code: def _calibrate_ir(radiance, coefs):
          
          logger.debug('Calibrating to brightness temperature')
  
          # Compute brightness temperature using inverse Planck formula
          n = coefs['n']
          bteff = C2 * n / xu.log(1 + C1 * n**3 / radiance.where(radiance > 0))
          bt = xr.DataArray(bteff * coefs['b'] + coefs['a'])
  
          # Apply BT threshold
          return bt.where(xu.logical_and(bt >= coefs['btmin'],
                                         bt <= coefs['btmax']))
docs: Convert IR radiance to brightness temperature
  
          Reference: [IR]
  
          Args:
              radiance: Radiance [mW m-2 cm-1 sr-1]
              coefs: Dictionary of calibration coefficients. Keys:
                     n: The channel's central wavenumber [cm-1]
                     a: Offset [K]
                     b: Slope [1]
                     btmin: Minimum brightness temperature threshold [K]
                     btmax: Maximum brightness temperature threshold [K]
  
          Returns:
              Brightness temperature [K]