code: def _ir_calibrate(self, data, key):
          
          # Not sure if Lv is correct, FCI User Guide is a bit unclear
  
          Lv = data.data * \
              self.nc[
                  '/data/{}/measured/radiance_unit_conversion_coefficient'
                  .format(key.name)][...]
  
          vc = self.nc['/data/{}/central_wavelength_actual'
                       .format(key.name)][...]
          a, b, dummy = self.nc[
              '/data/{}/measured/radiance_to_bt_conversion_coefficients'
              .format(key.name)][...]
          c1, c2 = self.nc[
              '/data/{}/measured/radiance_to_bt_conversion_constants'
              .format(key.name)][...]
  
          nom = c2 * vc
          denom = a * np.log(1 + (c1 * vc**3) / Lv)
  
          data.data[:] = nom / denom - b / a
docs: IR channel calibration.