Add support for MERSI-1 on FY-3A/B/C

[yukaribbba]

• Tests added
• Fully documented
• RSR for pyspectral

Datasets for test:
https://drive.google.com/file/d/1cCoC14AioC2l34jFfxa19F88k5NXuqpi/view?usp=sharing

1. FY-3A:
   

2. FY_3B:
   

3. FY_3C:
   

[yukaribbba]

pre-commit.ci autofix

[yukaribbba]

@djhoese One of the CI test keeps failing on macos-latest, 3.9, false. I don't know what's going on.

=========================== short test summary info ============================
FAILED satpy/tests/reader_tests/test_sar_c_safe.py::TestSAFEGRD::test_read_lon_lats - AssertionError: 
Not equal to tolerance rtol=1e-07, atol=0

Mismatched elements: 3 / 256 (1.17%)
Max absolute difference: 4.98866104e-09
Max relative difference: 2.33333333
 x: array([[ 2.081090e-16,  5.91[666](https://github.com/pytroll/satpy/actions/runs/8872941895/job/24358006466?pr=2795#step:9:667)7e-01,  9.097222e-01,  1.000000e+00,
         9.083333e-01,  6.805556e-01,  3.625000e-01, -1.110223e-16,
        -3.611111e-01, -6.750000e-01, -8.958333e-01, -9.777778e-01,...
 y: array([[ 3.794929e-16,  5.916[667](https://github.com/pytroll/satpy/actions/runs/8872941895/job/24358006466?pr=2795#step:9:668)e-01,  9.097222e-01,  1.000000e+00,
         9.083333e-01,  6.805556e-01,  3.625000e-01,  8.326673e-17,
        -3.611111e-01, -6.750000e-01, -8.958333e-01, -9.777778e-01,...
= 1 failed, 2541 passed, 4 skipped, 5 xfailed, 1 xpassed, 443 warnings in 352.85s (0:05:52) =

[djhoese]

Yes. This is a known problem with a scipy update causing a test failure. It is being looked at.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.94%. Comparing base (3b9c04e) to head (f48d740).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2795      +/-   ##
==========================================
- Coverage   95.95%   95.94%   -0.01%     
==========================================
  Files         379      379              
  Lines       53888    53764     -124     
==========================================
- Hits        51708    51585     -123     
+ Misses       2180     2179       -1     

Flag	Coverage Δ
behaviourtests	4.10% <0.00%> (+<0.01%)	⬆️
unittests	96.04% <100.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

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[djhoese]

I know this is still a draft, but I'm curious if there are actual differences between the datasets for the 3 satellite instruments. If they're the same channels then maybe the 3 readers could be combined into a single "mersi_l1b" reader?

[yukaribbba]

Well it's kinda annoying here that there are no genuine differences inside the datasets but they are still organized in different forms. So I think merging them into one could be a little bit messy for the users...

[djhoese]

Yeah MERSI and AGRI were the two instruments I think of with designs like that (new version of the instrument, but completely different numbering/ordering of channels).

[yukaribbba]

pre-commit.ci autofix

[yukaribbba]

pre-commit.ci autofix

[yukaribbba]

@djhoese Some of the CI failed again. But at least the tests passed.

[djhoese]

I restarted the CI. Very odd error from the test coverage reporting tool so let's see if it fixes itself...

[yukaribbba]

Failed again....

[djhoese]

Looks like a major release of the coveralls python package causing issues: https://pypi.org/project/coveralls/

I have appointments half of today, but I'll try debugging later.

[coveralls]

Pull Request Test Coverage Report for Build 9171394924

Details

• 261 of 261 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.007%) to 96.025%

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Totals
Change from base Build 9157044280:	-0.007%
Covered Lines:	51457
Relevant Lines:	53587

---

💛 - Coveralls