Re: [Orekit Users] TLEPropagator Question

[Thomas Neidhart <thomas.neidhart@spaceapplications.com>]

Dear Luc,

On 03/16/2011 04:37 PM, MAISONOBE Luc wrote:
>
> This is true, but I would not say that the TLE model is "sophisticated"
> and yields "accurate" results. This model is known to have many
> drawbacks and is clearly suited neither for long term propoagation nor
> for accurate orbit propagation. Apart from the model by itself, the
> published TLE data often has large errors. Several studies have shown
> that you may get several hundreds or even thousands of kilometers errors
> propagating TLE a few days (yes, these orders of magnitude are in
> kilometers, not in meters).

[snip]

thanks for the clarification on this, I understand now much better. I
was already aware that a propagation based on TLEs may not be very
accurate, but that it can accumulate errors of several thousands of km
was a surprise to me. In our case multiple orbit prediction sources will
be used, where TLEs are used as the initial, broad estimation.

> We are aware of this missing feature and it has been fixed. If you want
> to give it a try, checkout the current development version of Orekit
> from the Git repository (it uses the newly released Apache Commons Math
> 2.2). In this version, TLEPropagator does implement the Propagator
> interface (which has also been improved) and can be used with visibility
> events detectors.

Very good, I already tried it out and got the expected results, thanks
for pointing it out. Just a small remark: are there plans to provide
orekit in a publicly available maven repository? By now I have
integrated it into our own continuous integration system / maven
repository and it works fine, but a public one would be even better.

> Yes but it does not mean that the results are "better", it means the
> results are consistent with the way the other sites compute them.
> Unfortunately, if you don't have access to better orbit data, you cannot
> have a better result.

Indeed, I was a bit imprecise here, I did not meant to use the term
accurate in an absolute manner, but relative to other tracking sites.

Thanks again & best regards,

Thomas
-- 
Thomas Neidhart, Software Engineer
Space Applications Services, www.spaceapplications.com
Leuvensesteenweg 325, B-1932 Zaventem, Belgium
Phone: +32-(0)2-721.54.84, Fax: +32-(0)2-721.54.44