Fix RSR band name retrieval for unconfigured sensors

[djhoese]

This adds the missing configuration for mapping MERSI-2 band names to the names used in the RSR files. It is basically "ruined" by the generic mapping mapping numeric band names to ch{:d}. This isn't the case for MERSI-2 which uses the same band name.

It turns out MERSI-2 does use the chN names in the RSR HDF5 files, but since it wasn't configured an if statement in the RSR Reader was failing with a KeyError before it was supposed to. This PR should fix this so that the "generic" band names are used as a fallback.

• Closes #xxxx
• Tests added
• Tests passed: Passes pytest pyspectral
• Passes flake8 pyspectral
• Fully documented

[codecov]

Codecov Report

Merging #158 (7152c17) into main (4224191) will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #158      +/-   ##
==========================================
+ Coverage   88.00%   88.02%   +0.01%     
==========================================
  Files          22       22              
  Lines        2468     2472       +4     
==========================================
+ Hits         2172     2176       +4     
  Misses        296      296              

Flag	Coverage Δ
unittests	88.02% <100.00%> (+0.01%)	⬆️

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Impacted Files	Coverage Δ
pyspectral/rsr_reader.py	77.99% <100.00%> (ø)
pyspectral/tests/test_rsr_reader.py	100.00% <100.00%> (ø)

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[djhoese]

I manually checked the HDF5 file and it seems like it is using the chN format of variable names, but with or without this PR I'm still getting these warnings:

WARNING  : Could not get the reflectance correction using band name: 1
WARNING  : Will try use the wavelength, however, this may be ambiguous!
WARNING  : A wavelength is provided instead of band name - disregard the relative spectral responses and assume it is the effective wavelength: 0.470000 (micro meter)

[adybbroe]

I manually checked the HDF5 file and it seems like it is using the chN format of variable names, but with or without this PR I'm still getting these warnings:

WARNING  : Could not get the reflectance correction using band name: 1
WARNING  : Will try use the wavelength, however, this may be ambiguous!
WARNING  : A wavelength is provided instead of band name - disregard the relative spectral responses and assume it is the effective wavelength: 0.470000 (micro meter)

@djhoese
This is from Satpy right? Just to be clear. We should change a logger.warningto a logger.exception instead I think!
That would help quite a bit in debugging Pyspectral. wouldn't it?

[adybbroe]

LGTM

[djhoese]

Yes, from Satpy. I don't think changing that logger is a good long term idea. I did actually add exc_info=True to the existing warning to find the exact exception location in pyspectral. I see that as a one time thing, especially considering this error is semi-expected for any sensors that aren't configured and don't have conversions in the generic dictionary.

Thanks for reviewing.