Which radiance unit is used by ATCOR?

[rese_support]

ATCOR employs the unit [mW cm[sup]-2[/sup] sr[sup]-1[/sup] micron[sup]-1[/sup]]. For each channel the at-sensor radiance L(i) and digital number DN(i) are related by   L(i) = c0(i) + c1(i)*DN(i) , where c0(i) and c1(i) are the offset (bias) and slope (gain) of the linear calibration equation. The metadata files of different sensors use different units, so care has to be taken to convert these numbers into the ATCOR radiance unit. The c0, c1 coefficients (with unit mW cm[sup]-2[/sup] sr[sup]-1[/sup] micron[sup]-1[/sup]) are specified in a "sensor.cal" file, e.g. "aviris.cal". Since the sensor configuration often changes with time due to hardware modifications we have to update the calibration files (center wavelengths, bandwidths, c0, c1 values). Therefore, the year of calibration data is often included in the sensor specification files and directories, e.g. aviris02 means AVIRIS with wavelength and radiometric calibration of 2002.For spectral bands in the thermal region (8-14 micron) the radiance unit [mW m[sup]-2[/sup] sr[sup]-1[/sup] micron[sup]-1[/sup]] is required in ATCOR.