thm.themis emissivity

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Description

Convert THEMIS radiance to THEMIS emissivity

Arguments and Return Values

Arguments: A THEMIS radiance cube and optional parameters

Return Value: An structure containing .emissivity and .maxbtemp elements

Usage

Syntax: thm.themis_emissivity(rad=VAL[, bandlist=INT][, ignore=VAL][, temp_rad_path=STRING][, b1=INT][, b2=INT][, max_emiss=FLOAT])

'rad' - any 3-D radiance array.

'bandlist' - an ordered list of THEMIS bands in rad. Default is 1//2//3//4//5//6//7//8//9//10.

'ignore' - non-data pixel value. Default is -32768 AND 0.

'temp_rad_path' - alternate path to temp_rad lookup table. Default is /themis/calib/temp_rad_v4. **temp_rad_path should not be specified since the default hhas changed.**

'b1' - first band to search for maximum brightness temperature. Default is 3.

'b2' - last band to search for maximum brightness temperature. Default is 9.

'max_emiss' - optional flag to designate the maximum allowable emissivity when searching for maximum brightness temperature.

thm.themis_emissivity() uses a lookup table to convert radiance in all bands to brightness-temperature. The maximum brightness temperature in bands 'b1' - 'b2' is used as the temperature of the surface. This temperature is used to calculate a blackbody radiance. Finally, the emissivity is the ratio of the measured radiance to the blackbody radiance.

This process is reversed using thm.emiss2rad.

Examples

dv> b
100x200x10 array of float, bsq format [800,000 bytes]

dv> c = thm.themis_emissivity(b)
.struct, 2 elements
    emiss: 100x200x10 array of float, bsq format [800,000 bytes]
    maxbtemp: 100x200x1 array of float, bsq format [80,000 bytes]

or a more verbose example:

dv> c = thm.themis_emissivity(rad=b, bandlist=1//2//3//4//5//6//7//8//9//10, 
            ignore=-32768, temp_rad_path = "/themis/calib/temp_rad_v4", b1=3, b2=9)
.struct, 2 elements
    emiss: 100x200x10 array of float, bsq format [800,000 bytes]
    maxbtemp: 100x200x1 array of float, bsq format [80,000 bytes]

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