<br><br><div class="gmail_quote">On Mon, Apr 6, 2009 at 2:04 PM, Keith Lofstrom <span dir="ltr"><<a href="mailto:keithl@kl-ic.com">keithl@kl-ic.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><div class="h5">An note for Tony - I wrote a little Perl program to process TLE's and<br>
identify "crossers" (though not grazers) from the 3 line catalog. I<br>
can send you the code, it might make a better starting point than SGP4.<br>
It might also be good to meet for lunch sometime this week and perhaps<br>
</div></div>do a coding session. I want to have some collision stuff ready for<br>
PLUG Advanced Topics on the 15th.<br>
<div class="im"><br>
I plot charts with gnuplot, but I am still learning how to do 3D<br>
</div>and animated stuff with it. Plotting the locuses of 13K objects<br>
on the r/v plot, or even 300 objects on the disk plot, will get<br>
<div class="im">"interesting". We probably want to use something else to do<br>
</div>the plots.<br>
<div class="im"><br>
Keith<br>
</div></blockquote><div><br>Keith,<br><br>I'm using a c++ package available <a href="http://www.zeptomoby.com/satellites/">here</a> to extract the orbit description data<br>from the TLEs (originally for MSVC++, modified by me for linux/g++). All<br>
the values you mentioned are made available as instance methods in one<br>of the defined classes. I know you have a penchant for Perl. I just went<br>this way when I thought we were gonna be looking at billions of data points.<br>
I put some code on the server-sky wiki at <br>ServerSky->OrbitsV01->EarthOrbits->OrbitSoftware->SxP4TestPatch.<br>I have an app that reads 3-line TLEs, feeds them to the orbit extractor,<br>and uses the result to predict the ascending node altitude. I need to beef it<br>
up to include the descending node. I have been retrieving the all-data sets<br>from Space-Track for about two weeks.<br><br>What concerns me is that any orbit defined by a single observation is a prediction<br>subject to error. It is too much to hope for that all objects for which data is<br>
available will have observations close to either node, but it is reasonable to expect that some will, and the probability should go up with the number of observations.<br><br>- tony<br></div></div><br>