Iridium 24871 tumbling; plus other Iridium obs
Ed Cannon (ecannon@mail.utexas.edu)
Sun, 07 Jun 1998 02:55:53 -0500
Saturday evening (about 4:36 Sunday 7 June UTC), Mike McCants and I
observed an Iridium, #24871, very obviously tumbling rapidly, about
mag. +5.5. It was easy to see using Mike's finder scope. However,
my recollection is that neither of us saw any bright flashes from
it; these were just ordinary maxima.
I'm not 100% sure what its correct ID or common name are. Below are
some elsets for comparison. It's definitely the one with slightly
higher mean motion (and lower orbital altitude). Alan Pickup and
Mike agree below that it's Iridium 20, 97-34C; OIG is still calling
it 18.
We also observed Iridium, #24872, and it did not display anything
unusual. Mike and Alan agree below that this is Iridium 18 (97-34D);
OIG is still calling it Iridium 20.
>From OIG Web site:
IRIDIUM 18
1 24871U 97034C 98156.14126553 +.00000184 +00000-0 +58259-4 0 01955
2 24871 086.4000 046.7386 0014659 096.7807 263.5066 14.34522202047507
IRIDIUM 20
1 24872U 97034D 98156.73671225 -.00000138 00000-0 -56337-4 0 1622
2 24872 86.3996 46.4950 0003939 121.9210 238.2362 14.34217366 47558
>From OIG telnet site:
Now cross-referencing the following SATELLITE CATALOG numbers:
24871
24872
CATALOG NUMBER INTERNATIONAL DESIGNATION
SATELLITE NUMBER 24871 WAS NOT FOUND.
SATELLITE NUMBER 24872 WAS NOT FOUND.
>From Alan's iridiums.tle file:
Iridium 20 att 3.0 0.0 0.0 6.0 d 787 x 766 km
1 24871U 97034C 98156.14126553 .00000184 00000-0 58259-4 0 1955
2 24871 86.4000 46.7386 0014659 96.7807 263.5066 14.34522202 47507
Iridium 18 3.0 0.0 0.0 6.0 d 781 x 775 km
1 24872U 97034D 98156.73671225 -.00000138 00000-0 -56337-4 0 1622
2 24872 86.3996 46.4950 0003939 121.9210 238.2362 14.34217366 47558
Mike's iridium.html file:
Iridium 20 att
1 24871U 97034C 98156.14126553 +.00000184 +00000-0 +58259-4 0 01955
2 24871 086.4000 046.7386 0014659 096.7807 263.5066 14.34522202047507
Iridium 18
1 24872U 97034D 98156.73671225 -.00000138 00000-0 -56337-4 0 1622
2 24872 86.3996 46.4950 0003939 121.9210 238.2362 14.34217366 47558
Besides those two, we also saw in twilight a *really* bright flare,
as predicted, from Iridium 53; we saw Iridium 11 do some very bright
flashes; and we saw Iridium 21 (24873, 97-34E), a non-operational
one stuck in the parking orbit, but it appeared steady and not very
bright.
Additionally, Saturday morning (6 June) I observed a flare from
Iridium 32; it was fainter than predicted (Iridflar -7, GSOC -5) as
compared to Jupiter, which was several degrees above it, but there
was definitely some haze, and it was only 20 degrees above the
horizon. I also watched Iridium 27 display 3 episodes of very bright
flashes (much brighter than Iridium 32) at approximately UTC 9:39:30
(two flashes), 9:42:45 (two flashes), and 9:43:19 (several flashes),
plus-or-minus a second or two.
Ed Cannon
ecannon@mail.utexas.edu
Austin, Texas, USA