# KOMPSAT-3/3A

KOMPSAT-3 and KOMPSAT-3A acquisitions are calibrated using the Orfeo Toolbox.

For the conversion from DN to spectral radiance (or ‘TOA radiance’) $$L$$, the following formula is used :

$L(b) = {DN(b) \times gain(b)} + bias(b)$

$$L$$ in $$W/m^2/steradians/micrometers$$ with $$b$$ being a band ID.

To convert TOA radiance to TOA reflectance, the following formula is used :

$R(b) = { {\pi \times L(b) \times d \times d} \over {ESUN(b) \times cos(θ)} }$

where :

• $$L(b)$$ is the spectral radiance for band b

• $$pi$$ is the famous mathematical constant

• $$d$$ is the earth-sun distance (in astronomical units) and depends on the acquisition’s day and month

• $$ESUN(b)$$ is the mean TOA solar irradiance (or solar illumination) in $$W/m^2/micrometers$$

• $$θ$$ is the solar zenith angle in degrees.

The values for the ESUN are provided in the tables below:

KOMPSAT-3

 Band Nominal bandpass (nm) 50% bandpass (nm) Center (nm) Bandwidth (nm) ESUN Blue 450 - 520 445.6 – 532.3 489.0 86.7 1970.281 Green 520 - 600 511.9 – 606.1 559.0 94.2 1814.155 Red 630 - 690 633.1 – 702.8 668.0 69.7 1516.303 NIR 760 - 900 756.0 – 932.2 844.1 176.2 1024.850

KOMPSAT-3A

 Band Nominal bandpass (nm) 50% bandpass (nm) Center (nm) Bandwidth (nm) ESUN Blue 450 - 520 445.6 – 532.3 489.0 86.7 2001 Green 520 - 600 511.9 – 606.1 559.0 94.2 1875 Red 630 - 690 633.1 – 702.8 668.0 69.7 1525 NIR 760 - 900 756.0 – 932.2 844.1 176.2 1027

## Input

The input is an ingested KOMPSAT-3 or KOMPSAT-3A, see details here.

## Output

The output is a STAC item geojson ... including the assets ...

## References

RW01 - OTB Optical calibration