JP-4070: Fix incorrect pixel offsets fed into grism transforms for wfss_contam

[emolter]

Resolves JP-4070

Closes #9694

This PR fixes an issue with the grism to detector WCS transform being used by the wfss_contam step, which was leading to multiple problems with the shapes of the spectral traces, including highly curved spectral traces in order -1 for NIRISS.

This comment explains the specific problem that is solved here.

Since I was working on understanding the WCS better, I also went ahead and updated the testing suite to mock the WCSs instead of getting them from file; there are therefore a few small changes to tests that aren't strictly related to the code changes.

Tasks

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[emolter]

initial round of regtests to see if the changes to the WCS in extract_2d break anything: https://github.com/spacetelescope/RegressionTests/actions/runs/16811629854

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.54%. Comparing base (6f198d4) to head (5e5d8fe).
⚠️ Report is 223 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9728      +/-   ##
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- Coverage   82.54%   82.54%   -0.01%     
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  Files         366      366              
  Lines       37248    37246       -2     
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- Hits        30748    30745       -3     
- Misses       6500     6501       +1     

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[emolter]

new regtests after fixing small issue with old-style WCS transforms:
https://github.com/spacetelescope/RegressionTests/actions/runs/16813664328

The failures of the wfss_contam regtests are expected.

[melanieclarke]

The general approach for the WCS looks good to me, and the code updates look reasonable at a surface level. I'd like @tapastro to review for a more WFSS-knowledgeable perspective, though.

Are there docs on the NIRISS WCS anywhere that should be updated for the new intermediate frame?

[emolter]

I missed Nadia's comment that she would like to see an in-line comment about why there's a new frame added, so I will update that. I don't see anything in the readthedocs of assign_wcs or extract_2d that's incorrect now. Is there a place where we specifically document what the WCS pipelines look like for certain modes?

Maybe I could just add one sentence to the docstring of extract_grism_objects?

[melanieclarke]

Is there a place where we specifically document what the WCS pipelines look like for certain modes?

I don't think so. There's some information in the assign_wcs docs with varying levels of detail for some modes, but it would be nice if we had a separate page to address all the WCS pipelines, since it's complicated and important. Perhaps we could add it as part of addressing JP-3959?

Maybe I could just add one sentence to the docstring of extract_grism_objects?

Better than nothing!

[emolter]

Let me know how 8869fc5 looks.

[emolter]

@tapastro I got some feedback from @gnoir0t on the JIRA ticket that he tested this and it seems to resolve issues with the order -1 and order +1 trace shapes for NIRISS. Along with my conversations with @NorPirzkal I think this has now been tested pretty well for both instruments and we can move ahead with the code review and try to get it merged. (of course this is probably the last message I'll send before vacation so take your time)

[emolter]

@tapastro @melanieclarke let me know how this looking from the code side. The INS teams are happy with it at this stage

[tapastro]

Code looks good, documentation looks good.

Agreed that our WCS objects should probably be better documented in a global sense, and describing the new frame/transform would go there, once the pages are built.