GREOPy: A General Relativistic Emitter-Observer problem Python algorithm

[irideselby]

Submitting Author: Jan P. Hackstein (@irideselby)
All current maintainers: (@irideselby)
Package Name: GREOPy
One-Line Description of Package: Calculate relativistic light rays sent by an emitter to a receiver in the presence of a gravitational field.
Repository Link: https://codeberg.org/JPHackstein/GREOPy
Version submitted: v0.2.1
EiC: @coatless
Editor: @jonas-eschle
Reviewer 1: @lpsinger
Reviewer 2: @Arya-AD
Archive: https://zenodo.org/records/14537866
JOSS DOI: TBD
Version accepted: TBD
Date accepted (month/day/year): TBD

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Description

GREOPy is a Python library for calculating relativistic light rays sent by an emitter to a receiver in the presence of a gravitational field. Finding a light ray connecting two events is sometimes called "Emitter-Observer" problem and is always present when it comes to communication between two observers, e.g. two satellites in orbit. GREOPy allows the emitter and receiver to move along arbitrary curves, making this an initial-value problem to solve from the emitter's perspective, and the gravitational field can be described by a rotating, non-accelerating central mass. Everything is being calculated in the general relativistic framework to include relativistic effects like light bending and the relativistic Doppler effect to be able to quantify their impact on error propagation. While only two spacetimes are implemented at the moment (even though further additions are planned), GREOPy is written in a way to allow the community to easily expand the number of spacetimes to suit their needs.

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Data processing/munging: GREOPy uses parametrised curves, e.g. orbit data, to simulate communication via relativistic light rays between them. This allows analysis of relativistic effects on light and by extension any corresponding observable in some chosen spacetime, giving insights into fundamental properties of the underlying spacetime.

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This package is mainly targeted for scientists working in geodesy; it can be used to simulate satellite-satellite or satellite-ground station communication and from this derive, e.g. how the Earth mass distribution changes over time due to for example climate change.

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Not the same thing. There exist of course Python packages that implement General Relativity, e.g. to be able to calculate light rays (lightlike/nulllike geodesics) as one can do with EinsteinPy for example. However there appear to be no packages that implement specifically the Emitter-Observer problem (initial-value problem with a variable target boundary) in terms of General Relativity.

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[coatless]

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Editor comments

Thanks for bearing with us as we hibernated over the holidays and assigned out a new EiC.

Regarding the package, I'm happy to work on assigning an editor.

However, I do want to bring to your attention a few concerns.

Specifically, the "How to find initial conditions" page linked on the documentation website is blank.

https://greopy.readthedocs.io/en/latest/about/initial_conditions.html

Also, the tutorial gallery only one tutorial is present ("Quick Start"). Do you envision additional tutorials being added during the review process?

https://greopy.readthedocs.io/en/latest/auto_tutorials/index.html

Lastly, the Quickstart example on the reduced grid also took about 15 minutes of compute time on Colab. Would it be possible to include a note on the documentation that computations may be long running?

[irideselby]

Hello!
Thank you very much for your answer and comments.
Concerning the blank page on the wiki. It has sadly been sitting there for a while while I was working on different aspects of the package and it has been slipping through until now, but I think now will be a good time to finally update it.
I definitely want to fill the tutorial gallery with more tutorials over time, and I think I have a good idea about a second small tutorial already. Now that I got the package into shape I can also focus more on tutorials.
Also thank your for the notice on computation times, I will add a note to the documentation.

I will begin working on the comments in the next couple of days and update everything accordingly, so thanks again!
Maybe one question: Between submitting the package and now, I have found a bug concerning the light ray calculation for which I have worked out a fix. May I just update the package while the review process is going on? I imagine that the review process will be conducted with the exact version I submitted, so in case the bug will be found by the reviewers as well, do I then just link to the package version/PR that fixes the bug?

[coatless]

@irideselby Okay, let's hold off on sending it out for the review until the bug regarding light ray calculation is fixed as that may impact what SME reviewers of the software respond with.

Sound okay?

[irideselby]

@coatless Thank you for waiting, I fixed the bug and bumped the version accordingly. I also edited the initial message in this thread to reflect this change, so now the submitted version is 0.2.1 instead of 0.2.0, I hope that's alright.

[coatless]

@irideselby thanks for letting me know. I'll start the process of assigning an editor.

[irideselby]

I have now added the paper.md for JOSS in a paper/ directory and added a tick for the corresponding bullet point in the initial submission message.

[lwasser]

hi @irideselby just a quick note that we are still onboarding new editors! We had a large group of packages submitted to us and are onboarding a bunch of new people. Thank you for your patience and for pulling the JOSS part together!

[coatless]

@irideselby Thank you for your patience! We've secured an editor to further move the review along.

We're happy to announce that @jonas-eschle will be the editor for your submission.

For next step, we'll be working toward getting reviewers assigned. This step is detailed here:

https://www.pyopensci.org/software-peer-review/how-to/author-guide.html#the-review-begins

[jonas-eschle]

Hi @irideselby! I'm excited to be the editor leading your reviews! I'm going to review everything and start working toward assigning reviewers for the software and will keep you updated here.

[irideselby]

@coatless Thank you very much! And hi @jonas-eschle, I'm looking forward to be working with you through the process.

[jonas-eschle]

Hi @irideselby, to give you a heads-up, I am looking for reviewers currently. I think the package overall suits well and I didn' find any major obstacle. Just a few minor things, they're not critical but good to know:

• the package seems barely discoverable. The only way I was able to find the package is via the link provided, but google does not return any result (DuckDuckGo does). Not sure what can be done, but just FYI.
• You seem to be the only contributor so far. Do you have any chance of involving other people, maybe for the long-term?
• Do you have any idea about the user-base?

I'll let you know once I found two reviewers!

[irideselby]

@jonas-eschle Thank you for the feedback. Concerning the second point, this package arose from research I'm currently doing in my PhD, which is why I have started out on my own. However, involving other people in the package's development is definitely something I would like to do in the future; that's the reason why I have put so much effort into trying to make the package accessible in the first place.
I have also already talked about maintaining and working on the package long-term with some colleagues and am currently working with them on papers that will cite the package, which in turn will hopefully help with discoverability. The papers are of course aimed at the user-base, and I shortly address it in the JOSS paper draft that I added to the repository as well.
I'm looking forward to the reviews!

[jonas-eschle]

@irideselby makes sense! And I am glad that you put the effort into making it maintainable and vetting it here. The comment about the hosting was also about familiarity, it's, IMH experience, just easier to get people on Github to contribute, because everyone has a Github account. But that's your decision of course, nothing to hold up the review.

And after searching for a while, I've finally found two reviewers, welcome @lpsinger and @Arya-AD! Thank you for volunteering to review!

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[irideselby]

@jonas-eschle Thank you for your time and effort!
And welcome to the thread, @lpsinger and @Arya-AD, I'm very excited to hear from you!