Setting standard gravitational parameter according to the central body and find a place for the constants

[hornig]

There are several places, where we are using mu, the standard gravitational parameter. Currently it is fixed to Earth in most cases.
it would be better to have it selectable and also to have it at a central location to not have duplicates.

That we should change.
Propose a better way! :)

For example it is in these files:

https://github.com/aerospaceresearch/orbitdeterminator/blob/master/orbitdeterminator/kep_determination/gauss_method.py#L27-L28

https://github.com/aerospaceresearch/orbitdeterminator/blob/master/orbitdeterminator/kep_determination/gibbs_method.py#L15

https://github.com/aerospaceresearch/orbitdeterminator/blob/master/orbitdeterminator/kep_determination/lamberts_method.py#L10

https://github.com/aerospaceresearch/orbitdeterminator/blob/master/orbitdeterminator/util/state_kep.py#L29

[NamamiShanker]

Hey! I am a new contributor and I recently discovered your project. Can I work on this issue?

[hornig]

@NamamiShanker sure, just start.
before you do a PR chat with us here https://aerospaceresearch.zulipchat.com/#narrow/stream/147024-OrbitDeterminator about it.

[pranjii]

Hey if this issue is still open I will work on it. Could you give me a few example of cases?

[20JE0187]

Hey! I am new to open source contributions and want to contribute to this project. Can you please explain a little bit that what is the problem actually, with an example and what I have to do here to resolve that issue ?

[20JE0187]

What things and topics of orbit determination we should learn to understand the code and resolve the issue ?

[Arunim10]

Hey! I am new to open source contributions and want to contribute to this project. Can you explain what do you mean by 'selectable' here ?

[Arunim10]

I have observed that different values of mu of Earth are being used. For example ,
in this link https://github.com/aerospaceresearch/orbitdeterminator/blob/master/orbitdeterminator/kep_determination/gibbs_method.py#L15
, mu of earth used = 398600.4418 km^3/sec^2
and in this link
https://github.com/aerospaceresearch/orbitdeterminator/blob/master/orbitdeterminator/util/state_kep.py#L29
mu of earth used = 398600.4405 km^3/sec^2

So shall we go with any one value or with both values ?