IR81 may have failed

Matson, Robert (ROBERT.D.MATSON@cpmx.saic.com)
Fri, 12 Mar 1999 13:55:29 -0800

Hi All,

I checked Daniel Deak's friend's observation, and there is little
doubt that Iridium 81 was the satellite observed at 0:30:34 UT
on March 9.  (Only one other satellite was anywhere near this
part of the sky traveling in the same direction as IR81, and it
was more than a minute later and a good 10 degrees lower in
elevation.  It was also predicted to be only about mag +7.4).

Adding support to the failure theory are recent orbital elements
for Iridium 81:

Iridium 81
1 25468U 98051B   99057.52939346 -.00000145  00000-0 -58789-4 0   702
2 25468  86.3993 295.4683 0002142  78.2082 281.9356 14.34214381 24571
Iridium 81
1 25468U 98051B   99068.13420461 -.00000016 +00000-0 -12897-4 0 01049
2 25468 086.3989 291.0370 0002276 075.5413 284.6035 14.34217962026098
Iridium 81    
1 25468U 98051B   99071.55284274  .00000595  00000-0  20554-3 0   743
2 25468  86.4001 289.6166 0001001 151.5164 208.6080 14.34223726 26588

In 10 1/2 days, the mean motion only increased by .0000358.  That's
about .0000034 per day.  In the following 3.42 days, the mean motion
increased by .00005764, or .0000169 per day.  This is a factor of
five increase.  People should definitely keep an eye on this satellite!

Cheers,
Rob