Preparing for Calibration

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4.3 Preparing for Calibration

There are a number of “a priori” calibration quantities that may need to be applied to the data before further calibration is carried out. These include

system temperature correction — turn correlation coefficient into correlated flux density (necessary for some telescopes),
gain curves — antenna gain-elevation dependence,
atmospheric optical depth — attenuation of the signal by the atmosphere, correcting for its elevation dependence.
flux density models — establish the flux density scale using “standard” calibrator sources, with models for resolved calibrators,
delays — antenna-based delay offsets,
antenna position errors — offsets in the positions of antennas assumed during correlation.

These are pre-determined effects and should be applied (if known) before solving for other calibration terms. If unknown, then they will need to be solved for (or subsumed in other calibration such as bandpass or gains).

We now deal with these in turn.

  4.3.1 System Temperature Correction
  4.3.2 Antenna Gain-Elevation Curve Calibration
  4.3.3 Atmospheric Optical Depth Correction
   4.3.3.1 Determining opacity corrections for JVLA data
   4.3.3.2 Determining opacity corrections for VLA data
  4.3.4 Setting the Flux Density Scale using (setjy)
   4.3.4.1 Using Calibration Models for Resolved Sources
  4.3.5 Correction for delay and antenna position offsets using gencal
  4.3.6 Applying JVLA switched power or ALMA Tsys using gencal
  4.3.7 Generate a gain table based on Water Vapor Radiometer data wvrgcal
  4.3.8 Other a priori Calibrations and Corrections

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