• VisibilityanddataCalibration

Visibility Data Calibration

Daniele Dallacasa

• The Correlator [Black Box] output:
• Interferometric measure
  • time, interf., baseline [u,v,(w)], amplitude
    • (RR,LL,RL,LR) phase, weight, flag ....
    • Bandwidth [IF(s) and CHANNEL(s) when relevant]
    • Time integration
  • Smearing / need of band pass calibration?
• Quality checks on the data: editing of bad points (easy for calibrators!)
• (sometimes invalid) Assumptions:
  • Calibrators are pointlike, at the field center
  • Instrumental and atmospheric parameters vary smoothly with time
• Raw data and primary calibrators
• The role of secondary calibrations
  • phase reference
  • checks on raw visibilities

• (?need of a calibration source for the instrumental polarisation)

Outcome --> good scheduling means easy calibration!

• (AIPS) Practical calibration: relevant tasks SETJY, CALIB, GETJY,CLCAL
• Important checks on (total intensity) calibration (e.g. SNPLT)
• What to do when something is wrong
• Error reckognition in the images

Optional(I guess this will be covered by Tim)

• Instrumental polarisation (parallactic angle, AN table, PCAL)
• Absolute orientation of the (Electric) polarisation vector (LISTR, CLCOR)
• When polarisation observations are critical