This image-file is produced by omdetect and the image shows the final background map it produced
after running the source-detection algorithms.
Intermediate background-image file produced by omdetect - eg I0123920101OMS493BCKIMAGE1000.FIT
For engineering-2 mode data, the four image segments are combined into a
composite image by omcomb (fits file, eg I0135720601OMS01700E2I.FIT) which is
then processed in the normal way.