Re: Shuttle seen from home in Quebec !

From: Gerhard HOLTKAMP (
Date: Wed Mar 12 2008 - 18:19:06 UTC

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    On Tuesday 11 March 2008 08:35, Daniel Deak wrote:
    > The TLE I used to prepare for my observation proved to be very reliable. It
    > can be used by anyone for the final moments of powered flight. I just don't
    > understand why NASA keeps on publishing incorrect MECO TLE every time.
    > Here is the TLE published by NASA before launch (MM 18.151 !!!) :
    > 1 00123U          08071.32561054  .00020000  00000-0  70000-3 0  9002
    > 2 00123  51.6370 161.2897 0408284 168.8587 192.2088 18.15107113    23
    After looking at the epochs of the various TLEs generated by NASA I finally 
    have a hunch why they get the MECO TLE wrong. The epochs of the TLEs given do 
    not correspond to the epoch of the state vector given for the same arc but 
    always fall on the next ascending node. So whatever program NASA is using 
    seems to propagate the given state vector to the next ascending node and then 
    perform the conversion to TLEs - don't ask me why. But if you propagate the 
    MECO state vector it will reenter before reaching the next ascending node. In 
    fact the epoch of the TLEs given above coincides with the time of decay I 
    would expect for these elements. If in addition I take the state vector as 
    propagated until it reaches a height of 70 to 80 km and then run Scott 
    Campbell's rv2el I end up with TLEs close to the ones issued by NASA.
    NASA flight dynamics would use numerical propagation of the state vector only 
    and not the TLEs in their work. In addition they seem to be the only 
    professionals in the field to ignore SeeSat-L or they would have taken notice 
    long time ago that their scheme is flawed!
    Gerhard HOLTKAMP
    Darmstadt, Germany
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