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bwinkel / cysgp4

A wrapper around the SGP4 package, for sat TLE calculations
Apache License 2.0
23 stars 2 forks source link

building TLE from linestring- ecc and ArgOfPer? #11

Closed RJ3 closed 4 years ago

RJ3 commented 4 years ago

Maybe this is a stupid question because of the way SGP4 works.

I'm using tle_linestrings_from_orbital_parameters function and noticed it is missing entries for Eccentricity and Argument of Perigee. Could this be added or is it not necessary? As-is the TLE only has 4 orbital elements, and it would need 6 to be complete. https://github.com/bwinkel/cysgp4/blob/afdd4bcfced2ce69de4dab864df002eb236f476b/cysgp4/utils.pyx#L245

bwinkel commented 4 years ago

Not at all a stupid question! In fact, it was me who made a stupid mistake ;-)

The function is based on a Jupyter notebook by @cbassa see starlink_sunlit_satellites.ipynb. For the SpaceX/Starlink constellation, the two orbital parameters that you mention weren't necessary. So I simply forgot to add them to the more general 'tle_linestrings_from_orbital_parameters' function. I will implement this asap.

Thanks for letting me know.

bwinkel commented 4 years ago

I implemented a fix. Would it be possible for you to check if this works for you, before I make a new release?

RJ3 commented 4 years ago

Thanks for your quick reply. That makes sense that the LEO objects didn't need those elements! I'll test out the new changes now!

Edit: It appears to be working, it took in the extra 2 fields and the TLE are printing correctly. I will open a new issue if I encounter anything else from more in depth testing.