Crazy Iridium TLEs

Edward S Light (
Tue, 2 Sep 1997 14:40:39 -0400 (EDT)

What's going on with the "morning" Iridium orbital elements?

On Sunday morning, 1997 Aug 31 at 09:19.6 UTC (05:19.6 EDT) I saw an obvious
Iridium-type flash, about as bright as Jupiter, about 5 degrees to the right
and slightly above beta Ceti (which itself was at 24 degs elevation, 216 degs
azimuth [measured clockwise from the North]. Since then, no elements I could
find fit that observation; my position may be a degree or so off, but the time
is good to, at worst, 5-10 seconds.

In examining the TLEs for these "newer" Iridia, I see wild values of M2 (the
acceleration term in the mean motion), whereas the older "evening" objects
have no such strangeness. Are the newer ones adjusting their orbits? Are
the ridiculous M2 terms just an artifact of such maneuvers and the method
by which OIG calculates M2?

Clear and dark skies!

Edward S. Light