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LASTON and LASTOFF GO FITS Keyword Values

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:

  1. 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.

  2. Whenever the Project ID is changed. You don't want to use someone else's data.

  3. Whenever the observer's name is changed. Again you don't want to use someone else's data.

  4. 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.

  5. 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.

  6. Whenever the observing mode is changed. You don't want to mix spectral line and pulsar observations for example.

  7. Whenever the receiver is changed.

  8. Whenever the frequency of the observation is changed. If you decide to go from using $f_1$ to $f_2$ then decide to go back to $f_1$ without doing a scan then it's ``sorry Charlie''. GO doesn't have a history of parameter values for the last scan.

  9. 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.

  10. 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.

  11. Whenever the source name is changed.

  12. 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.

  13. Whenever the switching signals are changed. We don't necessarily want to compare total power without cal and total power with cal.

  14. Whenever the switching signals master is changed.

  15. Whenever the bandwidth in the back-end is changed.


next up previous
Next: Keywords Automatically Set By Up: Position Switching Previous: Position Switching
Bob Garwood 2011-07-23