def METHOD_NAME(self, data):
    """Estimate minimum radiance from Rad DataArray."""
    attrs = data.attrs
    scale_factor = attrs["scale_factor"]
    add_offset = attrs["add_offset"]
    count_zero_rad = - add_offset / scale_factor
    count_pos = np.ceil(count_zero_rad)
    min_rad = count_pos * scale_factor + add_offset
    return min_rad