Set up¶
[relevant workers: general, getdata, obsconf]
Directories and input file names¶
A run of CARACal must always start by setting up a number of directory and file names. This is done through the general and getdata workers.
In the general worker users give:
- if necessary, the rawdatadir directory where to find the files that should be converted to .MS format (general: rawdatadir);
- the msdir directory where to find/write .MS files (general: msdir);
- the output directory where to write all output data products (general: output);
- the input directory where to find various input files, such as AOflagger strategies etc. (general: input);
- the prefix for the output data products (general: prefix).
If they do not exist yet, the above directories can be created by setting general: prep_workspace to true. This also copies files from the caracal/data/meerkat_files directory to the input directory set above.
In the getdata worker users give the name of the .MS files to be processed (getdata: dataid). Furthermore, the following optional steps are available:
- convert from HDF5/MVF format to .MS (getdata: mvftoms);
this step includes the following additional conversion options:
- create a .MS.TAR file,
- convert only visibilities in a selected channel range,
- discard cross-polarisation products;
- untar an existing .MS.TAR file (getdata: untar);
- EXPERIMENTAL – virtually concatenate all .MS input files (getdata: combine); optionally users can delete an existing concatenate file and tar/untar the concatenated file.
Metadata¶
Finally, before starting the actual data processing users need to provide some info about the content of the input .MS files through the obsconf worker. Target and calibrators name can be set by editing the relevant parameters of this worker:
In fact, CARACal can automatically extract most of these info from the .MS files themselves. To do so users should enable the obsconf: obsinfo parameter. This writes a .JSON and a .TXT file to disc. Once the .JSON file is on disc, the above parameters can be read automatically from that file. Users can, however, set any of the above manually.
Special attention should be paid to the choice of a reference antenna. Users should carefully select a good reference antenna for calibration with the obsconf: refant parameter.