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Two GO FITS keywords are defined as LASTON and LASTOFF.
These will contain the last known scan numbers that are valid to use in
combination with the current scan in data reduction.
There are cases when GO will not know what valid
values for the LASTON and LASTOFF FITS Keywords should be. When this
occurs GO will need to "reset" LASTON and LASTOFF to zero values.
This occurs when:
- Whenever GO is started. This means
that if you need to stop GO and then restart it you will lose what
these values were. GO does not have any ``prior knowledge'' of non-YGOR
parameters built into it.
- Whenever the Project ID is changed. You
don't want to use someone else's data.
- Whenever the observer's name is changed. Again you
don't want to use someone else's data.
- Whenever the scan number is changed by the operator. This can only
be done in CLEO or if the Scan Coordinator manager is restarted.
When the scan number is changed by the operator (or Scan Coordinator restart)
GO can no longer guarantee that it knows what is going on.
- Whenever the back-end selected is changed.
You don't want to use DCR off's for the
Spectrometer. This means that anytime the Scan Coordinator
manager is restarted during an observation we might loose the LASTON
and LASTOFF information - depending on what actually happens as far as
the events that GO receives from the Scan Coordinator.
- Whenever the observing mode is changed. You don't want to mix spectral
line and pulsar observations for example.
- Whenever the receiver is changed.
- Whenever the frequency of the observation is changed. If you
decide to go from using to then decide to go back to without
doing a scan then it's ``sorry Charlie''. GO doesn't have a history of
parameter values for the last scan.
- Whenever any switches or filters are changed in the IF system.
This will constitute a new observing setup and new ons and offs will
be assumed to be needed.
- Whenever a different procedure is used. If you change from OffOn
to OnOff you are OK but if you go from OffOn to OffOnOff you probably
want to reset things.
- Whenever the source name is changed.
- Whenever the scan length changes.
Comparing a 30 second off with a 5 minute scan is not
the right thing to do in all cases.
- Whenever the switching signals are changed. We don't necessarily
want to compare total power without cal and total power with cal.
- Whenever the switching signals
master is changed.
- Whenever the bandwidth in the back-end is changed.
Next: Keywords Automatically Set By
Up: Position Switching
Previous: Position Switching
Bob Garwood
2011-07-23