                       352 193  495 miles

Here are the Iridiums in non-operational orbits (excluding, of course,
the recently-launched ones that are still climbing):

Iridium 11       3.0  0.0  0.0  6.0 d            763 x 759 km
1 24842U 97030G   98002.26834903  .00000196  00000-0  56709-4 0  1475
2 24842  86.3993  79.0661 0003218   3.8618 356.2604 14.39254695 28485
Iridium 21       3.0  0.0  0.0  6.0 d            645 x 626 km
1 24873U 97034E   97364.79757766  .00000380  00000-0  48980-4 0   816
2 24873  86.3968 107.5212 0013550   4.8358 355.2992 14.77979544 25735
Iridium 27       3.0  0.0  0.0  6.0 d            559 x 552 km
1 24947U 97051D   98002.57785639  .00002579  00000-0  18572-3 0   986
2 24947  86.6369  14.5483 0005223 224.4997 135.5819 15.03755724 16626

 Craig Cholar    3432P@VM1.CC.NPS.NAVY.MIL
 Marina, California
 36 41 10.3N,  121 48 17.9W    (36.6862, -121.8050)      UTC -8