Fix satellite altitude being in kilometers in ABI L2 reader

[aronnem]

The attribute data assumes the satellite altitude is stored
in meters, while the ABI L2 data stores this value in km;
we simply need to insert factor of 1000 to convert the units.
This matches what happens in the ABI L1b reader.

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[mraspaud]

@yufeizhu600

[djhoese]

Thanks for the PR. Just to be clear @aronnem, this is a difference between the L1b and L2 files or is this a change that is done in the L1b reader but wasn't being done in the L2 reader?

[yufeizhu600]

I have checked the GOES-R PUG, the satellite height is in km.

nominal_satellite_height 
value = 35786.023

@djhoese I have checked the code, @sfinkens has corrected the unit error in the abi l1b reader two years ago.
https://github.com/pytroll/satpy/commit/b9f92ad58ea4e09485e97aa90b392a0bc606c20a

@aronnem. Thanks for the PR, could you please also update the unit tests.

[aronnem]

@yufeizhu600 I can update the tests, but need a little more direction (sorry, I am new at this.) I see a couple spots in reader_tests, for the data mockup and the test, for example:

https://github.com/pytroll/satpy/blob/master/satpy/tests/reader_tests/test_abi_l2_nc.py#L70

Is that all I need to update?

[djhoese]

Yes @aronnem that will update the fake data that goes into the tests so the test will also need to be updated.

1. Update the fake data:

   satpy/satpy/tests/reader_tests/test_abi_l2_nc.py

   Line 70 in fac76a7

   "nominal_satellite_height": np.array(35786020.),

2. Update the test expected values:

   satpy/satpy/tests/reader_tests/test_abi_l2_nc.py

   Lines 105 to 107 in fac76a7

   	'satellite_altitude': 35786020.,
   	'satellite_latitude': 0.0,
   	'satellite_longitude': -89.5,

3. Run the tests by doing pytest satpy/tests/reader_tests/test_abi_l2_nc.py and make sure everything passes.

[codecov]

Codecov Report

Merging #1631 (4571783) into master (fac76a7) will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1631      +/-   ##
==========================================
+ Coverage   92.61%   92.62%   +0.01%     
==========================================
  Files         258      258              
  Lines       37761    37810      +49     
==========================================
+ Hits        34972    35022      +50     
+ Misses       2789     2788       -1     

Flag	Coverage Δ
behaviourtests	4.81% <ø> (-0.01%)	⬇️
unittests	92.76% <ø> (+0.01%)	⬆️

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

Impacted Files	Coverage Δ
satpy/readers/abi_l2_nc.py	70.00% <ø> (ø)
satpy/tests/reader_tests/test_abi_l2_nc.py	100.00% <ø> (ø)
satpy/tests/test_data_download.py	98.66% <0.00%> (-1.34%)	⬇️
satpy/aux_download.py	97.60% <0.00%> (-0.70%)	⬇️
satpy/tests/reader_tests/test_aapp_l1b.py	100.00% <0.00%> (ø)
satpy/readers/aapp_l1b.py	89.82% <0.00%> (+0.44%)	⬆️
satpy/modifiers/_crefl.py	100.00% <0.00%> (+1.11%)	⬆️
satpy/modifiers/geometry.py	87.09% <0.00%> (+3.22%)	⬆️

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[aronnem]

@yufeizhu600 @djhoese yes, I only needed to make one change. The mockup dataset needs to match the real netCDF (which has the altitude in km).

[yufeizhu600]

@aronnem, thanks for updating, it looks goods to me. Congrats for the first PR, don't forget to add your name to the authors document.
https://github.com/pytroll/satpy/blob/master/AUTHORS.md
You can update it in your PR and the authors doc will be updated as your PR merged.

[djhoese]

If the tests weren't failing before and they aren't failing now, then the change made to the reader isn't being tested. The test needs to be updated.

[mraspaud]

The tests were failing before 115d4f2

[djhoese]

Ah, right you are. Looks good then. Thanks.

[djhoese]

Oh but as @yufeizhu600 said, could you add yourself to the AUTHORS.md?