"- pi is the famous mathematical constant (3.14159...) \n"

"- d is the earth-sun distance (in astronomical units) and depends on the acquisition's day and month \n"

"- ESUN(b) is the mean TOA solar irradiance (or solar illumination) in W/m²/micrometers\n"

"- ESUN(b) is the mean TOA solar irradiance (or solar illumination) in W/m2/micrometers\n"

"- θ is the solar zenith angle in degrees. \n"

"Note that the application asks for the solar elevation angle, and will perfom the conversion to the zenith angle itself (ze. angle = 90° - el. angle).\n"

"Note also that ESUN(b) not only depends on the band b, but also on the spectral sensitivity of the sensor in this particular band. "