Re: ISS TLE's

rkresken@esoc.esa.de
Fri, 27 Nov 1998 10:09:29 +0100

>just a warning for those making predictions of ISS passes. The
>orbital elements appear to be very unstable, leading to vastly
>different results even over the relatively short time span of
>one week. I suspect the culprit is the drag term, as exemplified
>by the following elsets which are no more than one day and a half
>apart:


Dear Seesaters, Bruno,

The fluctuations in the drag term you mentioned are reality! As Jason
Hatton pointed out yesterday, Zarya is performing multiaxis spins
(some people call that barbecue spins) until the docking of the shuttle.
That means that projected surface in v-direction changes permanently
and this in turn causes the drag term to change. Interesting effect.

So be careful with longer-term predictions for ISS for the time being.

Rainer