def METHOD_NAME(data,
               chn,
               calib_type,
               mask=True):
    """Calibrate channel data.
    *calib_type* in brightness_temperature.
    """
    if calib_type not in ['brightness_temperature']:
        raise ValueError('Calibration ' + calib_type + ' unknown!')
    channel = da.from_array(data["btemps"][:, :, chn] / 100., chunks=(LINE_CHUNK, 90))
    mask &= channel != 0
    if calib_type == 'counts':
        return channel
    channel = channel.astype(np.float_)
    return da.where(mask, channel, np.nan)