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Re: [Orekit Developers] Earth Centered ICRF



Hank Grabowski <hank@applieddefense.com> a écrit :

Sounds good.  I'm not sure that I do.  What are we traditionally
benchmarking our frame accuracies against?

As frames are really key to accuracy, we try to go as far as we can and to check against the most accurate reference results we find. It is not always easy to find reference results though. For the IERS conventions, we did use a set of results from Vallado, some values recomputed with SOFA library with controlled input parameters, and from some random orbital bulletins for which we got two frames. For body-centered ICRF, I don't know what you can find (perhaps only making sure they remain parallel to each other when the body is changed, and that the body centers distances remain constant in all frames. For B1950, the only reference I found was regular bulletins published by NASA for ISS.

best regards,
Luc


On Sat, Oct 18, 2014 at 3:54 AM, MAISONOBE Luc <luc.maisonobe@c-s.fr> wrote:

Hi Hank,

Hank Grabowski <hank@applieddefense.com> a écrit :


 Hello all,

Looking over the coordinate systems that are available, I can't figure out
a way to get an earth-centered (or for that matter central body centered)
ICRF coordinate system directly. I know I may just be overlooking
something.  If it isn't possible, would this be something that others
would
be interested in having in the Orekit FramesFactory object?


If you have a use case for this, why not?
Adding predefined frames in FramesFactory is not costly as they are built
only as needed, so we can add as much as we want.

By the way, if you have an accurate definition of what the old B1950 frame
really is, this is also one frame that could be worth adding. There is a
B1950-frame branch in the Git repository, but it was never sufficiently
validated. It is also not in sync with master. If anybody want to give a
look at it, they are welcome.

best regards,
Luc


Hank




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