RE: Confused over STS116 TLEs.

From: Ted Molczan (molczanseesat@rogers.com)
Date: Wed Dec 13 2006 - 11:54:29 EST

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    Atul Sowani asked:
    
    > I am currently looking at the shuttle TLEs given at 
    > spaceflight website of NASA.
    > http://spaceflight.nasa.gov/realdata/sightings/SSapplications/
    > Post/JavaSSOP/orbit/SHUTTLE/SVPOST.html
    > 
    > There seem to be many TLEs corresponding to different phases 
    > of the mission. Which one should I use? In other words, how 
    > should I correlate the TLE that Heavens-Above uses and the 
    > TLEs given at NASA's site?
    
    As far as I know, Heavens-Above employs recent elements based on tracking, which
    enables accurate predictions as long as the shuttle does not manoeuvre. NASA's
    elements take into account planned manoeuvres, which makes them superior for
    long term predictions.
    
    To decide whether or not you need to use NASA's elements, look near the top of
    their web page, for the following section:
    
    Maneuvers contained within the current ephemeris are as follows:
    
    
    IMPULSIVE TIG (GMT)   M50 DVx(FPS)      LVLH DVx(FPS)      DVmag(FPS) 
    IMPULSIVE TIG (MET)   M50 DVy(FPS)      LVLH DVy(FPS)      Invar Sph HA
    DT                    M50 DVz(FPS)      LVLH DVz(FPS)      Invar Sph HP 
    ------------------------------------------------------------------------
    352/22:41:38.169           0.5              -1.5              1.5    
    008/20:54:03.196          -1.3              -0.0              192.6  
    000/00:00:06.392          -0.6               0.0              176.0  
    
    352/23:09:42.456           5.8             -10.0              10.0   
    008/21:22:07.483           2.8              -0.0              192.6  
    000/00:00:14.966           7.6              -0.1              170.4  
    
    352/23:52:55.314          -6.4              -9.6              9.6    
    008/22:05:20.341          -1.4               0.0              187.4  
    000/00:00:14.301          -7.0              -0.1              170.1  
    
    354/20:01:26.788           0.9               2.0              2.0    
    010/18:13:51.815           0.9              -0.0              188.9  
    000/00:00:08.504           1.6               0.0              169.5  
    
    
    The next manoeuvre will be on day 352, i.e. Dec 18, at 22:41:38.169 UTC;
    therefore, until that time you can safely use Heavens-Above's elements (as long
    as they are reasonably current and reliable).
    
    To find the elset corresponding to the next manoeuvre, scroll down the page
    until you find a "Coasting Arc" with a Vector Time at or just after the time of
    the manoeuvre; in this case it is:
    
    Coasting Arc #8 (Orbit 141)
     
    Vector Time (GMT): 2006/352/22:41:41.365
    
    for which the following elset applies:
    
    1 29647U 06055A   06352.99888702  .00014500  00000-0  95600-4 0  907
    2 29647  51.6312 314.7118 0023039 349.5036  10.5644 15.76357970  1427
    
    There may be several manoeuvres during which the shuttle will not be within
    range of your location, in which case you can skip ahead until the final
    manoeuvre prior to the pass that you wish to observe.
    
    You may also wish to look at Calsky, which mentions taking planned orbital
    manoeuvres into account, but apparently only pre-launch (unless I have
    misunderstood):
    
    http://www.calsky.com/?shuttle=&interval=7
    
    Ted Molczan
    
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