Re: Decay Watch: #21892

Ron Lee (ronlee@pcisys.net)
Sun, 22 Mar 1998 06:29:42 -0700

Alan correctly points out what I MISSED in my initial post.  I looked 
at the mean motion and the eccentricity but failed to mentally 
calculate the PERIGEE.  Had I done that, or used an elset with the
perigee and altitude, I would have known that drag was a major factor.

Thanks for the "education" Alan.

Ron


At 09:08 AM 3/22/98 +0000, you wrote:
>Regarding his binocular obs of this GPS PAM-D, Ron Lee
><ronlee@pcisys.net> writes
>>...
>>21892
>>1 21892U 92009C   98080.88376902  .02011925 -67434-6  80885-3 0  5618
>>2 21892  34.4286   7.5870 0932503 256.3201  93.2584 14.2112852414899
>>...
>>Just looking at the elset with a mean motion of 14.2, sure seems odd
>>that it is due to decay around 21 April.
>
>But its perigee is around 150-155 km and it is certainly feeling the
>drag. It passed through mm=12.0 on December 21, mm=13.0 on February 14
>and mm=14.0 on March 16. An evolution to decay on April 21 has it
>reaching mm=15.0 on April 9 and mm=16 about 28 hours before re-entry. In
>fact, my prediction of April 21 (as for many of the dates in my latest
>decay list) assumes that the mean atmosphere density will decrease a
>little from its recent high value - if current conditions continue, its
>decay could occur a few days earlier still. I include current elsets for
>this in both dklist.tle and select.tle, available via my WWW page.
>
>Alan
>-- 
> Alan Pickup | COSPAR site 2707:   55d53m48.7s N   3d11m51.2s W    156m asl
> Edinburgh   | Home:      alan@wingar.demon.co.uk       +44 (0)131 477 9144
> Scotland    | SatEvo satellite page: http://www.wingar.demon.co.uk/satevo/
>
>
>