def METHOD_NAME(input_file, mission_name):
    f = Dataset(input_file, 'r')
    mid = f.variables['mission_ID'][:].tolist().index(mission_name)
    valid_time = calculate_valid_time(f, mid)
    valid_time_mid = valid_time.strftime("%Y%m%d%H%M") 
    return valid_time_mid