The reduction file is a Starlink sdf file used to contain objects produced during the various stages of the reduction. For example, a list of order locations, wavelength polynomial fits, etc.
The file is created at the start of a reduction cycle with a user- provided name, and grows in size until the reduction is complete. At this point it contains a fairly complete record of any intermediate results, thus allowing particular sections of a reduction to be tuned and repeated as required.
Usually it will not be necessary to access the file except via ECHOMOP commands. The package provides facilities for examining and plotting data from all the objects in the file.
The reduction file also contains a HISTORY object which provides a record of all significant processing decisions taken, and the data frames involved. Options are provided to trim the size of reduction files once a reduction is complete. They should, however, be saved alongside the resulting data file (spectrum) to assist any future analysis.
Martin Clayton