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[cf-satellite] Calibration Look Up tables

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Raw satellite data are generally stored as integers (DN=digital numbers) that are then 1. converted to radiances linearly (or sometimes non-linearly) that can then be 
2. converted to brightness temperatures.
With steps that are nonlinear, the scale factor offset doesn't work. If a coefficient is tweaked/corrected, then the entire variable would need to be rewritten.
Satellite data often use lookup tables to more easily and quickly convert from DN to whatever (radiance/temperature). Updates would then be made to calibration tables, rather than equations.
So I would propose something like the following CDL where variable /image/ has range from 0-255 and its attribute /lookup/ means that the table to convert to meaningful units is /table_1 

/

dimensions:
    lat = 100
    lon = 100
    num_bins = 256

int image(lat,lon)
    image:long_name = "GOES Water vapor channel"
    image:units = "digital number"
    image:lookup = "table_1"
    image:valid_range = 0, 255

float table_1(num_bins)
    table_1:long_name = "Brightness temperature"
    table_1:units = "Kelvin"

Thoughts?
-Ken

--
Ken Knapp
Remote Sensing and Applications Division
National Climatic Data Center
151 Patton Ave
Asheville, NC 28801
828-271-4339 (voice) 828-271-4328 (fax)
IBTrACS:  http://www.ncdc.noaa.gov/oa/ibtracs/
ISCCP B1: http://www.ncdc.noaa.gov/oa/rsad/isccpb1/
HURSAT:   http://www.ncdc.noaa.gov/oa/rsad/hursat/
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