-- AnthonySowinski - 2021-06-02

VLBA Real-time Data Quality Test Instructions

The rtvlba program will download and correlate small amounts of data as a real-time fringe checking system. Run this program for TR039 tests, and also attempt with DQ tests, USNO P-series and Z-series, and USNO CRD observations.

1. Initiate transfer and correlation of data. Start the rtvlba program about 30 minutes before the observation starts. This provides time for troubleshooting if there are problems.

ssh vlbaops@swc000 (old instructions for rtdq: ssh difx@swc000)
wt
cd /home/vlbiobs/astronomy/mmmYY/<project>/
rtvlba <project>.vex
(old instructions for rtdq: rtdq <project>.vex)

The text output in this terminal is often informative. Please familiarize yourselves with the output both when there are problems and when there are not.

If there is a problem at a site that cannot be fixed, you can run rtvlba program without that site. The data will still be recorded by the Mark6 for later correlation.

rtvlba -NL <project>.vex or rtvlba -NL -SC <project>.vex
 
If you start rtvlba with the wrong stations you can kill it and restart it without them but because files have been already generated you need to use the resume switch otherwise the program will not start.
 
rtvlba -r -NL -SC <project>.vex :

2. Monitor correlation weights. If the weights are zero then data is not being downloaded for that site.

ssh difx@swc000 or ssh vlbaops@swc000 (actually, this should work on zwicky just as well as on swc000)
wt
statemon

3. Plot the fringes. This is independent of the correlation and can be started and stopped without affecting the data.

ssh vlbaops@zwicky
cd /home/vlbiobs/astronomy/mmmYY/<project>/rtvlba
(old instructions for rtdq: cd /home/swc/difx/rtdq/<project>)
py
difxPlot.py -l -r FD -a 15 <project>rt_01
 
If you are already logged into zwicky as vlbaops, just open a new terminal instead of the first line (ssh vlbaops@zwicky).
The directory .../<project>/rtvlba won't exist until rtvlba has been run (Step 1).
The reference antenna can be changed. It is FD in the example above.
If you restart difxPlot during the observation, replace the job number (01 in the example above) with the current job number. Refer to statemon (Step 2) to determine the current job number.
After the test is finished, difxPlot can be run on any of the jobs. Omit the "-l" in this case ("l" for "live") and select the desired job number.

4. If the test is being run during work hours, there will often be a dedicated Mattermost channel for discussion. Check here to look for a link:

Topic revision: r4 - 2021-12-10, AnthonySowinski
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