This special mode enables several sets of numbers of to be extracted
from PSS into external data files (usually IMPORT compatible). It is
intended as a tool for use by experienced users and the author to
help in diagnosing problems. Use the DIAG keyword to switch it on.
The options available are,
A - Chi-squared vs. flux per source at image position
B - Chi-squared vs. gaussian convolution of psf
C - Output background rescale map
V - Validate input data thoroughly
Z - Performance figures
To specify options, enter the codes, eg. ABC turns on the first three.