Re: Decay rate of USA 129 r, #24681

Bjoern Gimle (
Tue, 21 Jan 1997 00:55:56 +0100 (MET)

>One factor which must be remembered is the apparent effect of the
>geomagnetic storm on January 10. Very many satellites show an increase
>in drag over the following few days, well above any expected from the
>normal progress of a decay. The perturbation is probably beyond anything
>which might be accommodated  by any smoothly varying curve. It is also
>apparent in the calculated ndot2s for USA 129 r, as in the following

But it is not apparent in the MM values, which should be much more
accurate. And I have not seen a short event have a lasting effect
over a day later.

But there is one fact that I overlooked, which is valid for the
entire period:

The perigee has been above 40 N, where there is winter (and probably
below average temperature across the longitudes). In winter the
atmosphere cools, and 'collapses', contrary to the swelling in summer
(and other excessive radiation)

This partially explains the low decay rate.

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