*** Warning: CYCLE not found or invalid in /tmp/imap_3.fits --- assuming 'P'

The CYCLE keyword is used to specify which exposures were used: P=primary, S=secondary. Most observations use the primary exposures, but interleaved mode observations (sometimes also refeered to as "alternating frame" observations) also use the secondary ones.

If you are working with interleaved mode, you may need to edit the header of the input file to have the correct keyword value for the "secondary" case; contact the CXC Helpdesk for details.