Sentinel-1 GRD Analysis Mode

[konstntokas]

• Add support for Sentinel-1 GRD analysis mode.
• Updated year in the headers.

Note: the notebook sentinel_1_analysis.ipynb in folder docs and examples is the same.

I think it might help to start with reading the changes in docs, to get a rough overview of the Sen1 processing.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

Files with missing lines	Coverage Δ
xarray_eopf/__init__.py	100.00% <ø> (ø)
xarray_eopf/amode.py	100.00% <100.00%> (ø)
xarray_eopf/amodes/__init__.py	100.00% <ø> (ø)
xarray_eopf/amodes/sentinel1.py	100.00% <100.00%> (ø)
xarray_eopf/amodes/sentinel2.py	100.00% <100.00%> (ø)
xarray_eopf/amodes/sentinel3.py	100.00% <ø> (ø)
xarray_eopf/backend.py	100.00% <ø> (ø)
xarray_eopf/constants.py	100.00% <100.00%> (ø)
xarray_eopf/filter.py	100.00% <ø> (ø)
xarray_eopf/flatten.py	100.00% <ø> (ø)
... and 4 more

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[pont-us]

Looks good, tests pass, notebook works. I made some comments and suggestions, but nothing vital (mainly docs) so feel free to postpone if merging is urgent. My review of the actual calculation parts was very shallow, but doing it thoroughly would take days (starting with Small, 2011...).