[McIDAS #CLT-967906]: update and some questions

Hi Ioan,

re: what calibration parameter(s) is(are) missing?

> Well, ... let's have a look
> 
> I made a multiband request to lead to fetch the calibration info for all
> channels
> 
> "aget RTGOESR FD 0 AU 0 0 X 1356 1356 LMAG=-8 EMAG=-8 BAND=1 2 3 4 5 6 7 8
> 9 10 11 12 13 14 15 16 DAY=2018-08-14 TIME=01:00 02:00 UNIT=RAW  SPAC=X
> CAL=X DOC=YES AUX=YES TRACE=0 VERSION=1"
> 
> The calibration block contains 18 elements for each band (16 bands)

I agree.

re:
> and here is the result as a python dict,  the keys in each dict represent
> the positional element for corresponding band...
> 
> 
> 
> 
> {1: 1, 2: 4699999, 3: 8121063, 4: -259366474, 5: 0, 6: 0, 7: 0, 8: 0, 9: 0,
> 10: 0, 11: 0, 12: 15983, 13: 0, 14: -9990000, 15: -9990000, 16:
> -2147483648, 17: -2147483648, 18: 1023}

Let's take a look at the calibration values for BAND 1 and not worry about the
rest for now.

The server code populates the calibration block for each image with the
following information (as per what I sent in my last email):

 0: ABIN

 1: image band #  from user request
 2: wavelength    from variable band_wavelength
 3: scale_factor  from variable Rad
 4: add_offset    from variable Rad
 5: 0.0
 6: 0.0
 7: 0.0
 8: 0.0
 9: 0.0
10: 0.0
11: 0.0
12: kappa         from variable kappa0
13: 0.0
14: planckFK1     from variable planck_fk1
15: planckFK2     from variable planck_fk2
16: planckBC1     from variable planck_bc1
17: planckBC2     from variable planck_bc2
18: VAR_FillValue from variable Rad


re:
> Most of the calibration data is there but notice that for channels [1-6]
> the element 14 and 15 are set to -9990000.

Correct.  I did an 'ncdump; for the variables that contain the values
for elements 14 and 15 for a randomly selected Channel 1 0.47 um image,
and the value returned was the fill value for the each parameter which
is -999.  For instance:

ncdump -v planck_bc1,planck_bc2 
OR_ABI-L1b-RadF-M3C01_G16_s20182271845486_e20182271856253_c20182271856297.nc
 ...
data:

 planck_bc1 = _ ;

 planck_bc2 = _ ;

And this shows that the planck_bc[12] values are missing so that the FillValue
should be used.

re:
> These two parameters correspond
> to esun and earth_sun_distance_anomaly_in_AU parameters

No, they don't.  They correspond to planck_bc1 and planck_bc2, respectively.

re:
> 
> float esun ;
>       esun:long_name = "bandpass-weighted solar irradiance at the
>       mean Earth-Sun distance" ;
>       esun:standard_name = "toa_shortwave_irradiance_per_unit_wavelength" ;
>       esun:_FillValue = -999.f ;
>       esun:units = "W m-2 um-1" ;
>       esun:coordinates = "band_id band_wavelength t" ;
>       esun:cell_methods = "t: mean" ;
> 
> float earth_sun_distance_anomaly_in_AU ;
>       earth_sun_distance_anomaly_in_AU:long_name = "earth sun
>       distance anomaly in astronomical units" ;
>       earth_sun_distance_anomaly_in_AU:_FillValue = -999.f ;
>       earth_sun_distance_anomaly_in_AU:units = "ua" ;
>       earth_sun_distance_anomaly_in_AU:coordinates = "t" ;
>       earth_sun_distance_anomaly_in_AU:cell_methods = "t: mean" ;

Correct, the variables you are looking for are esun and 
earth_sun_distance_anomaly_in_AU.
These are _not_ part of the AREA calibration block, and from what I can find, 
they
should not be part of the calibration block.

re:
> I use these parameters to calibrate the channel 2 (cloud detection)....

McIDAS does not use these two variables to calibrate imagery.

re:
> I can approximate  these two parameters but I do not want to play around
> with such things because it can affect negatively the calibration of vis
> channels (1-6)
> 
> I hope this info shed some light on the matter.

Yes, it does.  It seems that the question comes down to how you are doing
your calibrations.  As I mentioned above, McIDAS is using the values in
the calibration block that it populates from netCDF values only.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: CLT-967906
Department: Support McIDAS
Priority: Normal
Status: Closed
===================
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