def _header_to_exptype_calver(header):
    """Given dataset `header`,  return the EXP_TYPE and CAL_VER values."""
    cal_ver = header.get("META.CALIBRATION_SOFTWARE_VERSION", header.get("CAL_VER"))
    exp_type = header.get("META.EXPOSURE.TYPE",  header.get("EXP_TYPE", "UNDEFINED"))
    return exp_type, cal_ver