ResourceSat-2 LISS-4
ResourceSat-2 LISS-4 acquisitions are calibrated using the Orfeo Toolbox.
DN to Radiance
ISRO provides the formula below to convert the DN into radiance:
Where:
- \(SR_{(b)}\) denotes the Saturation Radiance and these values (mW/(cm2-sr-um) are for LISS-4:
Common band name | Band | SR |
green | B2 | 47.5614 |
red | B3 | 45.6990 |
nir | B4 | 31.5000 |
For the conversion from \(DN\) (for Digital Numbers) to spectral radiance (or ‘TOA radiance’) \(L \), the following formula is used :
As such, the calibration uses:
and
\(L \) in \(W/m^2/steradians/micrometers\) with \(b\) being a band ID.
Radiance to Reflectance
To convert TOA radiance to TOA reflectance, the following formula is used :
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 \(ESUN(b)\) for LISS-4 are provided in the table below:
Common band name | Band | Mean TOA solar irradiance |
green | B2 | 181.89 |
red | B3 | 156.96 |
nir | B4 | 110.48 |
Input
The input is an ingested ResourceSat-2 LISS-4, see details here.
Output
The output is a STAC item geojson ... including the assets ...
References
RW01 - OTB Optical calibration
RE-01 - At-sensor Solar Exo-atmospheric Irradiance, Rayleigh Optical Thickness and Spectral parameters of RS-2 Sensors