FW: SPRE & STS-72 keps - was Re: APRTRAK orbital element updates.

Jeff Hunt (jhunt@eagle1.eaglenet.com)
Fri, 5 Jan 96 08:51:08 EST

Here's an interesting article from Philip Chien who I know monitors 
seesat-l.  It helps explain why OIG has been slow (IMO) in putting out 
updated TLEs.  And yes, I have strayed and gone and looked at the other side 
;-)(hearsat-l which is for radio monitoring of sats) because the weather has 
been so bad this Winter in the NE U.S.  
The U.S. Government partial S/D has already resulted in a lot of space 
related information from not being disseminated on most NASA sites.  Some 
additional non-NASA sites that might be used to obtain predicted and current 
STS TLEs would be:
Regards, Jeff Hunt <jhunt@eagle1.eaglenet.com>
---------------Original Message---------------
Ken McCaughey - N3FZX said:
>Updated elements for SPRE and STS-72 will be available from the SPRE FTP
>site as we get them from NASA.
>URL ftp://w3eax.umd.edu/pub/spre/info

With the federal government shutdown it make take more time for elements to
get distributed than normal.  Satellite tracking is still considered a
critical government function, but is operating with minimal personnel.  In
addition many folks who normally help distribute elements are not able to
access their E-mail and other resources.

There is a good trick to tracking a spacecraft, like Spartan, which is
deployed and retrieved by the shuttle.  Just use the latest available keps
for the shuttle before it deploys the Spartan spacecraft.  Remember that
Spartan has no onboard propulsion system which would move it in to a
different orbit - just extremely small cold gas thrusters which are used
for attitude control.  So the Spartan remains in the orbit the shuttle
leaves it in.  Then the shuttle maneuvers in to a slightly different orbit,
eventually ending up at a stationkeeping position about 40 nm away from
Spartan, and then the shuttle begins a set of maneuvers to rendezvous with
Spartan, ultimately ending up in the same orbit where Spartan was
originally released!

On previous Spartan and SPAS missions I have tracked the predicted location
where the shuttle would catch up with the free-flyer very accurately using
the pre-release keps for the shuttle.

It's also important to note that 40 nm. is a fairly small distance in terms
of orbital dynamics - while the two spacecraft will appear as separate dots
visually, only the narrowest beams will care about which target it is
pointed towards.

*sigh* - I really hope the government is back up to speed by the time the
shuttle launches.  This shutdown is a real pain in the modem!

Philip Chien, Earth News - space writer and consultant  PCHIEN@IDS.NET
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