As many of you will be aware, NOAA-18 MHS has not been working since 20th October, due to a problem with the scan system. See https://www.ospo.noaa.gov/data/messages/2018/MSG2940854.html
The data are currently unusable and mhscl (which does the calibration) fails in AAPP. Therefore you are advised to disable processing of NOAA-18 MHS. If you use the script AAPP_RUN_NOAA, you should remove MHS from the list of instruments to be processed.
We will let you know if there is a status update.
Regards,
Nigel