observation related: DATE_OBS and DURATION
required by XMM-SOC-ICD-0006-SSC ([3]),
write also DATE_END and OBSSTART, OBSSTOP
exposure related: DATE-OBS and DATE-END
required by XMM-SOC-ICD-0004-SSD ([1]),
write also EXPSTART, EXPSTOP
SAS_VERBOSITY should be set to `Sparse' (4) for normal processing
and `Verbose' (5) for more detailed processing. Values of 6 and higher may
yield quite a number of messages related to rejected events (MIPs)
depending on CCD number and instrument mode.
SAS_MEMORY_MODEL should be set to `high' for normal processing.
Information about possible errors in the ODF is needed to
decide about additional criteria to flag wrong frames and events:
can the ODF still be corrupted by transfer jumps, bit flips, etc.
or are these checks done elsewhere?
