[Server-sky] NORAD TLE's (3)

[Tony Rick]

On Mon, Apr 6, 2009 at 2:04 PM, Keith Lofstrom <keithl at kl-ic.com> wrote:

> An note for Tony - I wrote a little Perl program to process TLE's and
> identify "crossers" (though not grazers) from the 3 line catalog.  I
> can send you the code, it might make a better starting point than SGP4.
> It might also be good to meet for lunch sometime this week and perhaps
> do a coding session.  I want to have some collision stuff ready for
> PLUG Advanced Topics on the 15th.
>
> I plot charts with gnuplot, but I am still learning how to do 3D
> and animated stuff with it.  Plotting the locuses of 13K objects
> on the r/v plot, or even 300 objects on the disk plot, will get
> "interesting".  We probably want to use something else to do
> the plots.
>
> Keith
>

Keith,

I'm using a c++ package available
here<http://www.zeptomoby.com/satellites/>to extract the orbit
description data
from the TLEs (originally for MSVC++, modified by me for linux/g++).  All
the values you mentioned are made available as instance methods in one
of the defined classes.   I know you have a penchant for Perl.  I just went
this way when I thought we were gonna be looking at billions of data points.
I put some code on the server-sky wiki at
ServerSky->OrbitsV01->EarthOrbits->OrbitSoftware->SxP4TestPatch.
I have an app that reads 3-line TLEs, feeds them to the orbit extractor,
and uses the result to predict the ascending node altitude.  I need to beef
it
up to  include the descending node.  I have been retrieving the all-data
sets
from Space-Track for about two weeks.

What concerns me is that any orbit defined by a single observation is a
prediction
subject to error.  It is too much to hope for that all objects for which
data is
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.

- tony
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