MeerKAT calibrators and CSV catalogues

Definition of target catalogues for the MeerKAT telescope can either be as CSV catalogue for standard observation script, or the YAML observation files for the observation framework.

CSV catalogue format

The CSV catalogue format is relevant for the following:

• Older MeerKAT observation using the image.py and track.py observations takes CSV catalogue files listing targets to observe as input. Also, all observation scripts available in the katsdpscripts repository.
• It is also the standard format for the MeerKAT observatory calibration catalogues.

The CSV observation catalogue format is very simple:

• header section consisting of observation meta-data for user information
  # <free form user string>
• target information as defined in target specification
  name, tags, X position, Y position, [optional flux model coefficients]

MeerKAT standard calibrator catalogues

MeerKAT telescope provides lists of standard primary and secondary calibrators in CSV format. The official location of these files on the operational systems is katconfig/user/catalogues. For offline and local system use, the catalogues are made available as part of the AstroKAT repository, astrokat/catalogues.

The MeerKAT calibrator sources and catalogues can be view in the repository: astrokat/catalogues

MeerKAT standard calibrator catalogues follow a specific calibrator naming convention:
Lband-<calibrator_classification>-calibrators.csv
and relevant calibrators will be added for each observation per band and calibrator type.

The following calibrator catalogues are available:

• Complex gain calibrators, identified in observation files using the gaincal tag.
  Gain calibrators are generally classified as secondary calibrators in the AstroKAT framework scripts and currently about 100 calibrator sources are provided with good sky coverage in Lband-gain-calibrators.csv.

• Bandpass calibrator sources are indicated with the bpcal tag.
  Bandpass calibrators are classified as primary calibrators in the AstroKAT framework scripts. These sources have good phase closure, but some are variable, Lband-bandpass-calibrators.csv.

• Currently MeerKAT only use 3 trusted flux calibrator sources. MeerKAT has models for these sources and they can be found in Lband-flux-calibrators.csv. Flux calibrators are primary calibrators and can also be used as bandpass calibrators, so when an observation selects a flux calibrator, indicated with the fluxcal tag, a second bandpass calibrator is not required --- unless, the flux calibrator is very far away from the observation target and an additional bandpass calibrator closer is required. When these targets are added to observation files they are indicated with both the bpcal and fluxcal tags by default.

• Similarly, MeerKAT currently has a limited set of 3 polarisation calibration sources listed in Lband-polarisation-calibrators.csv. Polarisation calibrators are indicated in the observation files using the polcal tag.