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Re: Re: Shuttle Keps




-----Original Message-----
From: Bruce Bostwick <lihan@ccwf.cc.utexas.edu>
To: Charles E. Gelm <gelmce@erinet.com>
Cc: sarex@AMSAT.Org <sarex@AMSAT.Org>
Date: Monday, November 09, 1998 9:53 AM
Subject: [sarex] Re: Shuttle Keps


>At 07:02 AM 11/9/98 -0800, you wrote:
>>Hi, James:
>>
>>I believe that:
>>
>>"If the shuttle elements are more than 12 hours old, they should be
updated."


This is only true following a thruster firing or other energy transfer.
With large maneuvers or sequences of several maneuvers, the element
prediction quality can "perish" even sooner.  Energy transfers do occur more
frequently than is typical on other satellites.  There are times, however,
when the Shuttle maintains a stable orbit for several days during a mission.

>> If this is true and if you received keplerian elements now,
>>they would be more than 12 hours old on December 6th.


When we say "12 hours old," it means 12 hours elapsed since the [reference]
epoch time of the elements.  The prediction quality usually deteriorates
with time elapsed since epoch.

Ken Ernandes
n2wwd@amsat.org
http://www.mindspring.com/~n2wwd


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