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Correlating your Data

Now that the fringe searching and (perhaps) pulsar gating has been done, you are ready to actually start correlator processing your data. The correlator schedule file controls all aspects of the correlator processing. The configuration of the correlator, the control of the S2 transports and the tapes, when it starts, stops etc.... You can look at a schedule file with an explanation of terms as an example in Appendix B.

The first thing to do is have a look at your schedule file to note the following things:

The correlator configuration is the correct one for your correlating.
Check the order of the stations and ensure you put the right sets of tapes into the correct transports.
Check that the correct lines are commented in/out so the right set of data is correlated (particularly check the align, stop, close file and newtapes commands).

Rewind the tapes and then start them playing by typing in lbaboss:

lbaboss	s2rewind
lbaboss	s2play

Note the time at which each of the tapes start playing. The latest time is the one that you will align the tapes to in a moment. For example if you have two sets of tapes and one starts playing at time 13:00:50 and the other at 13:02:20, then you will align them to 13:02:20.

Now we will stop the tapes, open a file for the correlator to write the data to, and start correlating:

lbaboss	s2stop
lbaboss	fo file_name.rpf
lbaboss	s2align 13:02:20
lbaboss	go

NB:
The fo command creates and opens the file named file_name.rpf for the correlator to write to. The standard format is; experimentname_starttime_passnumber.rpf - eg v088d3_1300_p1.rpf. Usually you will have a line
FILE file_name.rpf
in the schedule file, so that this file open command is not necessary.

After typing the s2align command hit return at the same moment as the time in the top right hand corner of the S2 windows ticks over to a mutliple of 10 seconds. The reason for having to do this is convoluted but has to do with blank data at particular time intervals. Once the tapes have aligned you will see the last digit of the seconds in the tape time corresponding to the last digit of the seconds in the top right corner of the S2 windows.

When you type ``go'', after a period of time, the tapes will realign themselves. This can take a minute or two and a lot of beeping will come out of lbaboss in the meantime. When everything is lined up and going the message
Underway at hh:mm:ss
will appear in the lbaboss message window. If this doesn't happen after a few minutes, get help. If it does get underway, check that the error rates on each S2 console is low by typing;

s2 console

transport display esterr

If errors on a particular transport are too high, wait and see if they reduce. If they don't get help.

To redisplay the time information on the tapes type;

s2 console

transport display time

Now the correlating is underway. You can see the products in TVD very similarly to how you would using VIS at the Compact Array. You can also view spectra using SPD in a similar way as you would at the Compact Array.

The correlating will continue, writing to the file filename.rpf until the schedule file reaches a closefile command and then a newtapes command at which point it will stop.

When the data has finished correlating on this set of tapes;

lbaboss	stop	to stop the correlator if it hasn't already been stopped within the schedule file
lbaboss	fc	to close the file
lbaboss	s2stop	to stop the tapes
lbaboss	s2rewind	to rewind the tapes
lbaboss	s2eject	to eject the s2 tapes

Alternatively, in your schedule file you can have the commands
STOP
REWIND
FILE CLOSE
to do most of this.

Subsections

• Correlating the Next Set of Data Using the Existing Schedule File

Next: Correlating the Next Set Up: index Previous: Setting up Pulsar Gating   Contents