<p>I'm well familiar with SGP4 and its implementations in various languages. I am curious if there are open-source implementations of J2Mean, J2, J3, J4, etc propagation techniques.</p>
<p>If my terminology is imprecise/incorrect, my apologies, this is slightly outside my area of expertise.</p>

CC BY-SA 4.0
2024-07-18T04:27:42.727Z
What did you find when you searched the internet? When I tried "non-SGP4 propagators", multiple pages (e.g. [this one](https://juliaspace.github.io/SatelliteToolbox.jl/v0.6/man/orbit/propagators/)) seemed worth further exploration – though personally I'm not expert enough to know what's being described. I'd encourage you to [edit](https://astronomy.stackexchange.com/posts/58109/edit) your post to add a summary of what you'd found when searching and why none of the pages provided what you need. :-)
Chappo Hasn't Forgotten
CC BY-SA 4.0
2024-07-18T09:08:43.623Z
You may know this already, but for readers who dont, SGP4 is designed to work directly with [Two Line Element sets](https://en.wikipedia.org/wiki/Two-line_element_set) - it's a closed system. You can't put actual orbital elements into SGP4 - it only works with the special TLEs which are calulated to provide pretty good positions and velocities for several days or longer around their epoch. For an actual propagator - something that uses state vectors and an [ODE](https://en.wikipedia.org/wiki/Ordinary_differential_equation) solver based on models of Earth's gravity you can almost write your own
uhoh
CC BY-SA 4.0
2024-07-18T09:13:38.460Z
Here's [some of my dabblings](https://space.stackexchange.com/a/23409/12102) See also [How does the poliastro python package "Going to Mars with Python" example work? What's it really doing?](https://space.stackexchange.com/q/28228/12102) and especially [Python Libraries: Numerical Propagators and Access Calculations](https://space.stackexchange.com/q/41755/12102) and [A software for orbit propagation, considering Moon, Sun and zonal harmonics](https://space.stackexchange.com/q/28301/12102) and [Low Earth orbit propagation in GMAT](https://space.stackexchange.com/q/28327/12102)...
uhoh
CC BY-SA 4.0
2024-07-18T09:23:43.800Z
...and [What are the choices today for orbital mechanics simulation software?](https://space.stackexchange.com/q/646/12102) My interest in orbital mechanics years ago pushed me to learn Python which is wonderful enabler. Here in Astronomy SE there's also [Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?](https://astronomy.stackexchange.com/q/13488/7982) - you might also like to try [Universe Sandbox](https://astronomy.stackexchange.com/search?q=universe+sandbox)
uhoh
CC BY-SA 4.0
2024-07-19T01:06:08.707Z
@uhoh I think your comments are enough to constitute an answer – even if you simply cut and pasted them (retaining the hyperlinks, of course). Comments aren't permanent, and it's always possible that someone down the track might be looking for info on SGP4 that your answer might help with. If the question is closed for lack of detail, it probably won't get auto-deleted, so it will remain in our Astronomy.SE library – and your answer would therefore remain a potentially useful resource. If you're disinclined to do so, I'd consider using your comments as a community wiki answer. Thoughts? :-)
Chappo Hasn't Forgotten
CC BY-SA 4.0
2024-07-19T08:00:09.243Z
@ChappoHasn'tForgotten Yes I have some experience in Stack Exchange; I'm familiar with these concepts. Several things could also happen; OP may refine their question based on a review of this information, OP may discover one or two items that really answer the question for them, at which point we might encourage them to write an answer themselves (always encouraged in SE) or someone else might write a real answer (rather than some comments pretending to be one) or this question may be migrated to Space SE (if the OP is more interested in artificial objects in low Earth orbit where drag is big)
uhoh
CC BY-SA 4.0
2024-07-19T08:00:36.853Z
@ChappoHasn'tForgotten so let's wait and see what happens and what others do first.
uhoh
<orbital-mechanics><artificial-satellite><software><modeling>
Do there exist open-source implementations of non-SGP4 propagators?
Michael Bonnet
# Do there exist open-source implementations of non-SGP4 propagators?

(Asked by: username_0 on 2024-07-17)

I'm well familiar with SGP4 and its implementations in various languages. I am curious if there are open-source implementations of J2Mean, J2, J3, J4, etc propagation techniques.

If my terminology is imprecise/incorrect, my apologies, this is slightly outside my area of expertise.

**Tags:** orbital-mechanics, artificial-satellite, software, modeling

> **Comments:**
> **username_1**: What did you find when you searched the internet? When I tried "non-SGP4 propagators", multiple pages (e.g. [this one](https://juliaspace.github.io/SatelliteToolbox.jl/v0.6/man/orbit/propagators/)) seemed worth further exploration – though personally I'm not expert enough to know what's being described. I'd encourage you to [edit](https://astronomy.stackexchange.com/posts/58109/edit) your post to add a summary of what you'd found when searching and why none of the pages provided what you need. :-)  
> **username_2**: You may know this already, but for readers who dont, SGP4 is designed to work directly with [Two Line Element sets](https://en.wikipedia.org/wiki/Two-line_element_set) - it's a closed system. You can't put actual orbital elements into SGP4 - it only works with the special TLEs which are calulated to provide pretty good positions and velocities for several days or longer around their epoch. For an actual propagator - something that uses state vectors and an [ODE](https://en.wikipedia.org/wiki/Ordinary_differential_equation) solver based on models of Earth's gravity you can almost write your own  
> **username_2**: Here's [some of my dabblings](https://space.stackexchange.com/a/23409/12102) See also [How does the poliastro python package "Going to Mars with Python" example work? What's it really doing?](https://space.stackexchange.com/q/28228/12102) and especially [Python Libraries: Numerical Propagators and Access Calculations](https://space.stackexchange.com/q/41755/12102) and [A software for orbit propagation, considering Moon, Sun and zonal harmonics](https://space.stackexchange.com/q/28301/12102) and [Low Earth orbit propagation in GMAT](https://space.stackexchange.com/q/28327/12102)...  
> **username_2**: ...and [What are the choices today for orbital mechanics simulation software?](https://space.stackexchange.com/q/646/12102) My interest in orbital mechanics years ago pushed me to learn Python which is wonderful enabler. Here in Astronomy SE there's also [Where can I find the positions of the planets, stars, moons, artificial satellites, etc. and visualize them?](https://astronomy.stackexchange.com/q/13488/7982) - you might also like to try [Universe Sandbox](https://astronomy.stackexchange.com/search?q=universe+sandbox)  
> **username_1**: @username_2 I think your comments are enough to constitute an answer – even if you simply cut and pasted them (retaining the hyperlinks, of course). Comments aren't permanent, and it's always possible that someone down the track might be looking for info on SGP4 that your answer might help with. If the question is closed for lack of detail, it probably won't get auto-deleted, so it will remain in our Astronomy.SE library – and your answer would therefore remain a potentially useful resource. If you're disinclined to do so, I'd consider using your comments as a community wiki answer. Thoughts? :-)  
> **username_2**: @username_1 Yes I have some experience in Stack Exchange; I'm familiar with these concepts. Several things could also happen; OP may refine their question based on a review of this information, OP may discover one or two items that really answer the question for them, at which point we might encourage them to write an answer themselves (always encouraged in SE) or someone else might write a real answer (rather than some comments pretending to be one) or this question may be migrated to Space SE (if the OP is more interested in artificial objects in low Earth orbit where drag is big)  
> **username_2**: @username_1 so let's wait and see what happens and what others do first.  

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## 0 answers

