ATNF VLBI Wiki

The first hour of every LBA experiment is used for setup and fringe testing. In the past this has been added for PIs, but we are now asking PIs to add this setup themselves. Please note that this is really important to check setup problems and failing to do this properly could result in losing all data for one or more telescopes. Do not be tempted to cut the fringe test short. It's fine to allow slew time from the fringe test source to be onsource at the end of the setup period.

You should choose a single source to observe for the entire time. You need to choose the brightest, most compact source that is visible to all telescopes at your given LST. There are trade off needs due when including the longest baselines (Hart) or at higher frequencies (22 GHz). The choice of best source depends on the observing frequency.

Preferably choose one of the following sources and consult with CASS staff if you cannot find a suitable sorurce for your timeslot.

The typical stanza to include fringe test would be something like:

  year     = 2015
  day      = 273
  start    = 19:00:00 

  station = ATCA, MOPRA, PARKES, HOB_DBBC, CDDBBC, HART, WARK12M, ASKAP, KATHERIN, YARRAGAD

  group=1 repeat=14
  grabto='file' grabtime=2,10
  SOURCE=0208-512      GAP=1:00  DUR=3:00    intent='FIND_FRINGE' /

  intent='OBSERVE_TARGET'
  grabto='none'

Note that the grabto is needed for Mark5 recorders. This grabs 2 seconds of data starting 10 seconds before the end of the scan. If you know there are no mark5 recorders being used, you can omit this and set gap to 0:00.

• If you are forced to use a weaker fringe finder or one which is partially resolved on longer baselines, you may need to increase the integration time (e.g., grabtime=4,10)
• If you have an experiment with multiple setups/frequencies etc you will need to make parallel fringe test experiments. Please consult with CASS staff to get allocated a fringe test code. Use the main schedule for one of the setups and the other setup in the test schedule. Please make it quite clear what you have done
• It may be impossible to get a good source strong which is visible to Parkes and Hartebeesthoek (and ASKAP). You may need to create a parallel schedule especially for Hart. Please consult with CASS staff.