Re: Incorrect prediction for Iridm 15 Dlt r

Alan Pickup (
Wed, 18 Mar 1998 23:10:55 +0000

In connection with this running early, Ron Lee <>
>If you look at the mean motion (15.9475xxxx), it is peobably subject
>to more drag forces than typical.  That may be part of it.  Alan Pickup
>had this object on a recent decay listing (decay about 10 April).
>You may want to keep observing it.  Objects close to decay move really
>quick as you noticed.

You are quite correct, Ron.

In fact, many objects showed a significant increase in drag, and a
corresponding decrease in predicted lifetime, around March 11 (since my
last SatEvo decay list). I am now predicting the decay of this Iridium
Delta 2 rocket for about March 30.

As objects near decay, of course, they experience increasing drag and
can be expected to appear early against any predictions which assume
that the drag is constant (though I don't know what technique SatSpy

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