How to Record Data using GUPPI

NOTE: As of 9/21/2009 the procedures on this page should not be used for standard GBT GUPPI observations. Up-to-date observing instructions can be found at GUPPIAstridGuide

These instructions describe how to record pulsar data using GUPPI. Unless otherwise indicated, all commands presented here should be run on the beef command line from your own account, eg:

[pdemores@beef ~]$

1. Check for Data Flow

First, follow the steps listed in the GUPPiUsersGuide to make sure the bee2 is initialized properly, signal input levels are correct, and data is being sent over the network and received on beef. You should also look at GUPPiUsersGuide if you want to tweak the observing bandwidth of GUPPI or the sampling rate of the data that GUPPI sends to beef. If you do not see packets flowing, stop now and figure out why! Continuing with the instructions on this page will be pointless. If that all worked well, though, quit the test_net_thread job by doing a 'ctrl-C'.

If you previously opened a monitor program (i.e. guppi_monitor), exit it now before continuing.

2. Set up environment

Open several (at least 2) beef xterms. In each, source guppi.csh or guppi.bash as appropriate for your login shell:
[pdemores@beef ~]$ source /opt/64bit/guppi/guppi_daq/guppi.sh
Opening additional xterms is fine also, just source this init file before running any guppi programs.

Users who are developing their own version of the guppi_daq software (ie, not using the stable copy in /opt/64bit) should not source this file. It is assumed these people will have their environment set correctly already.

3. Set GUPPI Status Parameters

Set up the GUPPI status buffer. First, make sure the buffer is initialized:
[pdemores@beef ~]$ guppi_set_params

Next, fill it with values appropriate for your observation (in this case, a calibration scan on the current source):
[pdemores@beef ~]$ guppi_set_params -c

Note that if you want to tweak the observing bandwidth of GUPPI or the sampling rate of the data that GUPPI sends to beef, please see the instructions in the GUPPiUsersGuide.

Full usage information for guppi_set_params can be found with the -h option:
[pdemores@beef ~]$ guppi_set_params -h
Usage: guppi_set_params.py [options]

Options:
  -h, --help            show this help message and exit
  -c, --cal             Setup for cal scan (folding mode)
  -n SCAN, --scannum=SCAN
                        Set scan number
  -i, --increment_scan  Increment scan num
  -T TSCAN, --tscan=TSCAN
                        Scan length (sec)
  -P PARFILE, --parfile=PARFILE
                        Use this parfile for folding
  -t TFOLD, --tfold=TFOLD
                        Fold dump time (sec)
  -b NBIN, --bins=NBIN  Number of profile bins for folding
  -I, --onlyI           Only record total intensity
  --dstime=DSTIME       Downsample in time (int, power of 2)
  --dsfreq=DSFREQ       Downsample in freq (int, power of 2)
  --obs=OBS             Set observers name
  --src=SRC             Set observed source name
  --ra=RA               Set source R.A. (hh:mm:ss.s)
  --dec=DEC             Set source Dec (+/-dd:mm:ss.s)
  --freq=FREQ           Set center freq (MHz)
  --bw=BW               Hardware total bandwidth (MHz)
  --nchan=NCHAN         Number of hardware channels
  --acc_len=ACC_LEN     Hardware accumulation length
  --gb43m               Set params for 43m observing
  --gbt                 Use values from gbtstatus (the default)
  --fake                Set params for fake psr

If you make more than one scan on the same source, you will need to use the "-i" option to increment the scan number, or overwrite the scan number using the "-n" option.

After running guppi_set_params, the text-based guppi_status monitor program should look something like the following: guppi status.png

4. Take calibrator or folding mode data.

Change to the directory where you want the data to end up. This should be on one of the beef RAIDs (/data1 or /data2).

For a cal scan, simply do:

[pdemores@beef ~]$ guppi_set_params -c
[pdemores@beef ~]$ guppi_fold

And you should see stuff start to happen. There will be a folding-mode PSRFITS file that will appear in your directory after 10-sec, and it will be complete after 1-min. You can view it using PSRCHIVE with:

[pdemores@beef ~]$ pav -X myfile_cal.fits

or

[pdemores@beef ~]$ psrplot -pC myfile_cal.fits

For folding regular pulsar data you need to use the "-P" option to specify your parfile. And the "-b", "-t", and "-T" options are all optional (and will default to reasonably sensible values). So the following is a fairly normal example:

[pdemores@beef /data1/paul/data]$ guppi_set_params -P 1937.par -t 10.0 -T 100.0
[pdemores@beef /data1/paul/data]$ guppi_fold

then when it is complete, you can view it using:

[pdemores@beef /data1/paul/data]$ pav -GTpd myfile_1937_0001.fits
[pdemores@beef /data1/paul/data]$ pav -SFT myfile_1937_0001.fits

While you are taking data, you can always watch the bandpass if you want by running "guppi_monitor".

[pdemores@beef ~]$ guppi_monitor

Note that the "onlyI", "dstime" and "dsfreq" options only apply to search mode datataking, and should be left at their default values if folding mode is in use. To reduce the number of polarizations, channels, subintegrations, or phase bins after your folded data has been recorded, use PSRCHIVE's "pam" program. The available options can be listed by running "pam -h".

5. Recording search-mode data.

Change to the directory where you want the data to end up. This should be on one of the beef RAIDs (/data1 or /data2).

This process is very similar to taking folding mode data. We first set parameters using guppi_set_params and then start the data flow using guppi_search.

For 800 MHz observations, by default the data recorded is at a time resolution of 40.96us with 2048-channels and Full Stokes. That means 200MB/s.

To downsample in time: use the "--dstime" option to guppi_set_params. To downsample in freq: use the "--dsfreq" option to guppi_set_params. To record only Stokes I: use the "--onlyI" option to guppi_set_params.

If you want to specify a scan length, you do it with "-T". Otherwise it will default to an 8-hour observation and you can interrupt it whenever you want by simply pressing control-C in the window where you ran "guppi_search".

As an example, here is how we would start a reasonable pulsar search run where there will be 1024 channels of only total-intensity and a scan duration of 1 hour:
[pdemores@beef /data1/paul/data]$ guppi_set_params --dsfreq=2 --onlyI -T 3600
[pdemores@beef /data1/paul/data]$ guppi_search

And once again, while you are taking data, you can always watch the bandpass if you want by running "guppi_monitor".

[pdemores@beef ~]$ guppi_monitor
Topic attachments
I Attachment Action Size Date Who Comment
guppi_monitor.pngpng guppi_monitor.png manage 33 K 2008-08-28 - 16:05 PaulDemorest guppi monitor screenshot
guppi_status.pngpng guppi_status.png manage 83 K 2008-08-28 - 15:51 PaulDemorest guppi_status screenshot
Topic revision: r6 - 2009-09-22, PaulDemorest
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